GUARD GP-ROTOR 1259076 - Caterpillar

The locking effect is due to the internal friction of the differential. It is produced by two multiple disc brakes arranged symmetrically in the differential cage. In the case of a conventional differential, one wheel can be braked or held in position when the vehicle is jacked up, the engine is running and the gear is engaged. The other wheel will then turn correspondingly faster. However, with a self-locking differential, the above procedure will be considerably more difficult due to the multiple disc brakes, in fact it will become more difficult with increasing input torque. This behavior is caused because the torque acting on the differential cage is transmitted to the differential axles (A) via two pressure rings (B), which are unable to turn radially but can move axially, whereas with a conventional differential, the torque is transmitted directly to the differential axles. The contact surfaces between the pressure rings and the differential axles are arranged against each other at an angle of 45°(C) Thrust is shown as (D).Outward axial forces are caused by the reaction at those surfaces when torque is transmitted, resulting in increased pressure on the discs. Since the outer discs engage with the differential cage and the inner discs with the axle bevel gears, relative motion between wheel axle shafts and differential cage is rendered more difficult and the two wheel axle shafts are locked together up to the capacity of the clutch packs. With a standard differential the two wheel axle shafts are never locked together, so the available torque is never greater than the wheel with the least traction. Assuming that each axle is taking equal torque, the power flow is shown as being transmitted to the axles from only one differential and differential bevel gear.Due to the outward forces, a load dependent locking torque is produced in the multiple disc clutches which is always directly proportional to the input torque. The locking effect; therefore, adapts itself to the variable engine torque, and also the torque increase in the gear speeds. This is especially useful for heavy off-road operations when large torques must be transmitted. The above illustration shows the torque path when moving straight ahead. In this case M1 + M2 is the torque input into the differential. The output torques, M2 and M1 are equal. When turning, or when conditions are slippery, the input torque is still M1 + M2. But, in this case M2 is less than M1. S is also the percent of torque transmitted by the friction clutches which significantly increases the traction available on the ground. This is because when a wheel spins out, it transfers the torque to the opposite wheel and multiplies it by the relation: So there is 82% more traction effort available with the self-locking differential over the standard differential at spin out.