Dunlop Maxaret

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The Maxaret of Dunlop was the first used on a large scale anti-lock braking system (ABS). The system was introduced in 1952 and quickly spread to aviation. Tests showed that the braking distance was shortened by up to 30% and prevented tire bursts and brake plates from locking wheels. From 1966 the Maxaret was also used in the Jensen FF as well as in other road vehicles on a trial basis. However, anti-lock braking systems did not gain acceptance in this area until the 1970s, when electronically controlled systems became available.

Use in aviation

In aircraft, the ratio between tire contact area and vehicle mass is significantly smaller than in road vehicles and braking takes place at higher speeds. In connection with the fluctuations in the wheel contact force during landing, the problem of locking wheels in aircraft therefore plays a special role. At the same time, the stuttering brake that is common in road vehicles without ABS to maintain steering ability is difficult to implement. Blocking tires cause brake plates to develop or the tire even bursts due to the heat input, so the durability of aircraft tires is significantly reduced. With this in mind, Dunlop developed the Maxaret in the 1950s.

In early tests with the Avro Canada CF-100 , the system enabled safe landings on ice-covered runways. Since the operating conditions of most aircraft are determined by the take-off and landing behavior in adverse weather conditions, a 15% higher total weight was possible. Another advantage was originally unexpected: the braking distance was reduced by up to 30% when using the Maxaret. While pilots without an anti-lock braking system only braked after a safe landing in order to avoid locking tires, braking with Maxaret was initiated directly when touching down. Later designs even allowed actuation before landing, in that the brake pressure was only built up after the wheels had turned.

functionality

The Maxaret works without electronics and mechanically prevents the wheels from locking. In the developed embodiment, an aircraft with a drum is connected via a torsion spring at each braked wheel flywheel mounted that allows a relative movement of up to 60 degrees. If the wheel locks, the flywheel initially continues to turn and actuates a valve that reduces the hydraulic brake pressure until the wheel turns again.

distribution

Developed by Dunlop in Great Britain, the Maxaret was used in most British military aircraft. These included the Handley Page Victor , the BAC TSR.2 and the English Electric Lightning . In civil aviation, aircraft like the Hawker Siddeley Trident were equipped with it. In the Fokker F-27 , the system originally developed for hydraulic brakes has been adapted for a pneumatic brake.

Other aircraft with Maxaret were:

In 1966 an electronic version, the Maxaret Mark X, was finally developed.

Use in road vehicles

In addition to aviation, the Maxaret was further developed for road vehicles. This included experimental implementations in the Royal Enfield Super Meteor motorcycle in 1958 and for semi-trailers .

Jensen FF

Jensen FF

It is best known for its use in the Jensen FF , the first series-produced passenger car with permanent all-wheel drive from Ferguson Research . Because of the combination of all-wheel drive and ABS, Sports Illustrated called the car "safest car in the world". The way the Maxaret works in the Jensen FF differs from the aircraft systems. The blocking of an axle is not detected directly on the individual wheel, but on the central differential via a flywheel. This flywheel activates an electrical switch and activates a valve that switches the pressure conditions on the pneumatic brake booster and thus reduces the braking force. The driver feels this through counter pressure on the brake pedal.

Individual evidence

  1. ↑ Non-Skid Braking. Flight International, October 30, 1953, accessed May 30, 2015 .
  2. ↑ Non-Skid Braking. Flight International, October 30, 1953, accessed May 30, 2015 .
  3. ↑ TSR.2. Flight International, April 9, 1964, accessed May 30, 2015 .
  4. ^ RE Gillman: Flying the Trident. Flight International, April 2, 1964, accessed May 30, 2015 .
  5. ↑ Jim Reynolds: Best of British Bikes . Patrick Stephens Ltd, 1990, ISBN 1-85260-033-0 .
  6. ^ John Lovesey, Safety With Exhilaration: The New Jensen, Sports Illustrated, Nov. 8, 1965
  7. ↑ Autocar: Road Test Number 2178, March 28, 1968