1113111
Vincent T5AM 500cc Marine Engine
Engine
44
1944-01-01

500cc opposed piston lifeboat engine.

(Text by Kim Siddorn whoi donated).

The Vincent Marine Engine 

A classic example of being conceived in good time but born too late, the Vincent marine engine was originally made for an air/sea rescue role and fitted to airborne lifeboats, a complete aluminium shell which could be dropped to men in the water from an aircraft. Vincents gave up motorcycle production during the war, concentrating on making specialist components at their Stevenage factory, one of which - for instance - was rocket fuses. Phil Vincent's agile mind was never far from a novel solution to a perceived problem and he found an Air Ministry brief for an engine in which which frugality of fuel consumption was vital - and the other parameters were tough too.

It had to be capable of being started by hand, fully radio screened, waterproof, light in weight and smooth running and able to run for long periods with little maintenance. The construction had to be compact so that the hull of the lifeboat would fit cleanly against the fuselage of the aircraft that carried it and be able to withstand a 5G deceleration as it hit the water. The specification called for 15 bhp at 3000 rpm from an engine that had to be able to run satisfactorily on any petrol, from 70 octane "pool" to highly leaded 120 octane aviation spirit. 

Worked up from an original concept by Phil Irving in 1942, the 500cc Lifeboat Engine (as it became known) was produced with Pacific rescue missions in mond. For a fuel consumption of 50 gallons, the boat seemed to be capable of a total mileage of over 1000 sea miles at an average speed of 5 knots compared to an Austin marine engine's best performance of 500 miles at 4 knots on the same quantity of petrol and the prototype passed its AID inspection out of the box. However, development of a reverse gear, electric start etc, and a vacillating Air Ministry kept Vincents busy until 1949 and that was too late, only fifty being made. Of this single batch, there are around a dozen left, this example having the s/n 44. 

For the technically minded, the device weighs just 256 lbs (116 kilos) and has a watercooled inlet manifold and exhaust. It is a two-stroke cycle, twin crankshaft opposed six, the pistons moving inwards to form a common combustion space, thus this six has three bores. The centre bore of the three provides compressed mixture for the outer two cylinders, the mixture not being compressed in the crankcase as in normal two-strokes. The pumping cylinders have cross heads like a steam engine, allowing straight, round section connecting rods to be sealed from the crankcase with gland seals. The mixture is circulated both "above" and "below" the pumping pistons, transfering to one set of power pistons on the inward stroke and to the other set on the outward stroke thus making best use of the capacity available.

On display
Fair
Vincent Engineers (Stevenage) Ltd
England
IF:2016:64
Yes
2016-06-12
Internal Fire Core Collection