Dubonnet suspension
The Dubonnet suspension or the Dubonnet spring knee is a wheel suspension system for motor vehicles . The suspension, suspension and shock absorbers of a wheel are combined in one assembly. It was used almost exclusively for steered front wheels.
The wheel-bearing, pushed crank arm is rotatably mounted in the housing, which can be pivoted about a stub axle bolt fixed to the frame. With an angled lever, with which it forms a knee ( spring knee ), it presses on the coil spring and the piston of the shock absorber inside the spring housing. The housing is filled with oil. It does not belong to the unsprung masses, but it has to be moved when steering. The damping of the piston that moved inside the spring (later a shock absorber with its own oil housing inserted into the spring) in the oil replaced the friction damping that had been common up until then, for example between the layers of the leaf springs .
The spring knee was developed in 1927 by the French engineer André Dubonnet in his company. It was patented in the USA in 1931. At Dubonnet, the aerodynamic prototype Xenia was later created with this wheel suspension on all wheels.
In 1932 he sold a production license to the US company General Motors , which left it to its subsidiaries Pontiac , Opel and Vauxhall . The Chevrolet Master Deluxe also received this suspension from 1935.
The patents registered in Germany were issued in 1934 with the numbers 644 372 and 697 702. The front Dubonnet spring knees used by Opel from 1934 together with a leaf-sprung rear rigid axle were highlighted in contemporary advertising as synchronous suspension , as both axles should be sprung with the same natural frequency . Opel wrote about this in its advertising: “The Opel synchronous suspension uses ... a soft front wheel suspension ... which vibrates in the same way as the soft, long, protruding leaf springs on the rear axle. H. Are 'synchronized' - hence the name synchronous suspension ... "
The disadvantage was the often occurring flutter ("shimmy") in the steering due to the greater mass of the steered swing arms, as well as the strong lateral inclination of the vehicle when cornering. The roll pole of this wheel suspension is at road level.
From 1934 to 1940, all Opel cars except the P4 and the Kapitän were fitted with synchronous suspension: the Opel 1.3 liter and Opel 6 (both from 1934), Olympia (1935), Kadett (1936; except for the “normal sedan” “), Super 6 and the Admiral (both from 1937). The rather elaborate construction was not used again in the Opel Olympia, which was produced again from 1947 . Later Opel models also got a different front suspension.
Fiat used the Dubonnet knee in the Fiat 1500 from 1935 , but also abandoned it from 1948. At times, Alfa-Romeo and Simca also used Dubonnet suspension.
For its Iso Isetta (1953), Iso used a slightly modified construction without an angle lever with a vertical, light sheet metal housing for the spring and shock absorber arranged close to the steering knuckle. This reduces the moment of inertia about the vertical axis and the tendency to flutter. BMW built the Isetta under license and took over the construction for the small car types 600 and 700 .
Individual evidence
- ^ A b c d Seherr-Thoss: Dictionary of famous personalities in the automobile World. Ivy House Publishing, Raleigh NC, USA, 1st edition; 2005; ISBN 1-57197-333-8 , p. 46 (André Dubonnet)
- ↑ a b Description of the Dubonnet spring knee on the Fiat 1500 with photo and drawings