Marles steering gear

[1] Ultimately its most popular form was an hour-glass shaped worm which engages with a double-toothed roller follower on the rocker shaft for the steering arm.

The Adwest product was fitted to several British luxury automobiles of the era, including; the Aston Martin V8, Daimler Sovereign, Jaguar 420 and Rover P6B 3500S.

[3] The hydraulic pump is of the vaned rotor type, typically of Saginaw manufacture, and is connected to the steering box via flexible feed and return hoses.

The varying pitch of the cam results in the variable steering ratio, with the lowest gearing being at the straight ahead, rising rapidly to either lock.

The rise in gearing (which in the Jaguar 420 was equivalent to a drop in ratio from 21.6:1 to 13:1) occurs almost entirely within the first half turn of the steering wheel from the straight ahead position.

The major benefit of the Variomatic system is the reduction in the amount of "arm twirling" and effort required when steering, particularly when a lot of cornering is involved.

The Variomatic system was also criticised for feeling too light at high speed, when greater weighting tends to give the driver more confidence in making fine steering adjustments.