The first tests

Introduction of the first achievements

Because of the high expenses of maintenance of the locomotives and the important costs inherent in the use of steam traction (excessive cost of coal), the Company had the tests of transformation of the locomotives into Diesel tractors carried out in its various workshops. The pioneers in this field were those of the Charentes and Saône-et-Loire networks, who made the first machines, followed some time later by the Neuillé-Pont-Pierre network.

The technique consisted of removing the boiler and mechanism from the locomotive. However, the wheel sets and connecting rods were retained. After overhauling and possibly shortening the underframe, a drive axle was wedged to the centre axle and controlled by an inverter and gearbox connected to the engine, located under the front hood. A centre cab and a rear hood protecting the auxiliaries and the fuel tank completed the new machine. This arrangement was practically generalized on the whole fleet resulting from the transformations of steam locomotives. However, two units were built by Private Industry, the first by Thomson-Houston, at the instigation of the State, the second by Petolat, for the C.F.D.'s own needs.

The Thomson-Houston tractor

As early as 1924, the C.F.D. Company thought of replacing steam traction by combustion engine engines. At that time, electric transmission seemed to open up a wide range of possibilities and the State encouraged promoters in this direction by giving them subsidies. It was in this spirit that the C.F.D. received aid for the construction of a semi-diesel tractor with an electric transmission (Ward-Leonard system), intended for the towing of convoys of goods on the Vivarais network and built by Thomson-Houston in 1925.

Description of the Thomson-Houston tractor

The vehicle, mounted on bogies, was equipped with two driver's cabs, a baggage room and an engine room for the generator and auxiliaries.

The generator set consisted of a 120 HP, two-cylinder, valveless, semi-diesel engine running at 325/400 rpm and a four-pole, variable-voltage dynamo with a maximum voltage of 600 volts, capable of delivering 77 Kw of power. The current produced was directed to the four series-type traction motors of 40 HP each.

An auxiliary 8 HP semi-Diesel engine drove a 100 Volt dynamo which varied the excitation of the main dynamo via a joystick.

Starting was by means of an exhaust gas compression system in a special tank and by heating a set of cones, placed on the injection cylinders. The disadvantage of this system was the heating time, which required a minimum of ten minutes and forced the engine to run during parking to avoid the very rapid cooling of the cones. The generator assembly was mounted on a subframe in order to reduce vibrations.

The driver's cabs, which were very cramped, were placed in the two left corners of the vehicle. One was located near the auxiliary power unit and the other was inside the baggage compartment.

This thing was painted dark green with a yellow belt. Its registration and company monogram were painted yellow on the left and right inside corners of the body, respectively. The bumper cross members were painted vermilion red and bore the same markings.

Thomson-Houston Tractor Delivery and Assignments

Registered TH 1, it was delivered to Tournon on December 13, 1925. After being put on wheels, it was towed to Cheylard, but was the victim of several derailments during its transport. One noted, then, a bad inscription in the tight curves of the line. Having undergone in the workshops of the Cheylard, a modification to the suspensions of the bogies, he made his tests in the service of the maneuvers, towing trains of 1001, then in line, where he towed a convoy of 201 on a 30°/°°° ramp at a speed of 10 km/h. Despite its great flexibility, it proved insufficient to ensure continuous service on the network's hard lines. On the other hand, its heavy weight of 351 made the track unusually fatiguing.

In the service of manoeuvres where his use would have been justified, was an inconvenient practice due to the location of the driver's cabs which did not allow the driver to have a sufficient view when backing up. In addition, its noisy operation prevented the driver from hearing the signals of the marshals. Because of these drawbacks, it was parked in 1926 and handed over to the manufacturer. The latter, with the help of the State, had it shipped on the Breton Network on June 6, 1928, to carry out a series of tests.

source : MTVS 1989-1