Christie Model 1919

Christie used the experience gained before and during World War I to develop his "Convertible Suspension", which allowed a vehicle to run on either tracks or wheels.

Most tanks of the time period weren't durable enough to be drive to the front on their own, so instead were delivered by trucks and then driven to where they were needed.

The Convertible Suspension was designed to overcome this deficiency by allowing for high speed on roads using tires and then having the tracks installed on the tank before entering the battlefield.

[2] The tank featured four large road wheels with rubber tires on the corners of the hull, a central bogie on each side with a pair of road wheels with coil springs which could be lowered or raised depending on if tires or tracks were used, and it was driven by an axle at the rear.

The M.1921 had added suspension and the turret was removed and the guns placed within the hull instead, but it was also rejected on the grounds of being unreliable and under-powered.