tag:blogger.com,1999:blog-235684792024-03-14T01:14:02.732-07:00HARBAILMECH. RULZ.harbailhttp://www.blogger.com/profile/09907681386203833739noreply@blogger.comBlogger35125tag:blogger.com,1999:blog-23568479.post-1146830444273719352006-05-30T04:59:00.000-07:002006-05-29T05:13:53.880-07:00MECHANICAL<img src="http://www.abobadr.net/3dsmax/tutorials/user/salman/images/tank_tracks/animated.gif"><br /><br /><br /> MECHANICAL ENGINEERSharbailhttp://www.blogger.com/profile/09907681386203833739noreply@blogger.comtag:blogger.com,1999:blog-23568479.post-1148904578775898882006-05-29T05:08:00.000-07:002006-05-29T05:09:38.873-07:00History of Battle TankWorld War One: The first tanks<br />The fighting conditions on the Western Front prompted the British Army to begin research into a self-propelled vehicle which could cross trenches, crush barbed wire, and would be impervious to fire from machine-guns. Having already seen a Rolls-Royce Armoured Car used by Royal Naval Air Service in 1914, and aware of schemes to create a tracked fighting vehicle, First Lord of the Admiralty Winston Churchill sponsored the Landships Committee to oversee development of this new weapon. Under the direction of Colonel Ernst Swinton, the Landships Committee created the first successful prototype tank, nicknamed Little Willie, which was tested by the British Army on September 6, 1915. Although initially termed landships by the Admiralty, the initial vehicles were colloquially referred to as water-carriers, later shortened to tanks, to preserve secrecy. The word tank was used to give the workers the impression they were constructing tracked water containers for the British army in Mesopotamia, and it was made official on December 24, 1915.<br /><br /> <br />This German photograph from World War I shows a captured British Mark II tank. The front part of the tracks are high off the ground in order to climb obstacles. The main guns are side-mounted to keep the centre of gravity lowThe first tank became operational when Captain H. W. Mortimore of the Royal Navy took a Mark I into action at Delville Wood during the Battle of the Somme on September 15, 1916. The French developed the Schneider CA1 working from Holt caterpillar tractors, and first used it on April 16, 1917. The first successful use of massed tanks in combat occurred at the Battle of Cambrai on November 20, 1917.<br /><br />The tank would eventually make trench warfare obsolete, and the thousands of tanks fielded during the war by French and British forces made a significant contribution.<br /><br />Initial results with tanks were mixed, with problems in reliability (and impatient high command) causing considerable attrition in combat. Deployment in small groups also lessened their tactical value and impact, which was still formidable during first encounters. German forces suffered from shock and lacked counter-weapons, though they did (accidentally) discover solid anti-tank shot, and the use of wider trenches to limit the British tanks' mobility.<br /><br />Changing battlefield conditions and continued unreliability forced Allied tanks to continue evolving for the duration of the war, producing models such as the very long Mark V, which could navigate large obstacles, especially wide trenches, more easily than many modern armoured fighting vehicles (AFVs).<br /><br />Germany fielded a small number of tanks, mainly captured, during World War I. They only produced approximately twenty of their own design, the A7V.<br /><br />Demands from infantry to have tanks close by during attacks would have pernicious effects on British tank design and tactics well into WW2.<br /><br /><br />1920s to the end of Second World War<br /> <br />Polish Vickers EWith the tank concept now established, several nations designed and built tanks between the two world wars. The British designs were the most advanced, due largely to their interest in an armoured force during the 1920s. France and Germany did not engage in much development during the early inter War years due to the state of their economy, and the Versailles Treaty respectively. The US did little development during this period because the Cavalry branch was senior to the Armoured branch and managed to absorb most of the funding earmarked for tank development. Even George S. Patton, with tank experience during WWI, transferred from the Armoured branch back to the Cavalry branch during this period.<br /><br />Throughout this period several classes of tanks were common, most of this development taking place in the United Kingom. Light tanks, typically weighing ten tons or less, were used primarily for scouting and generally mounted a light gun that was useful only against other light tanks. The medium tanks, or cruiser tanks as they were known in the United Kingdom, were somewhat heavier and focussed on long-range high-speed travel. Finally, the heavy or infantry tanks were heavily armoured and generally very slow. The overall idea was to use infantry tanks in close concert with infantry to effect a breakthrough, their heavy armour allowing them to survive enemy antitank weapons. Once this combined force broke the enemy lines, groups of cruiser tanks would be sent through the gap, operating far behind the lines to attack supply lines and command units. This one-two punch was the basic combat philosophy of the British tank formations, and was adopted by the Germans as a major component of the blitzkrieg concept. J.F.C. Fuller's doctrine of WWI was the fount for work by all the main pioneers: Hobart in Britain, Guderian in Germany, Chaffee in the U.S., de Gaulle in France, and Tukhachevsky in the USSR. All came to roughly the same conclusions, Tukhachevsky's integration of airborne pathfinders arguably the most sophisticated; only Germany would actually put the theory to practise, and it was their superior tactics, not superior weapons, that made blitzkrieg so formidable.<br /><br />There was thought put into tank-against-tank combat, but the focus was on powerful antitank guns and similar weapons, including dedicated antitank vehicles. This achieved its fullest expression in the United States, where tanks were expected to avoid enemy armour, and let dedicated tank destroyer units deal with them. Britain took the same path, and both produced light tanks in the hope that with speed, they could avoid being hit, comparing tanks to ducks. In practice these concepts proved dangerous. As the numbers of tanks on the battlefield increased, the chance of meetings grew to the point where all tanks had to be effective antitank vehicles as well. However, tanks designed to cope only with other tanks were relatively helpless against other threats, and were not well suited for the infantry support role. Vulnerability to tank and anti-tank fire led to a rapid up-armouring and up-gunning of almost all tank designs. Tank shape, previously guided purely by considerations of obstacle clearance, now became a trade-off, with a low profile desirable for stealth and stability.<br /><br />World War II saw a series of advances in tank design. Germany for example, initially fielded lightly armoured and lightly armed tanks, such as the Panzer I, which had been intended for training use only. These fast-moving tanks and other armoured vehicles were a critical element of the Blitzkrieg. However, they fared poorly in direct combat with British tanks and suffered severely against the Soviet T-34, which was superior in armour and weaponry. By the end of the war all forces had dramatically increased their tanks' firepower and armour; for instance, the Panzer I had only two machine guns, and the Panzer IV, the "heaviest" early war German design, carried a low-velocity 75mm gun and weighed under twenty tonnes. By the end of the war the standard German medium tank, the Panther, mounted a powerful, high-velocity 75mm gun and weighed forty-five tonnes.<br /><br />Another major wartime advance was the introduction of radically improved suspension systems. Although this might not sound important, the quality of the suspension is the primary determinant of a tank's cross-country performance. Tanks with limited suspension travel subject their crew to massive shaking, making operation difficult, limiting speed, and making firing on the move practically impossible. Newer systems like the Christie or torsion bar suspension dramatically improved performance, allowing the late-war Panther to travel cross country at speeds that would have been difficult for earlier designs to reach on pavement.<br /><br />By this time most tanks were equipped with radios (all U.S. and German, some Soviet; British radios were common, but often of indifferent quality), vastly improving the direction of units. Tank chassis were adapted to a wide range of military jobs, including mine-clearing and combat engineering tasks. All major combatant powers also developed specialised self-propelled guns: artillery, tank destroyers, and assault guns (armoured vehicles carrying large-calibre guns). German and Soviet assault guns, simpler and cheaper than tanks, had the heaviest guns in any vehicles of the war, while American and British tank destroyers were scarcely distinguishable (except in doctrine) from tanks.<br /><br />Turrets, which were not previously a universal feature on tanks, were recognised as the way forward. It was appreciated that if the tank's gun was to be used to engage armoured targets then it needed to be as large and powerful as possible, making having one large gun with an all-round field of fire vital. Multiple-turreted tank designs like the Soviet T-35 were abandoned by World War II. Most tanks retained at least one hull machine gun. Even post-war, the M60 MBT had a smaller secondary turret for the commander's cupola.harbailhttp://www.blogger.com/profile/09907681386203833739noreply@blogger.comtag:blogger.com,1999:blog-23568479.post-1148904387033145052006-05-29T05:04:00.000-07:002006-05-29T05:06:27.143-07:00History of Car (automobile)The first automobile patent in the United States was granted to Oliver Evans in 1789 for his "Amphibious Digger". It was a harbor dredge scow designed to be powered by a steam engine and he built wheels to attach to the bow. In 1804 Evans demonstrated his first successful self-propelled vehicle, which not only was the first automobile in the US but was also the first amphibious vehicle, as his steam-powered vehicle was able to travel on wheels on land as he demonstrated once, and via a paddle wheel in the water. It was not successful and eventually was sold as spare parts.<br /><br />The Benz Motorwagen, built in 1885, was patented on 29 January 1886 by Karl Benz as the first automobile powered by an internal combustion engine. In 1888, a major breakthrough came with the historic drive of Bertha Benz. She drove an automobile that her husband had built for a distance of more than 106 km (i.e. - approximately 65 miles). This event demonstrated the practical usefulness of the automobile and gained wide publicity, which was the promotion she thought was needed to advance the invention. The Benz vehicle was the first automobile put into production and sold commercially. Bertha Benz's historic drive is celebrated as an annual holiday in Germany with rallies of antique automobiles.<br /><br />In 1892 Rudolf Diesel gets a patent for a "New Rational Combustion Engine" by modifying the Carnot Process. And in 1897 he builds the first Diesel Engine.<br /><br />On 5 November 1895, George B. Selden was granted a United States patent for a two-stroke automobile engine (U.S. Patent 549160). This patent did more to hinder than encourage development of autos in the USA. Steam, electric, and gasoline powered autos competed for decades, with gasoline internal combustion engines achieving dominance in the 1910s.<br /><br /> <br />Ransom E. Olds, the creator of the first automobile assembly lineThe large-scale, production-line manufacturing of affordable automobiles was debuted by Ransom Eli Olds at his Oldsmobile factory in 1902. This assembly line concept was then greatly expanded by Henry Ford in the 1910s. Development of automotive technology was rapid, due in part to the hundreds of small manufacturers competing to gain the world's attention. Key developments included electric ignition and the electric self-starter (both by Charles Kettering, for the Cadillac Motor Company in 1910-1911), independent suspension, and four-wheel brakes.<br /><br />Felix Wankel invented the Wankel engine in 1954, which had a very unconventional structure that would reduce the wear the engine effected upon itself as it worked.harbailhttp://www.blogger.com/profile/09907681386203833739noreply@blogger.comtag:blogger.com,1999:blog-23568479.post-1147944415996553912006-05-09T02:16:00.000-07:002006-05-18T02:36:21.610-07:00Lathe MachineThe purpose of a lathe is to rotate a part against a tool whose position it controls. It is useful for fabricating parts and/or features that have a circular cross section. The spindle is the part of the lathe that rotates. Various workholding attachments such as three jaw chucks, collets, and centers can be held in the spindle. The spindle is driven by an electric motor through a system of belt drives and/or gear trains. Spindle speed is contolled by varying the geometry of the drive train.<br /><br /><img src="http://teched.vt.edu/ElectronicPortfolios/Schnitz.ep/MachineSafety/ImagesEtc/WoodLatheAnimated.gif"><br />The tailstock can be used to support the end of the workpiece with a center, or to hold tools for drilling, reaming, threading, or cutting tapers. It can be adjusted in position along the ways to accomodate different length workpices. The ram can be fed along the axis of rotation with the tailstock handwheel.<br /><br />The carriage controls and supports the cutting tool. It consists of: <br /><br />A saddle that mates with and slides along the ways. <br />An apron that controls the feed mechanisms. <br />A cross slide that controls transverse motion of the tool (toward or away from the operator). <br />A tool compound that adjusts to permit angular tool movement. <br />A toolpost T-slot that holds the toolpost. <br /><br /><br />Choosing a Cutting Tool<br /><br />Facing tools are ground to provide clearance with a center. <br /><br />Roughing tools have a small side relief angle to leave more material to support the cutting edge during deep cuts. <br /><br />Finishing tools have a more rounded nose to provide a finer finish. <br /><br />Round nose tools are for lighter turning. They have no back or side rake to permit cutting in either didection. <br /><br />Left hand cutting tools are designed to cut best when traveling from left to right. <br /><br />Aluminum is cut best by specially shaped cutting tools (not shown) that are used with the cutting edge slightly above center to reduce chatter. <br /><br /><br />Installing a Cutting Tool<br /><br /><br />Lathe cutting tools are held by tool holders. To install a tool, first clean the holder, then tighten the bolts<br /><br />The tool post is secured to the compound with a T-bolt. The tool holder is secured to the tool post using a quick release lever<br /><br /><br />Positioning the Tool<br /><br />In order to move the cutting tool, the lathe saddle and cross slide can be moved by hand. <br /><br />There are also power feeds for these axes. Procedures vary from machine to machine.<br /><br />A third axis of motion is provided by the compound. The angle of the compound can be adjusted to allow tapers to be cut at any desired angle. First, loosen the bolts securing the compound to the saddle. Then rotate the compound to the desired angle referencing the dial indicator at the base of the compound. Retighten the bolts. Now the tool can be hand fed along the desired angle. No power feed is available for the compound. If a fine finish is required, use both hands to achieve a smoother feed rate. <br /><br />The cross slide and compound have a micrometer dial to allow accurate positioning, but the saddle doesn't. To position the saddle accurately, you may use a dial indicator mounted to the saddle. The dial indicator presses against a stop .<br /><br /><br /><br /><br />Feed, Speed, and Depth of Cut<br /><br /><br />Cutting speed is defined as the speed at which the work moves with respect to the tool (usually measured in feet per minute). Feed rate is defined as the distance the tool travels during one revolution of the part. Cutting speed and feed determines the surface finish, power requirements, and material removal rate. The primary factor in choosing feed and speed is the material to be cut. However, one should also consider material of the tool, rigidity of the workpiece, size and condition of the lathe, and depth of cut. For most Aluminum alloys, on a roughing cut (.010 to .020 inches depth of cut) run at 600 fpm. On a finishing cut (.002 to .010 depth of cut) run at 1000 fpm. To calculate the proper spindle speed, divide the desired cutting speed by the circumference of the work. Experiment with feed rates to achieve the desired finish. In considering depth of cut, it's important to remember that for each thousandth depth of cut, the work diameter is reduced by two thousandths.<br /><br /><br />Facing<br />A lathe can be used to create a smooth, flat, face very accurately perpendicular to the axis of a cylindrical part. First, clamp the part securely in a lathe chuck . Then, install a facing tool. Bring the tool approximately into position, but slightly off of the part. Always turn the spindle by hand before turning it on. This ensures that no parts interfere with the rotation of the spindle. Move the tool outside the part and adjust the saddle to take the desired depth of cut. Then, feed the tool across the face with the cross slide. The following clip shows a roughing cut being made; about 50 thousandths are being removed in one pass. If a finer finish is required, take just a few thousandths on the final cut and use the power feed. Be careful clearing the ribbon-like chips; They are very sharp. Do not clear the chips while the spindle is turning. After facing, there is a very sharp edge on the part. Break the edge with a file<br /><br /><br /><br />Parting<br /><br /><br />A parting tool is deeper and narrower than a turning tool. It is designed for making narrow grooves and for cutting off parts. When a parting tool is installed, ensure that it hangs over the tool holder enough that the the holder will clear the workpiece (but no more than that). Ensure that the parting tool is perpendicular to the axis of rotation and that the tip is the same height as the center of the part. A good way to do this is to hold the tool against the face of the part. Set the height of the tool, lay it flat against the face of the part, then lock the tool in place. When the cut is deep, the side of the part can rub against sides of the groove, so it's especially important to apply cutting fluid. <br /><br /><br /><br />Drilling<br /><br /><br />A lathe can also be used to drill holes accurately concentric with the centerline of a cylindrical part. First, install a drill chuck into the tail stock. Make certain that the tang on the back of the drill chuck seats properly in the tail stock. Withdraw the jaws of the chuck and tap the chuck in place with a soft hammer.<br />Move the saddle forward to make room for the tailstock. Move the tailstock into position, and lock the it in place (otherwise it will slide backward as you try to drill). Before starting the machine, turn the spindle by hand. You've just moved the saddle forward, so it could interfere with the rotation of the lathe chuck. Always use a centerdrill to start the hole. You should use cutting fluid with the centerdrill. It has shallow flutes (for added stiffness) and doesn't cut as easily as a drill bit. Always drill past the beginning of the taper to create a funnel to guide the bit in. In this clip, a hole is drilled with a drill bit. Take at most one or two drill diameters of material before backing off, clearing the chips, and applying cutting fluid. If the drill bit squeeks, aplly solvent more often. The drill chuck can be removed from the tail stock by drawing back the drill chuck as far as it will easily go, then about a quarter turn more. A pin will press the chuck out of the collet. <br /><br /><br /><br />Boring<br /><br /><br />Boring is an operation in which a hole is enlarged with a single point cutting tool. A boring bar is used to support the cutting tool as it extends into the hole. Because of the extension of the boring bar, the tool is supported less rigidly and is more likely to <br />chatter. This can be corrected by using slower spindle speeds or by grinding a smaller radius on the nose of the tool.<br /><br /><br />Single Point Thread Turning<br /><br /><br />External threads can be cut with a die and internal threads can be cut with a tap. But for some diameters, no die or tap is available. In these cases, threads can be cut on a lathe. A special cutting tool should be used, typically witha 60 degree nose angle. To form threads with a specified number of threads per inch, the spindle is mechanically coupled to the carriage lead screw. Procedures vary for different machines. <br /><br /><br /><br /><br />Advanced Work Holding<br /><br /><br />Some parts require special techniques to hold them properly for lathe work. For instance, if you wish to cut on the entire outside diameter of a part, then the part cannot be held in a chuck or collet. If the part has a hole through it, you can press it on to a lathe arbor (a slightly tapered shaft), and clamp onto the arbor rather than the part itself. The hole must have an adequate aspect ratio or the part will not be firmly supported.<br />If the part has a very large hole through it, a lathe arbor may not be a practicable solution. You may instead use the outside of the jaws to hold the inside diameter of the part.<br /><br />If the part has a very complex geometry, it may be neccesary to install the part onto a face plate. The face plate is then attached to the spindle.harbailhttp://www.blogger.com/profile/09907681386203833739noreply@blogger.comtag:blogger.com,1999:blog-23568479.post-1146819729892426032006-05-06T02:28:00.000-07:002006-05-05T04:58:27.423-07:00Mechanical engineersMechanical engineers are a class of engineers who deal with anything related to machines. These machines range from internal combustion engines, refrigerators and air conditioners and automobiles to production equipment like lathes, drilling machines and milling machines.<br /><br />Mechanical engineering is divided into three fields: design, thermal and production. Design deals with the design of various machine elements. Thermal deals with the basics of heat work conversion and the machines related to it. Production deals with the various methods needed to produce various components ranging from computer chips to airplane bodies.harbailhttp://www.blogger.com/profile/09907681386203833739noreply@blogger.comtag:blogger.com,1999:blog-23568479.post-1146896199768452602006-05-05T23:11:00.000-07:002006-05-06T00:27:35.843-07:00Heat treatment 2Full annealing is the process of slowly raising the temperature about 50 ºC (90 ºF) above the Austenitic temperature line A3 or line ACM in the case of Hypoeutectoid steels (steels with < 0.77% Carbon) and 50 ºC (90 ºF) into the Austenite-Cementite region in the case of Hypereutectoid steels (steels with > 0.77% Carbon). <br /><br />It is held at this temperature for sufficient time for all the material to transform into Austenite or Austenite-Cementite as the case may be. It is then slowly cooled at the rate of about 20 ºC/hr (36 ºF/hr) in a furnace to about 50 ºC (90 ºF) into the Ferrite-Cementite range. At this point, it can be cooled in room temperature air with natural convection. <br /><br /><br />Normalizing<br /><br />Normalizing is the process of raising the temperature to over 60 º C (108 ºF), above line A3 or line ACM fully into the Austenite range. It is held at this temperature to fully convert the structure into Austenite, and then removed form the furnace and cooled at room temperature under natural convection. This results in a grain structure of fine Pearlite with excess of Ferrite or Cementite. The resulting material is soft; the degree of softness depends on the actual ambient conditions of cooling. This process is considerably cheaper than full annealing since there is not the added cost of controlled furnace cooling. <br /><br />The main difference between full annealing and normalizing is that fully annealed parts are uniform in softness (and machinablilty) throughout the entire part; since the entire part is exposed to the controlled furnace cooling. In the case of the normalized part, depending on the part geometry, the cooling is non-uniform resulting in non-uniform material properties across the part. This may not be desirable if further machining is desired, since it makes the machining job somewhat unpredictable. In such a case it is better to do full annealing. <br /><br />Process Annealing <br /><br />Process Annealing is used to treat work-hardened parts made out of low-Carbon steels (< 0.25% Carbon). This allows the parts to be soft enough to undergo further cold working without fracturing. Process annealing is done by raising the temperature to just below the Ferrite-Austenite region, line A1on the diagram. This temperature is about 727 ºC (1341 ºF) so heating it to about 700 ºC (1292 ºF) should suffice. This is held long enough to allow recrystallization of the ferrite phase, and then cooled in still air. Since the material stays in the same phase through out the process, the only change that occurs is the size, shape and distribution of the grain structure. This process is cheaper than either full annealing or normalizing since the material is not heated to a very high temperature or cooled in a furnace. <br /><br />Stress Relief Annealing <br /><br />Stress Relief Anneal is used to reduce residual stresses in large castings, welded parts and cold-formed parts. Such parts tend to have stresses due to thermal cycling or work hardening. Parts are heated to temperatures of up to 600 - 650 ºC (1112 - 1202 ºF), and held for an extended time (about 1 hour or more) and then slowly cooled in still air<br /><br /><br />Spheroidization<br /><br />Spheroidization is an annealing process used for high carbon steels (Carbon > 0.6%) that will be machined or cold formed subsequently. This is done by one of the following ways: <br /><br /> 1. Heat the part to a temperature just below the Ferrite-Austenite line, line A1 or below the Austenite-Cementite line, essentially below the 727 ºC (1340 ºF) line. Hold the temperature for a prolonged time and follow by fairly slow cooling. Or <br />2. Cycle multiple times between temperatures slightly above and slightly below the 727 ºC (1340 ºF) line, say for example between 700 and 750 ºC (1292 - 1382 ºF), and slow cool. Or <br />3. For tool and alloy steels heat to 750 to 800 ºC (1382-1472 ºF) and hold for several hours followed by slow cooling. <br /><br /> <br /> <br /> All these methods result in a structure in which all the Cementite is in the form of small globules (spheroids) dispersed throughout the ferrite matrix. This structure allows for improved machining in continuous cutting operations such as lathes and screw machines. Spheroidization also improves resistance to abrasion.harbailhttp://www.blogger.com/profile/09907681386203833739noreply@blogger.comtag:blogger.com,1999:blog-23568479.post-1146895787014975622006-05-05T23:07:00.000-07:002006-05-18T02:39:41.506-07:00SpringsHooke's Law <br /><br />Springs are fundamental mechanical components which form the basis of many mechanical systems. A spring can be defined to be an elastic member which exerts a resisting force when its shape is changed. Most springs are assumed linear and obey the Hooke's Law, <br /><br /><br />where F is the resisting force, D is the displacement, and the k is the spring constant. <br /><br />For a non-linear spring, the resisting force is not linearly proportional to its displacement. Non-linear springs are not covered in depth here. <br /> <br /><br />History of Springs <br /><br />Like most other fundamental mechanisms, metal springs have existed since the Bronze Age. Even before metals, wood was used as a flexible structural member in archery bows and military catapults. Precision springs first became a necessity during the Renaissance with the advent of accurate timepieces. The fourteenth century saw the development of precise clocks which revolutionized celestial navigation. World exploration and conquest by the European colonial powers continued to provide an impetus to the clockmakers' science and art. Firearms were another area that pushed spring development. <br />The eighteenth century dawn of the industrial revolution raised the need for large, accurate, and inexpensive springs. Whereas clockmakers' springs were often hand-made, now springs needed to be mass-produced from music wire and the like. Manufacturing methodologies were developed so that today springs are ubiquitous. Computer-controlled wire and sheet metal bending machines now allow custom springs to be tooled within weeks, although the throughput is not as high as that for dedicated machinery.<br /><img src="http://www.canadianarchitect.com/asf/enclosure_detailing/future_details/spring_damper_4d.gif">harbailhttp://www.blogger.com/profile/09907681386203833739noreply@blogger.comtag:blogger.com,1999:blog-23568479.post-1146895218033875122006-05-05T22:58:00.000-07:002006-05-05T23:00:18.783-07:00AluminumGeneral Information<br /><br />Aluminum is a silverish white metal that has a strong resistance to corrosion and like gold, is rather malleable. It is a relatively light metal compared to metals such as steel, nickel, brass, and copper with a specific gravity of 2.7. Aluminum is easily machinable and can have a wide variety of surface finishes. It also has good electrical and thermal conductivities and is highly reflective to heat and light. <br /><br /><br />Characteristics<br /> <br />At extremely high temperatures (200-250°C) aluminum alloys tend to lose some of their strength. However, at subzero temperatures, their strength increases while retaining their ductility, making aluminum an extremely useful low-temperature alloy. <br />Aluminum alloys have a strong resistance to corrosion which is a result of an oxide skin that forms as a result of reactions with the atmosphere. This corrosive skin protects aluminum from most chemicals, weathering conditions, and even many acids, however alkaline substances are known to penetrate the protective skin and corrode the metal. <br /><br />Aluminum also has a rather high electrical conductivity, making it useful as a conductor. Copper is the more widely used conductor, having a conductivity of approximately 161% that of aluminum. Aluminum connectors have a tendency to become loosened after repeated usage leading to arcing and fire, which requires extra precaution and special design when using aluminum wiring in buildings. <br /><br />Aluminum is a very versatile metal and can be cast in any form known. It can be rolled, stamped, drawn, spun, roll-formed, hammered and forged. The metal can be extruded into a variety of shapes, and can be turned, milled, and bored in the machining process. Aluminum can riveted, welded, brazed, or resin bonded. For most applications, aluminum needs no protective coating as it can be finished to look good, however it is often anodized to improve color and strength.harbailhttp://www.blogger.com/profile/09907681386203833739noreply@blogger.comtag:blogger.com,1999:blog-23568479.post-1146824969512709002006-05-05T03:28:00.000-07:002006-05-18T02:31:41.460-07:00History of Washing MachineThe first British patent under the category of Washing and Wringing Machines was issued in 1691. A drawing of an early washing machine appeared in the January 1752 issue of "The Gentlemen's Magazine," an English publication. In 1782 Henry Sidgier was issued a British patent for a rotating drum washer.<br /><br />The first United States Patent titled "Clothes Washing" was granted to Nathaniel Briggs of New Hampshire in 1797. However, there is no drawing or description of the patent so whether it was for a washing machine or something else related to washing, remains a mystery.<br /><br />The electric washing machine was first mass produced in 1906. It is not known who first "invented the electric" washer. A.J. Fisher has been incorrectly credited with the invention of the electric washer. The US patent office shows at least one patent issued before Mr. Fisher's for a washing machine with an electric motor. The first automatic washer was introduced by Bendix in 1937.harbailhttp://www.blogger.com/profile/09907681386203833739noreply@blogger.comtag:blogger.com,1999:blog-23568479.post-1146824882907580962006-05-05T03:26:00.000-07:002006-05-18T02:41:34.836-07:00ImpellerAn impeller is a rotor inside a tube or conduit to increase the pressure and flow of a fluid.<br /><img src="http://www.thamesrivertube.com/AnimatedImpeller.gif"><br />Impellers in Pumps<br /><br />An impeller is a rotating component of a pump , usually made of iron, steel, aluminum or plastic, which transfers energy from the motor that drives the pump to the fluid being pumped by forcing the fluid outwards from the centre of rotation. Impellers are usually short cylinders with protrusions forming paddles to push the fluid and a splined center to accept a driveshaft.<br /><br /><br />Impellers in Water Jets<br /><br />Some impellers are similar to small propellers but without the large blades. Among other uses, they are used in water jet to power high speed boats.<br /><br />Since impellers have no large blades to turn, they can spin at much higher speeds than propellers. The water forced through the impeller is channelled by the housing, creating a water jet that propels the vessel forward. The housing is normally tapered into a nozzle to increase the speed of the water, which also creates a Venturi effect in which low pressure behind the impeller pulls more water towards the blades, so tending to increase the speed.<br /><br />To work efficiently, there must be a close fit between the impeller and the housing. The housing is normally fitted with a replaceable wear ring which tends to wear as sand or other particles are thrown against the housing side by the impeller.<br /><br />Vessels using impellers are normally steered by changing the direction of the water jet.<br /><br />Compare to propeller and jet aircraft engines.harbailhttp://www.blogger.com/profile/09907681386203833739noreply@blogger.comtag:blogger.com,1999:blog-23568479.post-1146824706310630462006-05-05T03:24:00.000-07:002006-05-18T02:32:41.583-07:00PneumaticsPneumatics, from the Greek πνευματικός (pneumatikos, coming from the wind) is the use of pressurized gases to do work in science and technology.<br /><br />Pneumatics was first documented by Hero of Alexandria in AD 60, but it was used before then.<br /><br />Pneumatics is employed in a variety of settings. In dentistry applications, pneumatic drills are lighter, faster and simpler than an electric drill of the same power rating (because the prime mover, the compressor, is separate from the drill and pumped air is capable of rotating the drill bit at extremely high rpm's). Pneumatic transfer systems are employed in many industries to move powders and pellets. Pneumatic tubes can carry objects over distances. Pneumatic devices are also used where electric motors cannot be used for safety reasons, such as mining applications where rock drills are powered by air motors to preclude the need for electric motors deep in the mine where explosive gases may be present.<br /><br />dentist's drill <br />pneumatic drill (jackhammer) used by road menders <br />pneumatic switch <br />pneumatic actuators <br />air compressors <br />vacuum pumps <br />barostat-systems used in Neurogastroenterology research <br />electricity <br />Cable Jetting - a way to install cables in ducts <br />Pneumatic logic systems are often used to control industrial processes. Pneumatic logic systems consist of primary logic units including:<br /><br />And Units <br />Or Units <br />'Relay or Booster' Units <br />Latching Units <br />'Timer' Units <br />Pneumatic logic is a reliable and functional control method for industrial processes. In recent years these systems have largely been replaced by electrical control systems, due to the size of the logic units and cost versus their electrical counterparts. They are still in use in processes where compressed air is the only energy source available or upgrade cost, safety, and other considerations outweigh the advantage of modern digital control.<br /><br />Industrial pneumatics may be contrasted with hydraulics, which uses incompressible liquid media such as oil or water instead of air. Air is compressible, is considered to be a fluid, and most industrial applications use approximately 80 to 100 pounds per square inch (psi) (500 to 700 kilopascals) gauge pressure, as compared to hydraulics which are commonly used from 1,000 to 5,000 psi (0.7 to 3.5 MPa), and in some cases 10,000 psi (7 MPa) and higher. Both pneumatics and hydraulics are applications of fluid power.<br /><br />Physical pneumatic principles conclude that the pressure forms in compressible liquids can be harnessed to a high potential of power. This gives us new potential of several pneumatically powered operations and henceforth creates many new devices which we may use to power our world.<br /><br />Common industrial pneumatic components include:<br /><br />pneumatic direct operated solenoid valve <br />pneumatic pilot operated solenoid valve <br />pneumatic external piloted solenoid valve <br />pneumatic manual valve <br />pneumatic valve with air pilot actuator <br />pneumatic filter <br />pneumatic pressure regulator <br />pneumatic lubricator <br />pneumatic pressure switch <br />pneumatic manual OSHA-type lock out and dump valve <br />pneumatic solenoid dump valve <br />pneumatic pressure vessel <br />pneumatic rodless cylinder <br />pneumatic gripper <br />pneumatic rotary actuator <br />pneumatic fitting <br />pneumatic flow control <br />pneumatic quick exhaust valve <br />pneumatic pressure booster <br />pneumatic polyurethane tubing <br />pneumatic quick disconnectharbailhttp://www.blogger.com/profile/09907681386203833739noreply@blogger.comtag:blogger.com,1999:blog-23568479.post-1146824639395389432006-05-05T03:09:00.000-07:002006-05-18T02:53:50.413-07:00PumpA pump is a mechanical device used to move gases, liquids, or slurries. A pump moves liquids or gases from a lower pressure to a higher pressure and is responsible for this difference in pressure.<br /><img src="http://www.wrightpump.com/images/circumferential_piston.jpg"><br />The earliest pump was described by Archimedes in the 3rd century BC and is known as the Archimedes screw pump. Pumps work by using mechanical forces to push the material, either by physically lifting, or by the force of compression.<br /><br />Types<br />Pumps fall into two categories: positive displacement pumps, which force fluid from one sealed chamber to another with little leakage, and dynamic pumps, which use the momentum of the fluid to move it across an unsealed chamber<br /><br />Positive displacement pump<br />This type of pump forces the fluid from one chamber to another by reducing the volume of the first chamber while increasing the volume of the second. Such a pump produces a constant flow regardless of intake pressure or outlet pressure, unless the intake pressure drops below a certain limit, causing cavitation, or the outlet pressure exceeds the capacity of the pump, causing pump failure. These pumps often have a relief valve to prevent the latter problem. The heart of animals is a natural example of this type of pump.<br /><br /> Reciprocating positive displacement pump<br /><br />Hydraulic ram <br />Pumpjack <br />Stirrup pump <br />Inductive Pumps <br />Piston pumps <br />Diaphragm pump, sometimes also called Membrane pump <br /><br /> Rotary positive displacement pump<br /><br />Screw (or progressing cavity) pump <br />Rotary vane pumps (with flexible or rigid vanes) <br />Gear pumps (internal and external) <br />Lobe pumps <br />Mono pump with compact metal helical spiral enclosed in rubber spiral and driven by shaft sometimes running down length of borehole <br />Peristaltic pump (uses a process similar to peristalsis in animals) <br />Circumferential piston pump <br />progressive cavity pump : pumps fluid by the rotation of a helical steel rotor inside a rubber pump body with a helical aperture <br />Roots blowers <br /><br /> Dynamic pump<br /><br />The dynamic pump causes the fluid to move from inlet to outlet under its own momentum. This type tends not to need a release valve, because as the outlet pressure rises the pump simply becomes less efficient. Fluid motion can be rotary, as in centrifugal pumps, or linear, as in reciprocating dynamic pumps.<br /><br />Rotary dynamic (centrifugal) pump<br />This type of pump contains a rotating part called the impeller inside a stationary cavity. The cavity may be a volute, diffuser, or ring type. The impeller forces the fluid to rotate, and thereby to move from inlet to outlet under its own momentum. As the fluid travels through the impeller passage its absolute velocity increases. In the volute, diffuser, or ring type cavity the fluid velocity is reduced and its energy converted to pressure energy.<br /><br />Examples:<br /><br />turbopump: the fluid is moved by the blades of a high-speed turbine. <br />submersible pump : the fluid is moved by a pump joined to a sealed motor and submerged in the fluid to be pumped. <br />split case centrifugal pump : the fluid is pumped by a horizontal or vertical pump with a split volute to allow maintenance access. <br />axial flow pump : the fluid is pumped by a propeller type impeller inside a section of pipe. <br /><br />Linear or reciprocating dynamic pump<br />The Vortec Transvector is one example of a no-moving-parts dynamic air pump. A film of fast moving air formed by releasing high pressure air through a slit is discharged adjacent a surface, and drags ambient air along with it. The higher the pressure of the primary air supply, the worse the efficiency.<br /><br />It is an example of an ejector pump. Steam ejectors are used to cool bleach water so it will retain the chlorine. They simply discharge a boiler into a tube, sucking water vapor out from above a sealed tank. The water inside slowly cools. Not very efficient, but it does something useful with waste steam, simply.<br /><br />A well pump is also a dynamic pump. Since water will boil if any attempt is made to "suck" it more than about thirty feet high, high pressure water is injected in at the bottom of a well, forcing the well water to flow upwards much more than thirty feet.<br /><br />Ejectors are used to augment the flow in turbojets, near the aft end.<br /><br />The Coanda effect is the tendency of such a moving stream to cling to a surface, even when the surface deflects the stream away from its original direction. The surface seems to pull the stream. It is a manifestation of Bernoulli's principle: since energy is conserved, a moving fluid has a lower pressure than a static fluid. The ambient fluid is moving more slowly, and so has a higher pressure; it forces the moving stream toward the surface.<br /><br />The USPTO issued a patent to Henri Coanda for the design of a jet engine using high pressure fuel vapor as the primary fluid supply. The Transvector patent references Coanda's patent. Such engines can be made light in weight but are not very efficient.<br /><br /><br /><br /><br />Centrifugal Pump Components<br /><br />Pump Casing - To keep the fluid in the pump.<br /><br />Impeller - The component that drives the fluid to a higher pressure<br /><br />Shaft - The rod that connects the motor to the impeller<br /><br />Motor - The part that powers the pump<br /><br />Mechanical Seal, labyrinth seal, gasket or Packing - To keep the fluid from leaking out to the atmosphere. There are some magnetically driven centrifugal pumps that do not need such seals or packing.<br /><br />Bearing - To keep the shaft rotating freely in place.<br /><br />Outboard bearing - Bearing at motor end of shaft<br /><br />Inboard bearing - Bearing at impeller side of pump. Need 2 bearing to hold shaft in place<br /><br />Oiler - To provide oil to lubricate the bearing so it will not jam. May use grease also, if so, grease gun inject grease through nipple to provide lubrication (A nipple is a type of joint with female threads in plumbing practice, but a grease nipple is mushroom shaped male fitting mating with a grease gun head.)<br /><br />Jet Pumps<br /><br />Jet pumps (such as eductors, eductor-jet pumps or air ejectors) use convergent/divergent nozzles and a feeder stream to create a point of low pressure. At this low pressure point, a line goes to the fluid to be pumped. The fluid is drawn into the eductor by the differential pressure and then entrained in the feeder stream.<br /><br />Jet pumps are exceedingly easy to use, because they have no moving parts and simply rely on their fluid dynamics. On the other hand, their use is limited to applications where a feeder stream is already available - thus they are commonly used to remove water, rather than supply it. Also, they have to be lit off in the right order, otherwise the feeder stream enters into the area being pumped, instead of drawing from it.<br /><br /><br />One of the most common examples of the jet pump is the eductor. This pump is often used on board ships for dewatering and pumping bilges. In this application, the feeder stream is always available in the form of the firemain system that already exists for fire fighting. But it must be operated correctly, as suggested above, or else flooding could result. The simple phrase "Dumb Freaking Sailor" (or less sanitized versions thereof) is self-mockingly used as a reminder: Discharge, Firemain (motive force), Suction (bilge).<br /><br />In system such as PDX, steam is accelerated to supersonic speed, and use the resulting shockwave to create a vacuum.harbailhttp://www.blogger.com/profile/09907681386203833739noreply@blogger.comtag:blogger.com,1999:blog-23568479.post-1146823505697258962006-05-05T03:03:00.000-07:002006-05-18T02:59:29.896-07:00History of AeroplaneThe dream of flight goes back to the days of pre-history. Many stories from antiquity involve flight, such as the legend of Icarus. Leonardo da Vinci drew an aircraft in the 15th century. With the first flight made by man (Francois Pilatre de Rozier and Francois d'Arlandes) in an aircraft lighter than air, a balloon, the biggest challenge became to create other craft, capable of controlled flight.<br /><img src="http://hprm.free.fr/photosite/cartesaviation/AVIATION-AEROPLANE%20FARMAN1.JPG"><br /> <br />In 1853, Englishman George Cayley made the first manned glider flight. In 1856, Frenchman Jean-Marie Le Bris made the first powered flight, by having his glider "L'Albatros artificiel" pulled by a horse on a beach. On 28 August 1883, the American John J. Montgomery made a controlled flight in a glider. Other aviators who had made similar flights at that time were Otto Lilienthal, Percy Pilcher and Octave Chanute.<br /><br />Sir George Cayley, the inventor of the science of aerodynamics, was building and flying models of fixed-wing aircraft as early as 1803, and he built a successful passenger-carrying glider in 1853, but it is known the first practical self-powered planes were designed and constructed by Clément Ader. On October 9, 1890, Ader attempted to fly the Éole, which succeeded in taking off and flying a distance of approximately 50 meters before witnesses. In August 1892 the Avion II flew for a distance of 200 metres, and on October 14, 1897, Avion III flew a distance of more than 300 metres.<br /><br />On August 28, 1903 in Hanover, the German Karl Jatho made his first flight.<br /><br />The Wright Brothers are commonly credited with the invention of the aircraft, but like Alexander Graham Bell's telephone, theirs was rather the first sustainable and well documented attempt. They made their first successful test flights on December 17, 1903 and by 1904 Flyer III was capable of fully controllable, stable flight for substantial periods. Strictly speaking, the Flyer's wings were not completely fixed, as it depended for stability on a flexing mechanism named wing warping. This was later superseded by the development of ailerons, devices which performed a similar function but were attached to an otherwise rigid wing.<br /><br />However, in some countries, particularly Brazil, Alberto Santos-Dumont is considered to be the "Father of Aviation". Though launched after the Wright Brothers' attempts, his 14-bis was the first to take off, fly, and land without the use of catapults, high winds, or other external assistance. Most Brazilians, as well as admirers of Santos-Dumont, consider him to be the true inventor of the aircraft, although the very concept of the invention of the first flying machine has substantial ambiguity.<br /><br />Wars in Europe, in particular World War I, served as initial tests for the use of the aircraft as a weapon. First seen by generals and commanders as a "toy", the aircraft proved to be a machine of war capable of causing casualties to the enemy. In the first world war, the fighter "aces" appeared, of which the greatest was the German Manfred von Richthofen, commonly called the Red Baron. On the side of the allies, the ace with the highest number of downed aircraft was René Fonck, of France.<br /><br />After the First World War, aircraft continued to advance their technology. Charles Lindbergh became the first person to cross the Atlantic Ocean in solo flight nonstop, on 20 May 1927. The first commercial flights took place between the United States and Canada in 1919. The turbine or the jet engine was in development in the 1930's, military jet aircraft began operating in the 1940's.<br /><br />Aircraft played a primary role in the Second World War, having a presence in all the major battles of the war, especially in the attack on Pearl Harbor, the battles of the Pacific and D-Day, as well as the Battle of Britain. They were also an essential part of several of the military strategies of the period, such as the German Blitzkrieg or the American and Japanese Aircraft carriers.<br /><br />In October 1947, Chuck Yeager, in the Bell X-1, was the first person to exceed the speed of sound. The Boeing X-43 is an experimental scramjet with a world speed record for a jet-powered aircraft - Mach 9.6, or nearly 7,000 mph.<br /><br />Aircraft in a civil military role continued to feed and supply Berlin in 1948, when access to railroads and roads to the city, completely surrounded by Eastern Germany, were blocked, by order of the Soviet Union.<br /><br />The first commercial jet, the de Havilland Comet, was introduced in 1952, and the first successful commercial jet, the Boeing 707, is still in use 50 years later. Boeing 707 would develop into the later in Boeing 737. The Boeing 727 was another widely used passenger aircraft, and the Boeing 747, was the biggest commercial aircraft in the world up to 2005, when it was surpassed by the Airbus A380.harbailhttp://www.blogger.com/profile/09907681386203833739noreply@blogger.comtag:blogger.com,1999:blog-23568479.post-1146823328043478432006-05-05T03:00:00.000-07:002006-05-18T03:12:00.216-07:00History of MotorcycleThe inspiration for the earliest motorcycles, and arguably the first motorcycle, was designed and built by the German inventors Gottlieb Daimler and Wilhelm Maybach in Cannstatt (since 1905 a city district of Stuttgart) in 1885. It was the first petroleum-powered vehicle ever, but for the provision of a pair of stabilizing wheels, a motorized bicycle, although they called their invention the Reitwagen ("riding car"). They had not set out to create a vehicle form but to build a simple carriage for the engine which was the focus of their endeavours. However,if one counts two wheels with steam propulsion as being a motorcycle, then the first one may have been American. One such machine was demonstrated at fairs and circuses in the eastern US in 1867, built by one Sylvester Howard Roper of Roxbury, Massachusetts. There is an existing example of a Roper machine, dated 1869. It's powered by a charcoal-fired two-cylinder engine, whose connecting rods directly drive a crank on the rear wheel. This machine predates the invention of the safety bicycle by many years, so its chassis is also based on the "bone-crusher" bike.<br /><img src="http://www.motorcycle.com/mo/mcmuseum/mcphotos/orient.jpg"><br /><br /><br />In 1894, the Hildebrand & Wolfmüller was the first motorcycle that was available for purchase.<br /><br />In the early period of motorcycle history there were many manufacturers as producers of bicycles adapted their designs for the new internal combustion engine. As the engines became more powerful and designs outgrew the bicycle origins, the number of motorcycle producers reduced.<br /><br /> <br />Up until the First World War, the largest motorcycle manufacturer was Indian. After that, this honour went to Harley Davidson, until 1928 when DKW took over as the largest manufacturer. After the Second World War, in 1951, the BSA Group became the largest producer of motorcycles in the world. The German NSU was the largest manufacturer from 1955 until the 1970s when Honda became the most prominent manufacturer, a title it retains to this day. British manufacturers (Triumph, BSA, Norton) held a dominant position in some markets until the rise of the Japanese manufacturers (led by Honda) in the late 1960s and early 1970s who were able to produce designs faster, cheaper and of better quality. Today, the Japanese manufacturers Honda, Kawasaki, Suzuki and Yamaha dominate the motorcycle industry, although Harley-Davidson still maintains a high degree of popularity in America.<br /><br />Recent years have also seen a resurgence in the popularity of many other brands, including BMW, Triumph and Ducati.harbailhttp://www.blogger.com/profile/09907681386203833739noreply@blogger.comtag:blogger.com,1999:blog-23568479.post-1146823045607073592006-05-05T02:53:00.000-07:002006-05-18T03:14:55.996-07:00History of the bicycleHistory of the bicycle <br /><br />No single time or person can be identified with the invention of the bicycle. However, it can probably be asserted that the two most prominent inventions were the dandy horse of Baron Karl von Drais in 1818, and the addition of pedals by either Pierre Lallement or Pierre Michaux in 1863.<br /><br />The bicycle's earliest known forebears were called velocipedes, and included many types of human-powered vehicles. One of these, the scooter-like dandy horse of the French Comte de Sivrac, dating to 1790, was long cited as the earliest bicycle. Most bicycle historians now believe that these hobby-horses with no steering mechanism probably never existed, but were made up by Louis Baudry de Saunier, a 19th-century French bicycle historian.<br /><br /> <br />The most likely originator of the bicycle concept is German Karl Drais, then still a baron, who designed his 1817 machine to replace starved horses. [1] In January 1818 he patented his draisine or velocipede, a number of which still exist, including one at the Paleis het Loo museum in Apeldoorn, the Netherlands. These were pushbikes, powered by the action of the rider's feet pushing against the ground: the need to balance on two wheels met the fears of the unknowing adults of those times who didn't dare to take their feet off the ground. Also Drais had been discouraged in his earlier attempts to create a transmission mechanism, and had by this time come to feel that propulsion by walking or running was more natural. Several other cartwrights also constructed these machines, most notably Denis Johnson of London who patented a "pedestrian curricle or velocipede" in 1819 which was more elegant than the draisine, but had no brake nor front-wheel trail.<br /><img src="http://upload.wikimedia.org/wikipedia/en/thumb/7/70/Bicycle_two_1886.jpg/280px-Bicycle_two_1886.jpg"><br /><br />Scottish blacksmith Kirkpatrick MacMillan may share creative credit with von Drais for adding a treadle drive mechanism, in 1839, that enabled the rider to lift his feet off the ground while driving the rear wheel. However, some reports describe MacMillan's vehicle as more of a "quadricycle", and no documentary evidence has been furnished to prove that his vehicle had 2 wheels.<br /><br />In the 1850s and 1860s, Frenchman Ernest Michaux and his pupil Pierre Lallement took bicycle design in a different direction, placing pedals on an enlarged front wheel; according to bicycle historian David Herlihy, Lallement was the person responsible for first attaching pedals to a dandy-horse, and in his bicycle patent -- the earliest and only one for the pedal-bike -- the drawings of his machine greatly resemble Johnson's "pedestrian curricle". This creation, which came to be called the "Boneshaker", featured a heavy cast iron frame on which they mounted wooden wheels with iron tires.<br /><br />Lallement emigrated to the United States, where he recorded a patent on his bicycle in 1866 in New Haven, Connecticut. The Olivier brothers formed a partnership with Michaux in Paris to create the first bicycle manufacturing company. When cast-iron proved to be too weak, the frame was redesigned as a single diagonal piece of wrought iron. The first bicycle craze swept Europe and the USA in 1868 and 1869, but then quickly faded due to bans (Herlihy p.120) everywhere except England, which became the site of the next series of improvements to its design.<br /><br />The Boneshaker was further refined by James Starley in the 1870s. His "Ariel" model mounted the seat more squarely over the pedals, so that the rider could push more firmly, and further enlarged the front wheel to increase the potential for speed. With tires of solid rubber, his machine became known as the ordinary. British cyclists later likened the disparity in size of the two wheels to their coinage, nicknaming it the penny-farthing. The primitive bicycles of this generation were difficult to ride, and the high seat and poor weight distribution made for dangerous falls. The "ordinary" continued to increase in popularity in the UK, and became known more and more throughout Europe during the 1870s. In 1878, Albert Pope introduced his "Columbia" high-wheeler in America, and the bicycle continued to increase in popularity all over the world.<br /><br /> <br />The subsequent dwarf ordinary addressed some of the ordinary's faults, by adding gearing, reducing the front wheel diameter, and setting the seat further back with no loss of speed. Having to both pedal and steer via the front wheel remained a problem. Starley's nephew, J. K. Starley, J. H. Lawson, and Shergold solved this problem by introducing the chain and producing rear-wheel drive. These models were known as dwarf safeties, or safety bicycles, for their lower seat height and better weight distribution. Starley's 1885 "Rover" is usually described as the first recognizably modern bicycle. Soon the seat tube was added, creating the double-triangle, diamond frame of the modern bike.<br /><br />While the Starley design was much safer, the return to smaller wheels made for a bumpy ride. The next innovations increased comfort and ushered in the 1890s Golden Age of Bicycles. In 1888 Scotsman John Boyd Dunlop introduced the pneumatic tire, which soon became universal. Shortly thereafter the rear freewheel was developed, enabling the rider to coast without the pedals spinning out of control. This refinement led to the 1898 invention of coaster brakes. Derailleur gears and hand-operated, cable-pull brakes were also developed during these years, but were only slowly adopted by casual riders. By the turn of the century, bicycling clubs flourished on both sides of the Atlantic, and touring and racing were soon the rage.<br /><br /> <br />Successful early bicycle manufacturers included Englishman Frank Bowden and German builder Ignaz Schwinn. Bowden started the Raleigh company in Nottingham in the 1890s, and soon was producing some 30,000 bicycles a year. Schwinn emigrated to the United States, where he founded his similarly successful company in Chicago in 1895. Schwinn bicycles soon featured widened tires and spring-cushioned, padded seats, sacrificing some efficiency for increased comfort. Facilitated by connections between European nations and their overseas colonies, European-style bicycles were soon available worldwide. By the mid-20th century bicycles had become the primary means of transportation for millions of people around the globe.<br /><br /> <br />In many western countries the use of bicycles levelled off or declined, as motorized transportation became affordable and car-centred policies led to an increasingly hostile road environment for bicycles. In North America, bicycle sales declined markedly after 1905, to the point where by the 1940s, they had largely been relegated to the role of children's toys. In other parts of the world however, such as China, India, and European countries such as Germany, Denmark, and the Netherlands, the traditional utility bicycle remained a mainstay of transportation, its design only gradually changing to incorporate hand-operated brakes and internal hub gears allowing up to seven speeds. In the Netherlands, such so-called 'granny bikes' have remained popular, and are again in production. Especially in Amsterdam they are often colourfully painted and/or otherwise decorated.<br /><br /> North America, increasing consciousness of physical fitness and environmental preservation spawned a renaissance of bicycling in the late 1960s. Bicycle sales in the United States boomed, especially after the 1973 oil crisis, largely in the form of the racing bicycles long used in such events as the hugely popular Tour de France. Sales were also helped by a number of technical innovations that were new to the US market, including higher performance steel alloys and gearsets with an increasing number of gears. While 10-speeds were the rage in the 1970s, 12-speed designs were introduced in the 1980s, and today most bikes feature 18 or more speeds. By the 1980s these newer designs had driven the three-speed bicycle from the roads. In the late 1980s the mountain bike became particularly popular, and in the 1990s something of a major fad. These task-specific designs led many American recreational cyclists to demand a more comfortable and practical product. Manufacturers responded with the hybrid bicycle, which restored many of the features long enjoyed by riders of the time-tested European utility bikes.harbailhttp://www.blogger.com/profile/09907681386203833739noreply@blogger.comtag:blogger.com,1999:blog-23568479.post-1146822687318475192006-05-05T02:32:00.000-07:002006-05-18T03:17:40.283-07:00TurbineA turbine is a rotary engine that extracts energy from a fluid flow. Claude Burdin coined the term from the Latin turbinis, or vortex, during an 1828 engineering competition. The simplest turbines have one moving part, a rotor assembly, which is a shaft with blades attached. Moving fluid acts on the blades, or the blades react to the flow, so that they rotate and impart energy to the rotor. Early turbine examples are windmills and water wheels.<br /><br />A turbine operating in reverse is called a compressor or turbopump. It converts mechanical energy to fluid energy (flow).<br /><br />Gas, steam, and water turbines usually have a casing around the blades that focuses and controls the fluid. The casing and blades may have variable geometry that allows efficient operation for a range of fluid-flow conditions.<br /><br /> Theory of operation<br /><br />A working fluid contains potential energy (pressure head) and kinetic energy (velocity head). The fluid may be compressible or non-compressible. Several physical principles are employed by turbines to collect this energy:<br /><br />Impulse turbines change the direction of flow of a high velocity fluid jet. The resulting impulse spins the turbine and leaves the fluid flow with diminished kinetic energy. There is no pressure change of the fluid in the turbine rotor blades. Before reaching the turbine the fluid's Pressure head is changed to velocity head by accelerating the fluid with a nozzle. Pelton wheels and de Laval turbines use this process exclusively. Impulse turbines do not require a pressure casement around the runner since the fluid jet is prepared by a nozzle prior to reaching turbine. Newton's second law describes the transfer of energy for impulse turbines.<br /><br />Reaction turbines develop torque by reacting to the fluid's pressure or weight. The pressure of the fluid changes as it passes through the turbine rotor blades. A pressure casement is needed to contain the working fluid as it acts on the turbine stage(s) or the turbine must be fully immersed in the fluid flow (wind turbines). The casing contains and directs the working fluid and, for water turbines, maintains the suction imparted by the draft tube. Francis turbines and most steam turbines use this concept. For compressible working fluids, multiple turbine stages may be used to efficiently harness the expanding gas. Newton's third law describes the transfer of energy for reaction turbines.<br /><br />Turbine designs will use both these concepts to varying degrees whenever possible. Wind turbines use a foil to generate lift from the moving fluid and impart it to the rotor (this is a form of reaction), they also gain some energy from the impulse of the wind, by deflecting it at an angle. Crossflow turbines are designed as an impulse machine, with a nozzle, but in low head applications maintain some efficiency through reaction, like a traditional water wheel. Gas turbines with multiple stages have the first stage reacting to impulse of the gas flow (because it is inefficient to increase the velocity when it is almost at the speed of sound) and later stages being designed for reaction in the decreasing velocity flow. Blades in many stages being arranged to be reaction over some parts (of their length) and impulse over the rest.<br /><br />Classical turbine design methods were developed in the mid 19th century. Vector analysis related the fluid flow with turbine shape and rotation. Graphical calculation methods were used at first. Formulas for the basic dimensions of turbine parts are well documented and a highly efficient machine can be reliably designed for any fluid flow condition. Some of the calculations are empirical or 'rule of thumb' formulae, and others are based on classical mechanics. As with most engineering calculations, simplifying assumptions were made.<br /><br /> <br />Velocity triangles can be used to calculate the basic performance of a turbine stage. Gas exits the stationary turbine nozzle guide vanes at absolute velocity Va1. The rotor rotates at velocity U. Relative to the rotor, the velocity of the gas as it impinges on the rotor entrance is Vr1. The gas is turned by the rotor and exits, relative to the rotor, at velocity Vr2. However, in absolute terms the rotor exit velocity is Va2. The velocity triangles are constructed using these various velocity vectors. Velocity triangles can be constructed at any section through the blading (for example: hub , tip, midsection and so on) but are usually shown at the mean stage radius. Mean performance for the stage can be calculated from the velocity triangles, at this radius, using the Euler equation:<br /><br /><br /><br />Whence:<br /><br /><br /><br />where:<br /><br /> acceleration of gravity<br /><br /> enthalpy drop across stage<br /><br /> turbine entry total (or stagnation) temperature<br /><br /> turbine rotor peripheral velocity<br /><br /> delta whirl velocity<br /><br />The turbine pressure ratio is a function of and the turbine efficiecy.<br /><br />Modern turbine design carries the calculations further. Computational fluid dynamics dispenses with many of the simplifying assumptions used to derive classical formulas and computer software facilitates optimization. These tools have led to steady improvements in turbine design over the last forty years.<br /><br />The primary numerical classification of a turbine is its specific speed. This number describes the speed of the turbine at its maximum efficiency with respect to the power and flow rate. The specific speed is derived to be independent of turbine size. Given the fluid flow conditions and the desired shaft output speed, the specific speed can be calculated and an appropriate turbine design selected.<br /><br />The specific speed, along with some fundamental formulas can be used to reliably scale an existing design of known performance to a new size with corresponding performance.<br /><br />Off-design performance is normally displayed as a turbine map or characteristic.<br /><br /><br />Types of turbines<br />Steam turbine <br />Gas turbine engines are sometimes referred to as turbine engines. Such engines usually feature an inlet, fan, compressor, combustor and nozzle (possibly other assemblies) in addition to one or more turbines. <br />transonic turbine The gasflow in most turbines employed in gas turbine engines remains subsonic throughout the expansion process. In a transonic turbine the gasflow becomes supersonic as it exits the nozzle guide vanes, although the downstream velocities normally become subsonic. Transonic turbines operate at a higher pressure ratio than normal but are usually less efficient and uncommon. <br />contra-rotating turbines Some efficiency advantage can be obtained if a downstream turbine rotates in the opposite direction to an upstream unit. However, the complication may be contraproductive. <br />statorless turbine Multi-stage turbines have a set of static (meaning stationary) inlet guide vanes that direct the gasflow onto the rotating rotor blades. In a statorless turbine the gasflow exiting an upstream rotor impinges onto a downstream rotor without an intermediate set of stator vanes (that rearrange the pressure/velocity energy levels of the flow) being encountered. <br />ceramic turbine Most turbine blades (and vanes) are made from nickel alloy and often require intricate air-cooling passages to prevent the metal from melting. In recent years, experimental ceramic blades have been manufactured and tested in gas turbines, with a view to increasing Rotor Inlet Temperatures and/or, possibly, eliminating aircooling. Unfortunately, like china cups, ceramic blades are very brittle and cannot withstand sudden shock. Ways of overcoming this problem are being investigated. <br />shrouded turbine Many turbine rotor blades have a shroud at the top, which interlocks with that of adjacent blades, to increase damping and thereby reduce blade flutter. <br />shroudedless turbine Modern practise is, where possible, to eliminate the rotor shroud, thus reducing the centrifugal load on the blade and the cooling requirements. <br /><img src="http://www.grc.nasa.gov/WWW/K-12/airplane/Animation/turbpar/Images/rtur.gif"><br />Water turbine <br />Wind turbine These normally operate as a single stage without nozzle and interstage guide vanes. <br />Water and Wind turbines have a thermodynamic cycle that is part of weather.harbailhttp://www.blogger.com/profile/09907681386203833739noreply@blogger.comtag:blogger.com,1999:blog-23568479.post-1146821470317357422006-05-05T02:29:00.000-07:002006-05-18T02:57:59.510-07:00Machinemachine is any mechanical or organic device that transmits or modifies energy to perform or assist in the performance of tasks. It normally requires some energy source ("input") and accomplishes some sort of work.<br /><br />People have used mechanisms and machines to amplify their abilities since before written records were available. Generally these devices decrease the amount of force required to do a given amount of work, alter the direction of the force, or transform one form of motion or energy into another.<br /><img src="http://z.about.com/d/inventors/1/0/O/2/wm.gif"><br />The mechanical advantage of a simple machine is the ratio between the force it exerts on the load and the input force applied. This does not entirely describe the machine's performance, as force is required to overcome friction as well. The mechanical efficiency of a machine is the ratio of the actual mechanical advantage (AMA) to the ideal mechanical advantage (IMA). Functioning physical machines are always less than 100% efficient.<br /><br />Modern power tools, automated machine tools, and human-operated power machinery complicate the definition of "machine" greatly. Machines used to transform heat or other energy into mechanical energy are known as engines.harbailhttp://www.blogger.com/profile/09907681386203833739noreply@blogger.comtag:blogger.com,1999:blog-23568479.post-1146820710941835532006-05-05T02:15:00.000-07:002006-05-18T03:20:04.626-07:00Crank ShaftA crank is a bent portion of an axle, or shaft, or an arm keyed at right angles to the end of a shaft, by which motion is imparted to or received from it; also used to change circular into reciprocating motion, or reciprocating into circular motion. Familiar examples of a crank for manual use include the crank on a manual pencil sharpener and the crankset that drives a bicycle via the pedals.<br /><img src="http://files1.turbosquid.com/Preview/Content_on_6_19_2005_13_06_31/piston1.jpg66733402-6d75-4676-aaa0-2becba21887cLarge.jpg"><br />Cranks were formerly common on some machines in the early 20th century; for example almost all phonographs before the 1930s were powered by clockwork motors wound with cranks, and internal combustion engines of automobiles were usually started with cranks before electric starters came into general use.harbailhttp://www.blogger.com/profile/09907681386203833739noreply@blogger.comtag:blogger.com,1999:blog-23568479.post-1146820533049128622006-05-05T02:14:00.000-07:002006-05-05T04:50:50.010-07:00CamshaftThe camshaft is an apparatus used in piston engines to operate poppet valves. It consists of a cylindrical rod running the length of the cylinder bank with a number of oblong lobes or cams protruding from it, one for each valve. The cams force the valves open by pressing on the valve, or on some intermediate mechanism, as they rotate.<br /><br />The relationship between the rotation of the camshaft and the rotation of the crankshaft is of critical importance. Since the valves control the flow of fuel intake and exhaust, they must be opened and closed at the appropriate time during the stroke of the piston. For this reason, the camshaft is connected to the crankshaft either directly, via a gear mechanism, or indirectly via a belt or chain called a timing belt or timing chain. In some designs the camshaft also drives the distributor and the oil and fuel pumps. Also on early fuel injection systems, cams on the camshaft would operate the fuel injectors.<br /><br />In a two-stroke engine that uses a camshaft, each valve is opened once for each rotation of the crankshaft; in these engines, the camshaft rotates at the same rate as the crankshaft. In a four-stroke engine, the valves are opened only half as often; thus, two full rotations of the crankshaft occur for each rotation of the camshaft.<br /><br />Depending on the location of the camshaft, the cams operate the valves either directly or through a linkage of pushrods and rockers. Direct operation involves a simpler mechanism and leads to fewer failures, but requires the camshaft to be positioned at the top of the cylinders. In the past when engines were not as reliable as today this was seen as too much bother, but in modern gasoline engines the overhead cam system, where the camshaft is on top of the cylinder head, is quite common. Some engines use one camshaft each for the intake and exhaust valves; such an arrangement is known as a double or dual overhead cam (DOHC), thus, a V engine may have 4 camshafts.<br /><br />Sliding friction between the surface of the cam and the cam follower which rides upon it is considerable. In order to reduce wear at this point, the cam and follower are both surface hardened, and modern lubricant motor oils contain additives specifically to reduce sliding friction. The lobes of the camshaft are usually slightly tapered, causing the cam followers or valve lifters to rotate slightly with each depression, and helping to distribute wear on the parts. The surfaces of the cam and follower are designed to "wear in" together, and therefore when either is replaced, the other should be as well to prevent excessive rapid wear.<br /><br />In addition to mechanical friction, considerable force is required to overcome the valve springs used to close the engine's valves. This can amount to an estimated 25% of an engine's total output at idle, reducing overall efficiency. Two approaches have been tried to reclaim this "wasted" energy but have proven difficult to implement:<br /><br />Springless valves, like the desmodromic system employed today by Ducati <br />Camless valvetrains using solenoids or magnetic systems have long been investigated by BMW, and are currently being prototyped by Valeo and Ricardoharbailhttp://www.blogger.com/profile/09907681386203833739noreply@blogger.comtag:blogger.com,1999:blog-23568479.post-1146820356965568352006-05-05T02:12:00.000-07:002006-05-06T00:30:54.483-07:00Refrigerantrefrigerant is a compound used in a heat cycle that undergoes a phase change from a gas to a liquid and back. The two main uses of refrigerants are refrigerators/freezers and air conditioners. Cf. coolant.<br /><br />The ideal refrigerant has good thermodynamic properties, is noncorrosive, and safe. The desired thermodynamic properties are a boiling point somewhat below the target temperature, a high heat of vaporization, a moderate density in liquid form, and a relatively high density in gaseous form. Since boiling point and gas density are affected by pressure, refrigerants may be made more suitable for a particular application by choice of operating pressure.<br /><br />Corrosion properties are a matter of materials compatibility with the components used for the compressor, piping, evaporator, and condenser. Safety considerations include toxicity and flammability.<br /><br />Early mechanical refrigeration systems employed sulfur dioxide gas or anhydrous ammonia, with small home refrigerators primarily using the former. Being toxic, sulfur dioxide rapidly disappeared from the market with the introduction of Freon. Ammonia is still used in some large commercial plants, well away from residential areas, where a leak will not cause widespread injuries.<br /><br />Until concerns about depletion of the ozone layer arose in the 1980s, the most widely used refrigerants were the halomethanes R-12 and R-22, with R-12 being more common in automotive air conditioning and small refrigerators, and R-22 being used for residential and light commercial air conditioning, refrigerators, and freezers. Some very early systems used R-11 because its low boiling point allows low-pressure systems to be constructed, reducing the mechanical strength required for components. R-134a and certain blends are now replacing chlorinated compounds.<br /><br />Use of liquified propane gas as a refrigerant is gaining favor, especially in systems designed for R-12, R-22 or R-134a.harbailhttp://www.blogger.com/profile/09907681386203833739noreply@blogger.comtag:blogger.com,1999:blog-23568479.post-1146820171114093042006-05-05T02:07:00.000-07:002006-05-05T04:49:53.033-07:00Computer Numerical Control (CNC)The abbreviation CNC stands for Computer Numerical Control, and refers specifically to the computer control of machine tools for the purpose of (repeatedly) manufacturing complex parts in metal as well as other materials, using a program written in a notation conforming to the EIA-274-D standard and commonly called G-code. CNC was developed in the late 1940s and early 1950s by the MIT Servomechanisms Laboratory. CNC machines were relatively briefly preceded by the less advanced NC, or Numerical(ly) Control(led), machines.<br /><br /><br /> Description<br /><br />The introduction of CNC machines radically changed the manufacturing industry. Curves are as easy to cut as straight lines, complex 3-D structures are relatively easy to produce, and the number of machining steps that required human action have been dramatically reduced.<br /><br />With the increased automation of manufacturing processes with CNC machining, considerable improvements in consistency and quality have been achieved. CNC automation reduced the frequency of errors and provided CNC operators with time to perform additional tasks. CNC automation also allows for more flexibility in the way parts are held in the manufacturing process and the time required to change the machine to produce different components.<br /><br />In a production environment, a series of CNC machines may be combined into one station, commonly called a "cell", to progressively machine a part requiring several operations. CNC machines today are controlled directly from files created by CAM software packages, so that a part or assembly can go directly from design to manufacturing without the need of producing a drafted paper drawing of the manufactured component. In a sense, the CNC machines represent a special segment of industrial robot systems, as they are programmable to perform many kinds of machining operations (within their designed physical limits, like other robotic systems).<br /><br />Basic ISO CNC Code<br />| <br />M03, M04, M05 Spindle CW, Spindle CCW, Spindle Stop <br />| <br />M08, M09 Coolant/lubricant on, Coolant/lubricant off <br />M02 Program Stop <br />M30 Program end, rewind <br />M99 Subprogram end <br />M00, M01 Program stop, optional stop <br />| <br />G96, G97 Constant surface speed, Constant Spindle speed <br />G50 Maximum spindle speed <br />G18, G19 Feed mm pr revolvation, feed mm/min <br />G00, G01 rapid movement, Linear Interpolation (cutting in a straight line) <br />| <br />F Feed <br />S Spindle Speed <br />| <br />direction Coordinats X Y Z A B C <br /><br /><br /><br />Example of a simple CNC lathe program<br /><br />the stock and the part the program producesO1234 <br />G50 S2000 <br />G96 S300 M03 <br />G00 T0606 (ROUGHT TURN TOOL) <br />G18 X37. Z0. <br />G01 X-1. F0.2 <br />Z1. <br />G00 X30. <br />G01 Z-20. <br />X33. <br />X35. Z-21. <br />Z-25. <br />X37. <br />G00 X150. Z300. <br />M01 <br />T0101 (18MM DRILL) <br />G97 S1000 <br />G19 M03 <br />X0. Z5. <br />G01 Z-25. F100 <br />G00 Z5. <br />X150. Z300. <br />M05 <br />M30 <br /><br /><br /><br />Example of a simple CNC milling program<br /><br />A simple example might be a 4" x 2" rectangle. The basic code might read something like:<br /><br /> <br />the stock and the part the program producesN1X0Y0T01<br />N2X0Y2000<br />N3X4000Y2000<br />N4X4000Y0<br />N5X0Y0<br />N6M00<br /><br />Line 1 (N1) tells the machine to traverse to grid point X0Y0 and to pick tool #1 <br />Line 2 tells the machine to traverse to grid point X0Y2.000 <br />Line 3 tells the machine to travel to grid point X4.000Y2.000 <br />Line 4 tells the machine to travel to grid point X4.000Y0 <br />Line 5 returns the machine to origin <br />Line 6 stops the machine <br />Note that the program does nothing to define the tool cutting path. If the machine is a router and uses a 1/8" radius cutter, the actual part will end up 1/4" smaller than designed (1/8" per side). To compensate, a G-code command (in this case) may be used to adjust the tool path. <br />N1G44M0125<br />N2X0Y0T01<br />N3X0Y2000<br />N4X4000Y2000<br />N5X4000Y0<br />N6X0Y0<br />N7M00<br /><br />In this case, the controller sees the first line and adjusts the location of the cutter to .125 (or 1/8") to the outside of the cutting profile. Now the machine will make a part that matches the one designed. Depending on the cutting tool, the compensation can be set as needed. For example, a laser with a very fine beam might have a compensation of .005", while a waterjet with a .060 inside tip diameter may need a compensation of .030harbailhttp://www.blogger.com/profile/09907681386203833739noreply@blogger.comtag:blogger.com,1999:blog-23568479.post-1146820006903994862006-05-05T02:04:00.000-07:002006-05-05T04:48:14.913-07:00Industrial engineeringIndustrial engineering is the engineering discipline that concerns the design, development, improvement, implementation and evaluation of integrated systems of people, knowledge, equipment, energy, material and process. Industrial engineering draws upon the principles and methods of engineering analysis and synthesis, as well as mathematical, physical and social sciences together with the principles and methods of engineering analysis and design to specify, predict and evaluate the results to be obtained from such systems. Industrial engineers work to eliminate wastes of time, money, materials, energy and other resources.<br /><br />Industrial Engineering is also known as Operations management, Production Engineering, Manufacturing Engineering or Manufacturing Systems Engineering; a distinction that seems to depend on the viewpoint or motives of the user. Recruiters or Educational establishments use the names to differentiate themselves from others. In healthcare Industrial Engineers are more commonly known as Management Engineers Engineering management, or even Health Systems Engineers.<br /><br />Whereas most engineering disciplines apply skills to very specific areas, industrial engineering is applied in virtually every industry. Examples of where industrial engineering might be used include shortening lines (or queues) at a theme park, streamlining an operating room, distributing products worldwide, and manufacturing cheaper and more reliable automobiles.<br /><br />The name "industrial engineer" can be misleading. While the term originally applied to manufacturing, it has grown to encompass services and other industries as well. Similar fields include operations research, systems engineering, ergonomics and quality engineering. The unicist approach to engineering considers industry as a complex system.<br /><br />There are a number of things industrial engineers do in their work to make processes more efficient, to make products more manufacturable and consistent in their quality, and to increase productivity.<br /><br /><br /> Areas of expertise<br /><br />The expertise required by an Industrial Engineer will include some or all of the following elements. People with limited education qualifications, or limited experience may specialise in only a few.<br /><br />On demand <br />Investigate problems relating to component quality or difficulties in meeting design and method constraints. <br />Investigate problems with the performance of processes or machines. <br />Implement design changes at the appropriate times. <br />Specifically per Product (short term) <br />Analysis of the complete product design to determine the way the whole process should be split into steps, or operations, and whether to produce sub-assemblies at certain points in the whole process. This requires knowledge of the facilities available in-house or at sub-contractors. <br />Specification of the method to be used to manufacture or assemble the product(s) at each operation. This includes the machines, tooling, jigs and fixtures and safety equipment, which may have to be designed and built. Notice may need to be taken of any quality procedures and constraints, such as ISO9000. This requires knowledge of Health and Safety responsibilities and Quality policies. This may also involve the creation of programs for any automated machinery. <br />Measurement or calculation of the time required to perform the specified method, taking account of the skills of the operator. This is used to cost the operation performed, to allow balancing of assembly or machining flow lines or the assessment of the manufacturing capacity required. This technique is known as Work Study. These times are also used in Value Analysis. <br />Specification of the storage, handling and transportation methods and equipment required for components and finished product, and at any intermediate stages throughout the whole process. This should eliminate the possibility for damage and minimize the space required. <br />Specifically per Process (medium term) <br />Determine the maintenance plan for that process. <br />Assess the range of Products passing through the process, then investigate the opportunities for process improvement through a reconfiguration of the existing facilities or through the purchase of more efficient equipment. This may also include the out-sourcing of that process. This requires knowledge of design techniques and of investment analysis. <br />Review the individual Products passing through the Process to identify improvements that can be made by redesign of the Product, to reduce (or eliminate) the cost that process adds, or to standardise the components, tooling or methods used. <br />Generically (long term) <br />Analyse the flow of Products through the facilities of the factory to assess the overall efficiency, and whether the most important Products have priority for the most efficient process or machine. This means maximizing throughput for the most profitable products. This requires knowledge of statistical analysis and queuing theory, and of facilities positional layout. <br />Training of new workers in the techniques required to operate the machines or assembly processes. <br />Project Planning to achieve timely introduction of new products and processes or changes to them. <br />Generally, a good understanding of the structure and operation of the wider elements of the Company, such as sales, purchasing, planning, design and finance; including good communication skills. Modern practice also requires good skills in participation in multi-disciplinary teams.<br /> <br /> Value engineering<br /> <br />Value engineering is based on the proposition that in any complex product, 80% of the customers need 20% of the features. By focusing on product development, one can produce a superior product at a lower cost for the major part of a market. When a customer needs more features, sell them as options. This approach is valuable in complex electromechanical products such as computer printers, in which the engineering is a major product cost.<br /><br />To reduce a project's engineering and design costs, it is frequently factored into subassemblies that are designed and developed once and reused in many slightly different products. For example, a typical tape-player has a precision injection-molded tape-deck produced, assembled and tested by a small factory, and sold to numerous larger companies as a subassembly. The tooling and design expense for the tape deck is shared over many products that can look quite different. All that the other products need are the necessary mounting holes and electrical interface.<br /><br /> Quality assurance/quality control<br /><br />Quality control is a set of measures taken to ensure that defective products or services are not produced, and that the design meets performance requirements. Quality Assurance covers all activities from design, development, production, installation, servicing and documentation. This field introduced the rules “fit for purpose” and “do it right the first time”.<br /><br />It is a truism that "quality is free." Very often, it costs no more to produce a product that always works, every time it comes off the assembly line. While this requires a conscious effort during engineering, it can considerably reduce the cost of waste and rework.<br /><br />Commercial quality efforts have two foci. First, to reduce the mechanical precision needed to obtain good performance. The second is to control all manufacturing operations to ensure that every part and assembly are within a specified tolerance.<br /><br />Statistical process control in manufacturing usually proceeds by randomly sampling and testing a fraction of the output. Testing every output is generally avoided due to time or cost constraints, or because it may destroy the object being tested (such as lighting matches). The variances of critical tolerances are continuously tracked, and manufacturing processes are corrected before bad parts can be produced.<br /><br />A valuable process to perform on a whole consumer product is called the "shake and bake." Every so often, a whole product is mounted on a shake table in an environmental oven, and operated under increasing vibration, temperatures and humidity until it fails. This finds many unanticipated weaknesses in a product. Another related technique is to operate samples of products until they fail. Generally the data is used to drive engineering and manufacturing process improvements. Often quite simple changes can dramatically improve product service, such as changing to mold-resistant paint, or adding lock-washed placement to the training for new assembly personnel.<br /><br />Many organizations use statistical process control to bring the organization to Six Sigma levels of quality. In a six sigma organization, every item that creates customer value or dissatisfaction is controlled to assure that the total number of failures are beyond the sixth sigma of likelihood in a normal distribution of customers - setting a standard for failure of fewer than four parts in one million. Items controlled often include clerical tasks such as order-entry, as well as conventional manufacturing processes.<br /><br /> Produceability<br /><br />Quite frequently, manufactured products have unnecessary precision, production operations or parts. Simple redesign can eliminate these, lowering costs and increasing manufacturability, reliability and profits.<br /><br />For example, Russian liquid-fuel rocket motors are intentionally designed to permit ugly (though leak-free) welding, to eliminate grinding and finishing operations that do not help the motor function better.<br /><br />Some Japanese disc brakes have parts toleranced to three millimeters, an easy-to-meet precision. When combined with crude statistical process controls, this assures that less than one in a million parts will fail to fit.<br /><br />Many vehicle manufacturers have active programs to reduce the numbers and types of fasteners in their product, to reduce inventory, tooling and assembly costs.<br /><br />Another produceability technique is near net shape forming. Often a premium forming process can eliminate hundreds of low-precision machining or drilling steps. Precision transfer stamping can quickly produce hundreds of high quality parts from generic rolls of steel and aluminum. Die casting is used to produce metal parts from aluminum or sturdy tin alloys (they are often about as strong as mild steels). Plastic injection molding is a powerful technique, especially if the special properties of the part are supplemented with inserts of brass or steel.<br /><br />When a product incorporates a computer, it replaces many parts with software that fits into a single light-weight, low-power memory part or micro-controller. As computers grow faster, digital signal processing software is beginning to replace many analog electronic circuits for audio and sometimes radio frequency processing.<br /><br />On some printed circuit boards (itself a producibility technique), the conductors are intentionally sized to act as delay lines, resistors and inductors to reduce the parts count. An important recent innovation was to eliminate the leads of "surface mounted" components. At one stroke, this eliminated the need to drill most holes in a printed circuit board, as well as clip off the leads after soldering.<br /><br />In Japan, it is a standard process to design printed circuit boards of inexpensive phenolic resin and paper, and reduce the number of copper layers to one or two to lower costs without harming specifications.<br /><br />It is becoming increasingly common to consider producibility in the initial stages of product design, a process referred to as design for manufacturability. It is much cheaper to consider these changes during the initial stages of design rather than redesign products after their initial design is complete.<br /><br /> Motion economy<br /><br />Industrial engineers study how workers perform their jobs, such as how workers or operators pick up electronic components to be placed in a circuit board or in which order the components are placed on the board. The goal is to reduce the time it takes to perform a certain job and redistribute work so as to require fewer workers for a given task.<br /><br />Frederick Winslow Taylor and Frank and Lillian Gilbreth did much of the pioneering work in motion economy. Taylor's work sought to study and understand what caused workers in a coal mine to become fatigued, as well as ways to obtain greater productivity from the workers without additional man hours. The Gilbreths devised a system to categorize all movements into subgroups known as therbligs (Gilbreths spelled backwards). Examples of therbligs include hold, position, and search. Their contributions to industrial engineering and motion economy are documented in the children's book Cheaper by the Dozen.<br /><br />Industrial engineers frequently conduct time studies or work sampling to understand the typical role of a worker. Systems such as MOST have also been developed to understand the work content of a jobharbailhttp://www.blogger.com/profile/09907681386203833739noreply@blogger.comtag:blogger.com,1999:blog-23568479.post-1146819615028557422006-05-05T01:58:00.000-07:002006-05-05T04:46:53.206-07:00RefrigerationRefrigeration (from the Latin frigus, frost) is generally the cooling of a body by the transfer of a portion of its heat away from it. Applications include conservation, especially of food, and lowering the temperature of drinks to one that is more agreeable for consumption. Domestic refrigerators are common in kitchens, with separate sections or separate machines for cooling and freezing.<br /><br />Cooling of something hot is often done by means of material at ambient temperature, for example the fan cooling of computer equipment.<br /><br />Where temperatures below that of any available natural cooling agent are required, refrigerators are used to produce the required cooling effect by taking in heat at low temperatures and rejecting it at temperatures somewhat above that of the natural cooling agent, which is generally water or air. The function of a refrigerating machine, therefore, is to take in heat at a low temperature and reject it at a higher one, using external energy to drive the process. A refrigerator is effectively a heat pump, a heat engine running in reverse. It is also possible to use eutectic salts.<br /><br /><br /> Thermodynamics of refrigerators<br /> <br />Most home and automotive refrigerators qualify as phase change heat pumps. They convert a refrigerant from gas to liquid and back again by compression in a refrigeration cycle. In principle, any endothermic process could be used provided it is balanced by an exothermic in another physical location so that it can operate in a cycle. For example, absorption of gaseous ammonia into water is used in most gas absorption refrigerators, and the Einstein refrigerator is a version of this which contains no moving parts — the cooling effect in this case coming from the heat absorbed by the ammonia when it evaporates from the water.<br /><br />Other processes which have been used on a small scale include the Peltier effect for thermoelectric cooling. They are significantly less efficient than typical (phase change) refrigerators, but scale down well, and research continues[1].<br /><br /> History of refrigeration<br /> <br />Ice houses <br />Making of ice cream <br />Refrigeration by well water <br /> <br /><br /> Development of the first refrigerators<br /><br />Many countries can claim to be the home of the inventor of the refrigerator, as the technology was developed over a period of time all over the world using different types of technology and for different purposes. Claimants to the name of inventor include Oliver Evans (USA), Jacob Perkins (USA and England), John Gorrie (USA), Alexander Catlin Twining (USA), James Harrison (pioneer) and Thomas Mort (Australia) and Carl von Linde (Germany). One of the first uses of "home" refrigeration was at Biltmore Estate in Asheville, North Carolina, USA, installed around 1895 [2], while in commercial refrigeration the Vestey Brothers opened one of the first refrigerated cold stores in London the same year.<br /><br />The gas absorption refrigerator, which cools by the use of a source of heat, was invented in Sweden by Baltzar von Platen in 1922. [3] It was later manufactured by Electrolux and Servel. Today it is used in homes that are not connected to the electrical grid, and in recreational vehicles.<br /><br /><br /> Science and Technology<br /><br />absolute zero <br />Chlorofluorocarbons (CFCs) (Freon) <br />Cryogenics and cryocoolers <br />Heat pump <br />Heat pipe <br />Liquefied gases <br />Magnetic refrigeration <br />Thermoelectric cooling <br />Vapor-compression refrigeration <br /><br /> Commerce<br /><br />Refrigerated transport <br />Refrigerated trucks (or simply refrigerators) are used to transport perishable goods, such as, for instance, frozen foods, fruit and vegetables, and temperature-sensitive chemicals. Most modern refrigerators keep temperature -40...+20 °C and have a maximum payload of around 24 000 kg. gross weight (in Europe). Surprisingly, refrigerated trucks are most wanted in winter, when there is a significant demand to transport chemicals under relatively high (+10...+20 °C) temperature. <br />Food hygiene <br />Ready meals <br />Cook/chill <br />Ice cream vans <br />Air conditioning <br />HVACharbailhttp://www.blogger.com/profile/09907681386203833739noreply@blogger.comtag:blogger.com,1999:blog-23568479.post-1146745807755638242006-05-04T05:29:00.000-07:002006-05-18T02:29:46.996-07:00RobotA robot is a mechanical device that can perform preprogrammed physical tasks. A robot may act under the direct control of a human (eg. the robotic arm of the space shuttle) or autonomously under the control of a pre-programmed computer. Robots may be used to perform tasks that are too dangerous or difficult for humans to implement directly (e.g. the space shuttle arm) or may be used to automate repetitive tasks that can be performed more cheaply by a robot than by the employment of a human (e.g. automobile production).<br /><br />The word robot is also used to describe an intelligent mechanical device in the form of a human. This form of robot (culturally referred to as androids) is common in science fiction stories. However, such robots are yet to become common-place in reality and much development is yet required in the field of artificial intelligence before they even begin to approach the robots of science fiction.<br /><br />Finally, bots are sometimes referred to as robots, because they perform mundane, repetitive tasks.<br /><br />Definition<br /> <br />A humanoid robot manufactured by Toyota "playing" a trumpetThe word robot is used to refer to a wide range of machines, the common feature of which is that they are all capable of movement and can be used to perform physical tasks. Robots take on many different forms, ranging from humanoid, which mimic the human form and way of moving, to industrial, whose appearance is dictated by the function they are to perform. Robots can be grouped generally as mobile robots (eg. autonomous vehicles), manipulator robots (eg. industrial robots) and Self reconfigurable robots, which can conform themselves to the task at hand.<br /><br />Robots may be controlled directly by a human, such as remotely-controlled bomb-disposal robots, robotic arms, or shuttles, or may act according to their own decision making ability, provided by artificial intelligence. However, the majority of robots fall in-between these extremes, being controlled by pre-programmed computers. Such robots may include feedback loops such that they can interact with their environment, but do not display actual intelligence.<br /><br />The word robot is also used in a general sense to mean any machine which mimics the actions of a human (biomimicry), in the physical sense or in the mental sense.<br /><br />The word robot comes from the Czech word robota, industrial labor. The word has first appeared in Karel Čapek's science fiction play R.U.R. (Rossum's Universal Robots) in 1921, and has probably been invented by author's brother, painter Josef Čapek. See the article about Karel Čapek for more detailed ethymological explanation.<br /><br /><br />History<br />The idea of artificial people dates at least as far back as the ancient legend of Cadmus, who sowed dragon teeth that turned into soldiers, and the myth of Pygmalion, whose statue of Galatea came to life. In classical mythology, the deformed god of metalwork (Vulcan or Hephaestus) created mechanical servants, ranging from intelligent, golden handmaidens to more utilitarian three-legged tables that could move about under their own power. Jewish legend tells of the Golem, a clay statue animated by Kabbalistic magic. Similarly, in the Younger Edda, Norse mythology tells of a clay giant, Mökkurkálfi or Mistcalf, constructed to aid the troll Hrungnir in a duel with Thor, the God of Thunder.<br /><br />The word robot was introduced by Czech writer Karel Čapek in his play R.U.R. (Rossum's Universal Robots) which was written in 1920 (See also Robots in literature for details of the play). However, the verb robotovat, meaning "to work" or "to slave", and the noun robota (meaning corvée) used in the Czech and Slovak languages, has been used since the early 10th century. It was suggested that the word robot had been coined by Karel Čapek's brother, painter and writer Josef Čapek.<br /><br /> <br />Roboraptor, a robotic dinosaur from wowee toysConcepts akin to today's robot can be found as long ago as 450 BC when the Greek mathematician Archytas of Tarentum postulated a mechanical bird he called "The Pigeon" which was propelled by steam. Al-Jazari (1136-1206) an Ortoqid (Artuk) Turkish inventor designed and constructed automatic machines such as water clocks, kitchen appliances and musical automats powered by water.<br /><br />One of the first recorded designs of a humanoid robot was made by Leonardo da Vinci in around 1495. Da Vinci's notebooks, rediscovered in the 1950s, contain detailed drawings of a mechanical knight able to sit up, wave its arms and move its head and jaw. The design is likely to be based on his anatomical research recorded in the Vitruvian Man. It is not known whether he attempted to build the robot.<br /><br />An early automaton was created 1738 by Jacques de Vaucanson, who created a mechanical duck that was able to eat grain, flap it's wings and excrete.<br /><br />Many consider the first robot in the modern sense to be a teleoperated boat, similar to a modern ROV, devised by Nikola Tesla and demonstrated at an 1898 exhibition in Madison Square Garden. Based on his patent 613,809 for "teleautomation", Tesla hoped to develop the "wireless torpedo" into an automated weapon system for the US Navy.<br /><br />In the thirties, Westinghouse made a humanoid robot known as Elektro. It was exhibited at the 1939 and 1940 World's Fairs while the first electronic autonomous robots were created by Grey Walter at Bristol University, England in 1948.<br /><br /><br />Contemporary uses of robots<br />Main Article: Industrial Robotics <br /> <br />KUKA Industrial Robots assembling a vehicle underbodyRobots are growing in complexity and their use in industry is becoming more widespread. The main use of robots has so far been in the automation of mass production industries, where the same, definable, tasks must be performed repeatedly in exactly the same fashion. Car production is the primary example of the employment of large and complex robots for producing products. Robots are used in that process for the painting, welding and assembly of the cars. Robots are good for such tasks because the tasks can be accurately defined and must be performed the same every time, with little need for feedback to control the exact process being performed. Industrial Robots can be manufactured in a wide range of sizes and so can handle much larger tasks than a human could.<br /><br />They are also useful in environments which are unpleasant or dangerous for humans to work in, for example the cleaning of toxic waste, bomb disposal, work in space or underwater and in mining. Hundreds of bomb disposal robots such as iRobot's Packbot are being used in Iraq and Afghanistan by the U.S. military to defuse roadside bombs, or improvised explosive devices (IED's).<br /><br />Automated Guided Vehicles (AGVs) are moveable robots that are used in large facilities such as warehouses[2], hospitals [3] and container ports, for the movement of goods[4], or even for safety and security patrols. Such vehicles follow wires, markers or laser-guidance to navigate around the location and can be programmed to move between places to deliver goods or patrol a certain area. Top manufacturers include Transbotics, FMC [5], and Jervis B Webb [6].<br /><br />Domestic robots are now available that perform simple tasks such as vacuum cleaning and grass cutting. By the end of 2004 over 1,000,000 vacuum cleaner units had been sold [7]. Examples of these domestic robots are the Scooba and Roomba robots from iRobot Corporation, Friendly Robotics' Robomower, and Electrolux's Automower.<br /><br />Other domestic robots have the aim of providing companionship (social robots) or play partners (ludobots) to people. Examples are Sony's Aibo, a commercially successful robot pet dog, Paro, a robot baby seal intended to soothe nursing home patients, and Wakamaru, a humanoid robot intended for elderly and disabled people. Other humanoid robots are in development with the aim of being able to provide robotic functions in a form that may be more aesthetically pleasing to customers, thereby increasing the likelihood of them being accepted in society[8].<br /><br />Robots are performing in large arts festivals and at museums with works by artists such as James Seawrights House Plants, 1983 in which an artificial flower opens in response to viewer interaction or Ken Rinaldo's Autotelematic Spider Bots, 2006 [9] where robots that appear like spiders, see like bats and act like ants interact with the public and structure eachothers behaviors through bluetooth communication.<br /><br />For education in schools and high schools and mechatronics training in companies robot kits are becoming more and more popular. On the schools side there exists kits from LEGO or Fischertechnik made of plastics components, on the more professional side there exists e.g. the qfix robot kit made of aluminium parts.<br /><br /><br />Current developments<br />The development of a robot with a natural human or animal gait is incredibly difficult and requires a large amount of computational power [10]. Now that background technologies of behavior, navigation and path planning have been solved using basic wheeled robots, roboticists are moving on to develop walking robots (eg. SIGMO, QRIO, Asimo & Hubo). One approach to walk control is Passive dynamics, where the robot's geometry is such that it will almost walk without active control.<br /><br />Initial work has focused on multi-legged robots (eg. Aibo), such as hexapods [11], as they are statically stable and so are easier to work with, whereas a bipedal robot must be able to balance. The balancing problem is taken to an extreme by the Robotic unicycle. A problem with the development of robots with natural gaits is that human and animal bodies utilize a very large number of muscles in movement and replicating all of those mechanically is very difficult and expensive. This field of robot research has become known as Biomorphic robotics.<br /><br />Progress is being made in the field of feedback and tactile sensors which allow a robot to sense their actions and adjust their behavior accordingly. This is vital to enable robots to perform complex physical tasks that require some active control in response to the situation.<br /><br /> <br />Robotic manipulators can be very precise, but only when a task can be fully described.Medical robotics is a growing field and recently regulatory approval has been granted for the use of robots in minimally invasive procedures. Robots are being considered for use in performing highly delicate, accurate surgery, or to allow a surgeon who is located remotely from their patient to perform a procedure using a robot controlled remotely.<br /><br />Experimental winged robots and other examples exploiting biomimicry are also in early development. So-called "nanomotors" and "smart wires" are expected to drastically simplify motive power, while in-flight stabilization seems likely to be improved by extremely small gyroscopes. A significant driver of this work is military research into spy technologies.<br /><br /><br />Future prospects<br />Some scientists believe that robots will be able to approximate human-like intelligence in the first half of the 21st century. The cybernetics pioneer Norbert Wiener discussed the issue of robots replacing humans in fields of work in his book The human use of human beings (1950), in which he speculated that robots taking over human jobs may initially lead to growing unemployment and social turmoil, but that in the medium-term it might bring increased material wealth to people in most nations. Human perception and acceptance of robots has been considered and has led to the proposition of the Uncanny Valley in analyzing human feelings about robots.<br /><br />Robotics will probably continue its spread in offices and homes, replacing "dumb" appliances with smart robotic equivalents. Domestic robots capable of performing many household tasks, described in science fiction stories and coveted by the public in the 1960s, are likely to be perfected.<br /><br />There is likely to be some degree of convergence between humans and robots. Some humans are already cyborgs with some body parts and even parts of the nervous system replaced by artificial analogues, such as Pacemakers. In many cases the same technology might be used both in robotics and in medicine.<br /><br /><br />Dangers and Fears<br />Although robots have yet to develop to the stage where they pose any threat or danger to society [12], fears and concerns about robots have been repeatedly expressed in a wide range of books and films. The principal theme is the robots' intelligence and ability to act could exceed that of humans, that they could develop a conscience and a motivation to take over or destroy the human race.<br /><br />Frankenstein (1818), sometimes called the first science fiction novel, has become synonymous with the theme of a robot or monster advancing beyond its creator. Probably the best known author to work in this area is Isaac Asimov who has placed robots and their interaction with society at the center of many of his works. Of particular interest are Asimov's Three Laws of Robotics.<br /><br />Currently, malicious programming or unsafe use of robots may be the biggest danger. Although industrial robots may be smaller and less powerful than other industrial machines, they are just as capable of inflicting severe injury on humans. However, since a robot can be programmed to move in different trajectories depending on its task, its movement can be unpredictable for a person standing in its reach. Therefore, most industrial robots operate inside a security fence which separates them from human workers. Manuel De Landa has theorized that humans are at a critical and significant juncture where humans have allowed robots, "smart missiles", and autonomous bombs equiped with artificial perception to make decisions about killing us. He believes this represents an important and dangerous trend where humans are transferring more of our cognitive structures into our machines[citation needed].<br /><br />Even without malicious programming, a robot, especially a future model moving freely in a human environment, is potentially dangerous because of its large moving masses, powerful actuators and unpredictably complex behavior. A robot falling on someone or just stepping on his foot by mistake could cause much more damage to the victim than a human being of the same size. Designing and programming robots to be intrinsically safe and to exhibit safe behavior in a human environment is one of the great challenges in robotics.<br /><br /><br />Robots in literature<br />Main article at Robots in literature; see also List of fictional robots and androids <br />Robots have frequently appeared as characters in works of literature and the first use of the word "robot" in literature can be found in Karel Capek's play R.U.R. (Rossum's Universal Robots), written in 1920. Isaac Asimov has written many volumes of science fiction focusing on robots in numerous forms and guises [13]. Asimov contributed greatly to reducing the Frankenstein complex, which dominated early works of fiction involving robots. His three laws of robotics have become particularly well known for codifying a simple set of behaviors for robots to remain at the service of their human creators.<br /><br />Numerous words for different types of robots are now used in literature. Robot has come to mean mechanical humans, while android is used for organic artificial humans and cyborg or "bionic man" for a human form that is a mixture of organic and mechanical parts. Organic artificial humans have also been referred to as "constructs" (or "biological constructs"). [citation needed]<br /><br /><br />Robotics<br />According to the Wiktionary, robotics is the science and technology of robots, their design, manufacture, and application. Robotics requires a working knowledge of electronics, mechanics, and software and a person working in the field has become known as a roboticist. The word robotics was first used in print by Isaac Asimov, in his science fiction short story "Liar!" (1941).<br /><br />Although the appearance and capabilities of robots vary vastly, all robots share the features of a mechanical, movable structure under some form of control. The structure of a robot is usually mostly mechanical and can be called kinematic chain (its functionality being akin to the skeleton of a body). The chain is formed of links (its bones), actuators (its muscles) and joints which can allow one or more degrees of freedom. Most contemporary robots use open serial chains in which each link connects the one before to the one after it. These robots are called serial robots and often resemble the human arm. Some robots, such as the Stewart platform, use closed parallel kinematic chains. Other structures, such as those that mimic the mechanical structure of humans, various animals and insects, are comparatively rare. However, the development and use of such structures in robots is an active area of research (e.g. biomechanics). Robots used as manipulators have an end effector mounted on the last link. This end effector can be anything from a welding device to a mechanical hand used to manipulate the environment.<br /><br />The mechanical structure of a robot must be controlled to perform tasks. The control of a robot involves three distinct phases - perception, processing and action (robotic paradigms). Sensors give information about the environment or the robot itself (e.g. the position of its joints or its end effector). Using strategies from the field of control theory, this information is processed to calculate the appropriate signals to the actuators (motors) which move the mechanical structure. The control of a robot involves various aspects such as path planning, pattern recognition, obstacle avoidance, etc. More complex and adaptable control strategies can be referred to as artificial intelligence.<br /><br />Any task involves the motion of the robot. The study of motion can be divided into kinematics and dynamics. Direct kinematics refers to the calculation of end effector position, orientation, velocity and acceleration when the corresponding joint values are known. Inverse kinematics refers to the opposite case in which required joint values are calculated for given end effector values, as done in path planning. Some special aspects of kinematics include handling of redundancy (different possibilities of performing the same movement), collision avoidance and singularity avoidance. Once all relevant positions, velocities and accelerations have been calculated using kinematics, methods from the field of dynamics are used to study the effect of forces upon these movements. Direct dynamics refers to the calculation of accelerations in the robot once the applied forces are known. Direct dynamics is used in computer simulations of the robot. Inverse dynamics refers to the calculation of the actuator forces necessary to create a prescribed end effector acceleration. This information can be used to improve the control algorithms of a robot.<br /><br />In each area mentioned above, researchers strive to develop new concepts and strategies, improve existing ones and improve the interaction between these areas. To do this, criteria for "optimal" performance and ways to optimize design, structure and control of robots must be developed and implemented.harbailhttp://www.blogger.com/profile/09907681386203833739noreply@blogger.comtag:blogger.com,1999:blog-23568479.post-1146745672693706722006-05-04T05:26:00.000-07:002006-05-05T04:46:20.846-07:00Heat TreatmentHeat Treatment is a group of manufacturing techniques used to alter the hardness and toughness of a material. The most common application is metallurgical. Heat treatments are also used in the manufacture of many other materials, such as glass.<br /><br />The techniques include annealing, case hardening, induction hardening, precipitation strengthening, tempering and quenching.<br /><br /> Heat treatment of swords and knives<br /><br />Usually a heat hardened item (of iron or its alloys) is too brittle for use until further treated with heat. Depending on the alloy used, it will be evenly heated to 200 to 500 degrees Fahrenheit (90 to 260 °C), held at that temperature (soaked) for an appropriate time (seconds or hours), then cooled slowly over an appropriate duration (minutes or hours). Each cycle of heating and cooling forms crystals within the metal.<br /><br />The exact heats and times the alloy endures generates specific proportions of certain types of metal crystals. Each type of crystal has a different size and character. Some give hardness, some toughness and flexibility.<br /><br />Contemporary research finds that all sorts of materials are toughened by cryogenic cooling (commonly soaking in liquid nitrogen) for hours or days. This includes forged metals. Crystal forms in the metals continue to modify when cooled to far below room temperature. Some knife and sword makers already incorporate this new addition to heat treatment options.<br /><br />Sometimes the entire item is given the same heat treatment, sometimes different areas of the item are heated and cooled at different rates. This is called differential hardening. It is common in high quality knives and swords. The Japanese katana is the best known for this. However, Chinese swords were traditionally done this way, as were Nepalese Khukuri, and many others.harbailhttp://www.blogger.com/profile/09907681386203833739noreply@blogger.com