Medium D tank.  Circa 1920.

 

Through contact with Lionel de Rothschild and his interests in the Vickers company, Armstrong Siddeley supplied a modified Puma engine as the power plant for the Medium D tank. As with many tank designs between the wars they were short lived as problems were met and overcome. Only five Puma engined M. D. tanks were made but this experience led Siddeley to consider the design of air-cooled engines for military vehicles. 

 

In 1922 the War Office began development of a tracked vehicle named the Artillery Dragon powered by an Armstrong Siddeley 90HP air cooled engine, which was excellent, but the project was dropped as the Dragon kept shedding its tracks and no solution could be found.

 

The engine was then used in the first of the Vickers medium tanks. Again a Vickers designed self -propelled gun tractor named the 'Birch Gun' was so powered. The gearbox fitted to these vehicles was also made at Parkside.