TM 9-2330-390-14&P1-18. BRAKE SYSTEM.a.The brake system is a full air with wedge-type brake assemblies at each wheel. Brakeshoes are made ofa non-asbestos organic compound.b.Air to operate the brakes is supplied by the towing vehicle and is routed to the dolly set through theintervehicular and intradolly air hoses. Service supply lines are routed along the right side of the dolly set; emergencysupply lines are routed along the left side.c.The service brakes apply and release the brakes when the brake pedal in the towing vehicle is pressedduring normal driving. Air to apply the brakes is directed from the air reservoirs through the relay emergency valve(front dolly) and full function valve (rear dolly) to the airbrake chambers mounted at each wheel of front and reardollies.d.The parking brake system operates on the rear doily only. It applies and releases the parking brakeswhen the parking brake lever is operated. Spring fail-safe airbrake chambers, mounted piggyback to the serviceairbrake chambers on the rear dolly, allow functioning of the parking brake system.(1)Parking brakes are applied by a large spring in the spring fail-safe airbrake chambers. The spring isnormally retracted by air pressure.(2)When the parking brake lever is raised, air pressure is removed from behind the spring and theparking brakes apply.(3)Parking brakes are released by restoring air pressure to the spring fail-safe airbrake chambers toretract the spring.e.The emergency breakaway system stops the dolly set by applying the brakes in the event that theemergency supply line from the towing vehicle is severed during a breakaway.f.With both the parking and emergency breakaway systems, loss of air pressure causes brakes to apply.Restoration of air pressure allows brakes to release. Brakes that have been applied due to air pressure loss can bemanually released (caged) to allow movement of the dolly set.g.Major components of the brake system include the following:1-33
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