[Closed] Pinder v Fox (again, briefly)

Dunno much about it, but I gather the dropout failed, or something, and he sustained horrible injuries as a result of a crash.

are you sure you've read the other thread (fred certainly hasnt)? read the linked articles.

http://www.ne.jp/asahi/julesandjames/home/disk_and_quick_release/index.html
http://spoomplim.blogspot.com/

His front wheel ejected under braking. The case rested around was this his fault for not doing it up properly or was it foxs fault for using the downward facing dropout and QRs which is a known design flaw

which is a known design flaw

which is an [i]alledged[/i] design flaw. It has never been proven that the vertical drop out design has resulted in a forced wheel ejection.

Thanks

Stoner - it has clearly been shown. Hence most for manufacturers moving away from this design.

Hence 15mm thru axles?

The issue is not so much the dropout as the precessional forces unscrewing the QR. The downward facing dropoout turns a failure into a potentially catastrophic failure

Stoner - it has clearly been shown

Where? I still maintain that it has flaws, but at the same time in 99% of cases I'm certain user error will be the contributory factor.

No - 15mm is about shimano/fox establishing a new separate standard from everyone else.

TJ - it has never been proven that the drop out design in this case or any other (vertical) contributed to a forced wheel ejection. There's plenty wrong with the design, but the defence suggested that less-apparent forces were substantial enough to prevent forced wheel ejection even though at FIRST GLANCE the dropout orientation is flawed in common sense.

Stoner - read James Annans stuff and sheldon brown and Kinetics ben - as well as others. The precessional forces are easily shown to be there and so is the force that ejects a wheel.

?So the forces that produce the effect are clearly experimentally and theoretically proven IMO of course

TJ - you're deliberately mis-reading what Ive written.

Ill repeat: the case was brought against Fox in respect of the design of the drop out being flawed because of its orientation. That the precessional forces exist was never contested. It has still not been found by a judge (nor evidenced by the two technical witnesses in court, James Annan's theoretical work or Ben's experiments) that the braking action can develop sufficient forces to pull the wheel out BY VIRTUE OF THE VERTICAL DROPOUT design.

Oh, right, ok.

But is this not the only case where someone has sustained such serious injuries? Has this 'design flaw' led to lots of other crashes?

Sorry, I'm just not up on all this, as quite frankly, I don't really find it very interesting.

The techy stuff, I mean; don't mean any disrespect to the poor young man who was paralysed.

His front wheel ejected under braking.

Did it?

I know he, his bike, half his forks and his front wheel were found at various points going down The Gap, but I'm not sure if it "ejected under braking".

Perhaps the QR failed under a torsional load, and the wheel fell out?

TJ, again, I draw you to my point in the other thread. There is a mass of real world data to draw from on this one - how many people have been using forks of an identical design, with discs, perfectly successfully for an extended period of time? I'd say a hell of a lot.

No-one is contesting that the forces exist, that's a mechanical fact. But, it's the extent of those forces being sufficient to cause the wheel to remove itself from the forks as they are presently designed that is the fact under contention. I don't believe, that without contributory negligence on the users part that they are. I'll happily be proved wrong, but at present I'm not aware of any evidence to do so.

Russ' evidence was that the wheel came out when he braked as a reflex to hearing a strange noise from his front wheel (believed to be the rubbing of the tyre on the inside of the left lower leg), the rubbing suggesting that the QR had worked loose. The allegded design flaw was that should a QR become loose, the orientation of the dorp out made forced wheel ejection possible under braking. A forward facing drop out would theoretically prevent it.

Stoner - I believe differently - I believe that the forces produced have easily been shown to be enough to eject a wheel. However solid proof is hard to come by on this sort of thing. James Annans work shows the magnitude of the forces - easily enough to rip the wheel out. disputed by others and there appears to be no unbiased views.

I still don't understand why ultimately he didn't go after the manufacturer of the QR if that's what they are maintaining actually caused the accident.

While (as previously stated) I do feel sorry for Russ I'd have to say the 10's of thousands (at least!) of other sets in constant use has got to go some way to showing that the setup, while (potentially) flawed isn't as dangerous as some would like us to believe.

I guess the sad thing is that now we'll never really know unless we get somebody from Fox very, very drunk 😉

TJ what you believe is still not proof of cause of failure. All the theoretical evidence presented in court (pretty much along the lines of Annans work etc) was compelling, but fell down on lack of evidential proof. Similarly, the defense could not calculate the resultant forace at the drop out either but made an equally compelling theoretical assertion as to the size of the frictional force acting against the resultant force in the direction of the dropout. This impasse leaves the proof wanting for either side not to mention the out of court settlement also robbing us of an unbiased interepretation of the evidence by a judge.

So I maintain, it's wrong to say it's a known design flaw.

IWH - Pinder's team claimed that precessional forces loosened the QR, although I agree some element of the accident could be attributed solely to the QR function. BUT, the claim against Fox related to the assertion that notwithstanding the cause of a loose QR, a vertical drop out permitted a forced ejection of the wheel under braking, where a properly tested design would have come up with a forward facing drop out to negate the risk of forced ejection. That design element was solely in the hands of Fox as QR orientation has no impact on IS mounts/OLN standards etc.

Fair enough stoner. I believe it has been proven. That does not mean it has been proven to everyones satisfaction. Balance of probabilities / beyond all reasonable doubt???.

Try an experiment - turn your bike upside down and slacken the QR. Spin the wheel and apply the brake - and watch it jump right out of the dropouts.

IWA - Its the dropout design that means a QR failure is catastrophic ( assuming you accept the arguments about magnitude of forces)

your experiment only proves that geometrically ejection is possible. That has never really been denied and I agree, at first glance geometrically that is the problem. It is the real life combination of forces that has been argued over and the defence maintained that when all forces are taken into account even if they are not able to each be isolated and measured, the resultant force is never sufficient to forcibly eject the wheel except under extreme non-real-life conditions (such as zero rider masss etc).

Try an experiment - keep your bike the right way up and remove the QR. Lift the wheel off the ground and shake the bike around. The wheel will fall out.

[i]Try an experiment - turn your bike upside down and slacken the QR. Spin the wheel and apply the brake - and watch it jump right out of the dropouts.[/i]

It may very well do that, but it's an utterly pointless experiment. Do the same thing with the bike sitting on it's wheels, and amazingly enough, nothing really happens at all. Don't know about you, but it's not often i find myself in the contrived position your experiment describes

I keep thinking these threads are about Sam Fox vs Lucy Pinder

NickC try it - you will be amazed the force with which the wheel comes out.

TJ, yes I know, I've tried your experiment myself ages ago when Annan started describing the phenomenon. It made me check my QRs. I can't see how in the real world it describes anything like a circumstance one might find ones-self in.

No one is disagreeing that a loose QR and disc brakes can be a dangerous combination, but if it demonstrated anything, the court case demonstrated that it wasn't as simple a case of a loose QR, as I posted on the bike thread, the independent technical witness summed it up eloquently when he said:

As to why Russ could have ridden many miles (and indeed the very trail of the accident at least 10 times) without the wheel coming out, the witness said [b]that whilst the theoretical sequence could be defined it was only in a combination of many complex factors (many of which he believed were either not able to be identified yet, or if they are not adequately explained) acting in exactly the right manner that the very unfortunate sequence could occur in real life.[/b]

Bikes should be banned

IWH - Perhaps the QR manufacturer doesn't have as deep pockets as Fox or as large a market share and image to protect. Even though I believe user error was the cause Fox couldn't really have risked a wrongful judgement and therefore an out of court settlement was always on the cards and no doubt Pinder was counting on this.

nickc i mentioned this on the original thread, if the bike leaves the ground, drop off, rough ground, and you apply the front brake that would make it much easier for the wheel to come out.

What i can't get my head round is how you don't notice the QR is undone?

What i can't get my head round is how you don't notice the QR is undone?

If the information [url= http://www.ne.jp/asahi/julesandjames/home/disk_and_quick_release/#unscrewing ]here[/url] is correct, vibration (or rather any motion between the interface and the bolt head) can loosen the QR. So maybe it was only loose for a few seconds, then he noticed the bike felt strange or heard a noise and instinctively pulled on the brake.

I expecyed this thread to be a comparison between a classic page 3 girl of the 80's to her modern contempory.
You can imagine my disappointment.....

Mrmo - braking over bumps cause a precessional force that unscrews the QR

Fox v Pinder? A much more interesting debate 😀

[img] [/img] v [img] [/img]

OP, in a really nice way- couldnt you have posed this question on the Pinder v Fox thread? After all the subject was being discussed there? Just a crazy thought I'd like to throw in there.

OP, in a really nice way- couldnt you have posed this question on the Pinder v Fox thread? After all the subject was being discussed there? Just a crazy thought I'd like to throw in there.

Seems like a reasonable thing to do, if you don't want to derail the original thread. It wasn't jimmy's fault people took the opportunity to have the same argument all over again on this thread as well.

TJ - just to re-emphasise the inadeqacy of your experiment, your construct describes a situation without wheel friction giving a retarding force under braking and without the normal force as a result of the rider mass. They are two of the three forces keeping the hub in the dropout (the other being QR clamping force). However, I do agree that [i]if the wheel has left the ground AND the QR is loose, then in theory on application of the brake, there are NO forces keeping the hub in the dropout [/i] and there is then potential for the resultant force created by braking around the caliper to forcibly eject the wheel if the drop out vertical.

However, with a forward facing drop out, even in your construct, the wheel CANNOT be forcibly ejected - this puts the onus on the dropout orientation IMO rather than any other aspect of the accident.

Stoner - I think we are arguing over minutiae.

From my understanding the forces even with the rider on the bike and the wheel on the ground are easily sufficient to eject the wheel. The leverage ratios and stuff easily will do it. I would do some experimenting but I only have discs on bikes with 20mm axles. James annan calculates a force od 1800N and cannondale give almost twice that figure for the force acting to push the wheel out of the dropout. Easily enough to lift the weight of the rider and bike. I can't see any flaw in either set of calculations

As you say tho - the orientation of the droppouts is the crucial thing

why should he get a payout - he should check his bike before use (and during if need be). Duty if care and all that is bollox, taking responsibility for yourself is where it should be at!

[i]why should he get a payout - he should check his bike before use (and during if need be). Duty if care and all that is bollox, taking responsibility for yourself is where it should be at.[/i]

Not necessarily, remember the Alan Ide case re defective handlebars. I also know for a fact that Halfords, Evans amd Cycle surgery have paid out before a case comes to court re shoddy bike builds where parts have catastrophically failed after a few rides due to shoddy workmanship

I understand that the vibration can undo the QR, to expand on my point, a QR needs to move a fair bit to get past the tabs, even slightly loose cones are noticeable, i just find it hard to believe that you wouldn't notice that the QR was loosening before the point where it became so loose that the wheel was able to come out.

At the end of the day the QR was undone the wheel did come out, whether it was "user error" or a mechanical defect is something i don't think will ever be known.

mrmo - and at the heart of the case it doesnt matter how the QR came loose, only that the fork design made it possible for the wheel to forcibly eject under braking. The QR question is a red herring.

If the experiement or the accident was repeatable and mathematically statistically tested and significantly proved dangerous then yes the manufacturer would be at fault.

I think he would have noticed a loose wheel within 5 secs of riding one.

Downhill I would never use a quick release e.g. whistler. Bolts or 20mm-which is what it was designed for.

Materials can fail though and there have been many recalls on shimano QRs!

Most of us haven't got a law degree or mechanical physics Phd.

Best we can do is learn and check out QRs before and during check points of trails. 😈

James annan calculates a force od 1800N and cannondale give almost twice that figure for the force acting to push the wheel out of the dropout. Easily enough to lift the weight of the rider and bike. I can't see any flaw in either set of calculations

Even if these calculations of force are correct (and the fact that 2 people have produced results that differ by a factor of 2 suggests that there's a lack of agreement on how to do this), in what direction are they acting?

Even in a 'vertical' dropout fork, the slot is typically in-line with the fork leg (Annan's involvement/interest originated in his custom fork with a backwards sloping dropout...). Given that the caliper is typically mounted on the back of the fork leg the force is going to be acting at around 20deg away from the perpendicular to the dropout. Although [i]part[/i] of the force is acting downwards, [i]more[/i] of it is acting into the back of the dropout.

In both cases the force quoted is the resultant force in the direction of the dropout. the difference is due to a difference in max deceleration used to calculate the force

stoner, i know the case revolves around the angle and placement of the dropout, and how the braking force acts so that it pushes the wheel out. Just unable to get my head round how the QR got so loose as to be able to come out without the rider noticing?

My experience is that when a wheel is no longer secure it is noticeable.

Fox paying out suggests they weren't confident of winning, which implies that there might be an issue, it might need a certain set of conditions to have been met, but there is something about dropout design and disk brakes that could be an issue.

Just unable to get my head round how the QR got so loose as to be able to come out without the rider noticing?

Have you ridden The Gap? It's quite bumpy.

Which I'd have thought would make it all the more obvious when something wasn't right on the bike in question...

I find this debate very depressing and can only wish Russ well and hope that the outcome helps ease his situation in any way possible.

In both cases the force quoted is the resultant force in the direction of the dropout. the difference is due to a difference in max deceleration used to calculate the force

OK; but presumably we are saying that this directional force is in the first instance created as a result of the interaction between the pads and disc rotor, creating a pivot point. A component of this force is then acting in a particular direction, in line with the dropout. This component will, clearly, be smaller in magnitude than the original force. So... if the pad/disc interface is sufficient to cause the larger decelerative force in the first place, how does the (smaller) component of this force become sufficient to break that same interface? Particularly when that directional force component must also overcome the clamping force of the QR at the same time?

Or am I missing something?

leverage ratios M

leverage ratios M

In what sense?

James Annan describes it better than I can.. Its to do with how far from the effective pivot the force is applied.

In Annan's own 'analysis' he states that the force at the disc is 2460N, whilst the force at the dropout is 2000N. If my understanding of his argument is correct, he is stating that this 2000N force, created as a result of the interaction between the pad and disc, is sufficient to overcome that interaction.

So effect is bigger than cause?