Lever arm shock absorbers were the first form of hydraulic shock absorber

Shock absorber

A shock absorber is a mechanical device designed to smooth out or damp shock impulse, and dissipate kinetic energy. It is a type of dashpot.-Nomenclature:...

 or damper

Damper

A damper is a device that deadens, restrains, or depresses.Damper may refer to:* Dashpot, a type of hydraulic or mechanical damper,* Shock absorber , a mechanical device designed to dissipate kinetic energy...

 used for car suspension

Suspension (vehicle)

Suspension is the term given to the system of springs, shock absorbers and linkages that connects a vehicle to its wheels. Suspension systems serve a dual purpose — contributing to the car's roadholding/handling and braking for good active safety and driving pleasure, and keeping vehicle occupants...

. They appeared in the 1930s and were most commonly used in the 1950s and 1960s, but were replaced by telescopic shock absorbers in the 1970s. One of the earliest patents for a hydraulic lever arm shock absorber was awarded in 1925 to Georges de Ram, who was already an established maker of friction disk shock absorber

Friction disk shock absorber

Friction disk shock absorbers or André Hartford dampers were an early form of shock absorber or damper used for car suspension. They were commonly used in the 1930s but were considered obsolete post-war.- Construction :...

s.

Hydraulic shock absorbers appeared as a development to replace the previous friction disk

Friction disk shock absorber

Friction disk shock absorbers or André Hartford dampers were an early form of shock absorber or damper used for car suspension. They were commonly used in the 1930s but were considered obsolete post-war.- Construction :...

s. These had, at best, provided a constant damping force, no matter what the size or speed of the suspension movement. With a viscous device using hydraulic oil, the resistance force increased with speed, so providing better damping for larger suspension bumps.

Rotary vane

The first hydraulic shock absorbers were of the rotary vane pattern. These consisted of a cylindrical oil-filled body, bolted to the chassis

Chassis

A chassis consists of an internal framework that supports a man-made object. It is analogous to an animal's skeleton. An example of a chassis is the underpart of a motor vehicle, consisting of the frame with the wheels and machinery.- Vehicles :In the case of vehicles, the term chassis means the...

. A lever arm was attached to the axle and inside the cylinder, this rotated a spindle carrying a vane or paddle. This vane had only a small hole in it, through which the hydraulic oil could pass. Resistance to flow through the hole provided the damping effect.

This type was most common pre-war

World War II

World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

.

Lever type

A post-war development was the lever shock absorber.A better name might have been the 'piston' type, as both types described here use similar levers. This had a large cast body containing a cylinder and a piston attached to a similar spindle and lever arm. Flow of hydraulic oil around the piston took place through valves mounted in the body. Separate valves were provided for each direction, giving the useful feature of a different resistance to bump and rebound. These valves were sometimes easily adjustable from outside the damper body.

Integral wishbones

Many cars of this period began to use independent front suspension, often a double wishbone

Double wishbone suspension

In automobiles, a double wishbone suspension is an independent suspension design using two wishbone-shaped arms to locate the wheel. Each wishbone or arm has two mounting points to the chassis and one joint at the knuckle. The shock absorber and coil spring mount to the wishbones to control...

. The upper wishbone could conveniently also be used as the lever of the shock absorber, reducing the mass and bulk of the suspension, and also avoiding at least one ball joint. The spindle of the shock absorber now became the upper suspension pivot, usually double-ended.

One of the last mass-production sports car

Sports car

A sports car is a small, usually two seat, two door automobile designed for high speed driving and maneuverability....

s to still use lever arm shock absorbers was the MG B. This had a lever arm shock absorber as the upper wishbone. A popular handling upgrade in later years was to fit telescopic shock absorbers instead. The lever arm wishbone was still retained, but now as a simple wishbone with no damping.

Obsolescence

During the 1960s, the lever arm was replaced by the telescopic shock absorber. This was encouraged by better roads and motorways, increasing average speeds and driver expectations of handling. The telescopic shock absorber dissipated heat more effectively, owing to its larger working volume of fluid and also the better ratio of surface area to fluid volume.