There are many names in the automotive industry that have very long histories and are respected brands – Dunlop is one of them thanks to being a major player in the tyre industry. However, Dunlop were also key inventors of other safety equipment and one such invention was Maxaret – the first Anti-lock Braking System to be commercialised.
In the late 1940s, Dunlop developed this system primarily for aircraft because landing a plane in wet or icy conditions was very dangerous with the wheels likely to skid or lock up. The idea was simple and lightweight and could be retro-fitted to many aircraft of the time. The important feature was that it was completely mechanical – electronic systems had not developed very far when this system was developed.
The Maxaret system consisted of two discs – one called a drum and one called a flywheel. The drum had a rubber disc attached that was also in contact with the wheel. The flywheel was attached to the drum with a one-way clutch that was also connected to a brake fluid regulator. The whole unit was housed in a shell that also rotated with the wheel. In normal operation the wheel, drum, flywheel and shell would spin at the same speed as they were all connected.
On landing, aircraft wheels may lock up due to the application of the braking system by the pilot. In this situation, with the wheel and shell locking up, the flywheel would still be spinning due to the clutch system. The flywheel would then drive the drum and would move it by about 60 degrees actuating the fluid regulator. This released some of the hydraulic fluid in the system, which in turn lowered the pressure in the braking system which released the wheel unit from the skid.
The unit was developed to be fitted to Dunlop wheels and tyres and was an instant success with testing showing a 30% reduction in stopping distances – with reduced wear and tear on the tyre. A winner in all areas!
By the end of the 1950s the system was fitted to many aircraft and engineers were looking at the cross-over to cars and motorcycles. The Transport Research Laboratory in the UK fitted a version to a Royal Enfield motorcycle and tested it, although the motorcycle manufacturer never put it into production.
It was Jensen though, who did put it into production on their FF model based on the Interceptor. It was described as the safest car in the world in 1965 when it was released. In some respects the FF needed it because it was one of the most technically advanced vehicles with Ferguson Four Wheel Drive and a big Chrysler Hemi V8 mated to a Torqueflite gearbox.
Today, hydraulics and electronics combine to do what the Maxaret system did – although much faster due to current computing speeds, however Dunlop’s system was a pioneer in road and aircraft landing safety.