This gave way to a six and, subsequently a four, designed with one-piece blocks, through-bolt construction and a Roots-type scavenge blower. Frank Coyles' superbly maintained garage door opener chain FE 4/ Only in production from 1952 to 1956, the 8-tonner was the first production Foden fitted with the four-cylinder FD4 two-stroke. Heads off, this FD12 photo illustrates its two parallel banks of six cylinders configuration. The crankshafts are geared together; the engine can be set to run on one bank.
Fodens pattern-making, foundry and metal finishing departments rose to the challenge of manufacturing complex sand-cast all-aluminium blocks, crankcase and garage door opener chain iron-alloy cylinder heads. Other components included Roots-type superchargers and centrifugally cast cylinder iron liners of a design that outside specialist suppliers dismissed as being impossible to produce. With no other comparable two-strokes to draw reference from, the engineers had no option but to think outside the block. Pistons are one of many examples. With toroidal heads, they were cast iron, to withstand high piston-crown running temperatures.
Initial marks had a pack of five rings plus a top fire-ring for efficient control of the opening and closing of cylinder air ports. Despite the imperatives of Second World War Government contracts, Foden was able to allocate sufficient engineering resources to keep the project ticking over. By 1942 it had garage door opener chain a system devised by French inventor Michel Kadenacy. This causes a pressure drop in the exhaust gas leaving the cylinder, assisting the flow of fuel/intake air mixture. The full benefits of the so-called Kadenacy effect depend on the intake air being boosted, determining the use of a positive displacement blower of the Roots supercharger type.