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Concept
Lever arm shock absorber
Résumé
Lever arm shock absorbers were the first form of hydraulic shock absorber or damper used for car suspension. 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 absorbers.
Hydraulic shock absorbers, invented by Ralph Peo in 1930, appeared as a development to replace the previous friction disks. 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.
The first hydraulic shock absorbers were of the rotary vane pattern, the so-called Houdaille shock absorbers. These consisted of a cylindrical oil-filled body, bolted to the chassis. 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.
These were first developed by Maurice Houdaille around 1906, but remained largely ignored in favour of the simpler friction devices for some years.
This type was most common pre-war, although Ferrari continued to use the Houdaille vane-type for Formula One racing cars into the late 1950s.
A design for a hydraulic lever arm shock absorber was patented by Georges de Ram in 1925, and the design was further developed during the post-war period. This type of shock absorber had a large cast body containing a cylinder and pistons attached to a similar spindle and lever arm. Some used a pair of pistons for bump and rebound, others used a single double-acting piston. Some, such as the VW Beetle until 1949–1951, had only single-acting shock absorbers, with no rebound damping.
Source officielle
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