The solution was the addition of a bellcrank, which changed the direction of motion from vertical to horizontal. The road wheels were individually mounted on a pipe that could move vertically only, at the top of which the bell crank rotated the direction of motion to the rear. Springs were mounted on the end of the crank, and could be as long as needed, lying along the inside of the hull. The result was a substantial increase in range of motion, from only some 10 cm in his original designs, to 25 cm on the M1928, 35 cm on the M1930, and 60 cm on the M1932. The most famous Christie-based tanks, the Soviet BT tank series and the T-34, used coil springs mounted vertically (on the BT) or at a slight angle from vertical (the T-34).