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NW Washington | Right on. The two track tractors use a hydraulically controlled planetary gearset to control the relative speed of each track. The controlled planetary gearset in the steering differential works similar to the CVT transmissions used in Fendt and now most other brands of tractors, the ring gear speed is controlled by a steering hydraulic motor which in turn controls the output speed of the gearset and makes the tractor turn.
A quad track steers just its 4x4 cousins, it bends in the middle, but it would not turn if it did not have differentials in each axle.
A little aside, the old Clectrac crawler tractors also were steered by a controlled differential, but since this was before fancy hydraulically controlled planetaries the Clectrac used a hand operated brake on the sun gear of its steering planetaries in the differential. And unlike the Challenger or steering clutch and brake systems used on other crawlers it could not stop one track and make a "spot" turn. | |
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Steering for tracked tractors
