1.
Screw thread
–
A screw thread, often shortened to thread, is a helical structure used to convert between rotational and linear movement or force. A screw thread is a ridge wrapped around a cylinder or cone in the form of a helix, with the former being called a straight thread, a screw thread is the essential feature of the screw as a simple machine and also as a fastener. The mechanical advantage of a screw depends on its lead. This characteristic is essential to the vast majority of its uses, the tightening of a fasteners screw thread is comparable to driving a wedge into a gap until it sticks fast through friction and slight elastic deformation. Screw threads have several applications, Fastening, Fasteners such as screws, machine screws, nuts. Connecting threaded pipes and hoses to each other and to caps, gear reduction via worm drives Moving objects linearly by converting rotary motion to linear motion, as in the leadscrew of a jack. Measuring by correlating linear motion to rotary motion, as in a micrometer, both moving objects linearly and simultaneously measuring the movement, combining the two aforementioned functions, as in a leadscrew of a lathe. In all of these applications, the thread has two main functions, It converts rotary motion into linear motion. It prevents linear motion without the corresponding rotation, every matched pair of threads, external and internal, can be described as male and female. For example, a screw has male threads, while its matching hole has female threads, the helix of a thread can twist in two possible directions, which is known as handedness. This is known as a thread, because it follows the right hand grip rule. Threads oriented in the direction are known as left-handed. By common convention, right-handedness is the default handedness for screw threads, therefore, most threaded parts and fasteners have right-handed threads. Left-handed thread applications include, Where the rotation of a shaft would cause a conventional right-handed nut to loosen rather than to tighten due to fretting induced precession, examples include, The left hand pedal on a bicycle. The left-hand grinding wheel on a bench grinder, the lug nuts on the left side of some automobiles. The securing nut on some circular saw blades - the large torque at startup should tend to tighten the nut. The spindle on brushcutter and line trimmer heads, so that the torque tends to tighten rather than loosen the connection In combination with right-hand threads in turnbuckles, in such a case, the coupling will have one right-handed and one left-handed thread. In some instances, for example early ballpoint pens, to provide a method of disassembly
2.
Stepper motor
–
A stepper motor or step motor or stepping motor is a brushless DC electric motor that divides a full rotation into a number of equal steps. Switched reluctance motors are very large stepping motors with a reduced pole count, DC brushed motors rotate continuously when DC voltage is applied to their terminals. The stepper motor is known by its property to convert a train of pulses into a precisely defined increment in the shaft position. Each pulse moves the shaft through a fixed angle, stepper motors effectively have multiple toothed electromagnets arranged around a central gear-shaped piece of iron. The electromagnets are energized by a driver circuit or a micro controller. To make the motor shaft turn, first, one electromagnet is given power, when the gears teeth are aligned to the first electromagnet, they are slightly offset from the next electromagnet. This means that when the electromagnet is turned on and the first is turned off. From there the process is repeated, each of those rotations is called a step, with an integer number of steps making a full rotation. In that way, the motor can be turned by a precise angle, there are two basic winding arrangements for the electromagnetic coils in a two phase stepper motor, bipolar and unipolar. An unipolar stepper motor has one winding with center tap per phase, each section of windings is switched on for each direction of magnetic field. Since in this arrangement a magnetic pole can be reversed without switching the direction of current, typically, given a phase, the center tap of each winding is made common, giving three leads per phase and six leads for a typical two phase motor. Often, these two phase commons are internally joined, so the motor has only five leads, a quick way to determine if the stepper motor is working is to short circuit every two pairs and try turning the shaft. Whenever a higher than normal resistance is felt, it indicates that the circuit to the winding is closed. Bipolar motors have a single winding per phase, the current in a winding needs to be reversed in order to reverse a magnetic pole, so the driving circuit must be more complicated, typically with an H-bridge arrangement. There are two leads per phase, none are common, static friction effects using an H-bridge have been observed with certain drive topologies. Dithering the stepper signal at a higher frequency than the motor can respond to will reduce this static friction effect, because windings are better utilized, they are more powerful than a unipolar motor of the same weight. This is due to the space occupied by the windings. A unipolar motor has twice the amount of wire in the same space, though a bipolar stepper motor is more complicated to drive, the abundance of driver chips means this is much less difficult to achieve
3.
Screw (simple machine)
–
A screw is a mechanism that converts rotational motion to linear motion, and a torque to a linear force. It is one of the six simple machines. The most common form consists of a shaft with helical grooves or ridges called threads around the outside. The screw passes through a hole in another object or medium, when the shaft of the screw is rotated relative to the stationary threads, the screw moves along its axis relative to the medium surrounding it, for example rotating a wood screw forces it into wood. In screw mechanisms, either the shaft can rotate through a threaded hole in a stationary object. Geometrically, a screw can be viewed as an inclined plane wrapped around a cylinder. Like the other simple machines a screw can amplify force, a rotational force on the shaft can exert a large axial force on a load. The smaller the pitch, the distance between the threads, the greater the mechanical advantage, the ratio of output to input force. Screws are widely used in threaded fasteners to hold objects together, other mechanisms that use the same principle, also called screws, dont necessarily have a shaft or threads. For example, a corkscrew is a rod with a sharp point. The common principle of all screws is that a rotating helix can cause linear motion, the screw was one of the last of the simple machines to be invented. It first appeared in ancient Greece, and by the first century BC was used in the form of the press and the Archimedes screw. Greek philosopher Archytas of Tarrentum was said by the Greeks to have invented the screw, the Greek philosopher Archimedes is credited with inventing the Archimedes screw water pump around 234 BC, although there is evidence it may have come from Egypt. Archimedes was first to study the screw as a machine, so he is considered the inventor of the screw. Greek philosophers defined the screw as one of the simple machines, because they had to be laboriously cut by hand, screws were only used as linkages in a few machines in the ancient world. Screw fasteners only began to be used in the 15th century in clocks, the screw was also apparently applied to drilling and moving materials around this time, when images of augers and drills began to appear in European paintings. The complete dynamic theory of machines, including the screw, was worked out by Italian scientist Galileo Galilei in 1600 in Le Meccaniche. The fineness or coarseness of a screws threads are defined by two related quantities, The lead is defined as the axial distance the screw travels in one complete revolution of the shaft
4.
Linkage (mechanical)
–
A mechanical linkage is an assembly of bodies connected to manage forces and movement. The movement of a body, or link, is studied using geometry so the link is considered to be rigid, the connections between links are modeled as providing ideal movement, pure rotation or sliding for example, and are called joints. A linkage modeled as a network of links and ideal joints is called a kinematic chain. Linkages may be constructed from open chains, closed chains, or a combination of open, each link in a chain is connected by a joint to one or more other links. Thus, a chain can be modeled as a graph in which the links are paths and the joints are vertices. The movement of a joint is generally associated with a subgroup of the group of Euclidean displacements. The number of parameters in the subgroup is called the degrees of freedom of the joint, mechanical linkages are usually designed to transform a given input force and movement into a desired output force and movement. The ratio of the force to the input force is known as the mechanical advantage of the linkage. The speed ratio and mechanical advantage are defined so they yield the number in an ideal linkage. A kinematic chain, in which one link is fixed or stationary, is called a mechanism, perhaps the simplest linkage is the lever, which is a link that pivots around a fulcrum attached to ground, or a fixed point. As a force rotates the lever, points far from the fulcrum have a greater velocity than points near the fulcrum. Because power into the lever equals the power out, a force applied at a point far from the fulcrum equals a larger force applied at a point near the fulcrum. The amount the force is amplified is called mechanical advantage and this is the law of the lever. Two levers connected by a rod so that a force applied to one is transmitted to the second is known as a four-bar linkage, the levers are called cranks, and the fulcrums are called pivots. The connecting rod is also called the coupler, the fourth bar in this assembly is the ground, or frame, on which the cranks are mounted. Linkages are important components of machines and tools, examples range from the four-bar linkage used to amplify force in a bolt cutter or to provide independent suspension in an automobile, to complex linkage systems in robotic arms and walking machines. The internal combustion engine uses a slider-crank four-bar linkage formed from its piston, connecting rod, relatively simple linkages are often used to perform complicated tasks. Interesting examples of linkages include the windshield wiper, the bicycle suspension, in these examples the components in the linkage move in parallel planes and are called planar linkages
5.
Circular motion
–
In physics, circular motion is a movement of an object along the circumference of a circle or rotation along a circular path. It can be uniform, with constant angular rate of rotation and constant speed, the rotation around a fixed axis of a three-dimensional body involves circular motion of its parts. The equations of motion describe the movement of the center of mass of a body, since the objects velocity vector is constantly changing direction, the moving object is undergoing acceleration by a centripetal force in the direction of the center of rotation. Without this acceleration, the object would move in a straight line, in physics, uniform circular motion describes the motion of a body traversing a circular path at constant speed. Since the body describes circular motion, its distance from the axis of rotation remains constant at all times, though the bodys speed is constant, its velocity is not constant, velocity, a vector quantity, depends on both the bodys speed and its direction of travel. This changing velocity indicates the presence of an acceleration, this acceleration is of constant magnitude. This acceleration is, in turn, produced by a force which is also constant in magnitude. For motion in a circle of radius r, the circumference of the circle is C = 2π r, the axis of rotation is shown as a vector ω perpendicular to the plane of the orbit and with a magnitude ω = dθ / dt. The direction of ω is chosen using the right-hand rule, likewise, the acceleration is given by a = ω × v = ω ×, which is a vector perpendicular to both ω and v of magnitude ω |v| = ω2 r and directed exactly opposite to r. In the simplest case the speed, mass and radius are constant, consider a body of one kilogram, moving in a circle of radius one metre, with an angular velocity of one radian per second. The speed is one metre per second, the inward acceleration is one metre per square second, v2/r. It is subject to a force of one kilogram metre per square second. The momentum of the body is one kg·m·s−1, the moment of inertia is one kg·m2. The angular momentum is one kg·m2·s−1, the kinetic energy is 1/2 joule. The circumference of the orbit is 2π metres, the period of the motion is 2π seconds per turn. It is convenient to introduce the unit vector orthogonal to u ^ R as well and it is customary to orient u ^ θ to point in the direction of travel along the orbit. The velocity is the derivative of the displacement, v → = d d t r → = d R d t u ^ R + R d u ^ R d t. Because the radius of the circle is constant, the component of the velocity is zero
6.
Linear actuator
–
A linear actuator is an actuator that creates motion in a straight line, in contrast to the circular motion of a conventional electric motor. Hydraulic or pneumatic cylinders inherently produce linear motion, many other mechanisms are used to generate linear motion from a rotating motor. Mechanical linear actuators typically operate by conversion of rotary motion into linear motion, by rotating the actuators nut, the screw shaft moves in a line. Wheel and axle, Hoist, winch, rack and pinion, chain drive, belt drive, rigid chain and rigid belt actuators operate on the principle of the wheel, a rotating wheel moves a cable, rack, chain or belt to produce linear motion. Cam, Cam actuators function on a similar to that of the wedge. As a wheel-like cam rotates, its eccentric shape provides thrust at the base of a shaft, some mechanical linear actuators only pull, such as hoists, chain drive and belt drives. Pneumatic and hydraulic cylinders, or lead screws can be designed to force in both directions. Mechanical actuators typically convert rotary motion of a knob or handle into linear displacement via screws and/or gears to which the knob or handle is attached. A jackscrew or car jack is a mechanical actuator. Another family of actuators are based on the segmented spindle, rotation of the jack handle is converted mechanically into the linear motion of the jack head. For accurate and repeatable positioning, index marks may be used on control knobs, some actuators include an encoder and digital position readout. These are similar to the adjustment knobs used on micrometers except their purpose is position adjustment rather than position measurement, hydraulic actuators or hydraulic cylinders typically involve a hollow cylinder having a piston inserted in it. An unbalanced pressure applied to the piston generates force that can move an external object, since liquids are nearly incompressible, a hydraulic cylinder can provide controlled precise linear displacement of the piston. The displacement is only along the axis of the piston, a familiar example of a manually operated hydraulic actuator is a hydraulic car jack. Typically though, the hydraulic actuator refers to a device controlled by a hydraulic pump. Pneumatic actuators, or pneumatic cylinders, are similar to hydraulic actuators except they use compressed gas to generate force instead of a liquid and they work similarly to a piston in which air is pumped inside a chamber and pushed out of the other side of the chamber. Air actuators are not necessarily used for heavy duty machinery and instances where large amounts of weight are present, one of the reasons pneumatic linear actuators are preferred to other types is the fact that the power source is simply an air compressor. Because air is the source, pneumatic actuators are able to be used in many places of mechanical activity
7.
Machine tool
–
A machine tool is a machine for shaping or machining metal or other rigid materials, usually by cutting, boring, grinding, shearing, or other forms of deformation. Machine tools employ some sort of tool that does the cutting or shaping, all machine tools have some means of constraining the workpiece and provide a guided movement of the parts of the machine. Thus the relative movement between the workpiece and the tool is controlled or constrained by the machine to at least some extent. The precise definition of the machine tool varies among users. While all machine tools are machines that help people to make things, today machine tools are typically powered other than by human muscle, used to make manufactured parts in various ways that include cutting or certain other kinds of deformation. With their inherent precision, machine tools enabled the production of interchangeable parts. In this view of the definition, the term, arising at a time when all tools up till then had been hand tools and this lathe produced screw threads out of wood and employed a true compound slide rest. The mechanical toolpath guidance grew out of various concepts, First is the spindle concept itself. The machine slide, which has many forms, such as dovetail ways, box ways, Machine slides constrain tool or workpiece movement linearly. If a stop is added, the length of the line can also be accurately controlled, tracing, which involves following the contours of a model or template and transferring the resulting motion to the toolpath. Cam operation, which is related in principle to tracing but can be a step or two removed from the traced elements matching the reproduced elements final shape. For example, several cams, no one of which matches the desired output shape. Abstractly programmable toolpath guidance began with mechanical solutions, such as in musical box cams, later, electromechanical solutions and soon electronic solutions were added, leading to numerical control and computer numerical control. The value that machine tools added to these human talents is in the areas of rigidity, accuracy and precision, efficiency, as an example, it is physically possible to make interchangeable screws, bolts, and nuts entirely with freehand toolpaths. But it is practical to make them only with machine tools. In the 1930s, the U. S. National Bureau of Economic Research referenced the definition of a tool as any machine operating by other than hand power which employs a tool to work on metal. The narrowest colloquial sense of the reserves it only for machines that perform metal cutting—in other words. These processes are a type of deformation that produces swarf, thus presses are usually included in the economic definition of machine tools
8.
Vise
–
A vise or vice is a mechanical apparatus used to secure an object to allow work to be performed on it. Vises have two jaws, one fixed and the other movable, threaded in and out by a screw. Woodworking vises are attached to a workbench, typically flush with its work surface and their jaws are made of wood or metal, the latter usually faced with wood, called cheeks, to avoid marring the work. The movable jaw may include a dog to hold work against a bench dog. Quick-release vises employ a split nut that allows the screw to engage or disengage with a half-turn of the handle, when disengaged the movable jaw may be moved in or out throughout its entire range of motion, vastly speeding up the process of adjustment. Common thread types are Acme and buttress, traditional workbench vises are commonly either face vises, attached to the front of the workbench, near the left end or end vises, attached to or forming part of the right end of the bench. An engineers vise, also known as a metalworking vise or machinists vise, is used to clamp metal instead of wood and it is used to hold metal when filing or cutting. It is sometimes made of cast steel or malleable cast iron, however, most heavy duty vises are 55,000 psi cast steel or 65,000 psi ductile iron. Some vises have a cast iron body but a steel channel bar, cast iron is popular because it is typically 30 ksi grey iron which is rigid, strong and inexpensive. The jaws are separate and replaceable, usually engraved with serrated or diamond teeth. Soft jaw covers made of aluminum, copper, wood or plastic may be used to protect delicate work, the jaw opening of an engineers vise is almost always the same size as the jaw width, if not bigger. An engineers vise is bolted onto the top surface of a workbench, the vise may include other features such as a small anvil on the back of its body. Most engineers vises have a swivel base, some engineers vises marketed as Homeowner Grade are not made of steel or cast iron, but of pot metal or a very low grade of iron, typically with a tensile strength of under 10 ksi. Most homeowners bench vises have an exposed screw, machine vises are mounted on drill presses, grinding machines and milling machines. Abrasive chop saws have a type of machine vise built into the saw. Some hobbyists use a machine vise as a bench vise because of the low cost, a vacuum vise is a hobbyists tool, commonly used to hold circuit boards, model airplanes and other small work. They are mounted with a cup and often have an articulated joint in the middle to allow the vise to pivot. Jewelers also use vacuum vises to hold jewelry, pipe vises are a plumbers tool, often used to hold pipes in place for threading and cutting
9.
Mechanical press
–
A forming press, commonly shortened to press, is a machine tool that changes the shape of a workpiece by the application of pressure. Good for general-purpose work in the mechanic shop, machine shop, garage or basement shops. Typically 1 to 30 tons of pressure, depending on size, classed with engine hoists and engine stands in many tool catalogs. A press brake is a type of machine press that bends sheet metal into shape. A good example of the type of work a press brake can do is the backplate of a computer case, other examples include brackets, frame pieces and electronic enclosures. Some press brakes have CNC controls and can form parts with accuracy to a fraction of a millimetre, bending forces can range up to 3,000 tons. A punch press is used to form holes, a screw press is also known as a fly press. A stamping press is a press used to shape or cut metal by deforming it with a die. It generally consists of a frame, a bolster plate. Capping presses form caps from rolls of foil at up to 660 per minute. A servomechanism press, also known as a press or a electro press, is a press driven by an AC servo motor. The torque produced is converted to a linear force via a ball screw, pressure and position are controlled through a load cell and an encoder. The main advantage of a press is its low energy consumption. When stamping, its really about maximizing energy as opposed to how the machine can deliver tonnage, up until recently, the way to increase tonnage between the die and workpiece on a mechanical press was through bigger machines with bigger motors. The press style used is in correlation to the end product. Press types are straightside, BG, geared, gap, OBI, hydraulic and mechanical presses are classified by the frame the moving elements are mounted on. The most common are the gap-frame, also known as C-frame, a straightside press has vertical columns on either side of the machine and eliminates angular deflection. A C-frame allows easy access to the die area on three sides and require less floor space, a type of gap-frame, the OBI pivots the frame for easier scrap or part discharge
10.
Jack (device)
–
A jack, screwjack or jackscrew is a mechanical device used as a lifting device to lift heavy loads or to apply great forces. A mechanical jack employs a screw thread for lifting heavy equipment, a hydraulic jack uses hydraulic power. The most common form is a car jack, floor jack or garage jack, jacks are usually rated for a maximum lifting capacity. Industrial jacks can be rated for many tons of load, the personal name Jack, which came into English usage around the thirteenth century as a nickname form of John, came in the sixteenth century to be used as a colloquial word for a man. From here, the word was applied to things which in some way take the place of a lad or man, scissor car jacks usually use mechanical advantage to allow a human to lift a vehicle by manual force alone. The jack shown at the right is made for a modern vehicle, earlier versions have a platform to lift on a vehicles frame or axle. Electrically operated car scissor jacks are powered by 12 volt electricity supplied directly from the cigarette lighter receptacle. The electrical energy is used to power these car jacks to raise, electric jacks require less effort from the motorist for operation. A house jack, also called a jack, is a mechanical device primarily used to lift buildings from their foundations for repairs or relocation. A series of jacks is used and then wood cribbing temporarily supports the structure and this process is repeated until the desired height is reached. The house jack can be used for jacking carrying beams that have settled or for installing new structural beams, on the top of the jack is a cast iron circular pad that the jacking post rests on. This pad moves independently of the jack so that it does not turn as the acme-threaded rod is turned with a metal rod. This piece tilts very slightly, but not enough to render the post dangerously out of plumb. In 1851, inventor Richard Dudgeon was granted a patent for a hydraulic press - the hydraulic jack. Hydraulic jacks are used for shop work, rather than as an emergency jack to be carried with the vehicle. Use of jacks not designed for a vehicle requires more than the usual care in selecting ground conditions, the jacking point on a vehicle. Hydraulic jacks are used to lift elevators in low and medium rise buildings. A hydraulic jack uses a liquid, which is incompressible, that is forced into a cylinder by a pump plunger, oil is used since it is self lubricating and stable
11.
Threading (manufacturing)
–
Threading is the process of creating a screw thread. More screw threads are produced each year than any other machine element, there are many methods of generating threads, including subtractive methods, deformative or transformative methods, additive methods, or combinations thereof. There are various methods for generating screw threads, in general, certain thread-generating processes tend to fall along certain portions of the spectrum from toolroom-made parts to mass-produced parts, although there can be considerable overlap. Threads of metal fasteners are usually created on a rolling machine. They may also be cut with a lathe, tap or die, rolled threads are stronger than cut threads, with increases of 10% to 20% in tensile strength and possibly more in fatigue resistance and wear resistance. A common method of threading is cutting with taps and dies, unlike drill bits, hand taps do not automatically remove the chips they create. A hand tap cannot cut its threads in a single rotation because it creates long chips which quickly jam the tap and it may be necessary to periodically remove the tap from the hole to clear the chips, especially when a blind hole is threaded. For continuous tapping operations specialized spiral point or gun taps are used to eject the chips, single-point threading, also colloquially called single-pointing, is an operation that uses a single-point tool to produce a thread form on a cylinder or cone. The tool moves linearly while the rotation of the workpiece determines the lead of the thread. The process can be done to create external or internal threads, in external thread cutting, the piece can either be held in a chuck or mounted between two centers. With internal thread cutting, the piece is held in a chuck, the tool moves across the piece linearly, taking chips off the workpiece with each pass. Usually 5 to 7 light cuts create the depth of the thread. Today engine lathes and CNC lathes are the used machines for single-point threading. On CNC machines, the process is quick and easy due to the ability to constantly track the relationship of the tool position. CNC software includes canned cycles, that is, preprogrammed subroutines, parameters are entered, and the machine does the rest. Threads may be milled with a milling cutter if the correct helical toolpath can be arranged. This was formerly arranged mechanically, and it was suitable for mass-production work although uncommon in job-shop work, there are various types of thread milling, including several variants of form-milling and a combination of drilling and threading with one cutter, called thrilling. Form-milling uses either a single- or multiple-form cutter, in one variant of form-milling, the single-form cutter is tilted to the helix angle of the thread and then fed radially into the blank
12.
Split nut
–
A split nut is a nut that is split lengthwise into two pieces so that its female thread may be opened and closed over the male thread of a bolt or leadscrew. This allows the nut, when open, to move along the screw without the screw turning. Then, when the nut is closed, it resumes the normal movement of a nut on a screw A split nut assembly is used in positioning systems. It is one of the elements that makes single-point threading practical on manual lathes. The very earliest screw-cutting lathes did not have them, but within a few decades, the two halves of the nut have chamfered ends, which helps the threads to find engagement during the closing action. Usually the screw and nut are also oiled for lubrication, such provisions prolong the service life of the threads by minimizing wear. Split nuts work best with trapezoidal threads
13.
Trapezoidal thread form
–
Trapezoidal thread forms are screw thread profiles with trapezoidal outlines. They are the most common used for leadscrews. They offer high strength and ease of manufacture and they are typically found where large loads are required, as in a vise or the leadscrew of a lathe. Standardized variations include multiple-start threads, left-hand threads, and self-centering threads, the original trapezoidal thread form, and still probably the one most commonly encountered worldwide, is the Acme thread form. The Acme thread was developed in 1894 as a well suited to power screws that has various advantages over the square thread. The trapezoidal metric thread form is similar to the Acme thread form and it is codified by DIN103. Although metric screw threads are more prevalent worldwide than imperial threads, the Acme thread is very common worldwide. This is not surprising, as manufacturers today are capable of making whichever threads are best for any given application. It may be that the tooling for Acme threads has been so dominant that customers tend to want Acme threads for power screws regardless of standards used elsewhere in the product. The Acme thread form has a 29° thread angle with a thread height half of the pitch and this shape is easier to machine than is a square thread. The tooth shape also has a base which means it is stronger than a similarly sized square thread. This thread form also allows for the use of a split nut and this is due to the need to avoid wedging of the thread flanks when subjected to radial loads, which would contribute substantially to friction forces and thread wear. Compared to square threads, disadvantages of the Acme thread form are lower due to higher friction. When created prior to 1895, Acme screw threads were intended to replace square threads, Acme screw threads are now extensively used for a variety of purposes. Long-length Acme threads are used for controlled movements on machine tools, testing machines, jacks, aircraft flaps, short-length threads are used on valve stems, hose connectors, bonnets on pressure cylinders, steering mechanisms, and camera lens movement. 01-in. Finally, there exists a stub Acme-thread standard, identical in all respects to the one just described except for the height of the basic thread being 0. 3P. In case of the thread form the angle is 30° instead of 29°. Trapezoidal threads are defined as follows by ISO standards, T r 60 ×9 where Tr designates a trapezoidal thread,60 is the diameter in millimeters
14.
Square thread form
–
The square thread form is a common screw thread form, used in high load applications such as leadscrews and jackscrews. It gets its name from the square cross-section of the thread and it is the lowest friction and most efficient thread form, but it is difficult to fabricate. The greatest advantage of square threads is that they have a higher intrinsic efficiency than trapezoidal threads. Due to the lack of an angle there is no radial pressure, or bursting pressure. This also increases the nut life, the greatest disadvantage is the difficulty in machining such a thread. The single-point cutting tools or taps and dies used to cut the thread cannot have efficient rake and relief angles, square threads also cannot carry as much load as a trapezoidal thread, because the root of the square thread is smaller. Also, there is no way to compensate for wear on the nut, square threads are defined as follows by ISO standards, S q 22 ×5 where Sq designates a square thread,60 is the nominal diameter in millimeters, and 9 is the pitch in millimeters. When there is no suffix it is a single start thread, if there is a suffix then the value after the multiplication sign is the lead and the value in the parentheses is the pitch. For example, S q 60 ×18 L H would denoted two starts, as the lead divided by the pitch is two, the LH denotes a left hand thread. Bhandari, V B, Design of Machine Elements, Tata McGraw-Hill, ISBN 978-0-07-061141-2
15.
Friction
–
Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. There are several types of friction, Dry friction resists relative lateral motion of two surfaces in contact. Dry friction is subdivided into static friction between non-moving surfaces, and kinetic friction between moving surfaces, fluid friction describes the friction between layers of a viscous fluid that are moving relative to each other. Lubricated friction is a case of fluid friction where a lubricant fluid separates two solid surfaces, skin friction is a component of drag, the force resisting the motion of a fluid across the surface of a body. Internal friction is the force resisting motion between the making up a solid material while it undergoes deformation. When surfaces in contact move relative to other, the friction between the two surfaces converts kinetic energy into thermal energy. This property can have consequences, as illustrated by the use of friction created by rubbing pieces of wood together to start a fire. Kinetic energy is converted to thermal energy whenever motion with friction occurs, another important consequence of many types of friction can be wear, which may lead to performance degradation and/or damage to components. Friction is a component of the science of tribology, Friction is not itself a fundamental force. Dry friction arises from a combination of adhesion, surface roughness, surface deformation. The complexity of interactions makes the calculation of friction from first principles impractical and necessitates the use of empirical methods for analysis. Friction is a non-conservative force - work done against friction is path dependent, in the presence of friction, some energy is always lost in the form of heat. Thus mechanical energy is not conserved, the Greeks, including Aristotle, Vitruvius, and Pliny the Elder, were interested in the cause and mitigation of friction. They were aware of differences between static and kinetic friction with Themistius stating in 350 A. D. that it is easier to further the motion of a moving body than to move a body at rest. The classic laws of sliding friction were discovered by Leonardo da Vinci in 1493, a pioneer in tribology and these laws were rediscovered by Guillaume Amontons in 1699. Amontons presented the nature of friction in terms of surface irregularities, the understanding of friction was further developed by Charles-Augustin de Coulomb. Coulomb further considered the influence of sliding velocity, temperature and humidity, the distinction between static and dynamic friction is made in Coulombs friction law, although this distinction was already drawn by Johann Andreas von Segner in 1758. Leslie was equally skeptical about the role of adhesion proposed by Desaguliers, in Leslies view, friction should be seen as a time-dependent process of flattening, pressing down asperities, which creates new obstacles in what were cavities before
16.
Buttress thread
–
The buttress thread form, also known as the breech-lock thread form, refers to two different thread profiles. One is a type of leadscrew and the other is a type of sealing thread form. The leadscrew type is used in machinery and the sealing type is often used in oil fields. In machinery, the thread form is designed to handle extremely high axial thrust in one direction. The load-bearing thread face is perpendicular to the screw axis, or at a slight slant The other face is slanted at 45°. The resulting thread form has the low friction properties as a square thread form. This thread form also is easy to machine on a milling machine. It can also compensate for nut wear using a split nut, buttress threads have often been used in the construction of artillery, particularly with the screw-type breechblock. They are also used in vises, because great force is only required in one direction. The image gallery shows some of the types of buttress threads. In oil field tubing, buttress thread is a thread form designed to provide a tight hydraulic seal. The thread form is similar to that of Acme thread the force is transmitted almost parallel to the axis, the new encyclopedia of machine shop practice, Wm. H. Wise & Company. Bhandari, V B, Design of Machine Elements, Tata McGraw-Hill, oberg, Erik, Jones, Franklin D. Horton, Holbrook L. Ryffel, Henry H. Machinerys Handbook, New York, Industrial Press Inc. Timings, Roger Leslie, Newnes Mechanical Engineers Pocket Book, Newnes, ISBN 978-0-7506-6508-7
17.
Boeing 747-8
–
The Boeing 747-8 is a wide-body jet airliner developed by Boeing Commercial Airplanes. Officially announced in 2005, the 747-8 is the generation of the 747, with a lengthened fuselage, redesigned wings. The 747-8 is the largest 747 version, the largest commercial aircraft built in the United States, the 747-8 is offered in two main variants, the 747-8 Intercontinental for passengers and the 747-8 Freighter for cargo. The first 747-8F performed the maiden flight on February 8,2010. Delivery of the first freighter aircraft occurred in October 2011 and the model began deliveries in 2012. As of January 2017, confirmed orders for the 747-8 total 136,88 of the freighter version, Boeing had considered larger-capacity versions of the 747 several times during the 1990s and 2000s. The 747-500X and -600X, proposed at the 1996 Farnborough Airshow, would have stretched the 747 and used a 777-derived wing, in 2000, Boeing offered the 747X and 747X Stretch derivatives as alternatives to the Airbus A3XX. This was a more modest proposal than the previous −500X and −600X, the 747X would increase the 747s wingspan to 229 ft by adding a segment at the root. The 747X was to carry 430 passengers up to 8,700 nmi, the 747X Stretch would be extended to 263 ft long, allowing it to carry 500 passengers up to 7,800 nmi. However, the 747X family was unable to attract enough interest to enter production, some of the ideas developed for the 747X were used on the 747-400ER. After the 747X program, Boeing continued to study improvements to the 747, the 747-400XQLR was meant to have an increased range of 7,980 nmi, with better fuel efficiency and reduced noise. Changes studied included raked wingtips similar to those used on the 767-400ER, although the 747-400XQLR did not move to production, many of its features were used for the 747 Advanced. In early 2004, Boeing announced tentative plans for the 747 Advanced that were eventually adopted, similar in nature to the 747X, the stretched 747 Advanced used technology from the Boeing 787 Dreamliner to modernize the design and its systems. On November 14,2005, Boeing announced that it was launching the 747 Advanced as the Boeing 747-8, the 747-8 was designed to be the first lengthened 747 to go into production. The 747-8 and shortened 747SP are the only 747 variants with a fuselage of modified length, the 747-8 was intended to use the same engine and cockpit technology as that of the 787, including the General Electric GEnx turbofan and partial fly-by-wire. Boeing said that the new design would be quieter, more economical, as a derivative of the already-common 747-400, the 747-8 has the economic benefit of similar training and interchangeable parts. Boeing firmed the 747-8 Freighters configuration in October 2006, the 747-8, as the current new development of Boeings largest airliner, is notably in direct competition on long-haul routes with the Airbus A380, a full-length double-deck aircraft now in service. For airlines seeking very large passenger airliners, the two have been pitched as competitors on various occasions, production of the first 747-8 Freighter began in Everett in early August 2008
18.
Ball screw
–
A ball screw is a mechanical linear actuator that translates rotational motion to linear motion with little friction. A threaded shaft provides a helical raceway for ball bearings which act as a precision screw, as well as being able to apply or withstand high thrust loads, they can do so with minimum internal friction. They are made to close tolerances and are suitable for use in situations in which high precision is necessary. The ball assembly acts as the nut while the shaft is the screw. In contrast to conventional leadscrews, ballscrews tend to be rather bulky, another form of linear actuator based on a rotating rod is the threadless ballscrew, a. k. a. rolling ring drive. In this design, three rolling-ring bearings are arranged symmetrically in a housing surrounding a smooth actuator rod or shaft, the bearings are set at an angle to the rod, and this angle determines the direction and rate of linear motion per revolution of the rod. An advantage of design over the conventional ballscrew or leadscrew is the practical elimination of backlash. They are also used in tools, robots and precision assembly equipment. High precision ball screws are used in steppers for semiconductor manufacturing, historically, the first precise screwshafts were produced by starting with a low precision screwshaft, and then lapping the shaft with several spring-loaded nut laps. By rearranging and inverting the nut laps, the errors of the nuts. Then, the very repeatable shafts pitch is measured against a distance standard, a similar process is sometimes used today to produce reference standard screw shafts, or master manufacturing screw shafts. To maintain their inherent accuracy and ensure long life, great care is needed to avoid contamination with dirt and this may be achieved by using rubber or leather bellows to completely or partially enclose the working surfaces. Another solution is to use a pressure of filtered air when they are used in a semi-sealed or open enclosure. While reducing friction, ball screws can operate with some preload and this feature is essential when they are used in computer-controlled motion-control systems, e. g. CNC machine tools and high precision motion applications. Depending upon their lead angle, ball screws can be due to their low internal friction. Cost is also a factor as Acme screws are cheaper to manufacture. Low friction in ball screws yields high mechanical efficiency compared to alternatives, a typical ball screw may be 90 percent efficient, versus 20 to 25 percent efficiency of an Acme lead screw of equal size. This, combined with their overall performance benefits and reduced power requirements, Ball screw shafts may be fabricated by rolling, yielding a less precise, but inexpensive and mechanically efficient product
19.
Roller screw
–
Planetary roller screws are used as the actuating mechanism in many electro-mechanical linear actuators. Due to its complexity the roller screw is a relatively expensive actuator, Roller screw mechanisms are commonly incorporated into motion/positioning systems in a variety of industries such as manufacturing and aerospace. A roller screw is a mechanical actuator similar to a screw that uses rollers as the load transfer elements between nut and screw instead of balls. The rollers are typically threaded but may also be grooved depending on roller screw type, Roller screws can surpass ball screws in regard to positioning precision, load rating, rigidity, speed, acceleration, and lifetime. Standard roller screw actuators can achieve dynamic load ratings above 130 tons of force, the three main elements of a typical planetary roller screw are the screw shaft, nut and planetary roller. The screw, a shaft with a multi-start V-shaped thread, provides a helical raceway for multiple rollers radially arrayed around the screw, the thread of the screw is typically identical to the internal thread of the nut. The rollers spin in contact with, and serve as low-friction transmission elements between screw and nut, the rollers typically have a single-start thread with convex flanks that limit friction at the rollers contacts with screw and nut. The rollers typically orbit the screw as they spin, and are known as planetary, or satellite. As with a screw or ball screw, rotation of the nut results in screw travel. For a given diameter and quantity of thread starts more rollers corresponds to higher static load capacity. Preloaded split nuts and double nuts are available to eliminate backlash, carl Bruno Strandgren developed some of the earliest effective forms of roller screws and applied for a patent in Nice, France on February 1942. The French patent #888.281 was granted in August 1943, the first commercial Roller Screw was designed and manufactured under his supervision in 1949 and was mounted on a narrow gauge locomotive which operated in a northern France coal mine. Subsequent units were produced and mounted on machine-tools and starting in 1955 on aircraft, Roller screw types are defined by the motion of the rollers relative to the nut and screw. The four commercially available types of screw are standard, inverted, recirculating. Differential roller screws, typically variants of the standard and recirculating types, are commercially available. Differential roller screws modify the speed ratios between the rollers and the screw by varying the flank angles and contact points of the threads or grooves. In that way differential roller screws change the lead of the screw. William J. Roantree received a US patent for the Differential Roller Nut in 1968, the standard planetary roller screw is also known as the non-recirculating roller screw
20.
Hydraulics
–
Hydraulics is a technology and applied science using engineering, chemistry, and other sciences involving the mechanical properties and use of liquids or fluids. At a very basic level, hydraulics is the version of pneumatics. Fluid mechanics provides the foundation for hydraulics, which focuses on the applied engineering using the properties of fluids. In fluid power, hydraulics are used for the generation, control, hydraulic topics range through some parts of science and most of engineering modules, and cover concepts such as pipe flow, dam design, fluidics and fluid control circuitry, pumps. The principles of hydraulics are in use naturally in the body within the heart. Free surface hydraulics is the branch of hydraulics dealing with surface flow, such as occurring in rivers, canals, lakes, estuaries. Its sub-field open channel flow studies the flow in open channels, the word hydraulics originates from the Greek word ὑδραυλικός which in turn originates from ὕδωρ and αὐλός. Early uses of water power date back to Mesopotamia and ancient Egypt, other early examples of water power include the Qanat system in ancient Persia and the Turpan water system in ancient Central Asia. The Greeks constructed sophisticated water and hydraulic power systems, an example is the construction by Eupalinos, under a public contract, of a watering channel for Samos, the Tunnel of Eupalinos. An early example of the usage of hydraulic wheel, probably the earliest in Europe, is the Perachora wheel, notable is the construction of the first hydraulic automata by Ctesibius and Hero of Alexandria. Hero describes a number of working machines using hydraulic power, such as the force pump, in ancient China there was Sunshu Ao, Ximen Bao, Du Shi, Zhang Heng, and Ma Jun, while medieval China had Su Song and Shen Kuo. Du Shi employed a waterwheel to power the bellows of a blast furnace producing cast iron, Zhang Heng was the first to employ hydraulics to provide motive power in rotating an armillary sphere for astronomical observation. In ancient Sri Lanka, hydraulics were used in the ancient kingdoms of Anuradhapura. The discovery of the principle of the tower, or valve pit. By the first century AD, several irrigation works had been completed. The coral on the rock at the site includes cisterns for collecting water. They were among the first to use of the siphon to carry water across valleys. They used lead widely in plumbing systems for domestic and public supply, hydraulic mining was used in the gold-fields of northern Spain, which was conquered by Augustus in 25 BC
21.
Pneumatics
–
Pneumatics is a branch of engineering that makes use of gas or pressurized air. Pneumatic systems used in industry are commonly powered by compressed air or compressed inert gases, a centrally located and electrically powered compressor powers cylinders, air motors, and other pneumatic devices. A pneumatic system controlled through manual or automatic solenoid valves is selected when it provides a lower cost, more flexible, pneumatics also has applications in dentistry, construction, mining, and other areas. Pneumatic systems in fixed installations, such as factories, use compressed air because a sustainable supply can be made by compressing atmospheric air, the air usually has moisture removed, and a small quantity of oil is added at the compressor to prevent corrosion and lubricate mechanical components. Factory-plumbed pneumatic-power users need not worry about poisonous leakage, as the gas is usually just air, smaller or stand-alone systems can use other compressed gases that present an asphyxiation hazard, such as nitrogen—often referred to as OFN when supplied in cylinders. Any compressed gas other than air is an asphyxiation hazard—including nitrogen, compressed oxygen would not asphyxiate, but is not used in pneumatically-powered devices because it is a fire hazard, more expensive, and offers no performance advantage over air. Carbon dioxide is an asphyxiant and can be a hazard if vented improperly. The origins of pneumatics can be traced back to the first century when ancient Greek mathematician Hero of Alexandria wrote about his inventions powered by steam or the wind, german physicist Otto von Guericke went a little further. He invented the pump, a device that can draw out air or gas from the attached vessel. He demonstrated the vacuum pump to separate the pairs of copper hemispheres using air pressures, the field of pneumatics has changed considerably over the years. It has moved from small handheld devices to large machines with multiple parts that serve different functions, both pneumatics and hydraulics are applications of fluid power. Pneumatics uses an easily compressible gas such as air or a suitable pure gas—while hydraulics uses relatively incompressible liquid media such as oil, most industrial pneumatic applications use pressures of about 80 to 100 pounds per square inch. Hydraulics applications commonly use from 1,000 to 5,000 psi, simplicity of design and control—Machines are easily designed using standard cylinders and other components, and operate via simple on-off control. Reliability—Pneumatic systems generally have long operating lives and require little maintenance, because gas is compressible, equipment is less subject to shock damage. Gas absorbs excessive force, whereas fluid in hydraulics directly transfers force, compressed gas can be stored, so machines still run for a while if electrical power is lost. Safety—There is a low chance of fire compared to hydraulic oil. Newer machines are usually overload safe, liquid does not absorb any of the supplied energy. Capable of moving much higher loads and providing much higher due to the incompressibility
22.
Gear
–
A gear or cogwheel is a rotating machine part having cut teeth, or cogs, which mesh with another toothed part to transmit torque. Geared devices can change the speed, torque, and direction of a power source, Gears almost always produce a change in torque, creating a mechanical advantage, through their gear ratio, and thus may be considered a simple machine. The teeth on the two meshing gears all have the same shape, two or more meshing gears, working in a sequence, are called a gear train or a transmission. A gear can mesh with a linear toothed part, called a rack, the gears in a transmission are analogous to the wheels in a crossed, belt pulley system. An advantage of gears is that the teeth of a gear prevent slippage, in transmissions with multiple gear ratios—such as bicycles, motorcycles, and cars—the term gear as in first gear refers to a gear ratio rather than an actual physical gear. The term describes similar devices, even when the ratio is continuous rather than discrete, or when the device does not actually contain gears. Early examples of gears date from the 4th century BC in China, examples of further development include, Ma Jun used gears as part of a south-pointing chariot. The Antikythera mechanism is an example of an early and intricate geared device. Its time of construction is now estimated between 150 and 100 BC, the water-powered grain-mill, the water-powered saw mill, fulling mill, and other applications of watermill often used gears. The first mechanical clocks were built in AD725, the 1386 Salisbury cathedral clock may be the worlds oldest working mechanical clock. The definite ratio that teeth give gears provides an advantage over other drives in precision machines such as watches that depend upon an exact velocity ratio, an external gear is one with the teeth formed on the outer surface of a cylinder or cone. Conversely, a gear is one with the teeth formed on the inner surface of a cylinder or cone. For bevel gears, a gear is one with the pitch angle exceeding 90 degrees. Internal gears do not cause output shaft direction reversal, spur gears or straight-cut gears are the simplest type of gear. They consist of a cylinder or disk with teeth projecting radially, though the teeth are not straight-sided, the edge of each tooth is straight and aligned parallel to the axis of rotation. These gears mesh together correctly only if fitted to parallel shafts, No axial thrust is created by the tooth loads. Spur gears are excellent at moderate speeds but tend to be noisy at high speeds, helical or dry fixed gears offer a refinement over spur gears. The leading edges of the teeth are not parallel to the axis of rotation, since the gear is curved, this angling makes the tooth shape a segment of a helix
23.
Worm drive
–
A worm drive is a gear arrangement in which a worm meshes with a worm gear. The two elements are called the worm screw and worm wheel. The terminology is confused by imprecise use of the term worm gear to refer to the worm. Like other gear arrangements, a drive can reduce rotational speed or transmit higher torque. A worm is an example of a screw, one of the six simple machines, a gearbox designed using a worm and worm-wheel is considerably smaller than one made from plain spur gears, and has its drive axes at 90° to each other. With a single start worm, for each 360° turn of the worm, therefore, regardless of the worms size, the gear ratio is the size of the worm gear - to -1. Given a single start worm, a 20 tooth worm gear reduces the speed by the ratio of 20,1, with spur gears, a gear of 12 teeth must match with a 240 tooth gear to achieve the same 20,1 ratio. There are three different types of gears that can be used in a worm drive, the first are non-throated worm gears. These dont have a throat, or groove, machined around the circumference of either the worm or worm wheel, the second are single-throated worm gears, in which the worm wheel is throated. The final type are double-throated worm gears, which have both gears throated and this type of gearing can support the highest loading. An enveloping worm has one or more teeth and increases in diameter from its middle portion toward both ends, double-enveloping wormgearing comprises enveloping worms mated with fully enveloping wormgears. It is also known as globoidal wormgearing and this can be an advantage when it is desired to eliminate any possibility of the output driving the input. If a multistart worm is used then the ratio reduces accordingly, Worm gear configurations in which the gear cannot drive the worm are called self-locking. Whether a worm and gear is self-locking depends on the angle, the pressure angle. The use of a worm screw reduced this effect, further worm drive development led to recirculating ball bearings to reduce frictional forces, which transmitted some steering force to the wheel. This aids vehicle control and reduces wear that could cause difficulties in steering precisely, Worm drives are a compact means of substantially decreasing speed and increasing torque. Worm drives are used in presses, rolling mills, conveying engineering, mining machines, on rudders. In addition, milling heads and rotary tables are positioned using high-precision duplex worm drives with adjustable backlash, Worm gears are used on many lift/elevator and escalator-drive applications due to their compact size and the non-reversibility of the gear
24.
Rack and pinion
–
A rack and pinion is a type of linear actuator that comprises a pair of gears which convert rotational motion into linear motion. For example, in a railway, the rotation of a pinion mounted on a locomotive or a railcar engages a rack between the rails and forces a train up a steep slope. For every pair of conjugate involute profile, there is a basic rack and this basic rack is the profile of the conjugate gear of infinite pitch radius. A generating rack is a rack outline used to indicate tooth details and dimensions for the design of a generating tool, such as a hob or a gear shaper cutter. Rack and pinion combinations are used as part of a simple linear actuator. The rack carries the load of the actuator directly and so the driving pinion is usually small. This force, thus torque, may still be substantial and so it is common for there to be a reduction gear immediately before this by either a gear or worm gear reduction, Rack gears have a higher ratio, thus require a greater driving torque, than screw actuators. Most Stairlifts today are operating using the Rack & Pinion system, a rack and pinion is commonly found in the steering mechanism of cars or other wheeled, steered vehicles. Rack and pinion provides an efficient mechanical advantage than other mechanisms such as recirculating ball. The mechanism may be power-assisted, usually by hydraulic or electrical means, the use of a variable rack was invented by Arthur Ernest Bishop in the 1970s, so as to improve vehicle response and steering feel, especially at high speeds. He also created a low cost press forging process to manufacture the racks, Rack railways are mountain railways that use a rack built into the center of the track and a pinion on their locomotives. This allows them to work on steep gradients, up to 45 degrees, additionally, the rack and pinion addition provides these trains with controlled brakes, and reduces the effects of snow or ice on the rails. A rack and pinion with two racks and one pinion is used in actuators, an example is pneumatic rack and pinion actuators that can be used to control valves in pipeline transport. The actuators in the picture on the right are used to control the valves of large water pipeline, in the top actuator, a gray control signal line can be seen connecting to a solenoid valve, which is used as the pilot for the actuator. The solenoid valve controls the air coming from the input air line. The output air from the valve is fed to the chamber in the middle of the actuator. The pressure in the actuators chamber pushes the pistons away, while the pistons are moving apart from each other, the attached racks are also moved along the pistons in the opposite directions of the two racks. The two racks are meshed to a pinion at the direct opposite teeth of the pinion, when the two racks move, the pinion is turned, causing the attached main valve of the water pipe to turn
25.
Electromagnetism
–
Electromagnetism is a branch of physics involving the study of the electromagnetic force, a type of physical interaction that occurs between electrically charged particles. The electromagnetic force usually exhibits electromagnetic fields such as fields, magnetic fields. The other three fundamental interactions are the interaction, the weak interaction, and gravitation. The word electromagnetism is a form of two Greek terms, ἤλεκτρον, ēlektron, amber, and μαγνῆτις λίθος magnētis lithos, which means magnesian stone. The electromagnetic force plays a role in determining the internal properties of most objects encountered in daily life. Ordinary matter takes its form as a result of forces between individual atoms and molecules in matter, and is a manifestation of the electromagnetic force. Electrons are bound by the force to atomic nuclei, and their orbital shapes. The electromagnetic force governs the processes involved in chemistry, which arise from interactions between the electrons of neighboring atoms, there are numerous mathematical descriptions of the electromagnetic field. In classical electrodynamics, electric fields are described as electric potential, although electromagnetism is considered one of the four fundamental forces, at high energy the weak force and electromagnetic force are unified as a single electroweak force. In the history of the universe, during the epoch the unified force broke into the two separate forces as the universe cooled. Originally, electricity and magnetism were considered to be two separate forces, Magnetic poles attract or repel one another in a manner similar to positive and negative charges and always exist as pairs, every north pole is yoked to a south pole. An electric current inside a wire creates a corresponding magnetic field outside the wire. Its direction depends on the direction of the current in the wire. A current is induced in a loop of wire when it is moved toward or away from a field, or a magnet is moved towards or away from it. While preparing for a lecture on 21 April 1820, Hans Christian Ørsted made a surprising observation. As he was setting up his materials, he noticed a compass needle deflected away from north when the electric current from the battery he was using was switched on. At the time of discovery, Ørsted did not suggest any explanation of the phenomenon. However, three later he began more intensive investigations
26.
Solenoid
–
A solenoid is a coil wound into a tightly packed helix. The term was invented by French physicist André-Marie Ampère to designate a helical coil, a solenoid is a type of electromagnet when the purpose is to generate a controlled magnetic field. If the purpose of the solenoid is instead to changes in the electric current. Not all electromagnets and inductors are solenoids, for example, the first electromagnet, in engineering, the term may also refer to a variety of transducer devices that convert energy into linear motion. Solenoid bolts, a type of locking mechanism, also exist. An infinite solenoid is a solenoid with infinite length but finite diameter, in short, the magnetic field inside an infinitely long solenoid is homogeneous and its strength neither depends on the distance from the axis, nor on the solenoids cross-sectional area. This is a derivation of the flux density around a solenoid that is long enough so that fringe effects can be ignored. In Figure 1, we know that the flux density vector points in the positive z direction inside the solenoid. We confirm this by applying the right hand rule for the field around a wire. If we wrap our right hand around a wire with the thumb pointing in the direction of the current, since we are dealing with a long solenoid, all of the components of the magnetic field not pointing upwards cancel out by symmetry. Outside, a similar cancellation occurs, and the field is pointing downwards. Now consider the imaginary loop c that is located inside the solenoid, by Ampères law, we know that the line integral of B around this loop is zero, since it encloses no electrical currents. We have shown above that the field is pointing upwards inside the solenoid, thus the integral of the up side 1 is equal to the integral of the down side 2. Note, though, that prohibits it from varying longitudinally. A similar argument can be applied to the loop a to conclude that the field outside the solenoid is radially uniform or constant, an intuitive argument can also be used to show that the flux density outside the solenoid is actually zero. Magnetic field lines only exist as loops, they diverge from or converge to a point like electric field lines can. The magnetic field lines follow the path of the solenoid inside. However, the volume outside the solenoid is much greater than the volume inside, now recall that the field outside is constant
27.
Free body diagram
–
In physics a free body diagram is a graphical illustration used to visualize the applied forces, movements, and resulting reactions on a body in a steady state condition. They depict a body or connected bodies with all of the forces and moments, as well as reactions. The body may consist of multiple members, for example. A series of bodies and other diagrams may be necessary to solve complex problems. Free body diagrams are used to visualize the forces and moments applied to a body and calculate the resulting reactions, in many types of mechanics problems. In the educational environment, learning to draw a free body diagram is an important step in understanding certain topics in physics, such as statics, dynamics, a free body diagram is not meant to be a scaled drawing. It is a diagram that is modified as the problem is solved, there is an art and flexibility to the process. The iconography of a body diagram, not only how it is drawn but also how it is interpreted. In dynamics the resultant forces and moments can be non-zero, free body diagrams may not represent an entire physical body. Using what is known as a cut only portions of a body are selected for modeling and this technique exposes internal forces, making them external, therefore allowing analysis. This technique is used several times, iteratively to peel back forces acting on a physical body. For example, a gymnast performing the iron cross, analyzing the ropes, then cut the person out and only show one rope. Then only look at the person, now you can get hand forces, now only look at the arm to get the shoulder forces and moments, and on and on until the component you intend to analyze is exposed. A body may be modeled in three ways, a particle and this model may be used when any rotational effects are zero or have no interest even though the body itself may be extended. The body may be represented by a small symbolic blob and the diagram reduces to a set of concurrent arrows, a force on a particle is a bound vector. Stresses and strains are of no interest but turning effects are, a force arrow should lie along the line of force, but where along the line is irrelevant. A force on a rigid body is a sliding vector. The point of application of a force becomes crucial and has to be indicated on the diagram, a force on a non-rigid body is a bound vector
28.
Fine adjustment screw
–
The term fine adjustment screw typically refers to screws with threads from 40-100 TPI and ultra fine adjustment screw has been used to refer to 100-508 TPI. Even though these are non-standard threads, both ISO metric screw thread designations and UNC designations have been used to call out thread dimensions, a typical use for a fine adjustment screw is in an optical mirror mount as an adjuster. Typically 80 TPI screws are used in mirror mounts, ultra fine adjuster screws are used in applications requiring extremely fine motion like laser alignment, fiber coupling. Fine and ultra fine adjustment screws are used in photonics applications as part of purchased equipment or built into lab made apparatus. Often, screws are purchased with matching bushings to be integrated into an experiment or commercial product once attained, fine adjustment screws and mirror mounts are available as standard items from most companies that sell optics hardware. The fine motion can most easily be calculated by using the pitch or TPI to determine how many micrometres per revolution the screw moves. The table below shows some common examples The screw turns 360° in one revolution and with well made screws, thus, with the ultra fine adjusters sub-micrometre motions are attainable. The material of choice for producing these screws is stainless steel typically 18-8, at the tip of the screw most commonly a stainless steel ball is either pressed or glued into place to provide a single point contact for the surface being moved. Common usage has shown the glue method of attaching the ball to be troublesome in many applications as some commonly used glues tend to outgas, each screw requires a nut/bushing which is critical in not only the length and class of the nut/busing but also the material itself. In low cost adjusters where grease can be used and wear and load is small, in High-end adjusters where tight tolerances are required as well as the capability to withstand wear and higher load, phosphor bronze is the preferred material. Phosphor bronze is considered a material that makes it ideal for grease free applications e. g. vacuum. Still, the use of grease will extend the lifetime of the nut/bushing and is recommended unless a free version is required. It is difficult to make screw threads finer than about 250 TPI, as of 2015 only a small handful of companies have the ability to consistently construct threads this fine. There are many commercially available versions of these at prices many times that of the fine threads. With this solution backlash is often a problem as backlash from the two threads combines additively, sub-micron Adjusters - These use a lever configuration or cone configuration to de-amplify the motion of a screw. These can be engineered to minimize backlash, prices are similar to differential adjusters
29.
Jackscrew
–
A jackscrew is a type of jack that is operated by turning a leadscrew. In the form of a screw jack it is used to lift moderately heavy weights. More commonly it is used as a support for heavy loads, such as the foundations of houses. These can support a load, but not lift it. This makes them safer than hydraulic jacks, for example. This derives from two factors, the simple advantage of a long operating handle and also the advantage of the inclined plane of the leadscrew. However, most screw jacks have large amounts of friction which increase the force necessary. Screw jacks are limited in their lifting capacity, increasing load increases friction within the screw threads. A fine pitch thread, which would increase the advantage of the screw, also reduces the size, longer operating levers soon reach a point where the lever will simply bend at their inner end. Screw jacks have now largely replaced by hydraulic jacks. The maximum mechanical advantage possible for a jack is not limited by the limitations on screw jacks. After World War II, improvements to the grinding of hydraulic rams, screw jacks still remain for minimal cost applications, such as the little-used tyre-changing jacks supplied with cars. The large area of sliding contact between the screw threads means jackscrews have high friction and low efficiency as power transmission linkages, so they are not often used for continuous transmission of high power, but more often in intermittent positioning applications. In heavy-duty applications, such as jacks, a square thread or buttress thread is used, because it has the lowest friction. The ball screw is an advanced type of leadscrew that uses a recirculating-ball nut to minimize friction. The thread profile of such screws is approximately semicircular to properly mate with the bearing balls, the disadvantage to this type of screw is that it is not self-locking. Ball screws are prevalent in powered leadscrew actuators, jackscrews are also used extensively in aviation, and are used to raise and lower horizontal stabilizers. The failure of a jackscrew on a Yakovlev Yak-42 airliner due to design flaws resulted in the crash of Aeroflot Flight 8641 in 1982, a similar failure on a McDonnell Douglas MD-80, resulting from a lack of grease, brought down Alaska Airlines Flight 261 in 2000
30.
International Standard Book Number
–
The International Standard Book Number is a unique numeric commercial book identifier. An ISBN is assigned to each edition and variation of a book, for example, an e-book, a paperback and a hardcover edition of the same book would each have a different ISBN. The ISBN is 13 digits long if assigned on or after 1 January 2007, the method of assigning an ISBN is nation-based and varies from country to country, often depending on how large the publishing industry is within a country. The initial ISBN configuration of recognition was generated in 1967 based upon the 9-digit Standard Book Numbering created in 1966, the 10-digit ISBN format was developed by the International Organization for Standardization and was published in 1970 as international standard ISO2108. Occasionally, a book may appear without a printed ISBN if it is printed privately or the author does not follow the usual ISBN procedure, however, this can be rectified later. Another identifier, the International Standard Serial Number, identifies periodical publications such as magazines, the ISBN configuration of recognition was generated in 1967 in the United Kingdom by David Whitaker and in 1968 in the US by Emery Koltay. The 10-digit ISBN format was developed by the International Organization for Standardization and was published in 1970 as international standard ISO2108, the United Kingdom continued to use the 9-digit SBN code until 1974. The ISO on-line facility only refers back to 1978, an SBN may be converted to an ISBN by prefixing the digit 0. For example, the edition of Mr. J. G. Reeder Returns, published by Hodder in 1965, has SBN340013818 -340 indicating the publisher,01381 their serial number. This can be converted to ISBN 0-340-01381-8, the check digit does not need to be re-calculated, since 1 January 2007, ISBNs have contained 13 digits, a format that is compatible with Bookland European Article Number EAN-13s. An ISBN is assigned to each edition and variation of a book, for example, an ebook, a paperback, and a hardcover edition of the same book would each have a different ISBN. The ISBN is 13 digits long if assigned on or after 1 January 2007, a 13-digit ISBN can be separated into its parts, and when this is done it is customary to separate the parts with hyphens or spaces. Separating the parts of a 10-digit ISBN is also done with either hyphens or spaces, figuring out how to correctly separate a given ISBN number is complicated, because most of the parts do not use a fixed number of digits. ISBN issuance is country-specific, in that ISBNs are issued by the ISBN registration agency that is responsible for country or territory regardless of the publication language. Some ISBN registration agencies are based in national libraries or within ministries of culture, in other cases, the ISBN registration service is provided by organisations such as bibliographic data providers that are not government funded. In Canada, ISBNs are issued at no cost with the purpose of encouraging Canadian culture. In the United Kingdom, United States, and some countries, where the service is provided by non-government-funded organisations. Australia, ISBNs are issued by the library services agency Thorpe-Bowker
31.
Epicyclic gearing
–
An epicyclic gear train consists of two gears mounted so that the center of one gear revolves around the center of the other. A carrier connects the centers of the two gears and rotates to carry one gear, called the planet gear, around the other, the planet and sun gears mesh so that their pitch circles roll without slip. A point on the circle of the planet gear traces an epicycloid curve. In this simplified case, the sun gear is fixed and the planetary gear roll around the sun gear. An epicyclic gear train can be assembled so the planet gear rolls on the inside of the circle of a fixed, outer gear ring, or ring gear. In this case, the curve traced by a point on the circle of the planet is a hypocycloid. The combination of gear trains with a planet engaging both a sun gear and a ring gear is called a planetary gear train. In this case, the gear is usually fixed and the sun gear is driven. Epicyclic gears get their name from their earliest application, which was the modeling of the movements of the planets in the heavens. Believing the planets, as everything in the heavens, to be perfect, they could travel in perfect circles. At around 500 BC, the Greeks invented the idea of epicycles, with this theory Claudius Ptolemy in the Almagest in 148 AD was able to predict planetary orbital paths. The Antikythera Mechanism, circa 80 BC, had gearing which was able to approximate the moons path through the heavens. Epicyclic gearing or planetary gearing is a system consisting of one or more outer gears, or planet gears, revolving about a central. Typically, the gears are mounted on a movable arm or carrier. Epicyclic gearing systems also incorporate the use of a ring gear or annulus. Planetary gears are classified as simple or compound planetary gears. Simple planetary gears have one sun, one ring, one carrier, Compound planetary gears involve one or more of the following three types of structures, meshed-planet, stepped-planet, and multi-stage structures. Compared to simple planetary gears, compound planetary gears have the advantages of larger reduction ratio, higher torque-to-weight ratio, and more flexible configurations
32.
Sun and planet gear
–
The sun and planet gear is a method of converting reciprocating motion to rotary motion and was used in the first rotative beam engines. It was invented by the Scottish engineer William Murdoch, an employee of Boulton and Watt and it was invented to bypass the patent on the crank, already held by James Pickard. It played an important part in the development of devices for rotation in the Industrial Revolution. The sun and planet gear converted the motion of a beam, driven by a steam engine, into circular motion using a planet. With the motion of the beam, this revolved around, and turned, the sun, the planet gear is fixed to the connecting rod and thus does not rotate around its own axis. This link appears, at first sight, to be similar to a crank, thus, it did not contravene the crank patent. Epicyclic gearing Sun and planet gear animation Henry Ford Museum Watt Rotative Engine
33.
Harmonic drive
–
A harmonic gear is a strain wave gear which can improve certain characteristics compared to traditional gearing systems. Harmonic Drive is trademarked by the Harmonic Drive company, the strain wave gear was invented in 1957 by C. W. Musser. It is very commonly implemented in robotics today and used in aerospace as well, for gear reduction but may also be used to increase rotational speed, the basic concept of strain wave gearing was introduced by C. W. Musser in his 1957 patent. It was first used successfully in 1960 by USM Co. and later by Hasegawa Gear Works, later, Hasegawa Gear Works, Ltd. became Harmonic Drive Systems Inc. located in Japan and USM Co. Harmonic Drive division became Harmonic Drive Technologies Inc, the electrically driven wheels of the Apollo Lunar Rover included strain wave gears in their gearing. Also, the used on Skylab to deploy the solar panels were powered using strain wave gears. Both of these system were developed by The Harmonic Drive Division of United Shoe Machinery Corp, on January 1,2006, Harmonic Drive Technologies/Nabtesco of Peabody, MA and HD Systems of Hauppauge, NY, merged to form a new joint venture, Harmonic Drive LLC. HD Systems, Inc. was a company of Harmonic Drive System. Offices are maintained in Peabody, MA, Hauppauge, NY, San Jose, CA and Oak Park, Harmonic Drive Systems, Inc. Japan is headquartered in Tokyo with its primary manufacturing location in Hotaka, Japan. Harmonic Drive AG has its European headquarters and manufacturing in Limburg/Lahn, the strain wave gearing theory is based on elastic dynamics and utilizes the flexibility of metal. The mechanism has three components, a wave generator, a flex spline, and a circular spline. More complex versions have a fourth component normally used to shorten the length or to increase the gear reduction within a smaller diameter. The wave generator is made up of two parts, an elliptical disk called a wave generator plug and an outer ball bearing. The gear plug is inserted into the bearing, giving the bearing an elliptical shape as well, the flex spline is shaped like a shallow cup. The sides of the spline are very thin, but the bottom is relatively rigid and this results in significant flexibility of the walls at the open end due to the thin wall, and in the closed side being quite rigid and able to be tightly secured. Teeth are positioned radially around the outside of the flex spline, the ball bearing lets the flex spine rotate independently to the wave generators shaft. The circular spline is a circular ring with teeth on the inside. The flex spline and wave generator are placed inside the circular spline, meshing the teeth of the flex spline and the circular spline
34.
Cycloidal drive
–
A cycloidal drive or cycloidal speed reducer is a mechanism for reducing the speed of an input shaft by a certain ratio. Cycloidal speed reducers are capable of relatively high ratios in compact sizes, the input shaft drives an eccentric bearing that in turn drives the cycloidal disc in an eccentric, cycloidal motion. The perimeter of this disc is geared to a ring gear and has a series of output shaft pins or rollers placed through the face of the disc. These output shaft pins directly drive the shaft as the cycloidal disc rotates. The radial motion of the disc is not translated to the output shaft, the input shaft is mounted eccentrically to a Rolling-element bearing, causing the cycloidal disc to move in a circle. The cycloidal disc will independently rotate around the bearing as it is pushed against the ring gear and this is similar to planetary gears, and the direction of rotation is opposite to that of the input shaft. The number of pins on the gear is larger than the number of pins on the cycloidal disc. This causes the disc to rotate around the bearing faster than the input shaft is moving it around. The cycloidal disc has holes that are larger than the output roller pins that go inside them. The output pins will move around in the holes to achieve steady rotation of the shaft from the wobbling movement of the cycloidal disc. The reduction rate of the drive is obtained from the following formula. R = P − L L Single stage efficiency approaches 93%, Single stage reductions are available commercially up to 119,1 and double stage up to 7569,1 Unlike many other drive mechanisms the cycloidal drive is not typically backdrivable. Due to the nature of the drive, if the cycloidal disk is not balanced by a second disk or a counterweight. This will cause increased wear on the teeth of the cycloidal disk
35.
Non-circular gear
–
A non-circular gear is a special gear design with special characteristics and purpose. Common applications include textile machines, potentiometers, CVTs, window shade panel drives, mechanical presses, a regular gear pair can be represented as two circles rolling together without slip. In the case of non-circular gears, those circles are replaced with anything different from a circle, for this reason NCGs in most cases are not round, but round NCGs looking like regular gears are also possible. Because of complicated geometry, NCGs are most likely spur gears, if the shape of the first wheel is known, the shape of the second can often be found using the above equations. If the relationship between the angles is specified, the shapes of wheels can often be determined analytically as well. It is more convenient to use the variable z = e i θ when analyzing this problem. This equation can be solved as, ln = ln + ∫ r 1 a − r 1 d z 1 z 1 where ln is a constant of integration. Noncircular Gears, Design and Generation by Faydor L. Litvin and Alfonso Fuentes A paper on designing of non-circular gears Maurice Lacroix Masterpiece Regulateur Roue Carree
36.
Bevel gear
–
Bevel gears are gears where the axes of the two shafts intersect and the tooth-bearing faces of the gears themselves are conically shaped. Bevel gears are most often mounted on shafts that are 90 degrees apart, the pitch surface of bevel gears is a cone. Two important concepts in gearing are pitch surface and pitch angle, the pitch surface of a gear is the imaginary toothless surface that you would have by averaging out the peaks and valleys of the individual teeth. The pitch surface of a gear is the shape of a cylinder. The pitch angle of a gear is the angle between the face of the surface and the axis. The most familiar kinds of gears have pitch angles of less than 90 degrees. This type of gear is called external because the gear teeth point outward. The pitch surfaces of meshed external bevel gears are coaxial with the gear shafts, Bevel gears that have pitch angles of greater than ninety degrees have teeth that point inward and are called internal bevel gears. Bevel gears that have angles of exactly 90 degrees have teeth that point outward parallel with the axis. Thats why this type of gear is called a crown gear. Miter gears are mating bevel gears with equal numbers of teeth and with axes at right angles, skew bevel gears are those for which the corresponding crown gear has teeth that are straight and oblique. Bevel gears are classified in different types according to geometry, Straight bevel gears have conical pitch surface and teeth are straight, spiral bevel gears have curved teeth at an angle allowing tooth contact to be gradual and smooth. Zerol bevel gears can be thought of as spiral bevel gears, which also have curved teeth, hypoid bevel gears are similar to spiral bevel but the pitch surfaces are hyperbolic and not conical. Pinion can be offset above, or below, the centre, thus allowing larger pinion diameter. In a limiting case of making the surface parallel with the axis of rotation. Hypoid gears were used in automobile rear axles. Mitre gears are a type of gears that have equal numbers of teeth. The shafts are positioned at angles from each other
37.
Crown gear
–
A crown gear is a gear which has teeth that project at right angles to the face of the wheel. In particular, a gear is a type of bevel gear where the pitch cone angle is 90 degrees. A pitch cone of any angle is simply called a bevel gear. Crown gears normally mesh with other gears, or sometimes spur gears
38.
Spiral bevel gear
–
A spiral bevel gear is a bevel gear with helical teeth. The main application of this is in a differential, where the direction of drive from the drive shaft must be turned 90 degrees to drive the wheels. The helical design produces less vibration and noise than conventional straight-cut or spur-cut gear with straight teeth. A spiral bevel gear set should always be replaced in pairs i. e. both the hand and right hand gears should be replaced together since the gears are manufactured and lapped in pairs. Note that a spiral bevel gear and pinion are always of opposite hand, also note that the designations right hand and left hand are applied similarly to other types of bevel gear, hypoid gears, and oblique tooth face gears. A hypoid is a type of bevel gear whose axis does not intersect with the axis of the meshing gear. The shape of a gear is a revolved hyperboloid, whereas the shape of a spiral bevel gear is normally conical. The hypoid gear places the pinion off-axis to the wheel which allows the pinion to be larger in diameter and have more contact area. In hypoid gear design, the pinion and gear are practically always of opposite hand, the hypoid pinion is then larger in diameter than an equivalent bevel pinion. A hypoid gear incorporates some sliding and can be considered halfway between a gear and a worm gear. Special gear oils are required for hypoid gears because the action requires effective lubrication under extreme pressure between the teeth. Hypoid gearings are used in power transmission products that are more efficient than conventional worm gearing and they are considerably stronger in that any load is conveyed through multiple teeth simultaneously. By contrast, bevel gears are loaded through one tooth at a time, the multiple contacts of hypoid gearing, with proper lubrication, can be nearly silent, as well. The spiral angle in a bevel gear is the angle between the tooth trace and an element of the pitch cone, and corresponds to the helix angle in helical teeth. Unless otherwise specified, the spiral angle is understood to be the mean spiral angle. Mean spiral angle is the designation for the spiral angle at the mean cone distance in a bevel gear. Outer spiral angle is the angle of a bevel gear at the outer cone distance. Inner spiral angle is the angle of a bevel gear at the inner cone distance
39.
Herringbone gear
–
A herringbone gear, a specific type of double helical gear, is a special type of gear that is a side to side combination of two helical gears of opposite hands. From the top, each helical groove of this looks like the letter V. Unlike helical gears, herringbone gears do not produce an additional axial load, like helical gears, they have the advantage of transferring power smoothly because more than two teeth will be in mesh at any moment in time. Their advantage over the helical gears is that the side-thrust of one half is balanced by that of the other half and this means that herringbone gears can be used in torque gearboxes without requiring a substantial thrust bearing. Because of this herringbone gears were an important step in the introduction of the turbine to marine propulsion. Precision herringbone gears are more difficult to manufacture than equivalent spur or helical gears and they are used in heavy machinery. The latter alignment is the defining characteristic of a Wuest type herringbone gear. A disadvantage of the gear is that it cannot be cut by simple gear hobbing machines. With the older method of fabrication, herringbone gears had a channel separating the two oppositely-angled courses of teeth. This was necessary to permit the shaving tool to run out of the groove, the development of the Sykes gear shaper made it possible to have continuous teeth with no central gap. Sunderland, also in England, also produced a herringbone cutting machine, the Sykes uses cylindrical guides and round cutters, the Sunderland uses straight guides and rack-type cutters. The W. E. Sykes Co. dissolved in 1983–84, since then it has been common practice to obtain an older machine and rebuild it if necessary to create this unique type of gear. Recently, the Bourn and Koch company has developed a CNC-controlled derivation of the W. E. Sykes design called the HDS1600-300. This machine, like the Sykes gear shaper, has the ability to generate a true apex without the need for a clearance groove cut around the gear and this allows the gears to be used in positive displacement pumping applications, as well as power transmission. Helical gears with low weight, accuracy and strength may be 3D printed, the logo of the car maker Citroën is a graphic representation of a herringbone gear, reflecting André Citroëns earlier involvement in the manufacture of these gears. Early Mors and Citroën cars used a bevel gear final drive in the rear axle. Panhard Dyna X and successor cars used double helical gears in the transaxle and for the camshaft timing gears in the engine
40.
Transmission (mechanics)
–
A transmission is a machine in a power transmission system, which provides controlled application of the power. Often the term refers simply to the gearbox that uses gears and gear trains to provide speed. In British English, the term refers to the whole drivetrain, including clutch, gearbox, prop shaft, differential. In American English, however, the term more specifically to the gearbox alone. The most common use is in vehicles, where the transmission adapts the output of the internal combustion engine to the drive wheels. Such engines need to operate at a high rotational speed, which is inappropriate for starting, stopping. The transmission reduces the engine speed to the slower wheel speed. Transmissions are also used on bicycles, fixed machines. Often, a transmission has multiple gear ratios with the ability to switch between them as speed varies and this switching may be done manually or automatically. Directional control may also be provided, single-ratio transmissions also exist, which simply change the speed and torque of motor output. The output of the transmission is transmitted via the driveshaft to one or more differentials, while a differential may also provide gear reduction, its primary purpose is to permit the wheels at either end of an axle to rotate at different speeds as it changes the direction of rotation. Conventional gear/belt transmissions are not the mechanism for speed/torque adaptation. Alternative mechanisms include torque converters and power transformation, automatic transmissions use a valve body to shift gears using fluid pressures in conjunction with an ecm. Early transmissions included the right-angle drives and other gearing in windmills, horse-powered devices, and steam engines, in support of pumping, milling, most modern gearboxes are used to increase torque while reducing the speed of a prime mover output shaft. This means that the shaft of a gearbox rotates at a slower rate than the input shaft. A gearbox can be set up to do the opposite and provide an increase in speed with a reduction of torque. Some of the simplest gearboxes merely change the rotational direction of power transmission. Many typical automobile transmissions include the ability to select one of several gear ratios, in this case, most of the gear ratios are used to slow down the output speed of the engine and increase torque
41.
Differential (mechanical device)
–
In automobiles and other wheeled vehicles, the differential allows the outer drive wheel to rotate faster than the inner drive wheel during a turn. This is necessary when the vehicle turns, making the wheel that is traveling around the outside of the turning curve roll farther and faster than the other, the average of the rotational speed of the two driving wheels equals the input rotational speed of the drive shaft. An increase in the speed of one wheel is balanced by a decrease in the speed of the other, when used in this way, a differential couples the input shaft to the pinion, which in turn runs on the ring gear of the differential. This also works as reduction gearing, on rear wheel drive vehicles the differential may connect to half-shafts inside an axle housing, or drive shafts that connect to the rear driving wheels. Front wheel drive tend to have the pinion on the end of the main-shaft of the gearbox. There are individual drive-shafts to each wheel, non-automotive uses of differentials include performing analog arithmetic. The ball was painted black and white in hemispheres, and graphically showed the phase of the moon at a point in time. See also the Chinese South-pointing chariot, an equation clock that used a differential for addition was made in 1720. In the 20th Century, large assemblies of many differentials were used as analog computers, calculating, for example, however, the development of electronic digital computers has made these uses of differentials obsolete. Practically all the differentials that are now made are used in automobiles, there are many claims to the invention of the differential gear, but it is possible that it was known, at least in some places, in ancient times. Some historical milestones of the include,100 BC–70 BC. Some such chariots may have used differential gears,658,666 AD, two Chinese Buddhist monks and engineers create south-pointing chariots for Emperor Tenji of Japan. 1720, Joseph Williamson uses a gear in a clock. 1810, Rudolph Ackermann of Germany invents a four-wheel steering system for carriages,1827, modern automotive differential patented by watchmaker Onésiphore Pecqueur of the Conservatoire National des Arts et Métiers in France for use on a steam wagon. 1832, Richard Roberts of England patents gear of compensation, a differential for road locomotives,1874, Aveling and Porter of Rochester, Kent list a crane locomotive in their catalogue fitted with their patent differential gear on the rear axle. 1876, James Starley of Coventry invents chain-drive differential for use on bicycles,1897, first use of differential on an Australian steam car by David Shearer. 1958, Vernon Gleasman patents the Torsen dual-drive differential, a type of differential that relies solely on the action of gearing, instead of a combination of clutches. An epicyclic differential can use epicyclic gearing to split and apportion torque asymmetrically between the front and rear axles, an epicyclic differential is at the heart of the Toyota Prius automotive drive train, where it interconnects the engine, motor-generators, and the drive wheels
