Above-cab Carrier
A platform above the cab that can be in a fixed or hydraulically adjustable position for transporting vehicles.
Accessory Load Electrification
The conversion of common vehicle accessory loads (power steering, power brakes, air conditioning, air compressor, etc.) from being engine-driven (belts or gearing) to being driven by electric motors. Electrically driven systems can be optimized to operate at a fixed speed, thereby increasing efficiency and making them compatible with hybrid vehicle propulsion systems.
Accumulator (Hydraulic)
An energy storage device in which a volume of non-compressible hydraulic fluid is held under pressure by an external source. Compressed gas is the most common external source used in vocational truck applications.
AF (Axle-to-Frame)
The distance from center of rear axle(s) to end of frame. See Chassis Dimensions.
Air Dam
Flexible air deflecting panel usually located below the radiator support.
Air Resistance
A measure of the “drag” on a vehicle moving through air. Air resistance increases as a square of the speed, thus power requirements increase much faster than vehicle speed.
Alternative Drive Systems
Any vehicle drive (propulsion) system other than a conventional internal combustion/mechanical transmission system. The most common systems are straight electric, hybrid electric and hybrid hydraulic drives.
Alternative Fuel
Any non-conventional fuel used to power a vehicle. In North America, conventional vehicle fuels are normally defined as gasoline and petroleum-based diesel. Alternative fuels currently in use or under development include:
- E-85 — A blend of 85% ethanol and 15% gasoline that is used to fuel E85-capable flexible fuel vehicles (FFVs), which are available in a variety of models from U.S. and foreign automakers.
- Biodiesel — A liquid fuel composed of fatty acid alkyl esters, fatty acid methyl esters or long-chain mono alkyl esters. It is produced from renewable sources such as new and used vegetable oils and animal fats, and is a cleaner-burning replacement for petroleum-based diesel fuel. It is normally blended with conventional petroleum-based diesel fuel for use.
- B-10 — A blend of 10% biodiesel and 90% petroleum-based diesel fuel.
- B-20 — A blend of 20% biodiesel and 80% petroleum diesel. B-20 is the most common biodiesel blend in the U.S. It provides substantial benefits but avoids many of the cold-weather performance and material compatibility concerns associated with B-100 (pure biodiesel).
- Compressed Natural Gas (CNG) — Natural gas is a mixture of hydrocarbons; predominantly methane (CH4). When used as transportation fuel, it is typically stored onboard a vehicle in tanks at high pressure (up to 3,600 PSI).
- Electricity — Electricity used to power pure electric vehicles (as opposed to electric hybrids) is generally provided by the electricity grid and stored in a vehicle’s battery. Fuel cells are being considered as a way to use electricity generated onboard the vehicle to power electric motors. Unlike batteries, fuel cells convert chemical energy from hydrogen to electricity (see Electric Drive Vehicle).
- Hydrogen —The simplest and most abundant element in the universe. The interest in hydrogen as an alternative transportation fuel stems from its clean-burning qualities, its potential for domestic production and the fuel cell’s potential for high efficiency (two to three times more efficient than gasoline vehicles).
- Liquefied Natural Gas (LNG) — Natural gas can be liquefied to store more energy onboard a vehicle in a smaller volume. To produce LNG, natural gas is purified and condensed into liquid by cooling to –260°F (–162°C). Since it must be kept at such cold temperatures, LNG is stored in double-wall, vacuum-insulated pressure vessels. LNG fuel systems are typically only used with heavy-duty vehicles. Propane — A three-carbon alkane gas (C3H8), also known as liquefied petroleum gas (autogas in Europe). Propane turns into a colorless, odorless liquid when stored under pressure inside a tank. As pressure is released, the liquid propane vaporizes and turns into gas that is used for combustion or that can be injected, under pressure, as a liquid fuel. An odorant, ethyl mercaptan, is added for leak detection.
Ambient Temperature
Surrounding air temperature.
Anchor Bar
Part of the tow sling or tow hitch that is placed under or against a vehicle to be towed. It must be fastened to the vehicle with two tow chains.
Approach Angle
(1) Ramp clearance angle for the front of a vehicle, measured from the forward edge of the front tire contact patch to the lowest part of the vehicle forward of the tire; (2) An angle made between the plane of the platform and the ground plane on a carrier body.
Auxiliary Engine
A small internal combustion engine carried on a vehicle to for purposes other than direct power. Typical uses include operation of refrigerator units, electric generators and welders, and vehicle-mounted equipment, such as cranes and aerial devices.
Auxiliary Equipment
Any equipment, in addition to the basic chassis, that is required for a piece of equipment/vehicle to perform its functions. For example, a winch would be auxiliary equipment for a tow truck.
Auxiliary Fuel Tanks
A type of drive axle in which the axle "floats" in the axle housing with all the truck weight and stress of the wheels on the housing, not the axle shaft.
Auxiliary Towing Lights
Stop, tail and turn-signal lights attached to the trailing end of the towed vehicle operated as part of the towing vehicle lighting system.
Auxiliary Transmission
A transmission with a limited number of speeds (usually two, three or four) that is mounted immediately in back of the main transmission. The auxiliary has its own control in the cab, and by using both transmissions the driver can get several times the number of forward speeds possible with just the main transmission. A five-speed main transmission with a three-speed auxiliary would give the driver 15 forward speeds.
Axle-Dead
A means of support for the wheels at each end. This is contrasted to a Live Axle, which is connected to the wheels and rotates with the wheels.
Axle-Drive
The axle that is connected to the truck engine and propels the truck.
Axle-Full Floating
A type of drive axle in which the axle “floats” in the axle housing with all the truck weight and stress of the wheels on the housing, not the axle shaft.
Axle-Live
A means of support for the wheels at each end that connects the wheels with members that rotate with the wheels.
Axle-Semi-floating
A type of drive axle in which the weight of the truck, with consequent load and wheel stress, is supported by the axle shaft.
Axle-Tandem Drive
Both axles of the tandem are driven by the vehicle engine.
Axle Rating
See GAWR.
