A clutch is a mechanical device that allows an output shaft to be disconnected from a rotating input shaft. The clutch's input shaft is typically attached to a motor, while the clutch's output shaft is connected to the mechanism that does the work.
Horsepower (hp) is a unit of measurement of power, or the rate at which work is done, usually in reference to the output of engines or motors. There are many different standards and types of horsepower. Two common definitions used today are the imperial horsepower as in "hp" or "bhp" which is about 745.7 watts, and the metric horsepower as in "cv" or "PS" which is approximately 735.5 watts.
Mechanical advantage is a measure of the force amplification achieved by using a tool, mechanical device or machine system. The device trades off input forces against movement to obtain a desired amplification in the output force. The model for this is the law of the lever. Machine components designed to manage forces and movement in this way are called mechanisms. An ideal mechanism transmits power without adding to or subtracting from it. This means the ideal machine does not include a power source, is frictionless, and is constructed from rigid bodies that do not deflect or wear. The performance of a real system relative to this ideal is expressed in terms of efficiency factors that take into account departures from the ideal.
In physics and mechanics, torque is the rotational analogue of linear force. It is also referred to as the moment of force. The symbol for torque is typically , the lowercase Greek letter tau. When being referred to as moment of force, it is commonly denoted by M. Just as a linear force is a push or a pull applied to a body, a torque can be thought of as a twist applied to an object with respect to a chosen point; for example, driving a screw uses torque, which is applied by the screwdriver rotating around its axis. A force of three newtons applied two metres from the fulcrum, for example, exerts the same torque as a force of one newton applied six metres from the fulcrum.
A machine is a physical system that uses power to apply forces and control movement to perform an action. The term is commonly applied to artificial devices, such as those employing engines or motors, but also to natural biological macromolecules, such as molecular machines. Machines can be driven by animals and people, by natural forces such as wind and water, and by chemical, thermal, or electrical power, and include a system of mechanisms that shape the actuator input to achieve a specific application of output forces and movement. They can also include computers and sensors that monitor performance and plan movement, often called mechanical systems.
A flywheel is a mechanical device that uses the conservation of angular momentum to store rotational energy, a form of kinetic energy proportional to the product of its moment of inertia and the square of its rotational speed. In particular, assuming the flywheel's moment of inertia is constant then the stored (rotational) energy is directly associated with the square of its rotational speed.
A tachometer is an instrument measuring the rotation speed of a shaft or disk, as in a motor or other machine. The device usually displays the revolutions per minute (RPM) on a calibrated analogue dial, but digital displays are increasingly common.
Dynamic braking is the use of an electric traction motor as a generator when slowing a vehicle such as an electric or diesel-electric locomotive. It is termed "rheostatic" if the generated electrical power is dissipated as heat in brake grid resistors, and "regenerative" if the power is returned to the supply line. Dynamic braking reduces wear on friction-based braking components, and regeneration lowers net energy consumption. Dynamic braking may also be used on railcars with multiple units, light rail vehicles, electric trams, trolleybuses, and electric and hybrid electric automobiles.
A speedometer or speed meter is a gauge that measures and displays the instantaneous speed of a vehicle. Now universally fitted to motor vehicles, they started to be available as options in the early 20th century, and as standard equipment from about 1910 onwards. Other vehicles may use devices analogous to the speedometer with different means of sensing speed, eg. boats use a pit log, while aircraft use an airspeed indicator.
A dynamometer or "dyno" is a device for simultaneously measuring the torque and rotational speed (RPM) of an engine, motor or other rotating prime mover so that its instantaneous power may be calculated, and usually displayed by the dynamometer itself as kW or bhp.
A cyclocomputer, cycle computer, cycling computer or cyclometer is a device mounted on a bicycle that calculates and displays trip information, similar to the instruments in the dashboard of a car. The computer with display, or head unit, usually is attached to the handlebar for easy viewing. Some GPS watches can also be used as display.
The mean effective pressure (MEP) is a quantity relating to the operation of a reciprocating engine and is a measure of an engine's capacity to do work that is independent of engine displacement. Despite having the dimension of pressure, MEP cannot be measured. When quoted as an indicated mean effective pressure (IMEP), it may be thought of as the average pressure acting on a piston during the different portions of its cycle. When friction losses are subtracted from the IMEP, the result is the brake mean effective pressure (BMEP).
A fluid coupling or hydraulic coupling is a hydrodynamic or 'hydrokinetic' device used to transmit rotating mechanical power. It has been used in automobile transmissions as an alternative to a mechanical clutch. It also has widespread application in marine and industrial machine drives, where variable speed operation and controlled start-up without shock loading of the power transmission system is essential.
A centrifugal clutch is an automatic clutch that uses centrifugal force to operate. The output shaft is disengaged at lower rotational speed and engages as the output increases to a certain speed. It is often used in mopeds, underbones, lawn mowers, go-karts, chainsaws, mini bikes, and some paramotors and boats to keep the engine from stalling when the output shaft is slowed or stopped abruptly, and to remove load when starting and idling. It has been superseded for automobile applications by the fluid coupling, torque converter and automated manual transmissions.
A water brake is a type of fluid coupling used to absorb mechanical energy and usually consists of a turbine or propeller mounted in an enclosure filled with water.
Brake-specific fuel consumption (BSFC) is a measure of the fuel efficiency of any prime mover that burns fuel and produces rotational, or shaft power. It is typically used for comparing the efficiency of internal combustion engines with a shaft output.
A torque amplifier is a mechanical device that amplifies the torque of a rotating shaft without affecting its rotational speed. It is mechanically related to the capstan seen on ships. Its most widely known use is in power steering on automobiles. Another use is on the differential analyser, where it was used to increase the output torque of the otherwise limited ball-and-disk integrator. The term is also applied to some gearboxes used on tractors, although this is unrelated. It differs from a torque converter, in which the rotational speed of the output shaft decreases as the torque increases.
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A chassis dynamometer, informally referred to as a rolling road or a dyno, is a mechanical device that uses one or more fixed roller assemblies to simulate different road conditions within a controlled environment, and is used for a wide variety of vehicle testing and development purposes.
This glossary of automotive terms is a list of definitions of terms and concepts related to automobiles, including their parts, operation, and manufacture, as well as automotive engineering, auto repair, and the automotive industry in general. For more specific terminology regarding the design and classification of various automobile styles, see Glossary of automotive design; for terms related to transportation by road, see Glossary of road transport terms; for competitive auto racing, see Glossary of motorsport terms.
