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Cannondale's tests of disks and QRs
At last, I've got hold of a report of Cannondale's disk brake/QR test
(you may recall that the CPSC asked them for help last year). It makes interesting reading. They tested a single fork/QR/brake combination. None of the components are named, although the brake seems to be Magura Louise (the brake _pads_ are described as such). The bicycle was secured in a test rig with powered rollers under each wheel, rotating at 15.5mph. I'm not going to type it all in, but this section is taken directly from the test description: "A light hand force of 5 lbs was applied to the brake lever every 10 seconds for 3 seconds duration. This caused braking torque to be applied to the wheel. The drums had 3 equally-spaced cleats (0.5" high the same as those used on wheel fatigue test T027) to create bumps for the front wheel to go over." And then we have: "Conclusion: "The conclusion is that the braking action of disc brakes is not causing the quick release mechanism to unscrew. This test is unable to cause loosening. At this time there are no reasons to believe that anything is missing or over constrained in this test." James -- If I have seen further than others, it is by treading on the toes of giants. http://www.ne.jp/asahi/julesandjames/home/ |
#2
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James Annan wrote:
"The conclusion is that the braking action of disc brakes is not causing the quick release mechanism to unscrew. This test is unable to cause loosening. At this time there are no reasons to believe that anything is missing or over constrained in this test." See Yellow Pages under "whitewash suppliers" Guy -- May contain traces of irony. Contents liable to settle after posting. http://www.chapmancentral.co.uk 88% of helmet statistics are made up, 65% of them at Washington University |
#3
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"Just zis Guy, you know?" wrote in message ...
James Annan wrote: "The conclusion is that the braking action of disc brakes is not causing the quick release mechanism to unscrew. This test is unable to cause loosening. At this time there are no reasons to believe that anything is missing or over constrained in this test." See Yellow Pages under "whitewash suppliers" I did, and found a firm called Brian Hutton & Co. ;-) David E. Belcher |
#4
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James Annan wrote:
snip "The conclusion is that the braking action of disc brakes is not causing the quick release mechanism to unscrew. This test is unable to cause loosening. At this time there are no reasons to believe that anything is missing or over constrained in this test." james, did you check out the pics i posted of my own disk brakes? dropout he http://home.comcast.net/~carlfogel/d...d/Img_3199.jpg info shot of setup he http://home.comcast.net/~carlfogel/d...d/Img_3196.jpg there's no evidence of slippage. there /is/ evidence of indentation where the axle serrations bite into the fork. |
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jim beam wrote:
James Annan wrote: snip "The conclusion is that the braking action of disc brakes is not causing the quick release mechanism to unscrew. This test is unable to cause loosening. At this time there are no reasons to believe that anything is missing or over constrained in this test." james, did you check out the pics i posted of my own disk brakes? Yes, but if you thought I'd be interested in a single case of "my wheel didn't slip" then you have missed the point very very badly indeed. Now, have you any "reasons to believe that anything is missing or over constrained in this test"? Inquiring minds want to know... James -- If I have seen further than others, it is by treading on the toes of giants. http://www.ne.jp/asahi/julesandjames/home/ |
#6
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James Annan wrote:
jim beam wrote: James Annan wrote: snip "The conclusion is that the braking action of disc brakes is not causing the quick release mechanism to unscrew. This test is unable to cause loosening. At this time there are no reasons to believe that anything is missing or over constrained in this test." james, did you check out the pics i posted of my own disk brakes? Yes, but if you thought I'd be interested in a single case of "my wheel didn't slip" then you have missed the point very very badly indeed. polite as always. james, the point is not my "single case" but the lack of cases that you present to the contrary. post some pics of forks evidencing slippage if you please. dismissal of evidence that contradicts your accusations does not add credibility to your case. bottom line is this; put yourself in the position of a manufacturer. are you going to pay attention to a guy on the net who, with respect, misses a vital part of their analysis, then descends to personal attack when challenged, or are you going to rely on your distributor network's return data? trust me, i have been carefully on the lookout for potential ejection problems among all the people i've ridden mountain with since you raised this issue, and you may be interested to learn that i have actually seen one case of slip! but problem is, there was no ejection and it was clearly attributable to an open cam skewer, badly crudded up, that the rider couldn't be bothered to close properly. so, like a broken chain that's attributable to it not being fitted correctly or an under-clamped brake cable slipping and causing brake failure, the only disk wheel slippage i've seen was due to incorrect skewer deployment. and even then, if i hadn't been specifically looking for the slippage, the rider would never have known because he hadn't, nor had he /ever/ had, any problems! certainly not anything as serious as ejection. now, to address your cannondale point, it is clearly a carefully guarded response, but i fail to see how you'd expect anything else in the face of a serious liability threat that's not supported by any statistical evidence. mtb brakes changed from cantilever to linear p.d.q. once it was established that incorrect usage combined with fouling could send a rider over the bar. i don't know the numbers, but i'll wager there were not many o.t.b's before manufacturers made the switch, however statistically unlikely. unless disk brake ejection is actually evidenced, then who is going to fix a problem that doesn't exist? Now, have you any "reasons to believe that anything is missing or over constrained in this test"? Inquiring minds want to know... James |
#7
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jim beam wrote in message ...
polite as always. james, the point is not my "single case" but the lack of cases that you present to the contrary. post some pics of forks evidencing slippage if you please. http://www.velotech.de/saz_12_-_03_-_05.pdf which I found by googling a previous post of mine in r.b.t, so don't pretend you haven't seen it before. Unfortunately, I can't find the rebuttal that you presumably offered, so I'd be grateful for a reminder. now, to address your cannondale point, it is clearly a carefully guarded response, but i fail to see how you'd expect anything else Is this really all you can bring yourself to say about it? Let me remind you of their test: "A light hand force of 5 lbs was applied to the brake lever every 10 seconds for 3 seconds duration. This caused braking torque to be applied to the wheel. The drums had 3 equally-spaced cleats (0.5" high the same as those used on wheel fatigue test T027) to create bumps for the front wheel to go over." And then we have: "Conclusion: "The conclusion is that the braking action of disc brakes is not causing the quick release mechanism to unscrew. This test is unable to cause loosening. At this time there are no reasons to believe that anything is missing or over constrained in this test." You describe that as "carefully guarded, but i fail to see how you'd expect anything else"! Remember that this is not just something they happened to have done and offered to throw into the ring, but a piece of work they were specifically commissioned to do by the CPSC in order to investigate whether there was a potential danger. Have you really no "reasons to believe that anything is missing or over constrained in this test"? You have no opinion beyond "carefully guarded, but i fail to see how you'd expect anything else"? I would be equally amused to hear Mark Hickey's assessment of this test, and Tony Raven's, too. James |
#8
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James Annan wrote:
jim beam wrote in message ... polite as always. james, the point is not my "single case" but the lack of cases that you present to the contrary. post some pics of forks evidencing slippage if you please. http://www.velotech.de/saz_12_-_03_-_05.pdf which I found by googling a previous post of mine in r.b.t, so don't pretend you haven't seen it before. Unfortunately, I can't find the rebuttal that you presumably offered, so I'd be grateful for a reminder. i have deep regret that 1. my german is not strong enough to follow all of the text 2. that i don't have either the time or the ax to grind to look for this stuff. only when i show up on r.b.t. do i ever get to see articles like that, so please james, emotive language like "don't pretend you've never seen it before" merely serves as antagonism. now, to address your cannondale point, it is clearly a carefully guarded response, but i fail to see how you'd expect anything else Is this really all you can bring yourself to say about it? Let me remind you of their test: "A light hand force of 5 lbs was applied to the brake lever every 10 seconds for 3 seconds duration. This caused braking torque to be applied to the wheel. The drums had 3 equally-spaced cleats (0.5" high the same as those used on wheel fatigue test T027) to create bumps for the front wheel to go over." And then we have: "Conclusion: "The conclusion is that the braking action of disc brakes is not causing the quick release mechanism to unscrew. This test is unable to cause loosening. At this time there are no reasons to believe that anything is missing or over constrained in this test." i did read it, thanks. what is restatement trying to achieve? You describe that as "carefully guarded, but i fail to see how you'd expect anything else"! Remember that this is not just something they happened to have done and offered to throw into the ring, but a piece of work they were specifically commissioned to do by the CPSC in order to investigate whether there was a potential danger. Have you really no "reasons to believe that anything is missing or over constrained in this test"? You have no opinion beyond "carefully guarded, but i fail to see how you'd expect anything else"? I would be equally amused to hear Mark Hickey's assessment of this test, and Tony Raven's, too. you're just too busy being a victim to make progress in this. if you're serious about getting traction, why don't /you/ commission an independent test from a reputable third party and have your attorney submit it? habeus corpus. any attorneys here want to represent james? |
#9
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James Annan wrote:
I would be equally amused to hear Mark Hickey's assessment of this test, and Tony Raven's, too. I'm staying out of this. My views are well known and there is not a lot of point repeating them in the church of the faith. I did plan to do what no-one seems to have done and go and find out what 5lbs force on the brake lever was like. I know I don't squeeze my brakes as hard as I possibly can so I know 100lbs is not realistic. However I have no idea at present what 5lbs represents in my normal range of braking. Is it top end, bottom end, middling? Can anyone here say yet because until they can then ridiculing the figure absent realistic reference points is conviction not scientific enquiry. Damn, I just got sucked in. Tony |
#10
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in message , jim beam
') wrote: James Annan wrote: jim beam wrote: James Annan wrote: snip "The conclusion is that the braking action of disc brakes is not causing the quick release mechanism to unscrew. This test is unable to cause loosening. At this time there are no reasons to believe that anything is missing or over constrained in this test." james, did you check out the pics i posted of my own disk brakes? Yes, but if you thought I'd be interested in a single case of "my wheel didn't slip" then you have missed the point very very badly indeed. polite as always. james, the point is not my "single case" but the lack of cases that you present to the contrary. post some pics of forks evidencing slippage if you please. dismissal of evidence that contradicts your accusations does not add credibility to your case. Darth Ben of Kinetics carried out his own independent tests and observed slippage under braking, with properly tightened skewers; and published his results on the net. If this happens in 0.01% of bicycles that's still an awful lot of very nasty crashes. The fact that it doesn't happen in 99.9% of bicycles is good news but does not prove there is no problem. -- (Simon Brooke) http://www.jasmine.org.uk/~simon/ ;; better than your average performing pineapple |
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