Change gear ratio range, in particular, using planetary transmission, the transmission ratio can be up to 100 ~ 200 (single stage), the growth rate for slow down or drive.

Gears of first stage are changeable so that the operator can change the gear ratio based on current field condition.

This paper brings out feasibility and applicability to make change drive of double step sliding gear by moving one gear width along axis under conditions of Corresponding ratio of gear.