Abstract
Many of the high-mobility wheeled vehicles used by the British Army employ permanent all-wheel drive transmission systems with just one transverse differential. Since all the wheels on each side of the vehicle rotate at the same angular velocity severe transmission wind-up can be developed on roads.
The possibility of using viscous couplings to alleviate this problem has been investigated by computer simulation backed up by practical trials on a 4 × 4 armoured reconnaissance vehicle. The results suggest that with a suitable choice of coupling characteristic this solution can dramatically reduce the wind-up torque during low-speed manoeuvres with no significant effect on off-road mobility or handling on roads. It can reduce the wind-up caused by non-uniform tyre wear but not to the extent anticipated. To safeguard handling stability under heavy braking there may be a need to bias the brake effort distribution to the front.
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