QR/disc brake theory to be referred to Oz standards authorities - BikeBiz

QR/disc brake theory to be referred to Oz standards authorities

After reading the articles about the QR/disc brake issue on BikeBiz.co.uk, the executive officer of Retail Cycle Traders Australia Inc, the Oz equivalent of the ACT, is to raise the matter with Standards Australia and the Australian Competition and Consumer Commission. Could the US CPSC be far behind? Possibly not as more US bike experts are lining up behind the supposed "scare-mongering" of James Annan. John Forester believes manufacturers could be guilty of "gross negligence".
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The RCTA's Graham Bradshaw said:

"I have flagged [the issue] to Bicycling Trade Magazine [of Australia], and a couple of others, so there are others out there helping raise [your story's] profile.

"I will be commenting on the subject in the members' newsletter later this month, and will also be raising it with Standards Australia, and the Australian Competition and Consumer Commission, who administer the mandatory standard for bicycles here."

James Annan said he had emailed the CPSC, the US safety body that can trigger product recalls, regarding his theory but had yet to get a response. Even relatively minor defects can result in costly recalls. Of course, the CPSC would have a tough job launching a general recall of all disc-brake equipped bicycles because that would involve too many bikes without Annan's "defects."

Bridgestone

In a case that could prove to provide some parallels, Bridgestone Tyres of the US voluntarily recalled 6.5 million tyres in August 2000.

According to Bridgestone, this was done "out of a commitment to public safety and consumer confidence, Bridgestone/Firestone has decided to recall the tires even though no definitive cause has been determined. The number of incidents reported has been relatively low in proportion to the vast number of tires on the road and miles driven."

QR tips

Back here in the UK, CTC technical officer Chris Juden said:

"I'm expecting that the main problem will be found to be poorly-designed after-market fasteners, but that designs of forks will nevertheless change. In the meantime I don't think anything nasty is likely if you have fasteners with radial steel serrations (like Shimano quick-releases or track nuts) and fasten them properly into forks with 'lawyers lips'. And that probably covers most disc-braked bikes, as originally sold."

Failure nodes

US writer John Forester, author of 'Effective Bicycling' and an expert witness in cycle-related court cases, believes the way wheels on some disc-brake equipped bikes continue to be attached by QRs is nothing short of "gross negligence."

"Any brake designer needs to know how the torque developed by the brake is transmitted to the frame of the bicycle.

"It is immediately obvious that with the caliper pads at the rear of the brake disk the torque developed by the brake is transmitted by a couple that consists of upward on the brake frame to the fork, and downward through the axle, again to the front fork. The near vertical slots in the conventional front fork are to permit the front wheel to be removed by downward motion, and are quite secure against the normal weight of the cyclist bearing down on them.

"But they are not designed to resist significant downward pull. The problem is not with the axle fastening system, but with the design of the brake. The brake pads should have been located so that the torque couple is transmitted, say, by forwards and backwards forces on the front fork, or even by an upward force on the axle assembly and a downward force resisted by some form of rigid fixing to the front fork."

On his website, Forester has an article entitled Some Examples of Failures in Bicycle Engineering that have Caused Accidents. He doesn't yet refer to the QR/disc brake problem but what he says could prove to be pertinent:

"In most cases the cause [of a cycling accident], whether it is easy or difficult to discover, is not a failure of engineering design, but of conditions that exceed the capabilities that have been designed into the bicycle or the facility, or of the operator.

"Bicycles are not expected to survive undamaged when being ridden against curbs, curves have a maximum safe speed, human beings cannot make decisions instantly. Engineering knowledge enables us to provide reasonable explanations for many accidents.

"However, there are other accidents that are caused by engineering error. As the eminent Professor Henry Petroski has wisely observed, "I believe that the concept of failure ... is central to understanding engineering, for engineering design has as its first and foremost objective the obviation of failure. ... To understand what engineering is and what engineers do is to understand how failures can happen and how they can contribute more than successes to advance technology." Every advance in engineering brings with it new failure patterns that must be understood before we can guard against them. I have investigated quite a few accidents in which the cause stemmed from the failure of new ideas whose failure modes were not properly understood by the initial designers."


http://www.rcta.org.au

http://www.bikeoz.com

http://www.johnforester.com/.../bicycle_eng.htm

The U.S. Consumer Product Safety Commission

The CPSC is "charged with protecting the public from unreasonable risks of serious injury or death from more than 15,000 types of consumer products under the agency's jurisdiction. Deaths, injuries and property damage from consumer product incidents cost the nation more than $700 billion annually. The CPSC is committed to protecting consumers and families from products that pose a fire, electrical, chemical, or mechanical hazard or can injure children. The CPSC's work to ensure the safety of consumer products - such as toys, cribs, power tools, cigarette lighters, and household chemicals - contributed significantly to the 30 percent decline in the rate of deaths and injuries associated with consumer products over the past 30 years."

http://www.cpsc.gov

PIC ABOVE is by Si Watts - http://www.siwis.co.uk

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