Updated: 11 June 2004
Friction-drive locomotives are rare, probably because having one frictional interface of doubtful dependability, between wheel and rail, is quite enough uncertainty for most people. Adding an extra one could be regarded as looking for trouble. The other friction-drive locomotives in the Museum, the Fontaine and the Holman, have not enhanced the reputation of the type; the first was wholly misguided and the second appears to have been of more interest to the criminologist than the engineer.
This rather rare beast, however, appears to be an honest if slightly misguided piece of engineering.
Left: The friction-drive engine "Fasolt". It was designated type D7, No 451
The aim here was the same as that of geared locomotives- to make a slow locomotive relatively powerful by operating the cylinders at a faster speed (giving more power for the same boiler pressure) than the driving wheels, there being a practical limit to how small the driving wheels could be made.
To this end the cylinders drove three coupled crankshafts placed above the driving wheels; these crankshafts carried small friction rollers that contacted the top of the driving wheel tyres. A system of springs pressed the friction rollers onto the wheels, and were adjustable so the vertical force could actually be greater than the adhesion weight on the track. The friction rollers could be lifted clear of the wheels if it became necessary to tow the locomotive.
The reduction ratio is unknown, but working from the picture above, and estimating the size of the friction rollers, it appears to be about 1:3. The design speed was only 10 km/hr.
Information is scanty but it appears that the friction mechanism gave trouble, though whether by slipping or in some more subtle way is not clear. The locomotive was later rebuilt to a more conventional form by removing all but the central upper crankshaft and coupling it with rods to the wheel beneath. This in turn was coupled to the other wheels by conventional coupling rods. In 1906 the locomotive was still in existence, as No 2044, but after that its fate is unknown.