How an invention made driving cars easier

Jahr100Wissen- ’s interview with Prof. Dr.-Ing. Uwe Janoske on the invention of power steering

The first power steering system was invented by Francis Davis in 1926. How did this make steering easier?

Uwe Janoske: To reduce the steering effort, Davis used hydraulic assistance. To achieve this , he used a system he had developed himself, which complemented the mechanical steering.

How does this hydraulic system work?

Uwe Janoske: Systems such as those used in hydraulic presses, which only built up pressure when required, suffered from numerous sealing and leakage problems. Davis therefore developed a special system that constantly pumped oil without pressure and built up pressure when required – i.e. during steering manoeuvres – thereby reducing the steering effort.

Technically speaking, the term ‘power steering’ is actually incorrect. Why is that?

Uwe Janoske: In most steering systems, the hydraulics serve only as a support and supplement to the mechanical steering. Power-assisted steering based on a purely hydraulic system is usually only used in specialised applications (tractors, mobile cranes). That is why the term ‘steering assistance’ is actually more appropriate.

After making his invention, Davis went to work for General Motors. However, they rejected the idea of introducing power steering. Why?

Uwe Janoske: Davis worked intensively on further developing power steering at General Motors. He worked on numerous details and refinements to enhance the steering feel, so that by 1933 the development was virtually ready for series production. However, the planned production volumes were so low due to the Great Depression that the tooling and manufacturing costs were too high, and GM rejected its use in series production.

It was not until 1951 – 25 years after its invention – that Chrysler became the first car manufacturer to introduce power steering in the Chrysler Imperial. Why so late?

Uwe Janoske: Davis began developing the system at Bendix in 1936, but the approach of the Second World War once again delayed its introduction in passenger cars. He was, however, able to fit military vehicles with the system; the breakthrough in the passenger car sector, however, had to wait until 1951.

In 1952, General Motors introduced its own power-assisted steering system based on Davis’s research, but this was superseded just one year later by the so-called Packard-Gemmer steering system developed by the Packard Motor Car Company. Why did this particular principle ultimately prevail?

Uwe Janoske: In Davis’s design, the power steering unit was mounted on the steering column, meaning damage was possible, for example due to steering movements whilst the vehicle was stationary. The Packard-Gemmer solution circumvented this problem by mounting the unit on the chassis, which is why it eventually became the standard.

Now, there are electric, electro-hydraulic and electromechanical drive systems for power steering. Since the 2000s, however, the electromechanical drive system has replaced hydraulic systems in passenger cars. Why is that?

Uwe Janoske: The electromechanical system has the advantage that it eliminates the need for hydraulic components, including hydraulic oil. This completely prevents leaks. The electromechanical system assists the driver’s steering movements and reduces the steering effort required.

Today, the first car manufacturers are already using so-called steer-by-wire systems, in which the mechanical connection between the steering wheel and the wheels is completely eliminated; steering commands are transmitted electronically and implemented electrically. This enables even more safety features – right up to autonomous driving. Is that the future?

Uwe Janoske: The first systems will go into series production in 2026. Direct control opens up new possibilities for autonomous driving, and the removal of the steering column also allows for new vehicle designs, meaning that further systems will follow in the future.

Uwe Blass

Prof. Dr.-Ing. Uwe Janoske heads the Chair of Fluid Mechanics in the school of mechanical engineering and safety engineering at the University of Wuppertal.