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The Mercedes-Benz single-joint swing axle of 1954
In March 1954, visitors to the Geneva Motor Show came in droves to the Daimler-Benz stand to admire the new Mercedes-Benz 220a (W 180) with six-cylinder engine, its looks identifying it immediately as a member of the Mercedes Ponton family. The first model in this lineup had been the 180 launched the year before.
Compared to the 180, the 220a had a 17 centimeter longer wheelbase, and this was highly becoming to its proportions, especially the front section and the passenger compartment. But its creators had not been concerned with balanced proportions alone. First and foremost, they had had the brief to give this new luxury-class sedan not only adequate performance but also more ride comfort and greater handling safety, the latter being a new aspect. The expert world was therefore primarily interested in what was hidden underneath the sheet-metal skin – and discovered a new rear axle, replacing the double-joint swing axle which had been introduced in the Mercedes-Benz 170 of 1931 and subsequently used in a large number of Mercedes models.
The lightweight single-joint swing axle was a new design that could almost be described as elegant. Its most distinctive feature was a single, common – and therefore lower – pivot point of the two half-shafts. The latter were therefore longer, with the effect of significantly reduced wheel camber and track changes during spring compression and rebound, especially since the wheels had a slight negative camber in unladen condition – i.e. in as-designed position, as this is called in engineering jargon.
This counteracted the tendency of the rear wheels to give way under strong spring rebound, in the direction of positive camber, as well as the resulting raised tilt moment – a condition with adverse effects on handling safety. The half-shafts were located by thrust arms. Coil springs combined with hydraulic shock absorbers were used for springing and damping.
In combination with the front subframe adopted from the 180, these highly positive capabilities of the single-joint swing axle resulted in most agreeable ride comfort and significantly improved handling safety.
From 1955, the single-joint swing axle was adopted for all cars in production and, of course, for all new Mercedes-Benz passenger car models. In the luxury models, it was complemented by an additional, horizontally arranged balancing coil spring, air spring bellows instead of the coil springs, hydro-pneumatic level control and an anti-roll bar.
The axle passed its acid test in the Silver Arrows – the Formula One and SLR racing sports cars – in 1954/55. It remained a feature of the Mercedes mid-series until the end of 1967, of the S-Class until 1972 and of the Mercedes 600 until as late as 1981.
In the famous Stroke Eight models, the successor to this axle was the diagonal swing axle, equipped with additional rubber springs and anti-roll bar.
Today, the proven Mercedes-Benz multi-link independent rear suspension is responsible for ride comfort and handling safety under the sheet-metal skin. This suspension features several separate links in elastic bearings, which restrict the wheels’ scope of movement in three-dimensional space. The design retains just one degree of freedom for the wheel: controlled spring compression and rebound.