Christie suspension

Christie suspension as used in his 1931 patent: When the roadwheel (3) is pushed up by an obstacle, the arm (1) it is mounted on is pushed upwards, pivoting around the mounting point where it is attached to the hull. That movement compresses the spring (2), pushing the arm down again.
Christie-derived suspension on Polish 10TP tank: roadwheel (1), spring (2) and arm (3)
T3E2 tank with Christie suspension crossing an obstacle during tests in 1936

The Christie suspension is a suspension system developed by American engineer J. Walter Christie for his tank designs. It allowed considerably longer movement than conventional leaf spring systems then in common use, which allowed his tanks to have considerably greater cross-country speed. The system was first introduced on his M1928 design, and used on all[citation needed] of his designs until his death in 1944.