Motorworld’s newspaper №85
René-Gillet company had a big role in the history of French semi-track motorcycles. July 31, 1931 André Maginot, French Minister of War, asked René Gillet to test two off-road motorcycles. On April 10, 1933, Colonel Mammessier received a letter from René-Gillet with the results of tests: “As a response to your letter, we had the opportunity to present our prototype on March 30, 1933 to General Bally and the staff of the Research Inspection Service & Technical Experiments of Artillery. General Bally asked us to make important changes to the first prototype and use them during the design of the second prototype. We are engaged in this work it should improve the construction. As soon as we can, we will deliver both prototypes.” The machine, built at the request of the Ministry of Defense, is worthy of the title of the monster Frankenstein: a monster with three caterpillars, which replaced the wheels, weighed 600 kg. General Bally, aware of the non-viability of such a design, asked for changes and on December 13, 1933, René-Gillet presented the second prototype. It was a motorcycle with a J-type engin carried forward by 20 cm to shift the center of gravity.
The first test of a new 100 kg machine was conducted on January 4, 1934. The machine was full of bad luck: the caterpillar was torn, the engine lacked traction, and it constantly overheated, it was necessary to stop every 10 km and wait until it cooled. The average speed in the 6 km section was 25,714 km / h, the maximum was 36 km / h. It would take a long time to complete the design, but the company René-Gillet was busy with a lot of military orders and the tests were stopped on January 25, 1934.
In the second half of the 1930s, two more crawler motorcycles appeared. In April 1935 appeared “La Courtot” (“Palace”), designed by Henri Drescr. He used a 1000-cc engine of his own design. Caterpillars were made of rubber, turns were executed via braking the caterpillar treads. The machine weighing 503 kg consumed 12 times more fuel than the 750-cc Terrot . The motorcycle was not put into mass production.
The second crawler motorcycle was presented by the Swiss inventor Adrien Mercier. The Mercier factory was located in France and was producing 50-cc mopeds with Lavalette engines, as well as 125/175-cc motorcycles with French Ydral engines. Since 1932, Mercier has been developing crawler motorcycles prototype in the small French town of Bois-Colombes, France. The military conducted the first test of Mercier’s invention on February 9, 1937 on a hilly terrain with a steepness of ascent to 45% (27 degrees).
The Mercier crawler motorcycle was equipped with a 350-cc OHV JAP engine around which the basic design of the machine was concentrated. Rating of the JAP engine was 10 hp. at 3000 rpm which allowed moving at a comfortable speed up to 65 km/h. Additional cooling of the cylinder head was provided by a fan, which was driven by the engine.
The Mercier crawler motorcycles were started with a kick starter, which could be reached even while riding a motorcycle. Motorcycles were equipped with a three-speed gearbox with manual gear shifting, produced by the French company Soyer.
The front part was a complicated construction with rubber 150 mm wide caterpillars and a suspension realized with semi-elliptic springs. The first prototype had a large armoured shield, because of which the motorcycle couldn’t ride through the dirt. The rear part of the motorcycle turned out to be quite long and simple. To the tubular frame were fastened: a saddle, footboards, a petrol tank and a 270/90 rear wheel.
Despite the problems of the prototype, the military found the prototype interesting and useful but didn’t order the motorcycle in industrial quantities.
Tests of the modified prototype No. 2 began on May 9, 1939, but the machine lost several rubber linings and the tests were resumed only on July 4th. Mercier was compared with the standard army motorcycle Sevitame. On the 147 km route consisting of bad roads Sevitame was slightly faster – 75 km/h against 66 km/h on the Mercier. The passability of Mercier was much better, but it was needed more fuel: 17.6 litres / 100 kilometres compared to 10 litres / 100 kilometres at Sevitame. Another problem was overcoming 1.2 m mud trench. The Mercier caterpillar got bogged down, while the light Sevatime overcame the ford. Despite these problems, the military recommended the production of a crawler motorcycle with a 540-cc Aubier Dunne engine but asked for some improvements.
Adrien Mercier refused production of the third prototype because he said, “he spent a lot of energy and money”. On July 27, 1939, a possible serial production project of the Mercier crawler trike was closed.
|Years of manufacture||1937-1939|
|Quantity produced, units||less then 5|
|ENGINE AND TRANSMISSION|
|Type||Single cylinder, OHV|
|Engine capacity, cc||349|
|Bore and stroke, mm|
|Engine rating||10 hp at 3000 rpm|
|FRAME AND WHEELBASE|
|Frame type||Steel, tubular|
|Front suspension||Own design|
|Length, mm||2 250*|
|Height, mm||1 100*|
|Wheelbase, mm||1 385*|
|Ground clearance, mm||130*|
|Gas tank size, l||
|Maximum speed, km/h||