This engine embodies certain features, notably the Ricardo combustion head, adopted under licence from Mr. H. R. Ricardo.
Dealing with the 30 / 36 h.p. Kelvin-Ricardo, a poppet-valve unit, the cylinder diameter is 4 1/2 ins. and the piston stroke 6 3/8 ins. The normal speed is 820 r.p.m. when the engine is arranged for paraffin operation, or 700 r.p.m. if designed for running only on petrol. On this model, a vaporizer and carburettor, with air silencer, are provided for each pair of cylinders, and for exceptionally slow running provision is made for cutting out one pair of cylinders in order that the working cylinders may be better loaded and maintain vaporizing temperature.
The side valves, which are on the starboard side of the engine, are of Sil-chrome steel, and work in renewable cast iron bushes. Hand operated water regulation valves enable the cylinder jackets to be maintained at the desired temperature when the engine is running slowly or under light load.
The water pump is of the uniflow type, with bronze, cotton packed plunger, said to be sand resisting. An independent water pump is furnished for each pair of cylinders, whilst to maintain the lubricating oil supply a plunger pump is fitted within the crankcase. Kelvin-Ricardo marine petrol and petrol-paraffin engines range from 7 1/2 / 9 h.p. to 60 / 72 h.p.