Free-piston Engine for Vehicles
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INTERESTING developments in the application of the free-piston engine to commercial vehicles were foreshadowed last week by the Free Piston Engine Co., Ltd., Park Lane Works, Wolverhampton. An entirely new engine is taking shape and it will cover three power ranges-250 g.h.p., 125 g.h.p. and something under 100 g.h.p.
The likely dimensions of a 125 g.h.p. unit would be as follows: Cylinder bore, 3.66 in.; compressor cylinder bore. 10.15 in.; overall length, 3.66 ft.; stroke at continuous maximum rating, 4.65 in. per piston. The probable weight would be 452 lb., giving a power-weight ratio of 3.62 lb.-g.h.p.
Thermal efficiency of the gasifier at full load, based on g.h.p., is said to be of the ordeir of 42 per cent. Taking a turbine efficiency of 80 per cent., the engine thermal efficiency would be 33.6 per ,cent.
It is agreed that this figure is not so good as that of the modern oil engine, but when the figures are translated in terms of vehicle m.p.g., the simplified transmission requirements of the freepiston engine should have the effect of narrowing the gap,