A Pitman arm is a shaft that translates rotary or angular movement into linear movement, or vice versa. Pitman arms are commonly found in water pumping windmills, automotive steering systems, and sewing machines.
In windmills, the Pitman arm connects the driving gear to the pumping arm. It translates the rotary power from the wind blades to the up-and-down motion of the pumping arm.
In automotive or truck steering systems, the Pitman arm acts as a linkage attached to the steering box (see recirculating ball) sector shaft, it converts the angular motion of the sector shaft into the linear motion needed to steer the wheels. The arm is supported by the sector shaft and supports the drag link or center link with a ball joint. It transmits the motion it receives from the steering box into the drag (or center) link, causing it to move left or right to turn the wheels in the appropriate direction. The idler arm is attached between the opposite side of the center link from the Pitman arm and the vehicle's frame to hold the center or drag link at the proper height.
"Pitman arm" can also refer to a component in a treadle sewing machine that connects the foot pedal to the crankshaft of the lower flywheel. In this case, the Pitman arm works similarly to a connecting rod in an engine in which the up and down force applied at one end of the arm translates to pushing and pulling alternately on the eccentric part of the crankshaft to achieve continuous rotation of the crankshaft and flywheel. The bearing connecting the Pitman arm to the crankshaft is known as the Pitman bearing. Early Pitman arms (up until around 1905) were made of wood, whereas later Pitman arms were made of steel. Wooden Pitman arms usually employed a simple wooden bushing around a steel shaft at both ends. The later steel Pitman arms usually used a ball joint at the lower pivot point and a ball bearing for the Pitman bearing at the top.
A crankshaft is a mechanical component used in a piston engine to convert the reciprocating motion into rotational motion. The crankshaft is a rotating shaft containing one or more crankpins, that are driven by the pistons via the connecting rods.
A bearing is a machine element that constrains relative motion to only the desired motion and reduces friction between moving parts. The design of the bearing may, for example, provide for free linear movement of the moving part or for free rotation around a fixed axis; or, it may prevent a motion by controlling the vectors of normal forces that bear on the moving parts. Most bearings facilitate the desired motion by minimizing friction. Bearings are classified broadly according to the type of operation, the motions allowed, or the directions of the loads (forces) applied to the parts.
Steering is the control of the direction of locomotion.
A crank is an arm attached at a right angle to a rotating shaft by which circular motion is imparted to or received from the shaft. When combined with a connecting rod, it can be used to convert circular motion into reciprocating motion, or vice versa. The arm may be a bent portion of the shaft, or a separate arm or disk attached to it. Attached to the end of the crank by a pivot is a rod, usually called a connecting rod (conrod).
A connecting rod, also called a 'con rod', is the part of a piston engine which connects the piston to the crankshaft. Together with the crank, the connecting rod converts the reciprocating motion of the piston into the rotation of the crankshaft. The connecting rod is required to transmit the compressive and tensile forces from the piston. In its most common form, in an internal combustion engine, it allows pivoting on the piston end and rotation on the shaft end.
Recirculating ball, also known as recirculating ball and nut or worm and sector, is a steering mechanism commonly found in older automobiles, off-road vehicles, and some trucks. Most newer cars use the more economical rack and pinion steering instead, but some upmarket manufacturers held on to the design until well into the 1990s for the durability and strength inherent in the design. A few, including Chrysler, General Motors and Lada, still use this technology in certain models including the Jeep Wrangler and the Lada Niva.
A drag link converts rotary motion from a crank arm, to a second bellcrank, usually in an automotive steering system.
Reciprocating motion, also called reciprocation, is a repetitive up-and-down or back-and-forth linear motion. It is found in a wide range of mechanisms, including reciprocating engines and pumps. The two opposite motions that comprise a single reciprocation cycle are called strokes.
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.
In an automobile, ball joints are spherical bearings that connect the control arms to the steering knuckles, and are used on virtually every automobile made. They bionically resemble the ball-and-socket joints found in most tetrapod animals.
A swashplate, also known as slant disk, is a mechanical engineering device used to translate the motion of a rotating shaft into reciprocating motion, or vice versa. The working principle is similar to crankshaft, Scotch yoke, or wobble/nutator/Z-crank drives, in engine designs. It was originally invented to replace a crankshaft, and is one of the most popular concepts used in crankless engines. It was invented by Anthony Michell in 1917.
In a reciprocating engine, the dead centre is the position of a piston in which it is either farthest from, or nearest to, the crankshaft. The former is known as top dead centre (TDC) while the latter is known as bottom dead centre (BDC).
Marles steering gear was an hour-glass-and-roller steering gear for mechanically propelled vehicles invented by British inventor and businessman Henry Marles (1871-1955) who also gave his name to his joint-venture Ransome & Marles a major British ball-bearing manufacturer. Aside from ease of use Marles' steering's great appeal to drivers was its lack of backlash.
A parallelogram steering linkage is called such because like its name sake the two sides of the linkage run parallel to each other and are equal in distance. This type of steering linkage uses four tie rods, one inner and one outer on each side that are connected by an adjustment sleeve, a center link, an idler arm on the passenger side, and a pitman arm on the driver side. The pitman arm attaches to the steering gear output shaft which is also commonly called the pitman shaft. The pitman arm attaches to the center link and is moved by turning the steering wheel. The center link bar transfers the movement from the pitman arm and pitman shaft to the idler arm on the passenger side. The inner tie rods are mounted to the center link and transfer steering motion to the steering arms and outer tie rods. All of the joints which mount these components are constructed of small ball and socket joints to provide the necessary freedom of movement required to maintain control over the vehicle while it is in motion. The most common type of steering is the parallelogram. The cross-steer and Haltenberger linkage designs are used on some trucks and vans.
A mechanical joint is a section of a machine which is used to connect one or more mechanical part to another. Mechanical joints may be temporary or permanent; most types are designed to be disassembled. Most mechanical joints are designed to allow relative movement of these mechanical parts of the machine in one degree of freedom, and restrict movement in one or more others.
The Lanchester Fourteen Roadrider is a six-cylinder automobile introduced by the Lanchester Motor Company in the beginning of September 1936. It was named "Roadrider" for its special suspension features, and billed as the lowest-priced six-cylinder Lanchester ever offered. This car replaced the previous 12 hp Light Six model with a larger six-cylinder engine again in the Lanchester Eleven chassis and body.
The Michel engine was an unusual form of opposed-piston engine. It was unique in that its cylinders, instead of being open-ended cylinders containing two pistons, were instead joined in a Y-shape and had three pistons working within them.
Their new Daimler 22 horsepower full-size luxury car was first displayed by Daimler in April 1902 at The Automobile Club’s Exhibition in London's Agricultural Hall. Daimler had elected to drop their multiple old low powered designs and restrict themselves to this 22 horsepower and a pair of 9 or 12 horsepower cars to the same design as the 22 but more lightly constructed. The King’s not quite finished new Daimler 22 was reported to be the chief attraction of the show.
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.
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