It’s Thursday and so:

-The weekend is nigh

-It’s time for a two stroke

Last week we looked at the Commer TS3, a flat opposed piston triple used in the 1950s and 1960s. Today, to continue the opoc theme, we meet a tank and its engine.

Meet some Chieftain tanks trundling in a rather smoky manner down Straße des 17. Juni in Berlin on as it happens the following day, the 18th June 1989 which turned out to be a year of some significance for Berlin. What interests us is the smoke, which is coming from Leyland L60 multi fuel engines.

The L60 was intended to be able to run on any kind of fuel with a sufficiently low octane number that it would ignite under compression although diesel was its usual choice.

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The L60 was an opposed piston two stroke engine with six cylinders, twelve pistons and a conventional crank set up - two, one at each end of the block. Unlike the TS3 it was fitted vertically. Also unlike the TS3 it was designed so that the upper crank only produced about one third of the power and was mainly used to power the supercharger and ancillaries while the lower crank provided most of the driving force.

Here’s a cutaway drawing by Terry Collins which dates from the days of actual drawings with paper and ink and not a computer in sight.

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Not that surprisingly for a Leyland engine it wasn’t very reliable and so the Challenger tank which followed the Chieftain used a Rolls Royce CV12, a conventional four stroke. The Challenger was followed by the Challenger 2, still the UK’s main battle tank, which has a Perkins CV12, actually the same engine as RR sold out to Perkins. Perkins in turn closed the factory which made their large diesels and there’s a shopping centre there now.