Donīt forget this either:
On Shermans
One of the most needed maintenance parts was spark plugs. Most of the M4 tanks had R975 Wright nine-cylinder air-cooled radial engines. When the engine was started the tank usually backfired with considerable noise which gave away the unitīs position.Most tank crews would idle the engines as slowly as possible when trying to maintain a defiladed position in the hedgegrows. Designed for high constant speeds in an aircraft the engine had excessive clearance between the cylinder walls and the pistons. In a tank, where the engine was run slowly, the excess clearance allowed then engine to pump oil which fouled the spark plugs.Each engine had nine cylinders and each cylinder had two spark plugs. This meant that eighteen spark plugs had to be changed every time the engine fouled.
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