Friction disk shock absorber

Treated leather had been used for clutches and although it offered good friction behaviour, it was prone to stiction when first moving off and also failed when overheated.

The damping force of a friction shock absorber is adjusted with the central pivot and clamping bolt.

These provided the stiff location that accurate suspension required, but reduced vibration and road noise, compared to earlier cars.

Georges de Ram invented and manufactured hydraulically actuated friction shock absorbers during the 1920s and 1930s.

These were a more sophisticated pattern, intended to provide variable, self-adjusting damping in order to work effectively at both low and high speeds.

A series of hydraulic pistons and valves varied pressure on the friction disk stack in proportion to the speed of the lever arm attached to the axle.

This is particularly a problem for fast driving, when repeated high forces may cause the friction plates to heat up and lose their efficiency.

A hydraulic control, with an inflatable rubber bag in the disk pack, could be used to increase the clamping force and thus their damping stiffness.

[11] Georges de Ram's hydraulically actuated friction shock absorbers also attempted to address this issue by automatically adjusting damping forces, rather than providing manual control.

These dampers used a series of hydraulic valves and pistons to vary the friction between plates, proportional to the speed of suspension movement.

This resulted in stiffer damping when encountering strong bumps at higher speeds, while remaining soft during slow or slight movements of the suspension.

This is adjustable by tightening or loosening the small bolts that hold the two halves of the leading links together, the friction discs being sandwiched between them.

André Hartford held patents on this design but the manufacturing technology required was simple, and so many other makers also produced them.