Sherman M4A2 diesel engine designation

[Rod Diery]

Originally posted by Richard Farrant
I seem to think they were all based on a German design, was it Junkers?

I definitely don't think this is right. According to a 1943 book of my Dad's called The Oil Engine Manual (diesel was a dirty word then, a bit too German), the Junkers engine was a 6 cylinder, 12 opposed piston engine. While it was a two stroke it used a centrifugal blower to scavenge the engine.

The 71 series engine has it's roots in designs drawn up by the Winton Engine Company in the early 1930s. General Motors acquired this company and merged it with some other new acquisistions to form Cleveland Diesel. It later merged Cleveland Diesel yet again with the Electro-motive Corp to form it's own Electro-Motive Division in about 1935. EMD produced the highly successful 567 2 stroke locomotive diesel which remained in production for more than 40 years.

The 71 series engine was developed in about 1937 using the same principles used in the 567, 2 stroke, unit fuel injection and the unique scavenging system which was patented and I seem to recall was called Uniflow. This system uses a Roots type blower to scavenge the exhaust gases out of the cylinders via an air box, bottom cylinder ports and overhead valves.

According to Fred W Crimson's US Military Tracked Vehicles of 1992, the 6046 is indeed the paired 6/71 engine pack. This is interesting because when I used to look after an LCM8 landing craft a few years ago powered by no less than four 6/71s in the same arrangement of two twin packs, each engine pack was referred to by it's makers as one engine, ie a 12 cylinder engine.

Cheers
Rod