Just when you think you've seen most variations of the old engines out there, along comes something like this, a 3 cylinder, opposed piston, two stroke engine from Vincent. It was built with the goal of powering air dropped aluminum lifeboats for World War II Royal Air Force aircrews downed in the ocean. The war ended before the engine project was completed, but it was finished afterwards. This engine turned up in the list of items for the Bonhams Las Vegas motorcycle auction.
The description is quite interesting, especially how the different cylinders worked:
Like many other companies, Vincent shut down motorcycle production after 1939 and the factory was turned over to the war effort, mainly the making of munitions. But in 1942 the Royal Air Force, expecting a protracted campaign against the Japanese, was looking for a lightweight, highly efficient lifeboat engine that could run reliably for extended periods of time.
Company boss Phil Vincent already held patents on a suitable design, which he turned over to Phil Irving for final engineering. The result was a 500cc opposed-cylinder design with three bores each containing two pistons. The outer two cylinders produced power, while the middle cylinder with double-acting pistons fed the other two. Unfortunately, this unique engine program wasn't completed before the end of hostilities, though in final form the motor seemed to meet all of its design goals. Producing 15bhp at 3,000 rpm, with 50 gallons of fuel on board, the Vincent two-stroke should have been good for up to 1,000 miles at a steady 5 knots
per hour, which certainly beats swimming or fighting off sharks. One batch of 50 engines was produced, and it's believed that this example is one of 12 to survive.
We mentioned the Vincent Picador drone engine some time back, so it looks like the company had every part of the land-sea-air triad covered. Very neat!
A big Thanks to Kim who found this and who was also responsible for bringing the Vincent drone engine to our attention many years ago.