sentences:  The drawback of this design compared to other multiple-differential designs is that applying the steering input to one track also increases the average speed of the two tracks, so the vehicle's speed is not constant.In double-differential steering, as in the Maybach double-differential system, power from a second transmission is fed an epicycle gear in the final drive of one side or the other.In this design, however, the average drive speed of the tracks is maintained by adding an idler to apply the opposite torque to the epicycle gear on other side of the turn.