This recently discovered photograph shows two 20HP Simplex petrol tractors undergoing maintenance at what seems to be an improvised workshop, believed to be somewhere in France during 1917.
It shows the primitive conditions within which these sturdy little engines had to be maintained.
The oil pump is driven from a rather curious skew-gear arrangement, with the driving skew gear being an integral part of the centre of the camshaft (between the lobes for the two sets of cylinder valve push rods.
