Examples of machines using hydro-mechanical transmissions

The use of Asynchro transmission

The Asynchro transmission has been used on a large number of tractors, locomotives or railcars such as 200 hp SNCF type tractors, 640 hp - 55 tons bogie locomotive, 800 -1200 hp locomotive.

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The 200 hp tractors, type S.N.C.F.

1 6-cylinder Poyaud engine, 1500 rpm, set at 207 hp.

The transmission used includes :

  • 1 hydraulic coupler 23?
  • 1 B.V. 8 speeds giving the following combinations :
  • 1st Speed 5.8 km/h
  • 2nd " 8.2 km/h
  • 3rd " 11.5 km/h
  • 4th " 16.5 km/h
  • 5th " 23 km/h
  • 6th " 33 km/h
  • 7th " 46 km/h
  • 8th " 66 km/h
  • 1 reverser-gearbox attacks by chain the 2 axles.

This tractor, which weighs 32 T., is designed for manoeuvring and servicing low-traffic lines over medium distances.

a bogie locomotive 640 hp - 55 tons

  • 1 12-cylinder Poyaud engine, 600 hp at 1500 rpm.
  • 1 coupler 26?.
  • 1 BV. 8 speeds.

This locomotive, as a result of the coupling of the 4 axles, has full adhesion. Moreover, the wheels, in case of slippage, cannot run away if the precaution is taken to set the engine at 1high idle speed.

As the peripheral speed of the wheels is low, the rolling coefficient remains good and sanding is efficient.

It is used for hill-climbing, station manoeuvres and branch line services.

On an experimental basis, it has been noted that loads of 1000 tonnes on a 10 o/00 gradient (65 wagons) could be easily mounted in 3rd gear at 1450 rpm, i.e. 11.4 km/h, i.e. a rim power of 520 hp, corresponding to an overall efficiency of the transmission and bearing of

The figure of 570 hp corresponds to the power of the engine at 1450 rpm, i.e. 600 hp from which 30 hp of auxiliary power has been deducted.

The absolutely complete transmission (coupler, gearbox, control, cardan shafts and axle drive) weighs 3.900 kg.

The locomotive 800 -1200 hp

This locomotive, which weighs 68 tons, can be equipped either with 2 400 hp engines (M.G.O. 8 cylinders or non-supercharged 12-cylinder Poyaud) or with 2 supercharged 12-cylinder Poyaud engines with a unit power of 600 hp.

Each engine drives a 26? hydraulic coupler and an 8-speed gearbox identical to that of the 600 hp single-engine.

Each of the 4 axles carries a reversing bridge connected to the gearboxes by cardan shafts.

This locomotive, with a maximum speed of about 80/90 km/h, is used for humping, throwing and medium line services.

It has a central cabin with 2 driver's cabs. It is designed for curves up to 80 metres long.

It should be noted that this twin-engine tractor has exactly the same double transmissions as the 600 hp. This results in a very significant maintenance saving when the same fleet uses both 600 hp and 1200 hp.

It should be noted that these 3 types of machines can be built in metric and wide gauge.

The Autorails

The Asynchro transmission is particularly designated as a railcar transmission. It is light, space-saving and efficient, and its automatic control allows several vehicles to be driven with a single operator.

It is currently very popular for 425/450 hp and 825 hp railcars.

The 425/450 hp transmission has a gearbox arranged like the engine, under the floor of the railcar. It has 6 gears giving the graduation :

  • 1st gear 27 km/h
  • 2nd " 37 km/h
  • 3rd " 50 km/h
  • 4th " 67 km/h
  • 5th " 92 km/h
  • 6th " 125 km/h

This gearbox includes a reverser with cylindrical gears.

It can be equipped with either a semi-automatic or an automatic control system, making it possible to drive several coupled units by a single operator.

The speed range is:

  • 1st Speed 25 km/h
  • 2nd " 33 km/h
  • 3rd " 41 km/h
  • 4th " 52 km/h
  • 5th " 68 km/h
  • 6th " 86 km/h
  • 7th " 110 km/h
  • 8th " 140 km/h

The output of the gearbox starts a reverse descent which drives fixed axles on each axle of a bogie by cardan shafts.

This type of transmission is also suitable for the construction of a 1600 hp twin-engine B.B. locomotive.

Given the good performance of the Asynchro gearbox, such a locomotive has the same operating characteristics as an 1800 hp electric transmission.

All these machines have an excellent grip: as the starting is done at low speed, the gear ratio is very high and the wheels that have reached the limit of grip turn slowly and cannot get out of grip. The coefficient of friction between rail and wheel therefore remains very high, and sandblasting makes it possible to stop the beginning of slippage without the need to significantly reduce engine regulation.

Currently, the S.N.C.F. has in service and on order more than 160 200 hp locomotives and 30 640 hp locomotives. These orders were placed after 3 to 4 years of testing on machines equipped with "Asynchro" transmissions.

source : Article "Hydro-mechanical transmissions for railcars and high-power diesel locomotives" by Pierre ZENS, engineer.

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