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Braking the mould with electricity

15th February 2001
Page 15
Page 15, 15th February 2001 — Braking the mould with electricity
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Which of the following most accurately describes the problem?

• by Kevin Swallow All-electro braking systems are not new, but replacing tried and tested pneumatic braking technology is a daunting prospect for truck and trailer manufacturers. There are already partial "braking-by-wire" electric truck braking techniques in operation, such as electronic braking systems (EBS) which use electronically controlled brake actuators.

But that final step has always been completed pneumatically—at least until EU regulations catch up.

Axle and suspension manufacturer BPW is working with the engineering arm of sports car manufacturer Porsche on a complete replacement of the air braking system.

BPW launched the Eon-Disc

Ironic concept at the IAA Show at Frankfurt last year, taking what many have seen as the next logical step forward in HGV braking systems. The base for this technology is a newly patented "fixed-caliper" disc brake, but braking-by-wire is still at a very early stage so any suggestion of its imminent arrival would be hasty—it's pencilled in for 2008.

The system separates the functions of actuating the pad and adjusting it for wear, and the symmetrical design of the disc is said to ensure that the load is distributed evenly This differentiates markedly from the brakes conventionally used in CVs as it replaces the floating caliper used in previous systems. On the Eco-Disc-Tronic the disc brake and hub are separated by a floating bearing and during the braking action the disc brake alters its position in response to brake pad wear.

The main benefit with EcoDisc-Tronic is said to be improved safety, with reduced braking distances and times. BPW claims the all-electronic system with its quicker mechanical reaction also improves those all-important fuel figures because the engine does not have to support an air braking system, eliminating the air compressor, brake boosters and slack adjusters.

BPW has already put electronic semi-trailer disc-braking systems into practice on an experimental model. Track tests produced encouraging results but the technology is still at an early stage.

BPW says the system would require a 42V electrical system. This is already in the pipeline as trucks' overall power requirements increase and a number of manufacturers, including Renault, have already produced higher-voltage prototypes (CM 18-24 Jan).

BPW says the entire compressed air system with its associated tanks, valves and piping will become obsolete, with cables replacing pneumatic lines. It also highlights their longer service life, reduced weight, lower cost—and reduced downtime as the caliper does not have to be removed to replace the disc (see box), below left. BPW adds that braking-bywire will make it possible to brake individual wheels in critical driving situations such as preventing a trailer from jackknifing onto counteract a skid.

The disadvantage is seemingly based on the current EU regulations and what sort of back-up system would be needed if the electrical system failed. Also, the process of changing the tractor/trailer coupling is something all truck manufacturers would have to agree to.

Further all-electronic technology is in the offing: in time steering, braking and changing gear will all be controlled "by wire". It's a logical step forward for the industry to take but it relies on policy decisionmakers being on the same wavelength and manufacturers taking the same route.

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Organisations: European Union
Locations: Frankfurt

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