Field Marshall

Field-Marshall is a brand of farm tractor which was manufactured by Marshall, Sons & Co. of Gainsborough, Lincolnshire in the United Kingdom.

Field-Marshalls were in production from 1945 to 1957. However, the first single-cylinder Marshall came into production in 1930.

The first single-cylinder Marshall tractor to be introduced was the Marshall 15/30 in 1930. It had a bore of 8 inches with a 10-inch stroke (= 8.237 liters) and the maximum r.p.m. was 550 (= 9.1666 per second).

In 1932 the 15/30 was upgraded to become the Marshall 18/30. This model featured the same bore and stroke dimensions but the maximum r.p.m. was increased and the tractor's transmission was modified heavily.

The next single-cylinder Marshall to be introduced was the Marshall 12/20 in 1935. This tractor was of a completely new design, with a 6-inch bore and a 9-inch stroke. There were many smaller modifications such as a redesigned injection pump and cylinder head. In 1938 the 12/20 model was redesigned and the model coding was changed so that the new model became the Marshall Model "M" tractor. During the war tractor production was reduced greatly due to Marshall's factory capacity being engaged on war work. However, after the war, in 1945, Marshall's of Gainsborough introduced the improved tractor they had developed as the "Field-Marshall"

It was diesel-powered.

The Field-Marshall and its Track Marshall tracked stable-mate (Marshall-engined Fowler VF and VFA), were distinctive because of the use of a single-cylinder two-stroke diesel engine (of about 6-litre capacity) coupled to a very large flywheel, whereas tractors such as the Fordson N used a multi-cylinder engine. This single-cylinder design was quite common in Europe at the time, the Lanz Bulldog being another example. The Lanz, though, used a hot bulb engine.

To start the Marshall a smouldering piece of special paper, containing saltpeter, is inserted into the cylinder head by means of the special screw-in holder in the cylinder head (this smouldering paper acts as a glow plug).

The engine is then turned over with a starting handle placed in the starting dog on the flywheel. This is aided by the decompression valve, which decompresses the engine and makes it easier to turn over to allow the flywheel to gain speed and inertia to turn the engine through compression, and get the engine to fire. A spiral groove on the perimeter of the flywheel carries a wheel on the decompressor mechanism and is used to determine the number of revolutions before the decompressor disengages. This is generally up to 3 revolutions, but can be anything up to 6 revolutions. Depending on the condition and mood of individual tractors, it is possible to get a thorough workout starting the Marshall.

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Wikipedia