Prior to the Mark IV, all British tanks had been made by two manufacturers - Fosters of Lincoln and the Metropolitan Carriage, Wagon and Finance Company in Oldbury, Birmingham.
When the War Office put plans in motion to build 1000 Mark IVs it was clear that other firms would have to be brought in, both as sub-contractors to assemble components and manufacturers to build complete tanks.
A country-wide effort
Firms all over the country were involved in building the Mark IV. Armour plate was made by William Beardmore & Co. of Glasgow as well as Cammell Laird and Vickers, both in Sheffield. Track links came from Fosters and Clayton & Shuttleworth, both based in Lincoln.
The six pounder guns came from Armstrong Whitworth in Newcastle, and the automotive components (engine, gearbox, flywheel, clutch, differential and radiator) were built as a self-contained unit by the Daimler Company in Coventry.
Tanks under construction at Fosters
These components would then be moved to factories up and down the country for final assembly. Metropolitan and Fosters were both able to assemble complete tanks from parts, but other firms lacked either the size or expertise to do this.
Armstrong Whitworth; Coventry Ordnance Works; Mirlees, Watson & Co. and William Beardmore & Co. all took in hulls assembled elsewhere and finished them by installing the tracks, automotives and sponsons.
Production ran from March 1917 to October 1918 with a total of 1,220 tanks produced in total. Metropolitan built 820 tanks, Fosters, Armstrongs and Coventry 100 each, and both Mirlees and Beardmore 50.
It is likely that other firms were also involved in building the Mark IV, however records of who they were and what they built haven’t survived
An engineering drawing of the Mark IV
Building the Mark IV
Unlike on a modern production line the tanks didn’t move whilst they were under construction. Instead the workers moved around the tank fitting parts, with the largest components brought in by trolley or crane.
A tank hull during assembly
The inner frames were constructed first, then the floor and lower body were riveted in place. The outer frames were then built and the track rollers, gears and drive sprockets fitted between outer and inner. The tracks themselves were laid out flat on the factory floor and the tank was lowered onto them.
The complete automotive sub-assembly was then lowered into the tank by crane and the rear and roof panels attached.
Smaller components including ammunition racks, the petrol tank and the sponsons were then added, before finally the tracks were joined up and the tank was driven out of the factory for delivery.