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Relay Valve
A relay valve is an air-operated valve typically used in Air brake (road vehicle), air brake systems to remotely control the brakes at the rear of a heavy truck or semi-trailer in a tractor-trailer combination. Relay valves are necessary in heavy trucks in order to speed-up rear-brake application and release, since air takes longer to travel to the rear of the vehicle than the front of the vehicle, where the front service brakes, foot-valve, parking-control valve, and trailer-supply valve (if applicable) are located. Without relay valves, it would take too long for sufficient air to travel from the brake pedal valve to the rear of the truck or trailer in order to apply the rear service brakes concurrently with the front service brakes, resulting in a condition known as brake lag. To correct this condition on a long-wheel-base vehicle, a relay valve is installed near the rear service brake chambers. In tractors as well as straight-trucks, a remote air-supply is provided in the form of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Air Brake (road Vehicle)
An air brake or, more formally, a compressed-air-brake system, is a type of friction brake for vehicles in which compressed air pressing on a piston is used to apply the pressure to the brake pad or brake shoe needed to stop the vehicle. Air brakes are used in large heavy vehicles, particularly those having multiple trailers which must be linked into the brake system, such as trucks, buses, trailers, and semi-trailers, in addition to their use in railroad trains. George Westinghouse first developed air brakes for use in railway service. He patented a safer air brake on March 5, 1872. Westinghouse made numerous alterations to improve his air pressured brake invention, which led to various forms of the automatic brake. In the early 20th century, after its advantages were proven in railway use, it was adopted by manufacturers of trucks and heavy road vehicles. Design and function Air brakes are typically used on heavy trucks and buses. Typical operating pressure is approximatel ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Semi-trailer
A semi-trailer is a trailer without a front axle. In the United States, the term is also used to refer to the combination of a truck and a semi-trailer; a tractor-trailer. A large proportion of a semi-trailer's weight is supported by a tractor unit, or a detachable front-axle assembly known as a dolly, or the tail of another trailer. The other portion of the semi-trailer's weight is semi-supported (half-supported) by its own wheels, which only support the rear of the semi-trailer. A semi-trailer is normally equipped with landing gear (legs which can be lowered) to support it when it is uncoupled. Many semi-trailers have wheels that are capable of being totally dismounted and are also relocatable (repositionable) to better distribute load to bearing wheel weight factors. Semi-trailers are more popular for transport than full trailers, which have both front and rear axles. Ease of backing is cited as one of the semi's chief advantages. A road tractor coupled to a semi-trailer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tractor-trailer
A semi-trailer truck, also known as a semitruck, (or semi, eighteen-wheeler, big rig, tractor-trailer or, by synecdoche, a semitrailer) is the combination of a tractor unit and one or more semi-trailers to carry freight. A semi-trailer attaches to the tractor with a type of hitch called a fifth wheel. Regional configurations Europe The noticeable difference between tractor units in Europe and North America is that almost all European models are cab over engine (called "forward control" in the UK), while the majority of North American trucks are "conventional" (called "normal control" or "bonneted" in the UK). European trucks, whether straight trucks or fully articulated, have a sheer face on the front. This allows shorter trucks with longer trailers (with larger freight capacity) within the legal maximum total length. Furthermore, it offers greater maneuverability in confined areas, a more balanced weight-distribution, and better overall view for the driver. The ma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Brake Pedal
Car controls are the components in automobiles and other powered road vehicles, such as trucks and buses, used for driving and parking. While controls like steering wheels and pedals have existed since the invention of cars, other controls have developed and adapted to the demands of drivers. For example, manual transmissions became less common as technology relating to automatic transmissions became advanced. Earlier versions of headlights and signal lights were fueled by acetylene or oil. Acetylene was preferred to oil, because its flame is resistant to both wind and rain. Acetylene headlights, which gave a strong green-tinted light, were popular until after World War I; even though the first electric headlights were introduced in 1898 (and those were battery-powered), it wasn't until high-wattage bulbs and more powerful car electrical generating systems were developed in the late 1910s that electric lighting systems entirely superseded acetylene. Steering The first automob ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 is a force that opposes the relative lateral motion of two solid surfaces in contact. Dry friction is subdivided into ''static friction'' ("stiction") between non-moving surfaces, and ''kinetic friction'' between moving surfaces. With the exception of atomic or molecular friction, dry friction generally arises from the interaction of surface features, known as asperities (see Figure 1). *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 elements making up a so ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hand Brake
In road vehicles, the parking brake, also known as a handbrake or emergency brake (e-brake), is a mechanism used to keep the vehicle securely motionless when parked. Parking brakes often consist of a cable connected to two wheel brakes, which is then connected to a pulling mechanism. In most vehicles, the parking brake operates only on the rear wheels, which have reduced traction while braking. The mechanism may be a hand-operated lever, a straight pull handle located near the steering column or a foot-operated pedal located with the other pedals. Overview While most automatic transmission vehicles have parking brakes, it is often not engaged by American drivers when parking. However, it is recommended to use it, as the parking pawl in the gearbox could fail due to stress or another vehicle striking the car, causing the car to roll. In manual transmission vehicles, the parking brake can be engaged to help keep the vehicle stationary. When parking on an uphill gradient, it is reco ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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