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An old principle becomes young again

Shock absorbers from Sachs for Ferrari's Formula 1 racer

The discovery of the beneficial effect of hydraulic shock absorbers on the handling of a car goes back more than 100 years. In 1923, Lancia had already provided telescopic shock absorbers for the Lambda, but in Europe, the lever shock absorber prevailed. There were numerous versions of these, but they all had problems with sealing. The oil inside them began to leak out after only a few thousand kilometres, and then the damping effect was over. So it was no wonder that the pressureless telescopic damper, which came to us via the diversions from America, was easily replaced. Despite the still inadequate sealing materials, the telescopic damper lasted considerably longer and now dominates the automotive industry. The lever shock absorber was completely forgotten and today serves at best as a scare device.
Until now - because now Sachs has rediscovered it. Almost two years ago, Ferrari asked Sachs for shock absorbers with the smallest possible footprint, because the telescopic shock absorbers used until then could no longer be accommodated in the increasingly slim rear end. Sachs then developed lever shock absorbers that fulfilled all Ferrari's wishes under the name of rotation dampers. These are now only fist-sized devices that simultaneously accommodate the ends of the torsion bar springs. Whereas with the old lever shock absorbers the housings were firmly bolted to the body and the movable lever inside the housing moved a wing in the damping oil, with Ferrari the wing is fixed while the housing is moved by the wheel carrier via a push rod. This is irrelevant for the function of the damper.
The principle is simple. In the old lever shock absorbers, the movable lever sat firmly on a shaft that carried a wing inside the housing that was also firmly connected to it. The wing divided the oil-filled chamber into two halves and usually also carried the damper valve with which the degree of damping was adjusted. When the corresponding wheel was sprung, the lever connected to the wheel carrier moved the wing in the oil chamber, which pressed the oil via the valve into the second half of the chamber. Sachs moved the damping valve outside for easier replacement. So that the damping effect can be precisely adjusted to the respective race track, Sachs supplies several valves with different characteristics to Ferrari.
Since the components of a racing car must not weigh anything, Sachs manufactures them from titanium. No wonder a shock absorber costs around 10,000 euros. The oil in the damper housing is preloaded with 10 to 15 bar, while the pressures created in the two oil chambers during compression and rebound are around 100 bar. The operating temperature on the gearbox housing, which also carries the two rear wheel dampers, is around 120 degrees Celsius. Apart from saving space, it was important that this new damper system is between 50 and 70 grams lighter. While a shock absorber for the VW Golf weighs between 2 and 2.5 kilograms, the complete damper system for the rear axle of the Ferrari weighs less than one kilogram. The two rotary wheel dampers are joined by a telescopic shock absorber lying horizontally on the gearbox.
Anyone who watches the Formula 1 races on TV will notice that the Ferraris are much quieter than their competitors: a success of the excellent shock absorption. Nevertheless, the whole development would only be worth a brief mention for Formula 1 if it could not gain significance for everyday automobile construction in the future. Designers will soon be asking Sachs for similar solutions for normal cars. This is because the telescopic shock absorbers, which are usually positioned vertically, take up space that is lost to the boot and restricts the load-through width in estate cars.

The drawing, which is already 70 years old, shows the construction of a lever shock absorber:
1) the housing bolted to the body, 2) the shaft connecting lever 3 )and wing 4). 6) and 7) holes for through oil passage, 5) damper valve.

The rotation dampers, on the other hand, could do their work somewhere under the luggage compartment floor. There would be many installation possibilities without limiting their function. For large series, however, they would not be made of titanium, but of steel and aluminium, while the damper valve would move back into the wing. Compensating for the light touch of oil used to lubricate the shaft seals would not be a problem either. Such rotation dampers would have the great advantage, besides the small space requirement, that they do not have a "breakaway torque" like telescopic shock absorbers, which is forced by the sealing of the piston rod. If the rotary dampers are combined with torsion bar springs, as is the case with Ferrari, the suspension and damping disappear completely into the ground. This can be extended to variable damping. Ultimately, the question of at what price such shock absorbers can be produced will be decisive. Rotary dampers are an answer to the frequently asked question of what sense racing makes for the further development of production cars.
Source: Frankfurter Allgemeine Zeitung

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