Abstract
The Italian State Railways (F.S.) have in service 150 two-and three-axle diesel shunting locomotives equipped with hydrostatic transmission, powered at rates from 150 to 450 hp.
In these locomotives some operating characteristics give better performance than locomotives equipped with hydrodynamic transmissions, specifically: easy running reversibility; high flexibility factor which allows elimination of the slow-fast running gears and simplicity of installation.
Other theoretical advantages of hydrostatic transmission were found to be unimportant in practice, for example: initial loss of power due to the transmission increases remarkably with service and the braking action is limited by the overrunning of the diesel engine.
Disadvantages of the hydrostatic transmissions in service are: the ‘rigid’ connection between the engine and the axles and the absence of ‘coasting’; the maintenance costs of the transmission increase more than linearly with power ratio.
In conclusion, the experience of the F.S. with hydrostatic transmission units shows that this type of transmission can be competitive in the field of diesel power of less than 150 kW.
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