Fell Diesel Mechanical Locomotive
Built by Adrian Ashford in September 2011 for the Festival of Britain Secretary’s Challenge
This is a model of what is described as a Diesel Express Locomotive in the October 1953 issue of Meccano Magazine. It is in fact based very closely on the experimental Fell Diesel Mechanical Locomotive which was completed at the Derby Works of British Railways in 1951 and entered service later that year, having been displayed with other new locomotives, as part of The Festival of Britain on the South Bank in London.
It was a bold attempt to build a main-line diesel locomotive with mechanical, as opposed to electric, transmission, with considerable savings in weight and the cost of a generator and electric motors. It was of a 4–8–4 wheel-arrangement (or 2-D-2 in diesel notation), based on a patented system of transmission proposed by Lt.-Colonel L. F. R. Fell, and developed by H. G. Ivatt, former C. M. E. of the London Midland Region of British Railways and Fell Developments Limited.
It was powered by four 500 b.h.p. engines, two at each end. Each pair drove the half shaft of a primary differential, via fluid couplings. The output of each primary differential was combined through a secondary differential, from which power was transmitted to the driving wheels through final reduction and reverse gears. This system enabled the engines to work together at different speeds. If used for shunting, it could work on only one engine, the combined ration of the two differentials giving a 4:1 reduction.
This model is driven by two Meccano Power Drive motors, one at each end. Each motor drives the half-shaft of a centrally-mounted spur differential, the cage of which drives a longitudinal shaft through a 1:1 belt drive; two worm gears on this shaft mesh with gears on the driving wheel axles. Thus the model can be run on one or both motors. Power is supplied from six AA-size batteries.
This was a very rewarding model to build; the instructions were very well written and easy to follow, and the model went together exactly as described, without any problems. Any minor changes made were to suit my own tastes. I used Narrow Strips for the coupling-rods(not available in 1953) and I also fitted a floor and bulk-head in the cabs, together with seats. As a point of interest, it couldn’t be built from the № 10 outfit, as it uses 28 1” Corner Brackets!