Rare Vincent Uniflow engine

December 2015


Two-stroke | Phil Vincent | RAF  | 500cc


Vincent two-stroke uniflow engine


Vincent Motorcycles and two-stroke engines are not usually spoken of in the same sentence. But this is a special case. It's a two-stroke motor designed and built  by Vincent Engineers (Stevenage) Ltd for use in WW2 lifeboats. Auction house Bonhams will have the rare privilege of searching for a buyer for this very unusual mechanical rubber band, and that will happen on Thursday 7th January 2016 at Bally's Hotel and Casino, Las Vegas, USA.


So what's the detail?


Well, it's a three-cylinder, electric-start, six piston, twin-crankshaft, liquid-cooled, horizontally-opposed, two-stroke engine displacing 500cc. The two outermost cylinders (with double acting pistons) provide the raw power, while the two innermost cylinders (also with double-acting pistons) are designed to "feed" its neighbours with an appropriate fuel/air/oil mix.


Vincent Motorcycles two stroke engine


The power output is said to be 15hp @ 3,000rpm. The lifeboats these were intended to be fitted to were designed to carry 50 gallons of fuel. At 5 knots, the range was said to be 1,000 miles, which equates to around 20mpg.


The Uniflow Engine was built by request of the RAF which required an ultra efficient power plant for aluminium lifeboats intended for deployment in the Japanese theatre of war in the Pacific Ocean. More specifically, the lifeboats were to be dropped from the air for use by downed RAF aircrew.


Vincent Uniflow Engine patent


Fifty of these engines were built, of which 12 survive. Phil Vincent held the design patents, and Phil Irving reworked the drawings to suit. The programme, however, was not completed until WW2 hostilities ceased.


So who's likely to buy this engine? Well possibly someone with a special interest in marine engineering. Or possibly by someone with a collection of Vincent motorcycle memorabilia. Or both. Either way, Bonhams has posted an estimate of 16,000 - 19,000 ($24,000 - $28,000).



Sam 7



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