Hydrotor Cranking systems operate on the pricipal of oil under pressure turning a fluid power motor to produce mechanical energy. The oil is stored under high pressure in hydropneumatic piston accumulators and released to the hydraulic cranking motor through a directional control valve which may be manually or electrically actuated.
The high pressure oil enters the cranking motor through the inlet port and is directed against a series of free pistons within the steel rotor assembly which is splined to the drive shaft. When the pistons receive the pressurised oil they move forward against the inclined thrust bearing causing rotation of the rotor.
The drive shaft carries the Bendix drive which is engaged with the engine ring gear. The oil is returned to the system reservoir through the outlet port of the Hydrotor motor.