The results obtained in service of the 400 HP diesel locomotive are as follows

The results obtained in service of the 400 HP diesel locomotive are as follows

The advantages of transmission

The 2x200hp Diesel locomotive was designed for the operation of a low traffic branch line in the South East Region of the S.N.C.F.

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Commissioning of the 400 hp diesel locomotive

Its first model could be put into service immediately, all its components having been tested on single-engine tractors. It tows daily trains of 200 tons; with this tonnage it climbs continuous 15°/00 ramps in 3rd gear at about 20 km/hour.

Tests conducted on the dynamometer car showed that the rim force at start-up was approximately 9 t and that, when the wheels reached the limit of adhesion, they did not run out of control. They spin at a very low speed of 3 km/h, corresponding to 1re engine idling speed; at this low speed the wheel-to-rail friction coefficient remains good and the hook load is maintained at around 8 t.

The privilege of choosing the transmission

This gives the mechanical transmission an advantage over electric or hydraulic transmissions, with which the axles tend to overrun when slippage occurs. For the same tonnage, the locomotive with mechanical transmission has the best traction of all locomotives.


These tractors can be equipped with hydraulic couplings, but, without couplings and for normal services on branch lines, the clutches resist well because the conventional regulator of the injection pump has been slightly modified and has a starting position which is such that the engine in this position has a stable speed between 500 and 600 rpm and can provide at this speed a torque close to the torque corresponding to 1re speed at the limit of adhesion. Thanks to this artifice, the engine starts at idle and in the most difficult conditions, the clutch slips only for a few seconds and at low revs.


Positive clutch control provides a high degree of precision during manoeuvring that can hardly be matched with other modes of transmission.

On the other hand, on gradients - and where the track service permits - it very often runs at 70 km/h, although its greatest multiplication corresponds to 55 km/h.


Its commercial speed is 27 km/h - and it travels between 120 and 140 km per day - with a fuel consumption of about 150 litres per 100 km, including shunting.

It has been checked that gear shifting is always absolutely silent, regardless of the locomotive's operation and the speed selected.

A machine that performs the program well, having been fixed

Based on the main components of the locomotive described above, it is possible to produce a range of machines to meet various requirements.

1° Hydraulic couplers may be interposed between the motors and the clutches, especially if the locomotive is to be used to manoeuvre heavy trains.

These couplings have no other drawbacks than increasing the price and reducing the efficiency of the transmission by 2 to 4%.

2° The 200 hp engines can be replaced by 300 hp engines, the transmission being able to accept this power.

3° In order to increase the grip, the number of axles of a twin-engine can be increased to 4, while leaving them "independent"; this results in a specialized tractor for large station manoeuvres.

A locomotive of this type, with a power of 600 hp, is already in the process of being built.

Fig. 14. - 1,200 hp, 60-ton diesel locomotive for normal track.
Fig. 14. - 1,200 hp, 60-ton diesel locomotive for normal track.

Moreover, the construction principle of these tractors allows, by using the same elements, to build more powerful tractors, by multiplying the number of engines.

The diagram above (Fig. 14) shows the layout of a 1,200 hp four-axle, 300 hp engine with four driving axles giving a grip of 60 to 70 tonnes. In this case, it seems advantageous to use hydraulic couplers in order to keep the advantage of soft starts while significantly increasing the multiplication of the transmission, so that this powerful locomotive is able to achieve a speed of 70 to 80 km/hr.

The above discussion shows that by using a single type of :

  • axle boxes,
  • axles,
  • axle attacks,

By using :

  • gearboxes with free wheel,
  • clutches,
  • gimbals,
  • of the couplers,
  • engines (200 and 300 hp),
  • multi-element radiators,

For serial use

Already built in series, the whole range of tractors from 200 hp up to 1,200 hp, required for the operation of branch lines, can be realized.

Series production would make it possible to lower the price of these components to the point where their cost price is much lower than the price of current "railway" parts. A depot with a reduced stock of these parts could service all tractors regardless of power.

The staff of this repository would also be efficient since they would maintain identical organs and would be familiar with their particularities and development.

Operators could be more easily transferred from a powerful machine to a lighter machine if the needs of the service require it, as their driving style is identical.

The possibility of starting only the necessary number of motors allows to use, if necessary, with a suitable efficiency, a large multi-motor machine for light rail trailer, also in case of high foot traffic

Finally, it is advisable not to underestimate the significant advantage, of multi-engine engines which can almost always, in the event of damage, continue their course with reduced power and thus avoid an expensive reserve.

It would seem that the simple means, described above, developed on the scale of the secondary lines, should make it possible to lower the cost price per tonne-kilometre to such an extent that an adjustment of fares could allow traffic to be recovered. The secondary lines would thus resume their true role as collectors of main lines.

source : Excerpt from the Revue Générale des Chemins de fer N° of September 1950

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