tag:blogger.com,1999:blog-13887692.post4151897016565530851..comments2024-03-21T03:15:06.288-04:00Comments on Cozy Beehive: Safety Moment : Speed Wobble and Jaw FractureRon Georgehttp://www.blogger.com/profile/18394865788996482667noreply@blogger.comBlogger29125tag:blogger.com,1999:blog-13887692.post-52734607065675100042010-09-26T20:15:48.923-04:002010-09-26T20:15:48.923-04:00speculation here, but maybe he fell on top of the ...speculation here, but maybe he fell on top of the wheel? the rim braking surface is barely worn for a 4 yr old wheel; the spokes are popped out of the hub but not broken, nor is the hub flange broken. having broken spokes (drive side rear revolutions, 10 at once, rim fine; front vs derailleur at laguna seca circuit race, again rim fine) and hub flanges (rear, spokes and rim fine)it's hard to imagine anything other than force directly on top of the wheel causing this mess. feel for the guy, but lawyers making shit up with expert witnesses (metallurgy for jurors..right) is a poor response.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-13887692.post-80412187844943050092010-09-15T20:00:06.648-04:002010-09-15T20:00:06.648-04:00Did the tire/tube remain inflated? I've seen f...Did the tire/tube remain inflated? I've seen failure like this at the rim joint due to a tube exploding. In one case I remembered immediately upon reading the above, it wasn't clear whether perhaps movement in the rim joint itself as the result of weakness or an impact had pinched/punctured the tube just prior to the blow out. This wheel was a standard but high quality road wheel with typical road pressures (120psi or thereabouts.) I cannot recall the brand of the rim, but at the time, there were a lot of Mavic Open4CD rims on the bikes we were selling. It was 10+ years ago, so that may make it not applicable to this situation. At any rate, spokes were broken, and the rider crashed when the wheel stopped turning. But again, it wasn't really clear which part of what came first. These were just my suspicions at the time.Jakenoreply@blogger.comtag:blogger.com,1999:blog-13887692.post-9282314632031429662010-09-08T16:59:46.420-04:002010-09-08T16:59:46.420-04:00those aren't broken spokes - they're strai...those aren't broken spokes - they're straight-pull spokes that are no longer attached to the hub. It appears to me the problem is related to the spokes coming loose from their slot in the hub. The failure of the rim (at the joint) is most likely an after effect of the crash.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-13887692.post-56996487185717311472010-09-07T23:13:44.646-04:002010-09-07T23:13:44.646-04:00and by bad it looks like pot metal...something was...and by bad it looks like pot metal...something was wrong w the compositionAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-13887692.post-76597628066721016612010-09-07T23:11:28.060-04:002010-09-07T23:11:28.060-04:00it looks like bad alloy...not a clean break
any on...it looks like bad alloy...not a clean break<br />any one know if mavic controls there own alloy prior to extruding?Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-13887692.post-59503010715918869422010-09-07T11:55:23.793-04:002010-09-07T11:55:23.793-04:00In the chicken & egg world ...It looks like th...In the chicken & egg world ...It looks like the rim failed at the joint...thus allowing the straight pull spokes to disengage from the spoke seats in the hub. This is my complaint with this hub design. It is extremely easy for the spokes to disengage from the hub during a rim incident. The plastic spoke retention ring on the hub flange is more decoration than functional<br />highlighted by there is barely a bend on the rim let alone a broken or bent spokeMicknoreply@blogger.comtag:blogger.com,1999:blog-13887692.post-79245274248570726592010-09-07T11:46:14.575-04:002010-09-07T11:46:14.575-04:00@Shlepzig
Actually, it looks to me like all of th...@Shlepzig<br /><br />Actually, it looks to me like all of the spokes pulled out of the hub with the flare to hold into the hub basically intact. Notice the plate on the side is bashed out of contact too from when they slipped out.<br /><br />So was it in fact the hub that failed first?Unknownhttps://www.blogger.com/profile/00403695097675640092noreply@blogger.comtag:blogger.com,1999:blog-13887692.post-55828709903724721292010-09-07T09:17:19.990-04:002010-09-07T09:17:19.990-04:00Is it possible one or more spokes failed prior to ...Is it possible one or more spokes failed prior to the crash. To which the wobble and loss of feedback in the steering could be attributed. It's hard to reconstruct the actual events when things happen so quickly in a crash.<br /><br />It sounds to me that the spokes might have failed, the wheel went floppy (the most technical term I can think of). Things go wrong pretty quickly from there when it is the front wheel.<br /><br />It appears some of them have pulled out of the hub, not snapped as is common in spoke failure.<br /><br />Hard to say what events prior to the crash might have led up to whatever failure occured.Shlepzighttps://www.blogger.com/profile/16874253261768203181noreply@blogger.comtag:blogger.com,1999:blog-13887692.post-46076350881927219742010-09-07T08:08:06.575-04:002010-09-07T08:08:06.575-04:00Ron-
SUP is mavic's marketing term for a weld...Ron-<br /><br />SUP is mavic's marketing term for a welded seam as opposed to pinned. The wheelset, as far as I know, has always been an open pro rim straight spoke laced to a pair of mavic's generic hubs. They are the same dimension/shape and I've been told by high end bike shop owners that I've worked at that they are the same rim.Natehttps://www.blogger.com/profile/05174378205222344598noreply@blogger.comtag:blogger.com,1999:blog-13887692.post-66328483495742734982010-09-06T23:23:25.178-04:002010-09-06T23:23:25.178-04:00Dear Marco,
To make my stance clear, I did not at...Dear Marco,<br /><br />To make my stance clear, I did not at any point claim that wobble led to this crash. However, wobble can occur at some low speeds and frequencies and depends on a number of factors. Most people agree that there is a component from bike geometry and then a component from a combination of tire and steering influences. For a while, I have been holding this theory that wobbles are something that low wheelbase, flexible bikes with low amount of trail see. Perhaps there is something to do with the moment of inertia of the front end of the bike, as someone mentioned before. In other words, if the mass of the front end components of the bike multiplied with the square of its distance from the COG is low, the bike may not be as stable as one whose front end moment of inertia is higher. However, after chatting with bicycle dynamics experts on this topic, all maintain that we're all neglecting a big factor in shimmy - whats happening at the tire-ground interface. I unfortunately have little expertise with that but would love to learn how that parameter plays into the equation. <br /><br />Either-way, I do agree - it seems a bit pointless now talking about shimmy. That rim crack seems much more interesting!Ron Georgehttps://www.blogger.com/profile/18394865788996482667noreply@blogger.comtag:blogger.com,1999:blog-13887692.post-30439644559872899472010-09-06T23:06:44.780-04:002010-09-06T23:06:44.780-04:00Nate : Observe the name of these rims though. Its ...Nate : Observe the name of these rims though. Its labelled "SUP". Any significance? Are they really open pros?Ron Georgehttps://www.blogger.com/profile/18394865788996482667noreply@blogger.comtag:blogger.com,1999:blog-13887692.post-56968379241853908692010-09-06T23:04:00.596-04:002010-09-06T23:04:00.596-04:00The cosmos are built with open pro rims. I have a...The cosmos are built with open pro rims. I have a pair a year or two older and the are pretty bomb proof. I've commuted and trained on them for 6 years withou tproblem. Nor sure what happened here but they have been good to meNatenoreply@blogger.comtag:blogger.com,1999:blog-13887692.post-88207999042932655482010-09-06T22:55:39.290-04:002010-09-06T22:55:39.290-04:00The rim could be defective - thus the reason why M...The rim could be defective - thus the reason why Mavic is no longer making them. If the rim cracks (especially at it's weakest point - where it is joined) then it's going to break spokes - particularly on this wheel design (with maybe 16 spokes) - if spokes break rapidly they will cause a sudden and dramatic wheel misaligment causing the rim to hit the brake pads on one or both sides - thus causing a sudden change in velocity on the front wheel = going over the bars.<br /><br />That is my theory after seeing many road accidents as a member of the US Team.Tedhttps://www.blogger.com/profile/10393957541874792262noreply@blogger.comtag:blogger.com,1999:blog-13887692.post-16099538019332049582010-09-06T22:41:46.498-04:002010-09-06T22:41:46.498-04:00@Andrew
There are numerous sources which describe...@Andrew<br /><br />There are numerous sources which describe speed wobble to varying degrees. At least one journal paper and plenty of technical works related to motorcycles.<br /><br />Not one really seems to talk about frame alignment with that issue.<br /><br />I'd definitely trust Sheldon Brown and his legacy and Jobst Brandt over Calfree any day of the week including holidays.<br /><br />No bike is perfectly aligned anyway. Bikes are built to tolerance, not absolute perfection.Unknownhttps://www.blogger.com/profile/00403695097675640092noreply@blogger.comtag:blogger.com,1999:blog-13887692.post-86850839356617273782010-09-06T22:20:39.855-04:002010-09-06T22:20:39.855-04:00I'd question a crack across the rim at the joi...I'd question a crack across the rim at the joint (or anywhere else) as the only cause of the failure. The force from the spokes should be pulling any crack like that closed & I'd guess you'd need a pretty strong (read: noticeable) outside force, like a pothole or sudden hard steering input, to make the crack open up enough to cause a failure.Unknownhttps://www.blogger.com/profile/12700667866361934800noreply@blogger.comtag:blogger.com,1999:blog-13887692.post-77426428840894945502010-09-06T20:58:02.561-04:002010-09-06T20:58:02.561-04:00It looks like the rim just failed where it is join...It looks like the rim just failed where it is joined together - yes very commonly where the decals are on most rims - opposite the valve stem.<br /><br />Does not look damaged from striking anything on the road as the rim would be dented.<br /><br />This brings back memories when I was a Junior on the US Cycling Team and my two team mates and I were racing in Poland for the summer.<br /><br />I had Mavic G-4 tubular wheels (later renamed to G40) and hit a couple of nasty bumps in training causing a big dent in the rim. The club's mechanic took out a hammer and a block of wood and fixed the rim and later trued it to just as good as new. I later even raced the Nationals with the same rim.<br /><br />In this incident - it looks like the rim cracked causing it to break the spokes throwing the rim radically out of true which hit the brakes and caused a dramatic speed reduction in the front wheel - throwing the rider over the bars.<br /><br />Not sure why all the talk of a speed wobble as that is not even a factor at speeds over 50 MPH on most bikes.Tedhttps://www.blogger.com/profile/10393957541874792262noreply@blogger.comtag:blogger.com,1999:blog-13887692.post-5846841835240886872010-09-06T19:38:01.232-04:002010-09-06T19:38:01.232-04:00that rim failure looks like it occurred at the par...that rim failure looks like it occurred at the part where they join the rims. the failure looks too straight and clean. and they usually put a sticker over that part to hide the line.<br /><br />Sometimes, that joint is pinned. sometimes welded.<br /><br />I call factory defect on that partnotpjhttps://www.blogger.com/profile/13564263519429316825noreply@blogger.comtag:blogger.com,1999:blog-13887692.post-7018133786759483572010-09-06T18:49:50.453-04:002010-09-06T18:49:50.453-04:00The break does appear to have happened at the spot...The break does appear to have happened at the spot where the rim is joined, I think in the case of this rim by welding.<br /><br />Here is a link to the Calfee paper:<br /><br />http://www.calfeedesign.com/forksymmetry.htm<br /><br />He offers the service of checking your fork for symmetry and claims his forks are more symmetrical than other manufacturers.Tripeltnoreply@blogger.comtag:blogger.com,1999:blog-13887692.post-69074914145567522662010-09-06T18:07:10.403-04:002010-09-06T18:07:10.403-04:00Jason, maybe you could cite some of the sources wh...Jason, maybe you could cite some of the sources which refute Calfee's article. On the face of it it does seem like having the front wheel mounted off-center would cause steering and stability problems, but I'm no expert. I don't think it's fair to dismiss the idea just because it came from a custom frame builder who you think charges too much for his work. <br /><br />To make an extreme example, imagine if the front wheel were mounted several inches off center. In order to stay upright while riding a straight line you would have to constantly lean toward one side, which would cause you to have to steer a little bit opposite the way you are leaning in order to keep going straight, which seems like the perfect setup for a rider-induced oscillation.Andrewnoreply@blogger.comtag:blogger.com,1999:blog-13887692.post-83263703872914748922010-09-06T17:00:00.706-04:002010-09-06T17:00:00.706-04:00Why must he instantly contact an attorney, can'...Why must he instantly contact an attorney, can't an accident just be an accident? The equipment is older and used and i'll bet nobody will admit to being the last person too touch that wheel with a spoke wrench.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-13887692.post-52301365666887720412010-09-06T16:56:56.780-04:002010-09-06T16:56:56.780-04:00Ouch, whats a jaw fracture like? Will be be able t...Ouch, whats a jaw fracture like? Will be be able to chew.Trackasaurusnoreply@blogger.comtag:blogger.com,1999:blog-13887692.post-44091659662431719842010-09-06T16:43:20.352-04:002010-09-06T16:43:20.352-04:00You can get wobble at lower speeds, but it's u...You can get wobble at lower speeds, but it's usually not a huge concern because you can actually control a wobble - the wheel isn't turning very fast so it takes less effort to hold onto the bars. I know this because I experience this when riding on the Cane Creek Speed Bars and I put a lot of weight on them. Typical speeds of 20 to 35 mph, on flat roads. If I ease up on them weight-wise the bike is fine, but I can feel the "potential wobble".<br /><br />Holding the regular parts of the bars (tops, drops) at high speeds (50+ mph) is fine. It's the very forward and low position of the Cane Creeks that seem to cause the wobble.<br /><br />I've used the bars (Cane Creek as well as Scott Rakes) on many other bikes and never had a problem. But the other frames put my bars closer to the saddle so I had less weight on the bars. This bike is much longer, 3 cm longer TT, much steeper seat tube angle (another 2 cm or so), and shorter head tube.<br /><br />On Will's crash, the wheel seems strangely straight for a crash, meaning it doesn't look like it broke on impact. The high number of broken spokes, with no bends etc that I noticed, seems to reinforce the idea that the wheel wasn't broken because of the crash.<br /><br />Interesting. In a bad way. I hope that Will recovers completely.Akihttps://www.blogger.com/profile/17968370190993297395noreply@blogger.comtag:blogger.com,1999:blog-13887692.post-84030953592918409862010-09-06T16:26:50.762-04:002010-09-06T16:26:50.762-04:00@Anon
"Calfee Design has an interesting arti...@Anon<br /><br />"Calfee Design has an interesting article about the cause of speed wobble, basically it is caused by fork asymmetry, which seems unlikely with modern production and quality control standards."<br /><br />Sorry but that's been shown to be patently untrue by numerous sources in numerous locations.<br /><br />Colour me sceptical about their motivations too, but I bet that statement was followed by claims how amazingly accurately they align their outrageously priced custom frames.Unknownhttps://www.blogger.com/profile/00403695097675640092noreply@blogger.comtag:blogger.com,1999:blog-13887692.post-26321017538025761182010-09-06T16:21:23.855-04:002010-09-06T16:21:23.855-04:00There is a paper out there that has a model for sp...There is a paper out there that has a model for speed wobble on a pedal bike - I can't find it right now again but from what I remember it seemed to indicate that significant speed was required for bikes with "big wheels" (ie 700c), high pressure tires and typical geometry. IIRC as well tire pressure was quite important.<br /><br />Wobble is not only an issue of resonance frequency it also requires some sort of in phase forcing to get it going and for the rider to not be "clamped in" with a proper riding position at speed. <br /><br />If you're talking about loose bearings/headsets it has nothing to do with speed wobble, that's just shitty worn out kit or a lousy setup.<br /><br />I'm more inclined to think something happened to the wheel and it lost it's dish for whatever reason and then things went even worse.<br /><br />I've never lost dish on a front wheel, but I have on a rear wheel (debris flew into the spokes and cleared out about 5 split between two sides and then locked up the rear wheel) and it feels very much like the bike no longer responds to steering and wobbles all over the place. Had I been going faster and that been the front I'm sure I would have gone down hard instead of swerving all over and then just toppling.Unknownhttps://www.blogger.com/profile/00403695097675640092noreply@blogger.comtag:blogger.com,1999:blog-13887692.post-20710337846210247552010-09-06T16:04:48.441-04:002010-09-06T16:04:48.441-04:00I'm pretty sure the crack is where the rim is ...I'm pretty sure the crack is where the rim is welded together, opposite the valve stem with a sticker covering it. It's difficult to conclude what caused Mr. Cheng to crash, but this serves as a reminder for all of us to frequently inspect critical components of our bike, especially right before a ride. Calfee Design has an interesting article about the cause of speed wobble, basically it is caused by fork asymmetry, which seems unlikely with modern production and quality control standards.Anonymousnoreply@blogger.com