Straight Air Brakes
The straight air brake system is typically used on heavy-duty commercial vehicles and trailers. Components of the air brake system for trailers are contained within the trailer structure and consist of appropriate compressed air storage tank(s), control valves, and hoses to support the number and capacities of the axles used.
Air chambers located on the trailer axles incorporate heavy springs to mechanically apply the trailer brakes for emergency situations and parking. These spring brakes must be released via compressed air in order to move the trailer. The spring brake release system is controlled separately from the service brake system and uses separate valves and hoses, though the air source may be common. The towing vehicle supplies compressed air to the trailer storage tank(s) and a modulated control signal through gladhand hose connections mounted on the trailer and tow vehicle.
The operator must first release the parking brakes, this occurs when compressed air is supplied to the trailer system. Once in motion, when the operator applies the tow vehicle service brakes, the tow vehicle air brake system provides a signal pressure in proportion to the tow vehicle’s service brake pressure. The trailer control valve receives this signal and compressed air from the trailer-mounted storage tank, modulated by the trailer control valve(s), is applied to the air chambers on the trailer axles. The air chambers exert mechanical force to apply the trailer service brakes.
Typical applications for straight air brakes are medium and heavy-duty tractor-drawn vans and flat trailers as well as equipment and special purpose trailers. ABS is required by federal statute 571.121. The trailer brakes may be applied independently of the tow vehicle brakes. The spring brakes apply braking force in the event air pressure is lost or the trailer becomes uncoupled from the tow vehicle.
ABS
An Antilock Braking System (ABS) is a sub-system designed to modulate the braking force at the vehicle wheels to prevent the wheels from sliding. The system monitors the rotational speed of the wheels on one or all axles, depending on the system specified, and automatically modulates brake pressure to give the most available braking force without the loss of wheel rotation and the resultant loss of control and tire flat spotting. ABS allows for maximum effort braking on slippery surfaces to bring the vehicle to a safe, controlled stop. The system is available in single or all axle configurations.