dave33 Posted December 6, 2009 Report Share Posted December 6, 2009 so have mony people snapped the axle on these, i know of a couple of people who have, and have you had them replaced? mine snapped after 3 months of comp and natuarl riding.... Quote Link to comment Share on other sites More sharing options...
cai Posted December 7, 2009 Report Share Posted December 7, 2009 Was this the bb that snapped at that Brimham comp?? Quote Link to comment Share on other sites More sharing options...
Matt Vandart Posted December 7, 2009 Report Share Posted December 7, 2009 Very poor show that Dave, I reckon there was a stress point in that BB from shitty manufacture, maybe someone made it on a monday/friday.I got mine almost exactly the same time as yours and mine is still fine, and I bet I do loads more hours riding than you (Loads more spare time) so mine shoulda gone first add that to the fact that I am not as smooth as well, and mine shoulda snapped ages ago. Oh dear I'm gonna be paranoid now, not what you want from BB that cost nearly £100 but then again mine has lasted this long so looks like I got a good one with no faults in it.Did you send it back/complain about it?I would, it hardly lasted at all.Where id you get it from?Did you buy it from E-bay cos if you did your more than likely f**ked for a replacement.What did the failure look like?Have you still got it?I can get one of my guys to analyze the failure if you want have a look at the crystal structure and all that to see what caused the failure.Gimme a shout if you want this to happen because that is pisspoor for such an expensive piece of kit and I am also interested in why it failed. Quote Link to comment Share on other sites More sharing options...
Ali C Posted December 7, 2009 Report Share Posted December 7, 2009 Dave, yours snapped because you had used some other spacers on the axel (same as the axel stops on trialtech and echo bbs). This made your cranks sit further out and increased the stress on the axel. Quote Link to comment Share on other sites More sharing options...
Matt Burrows Posted December 7, 2009 Report Share Posted December 7, 2009 I reckon Dave snapped his so quick cuz he's a dirty fat basher 1 Quote Link to comment Share on other sites More sharing options...
Matt Vandart Posted December 7, 2009 Report Share Posted December 7, 2009 Dave, yours snapped because you had used some other spacers on the axel (same as the axel stops on trialtech and echo bbs). This made your cranks sit further out and increased the stress on the axel.Explain please Ali cos I don't get what you are saying.Seems to me if he had spaced them out then he would not have got his cranks on tight?How wide were these spacers?They would have to be pretty wide to make any difference. Quote Link to comment Share on other sites More sharing options...
Ali C Posted December 7, 2009 Report Share Posted December 7, 2009 the spacers are about 3mm each, I am not sure about the tightness, you would need to ask Dave. Quote Link to comment Share on other sites More sharing options...
cai Posted December 7, 2009 Report Share Posted December 7, 2009 Matt, these spacers Ali are talking about are around 2-3 millimetres - surely not wide enough to add the extra leverage needed to snap a bb! Quote Link to comment Share on other sites More sharing options...
Ali C Posted December 7, 2009 Report Share Posted December 7, 2009 I think part of the problem was that where the cranks ended up sitting was exactly where the internal threads ended meaning all the stress of the rider was going straight into the most stressed point. If the crank was further onto the axel, it would have gone past that point and there wouldn't have been a problem. Quote Link to comment Share on other sites More sharing options...
Matt Vandart Posted December 7, 2009 Report Share Posted December 7, 2009 (edited) No way is that the cause of the axle snapping. Did it snap on both sides?Why were the spacers on there in the first place? Mine doesn't have spacers.Is the axle bent at all?How much wear is in the bearings?Is it a shear failure or is there torsional distortion? Dave have you got the axle? give it to me I wanna look at it. I wanna know if mine is likely to go as well.Edit: the spacers would not have made a significant difference as the load would still be acting at the same distance from the resisting force i.e the plane at the face of the bearing.the only way this load would have been increased significantly is if Dave had increased the length of the axle.You could say that the force applied at the end of the axle was increased because the crank was spaced over 3mm but that is nonsense because different cranks have different offsets, pedals have different length axles.I have two bikes here with total offset differences of more than 3mm (Crank offset + pedal axle length).Also people have significantly different weights which would make more of a difference to the force applied at the end of the axle. Edited December 7, 2009 by Matt Vandart Quote Link to comment Share on other sites More sharing options...
N.Wood Posted December 7, 2009 Report Share Posted December 7, 2009 Mr Vandart, no offense intended but from what I can see you're still a new rider. Dave definately isn't. Quote Link to comment Share on other sites More sharing options...
Matt Vandart Posted December 7, 2009 Report Share Posted December 7, 2009 No offense either but I am a mechanical engineer that specializes in failure mode and effect analysis. Quote Link to comment Share on other sites More sharing options...
Ashley-Wood Posted December 7, 2009 Report Share Posted December 7, 2009 matt vandart does seem to know what hes talking about, i dont see how 3mm could make that much diffrence for it to snap.. as vandart said diffrent pedal lengths would do the same surly.. only thing i can see the 3mm of spacing can do is make it more likly for your to "round" your cranks? as they aint on as far as they could be.. Quote Link to comment Share on other sites More sharing options...
Mark W Posted December 7, 2009 Report Share Posted December 7, 2009 It's impressive how much people can know as a certainty about things they haven't ever seen... Quote Link to comment Share on other sites More sharing options...
AdamR28 Posted December 7, 2009 Report Share Posted December 7, 2009 Product was designed (and passed CN tests to the same level as the Cromo axle) in situation 1, was used in situation 2, pretty clear which one is more likely to break? Quote Link to comment Share on other sites More sharing options...
Luke_zoo Posted December 7, 2009 Report Share Posted December 7, 2009 Product was designed (and passed CN tests to the same level as the Cromo axle) in situation 1, was used in situation 2, pretty clear which one is more likely to break?2 would be the easyest to breake as theres nothing holding the crank arm. Quote Link to comment Share on other sites More sharing options...
Ashley-Wood Posted December 7, 2009 Report Share Posted December 7, 2009 so if i was to put spacers on 3mm thickness, id snap my bb? and if i wasnt to have these spacers on it would be fine.. im sorry but i cant see how 3mm would make that much diffrence to snap an axel... there is more than 3mm in pedal lengths etc, so surly it could be the pedals you run aswell? that picture doesnt exactly seem fair imo to make it fair would you not have to consider where you stand on the pedals the length of the pedals the length of cranks... Quote Link to comment Share on other sites More sharing options...
Rafal Posted December 7, 2009 Report Share Posted December 7, 2009 (edited) So if i have new cranks and i can't put it on completely to the reset axle because they're too tight yet, should i worry too? Or maybe i supose to take big pipe and get in on my 8mm allen key and push it to the end? titanium thread in axle is weaker than steel, isn't it? Edited December 7, 2009 by Rafal Quote Link to comment Share on other sites More sharing options...
Mark W Posted December 7, 2009 Report Share Posted December 7, 2009 so if i was to put spacers on 3mm thickness, id snap my bb? and if i wasnt to have these spacers on it would be fine.. im sorry but i cant see how 3mm would make that much diffrence to snap an axel... there is more than 3mm in pedal lengths etc, so surly it could be the pedals you run aswell? that picture doesnt exactly seem fair imo to make it fair would you not have to consider where you stand on the pedals the length of the pedals the length of cranks...It's more where the crank sits relative to the lip on the spindle rather than how spaced out your pedals are or whatever...So if i have new cranks and i can't put it on completely to the reset axle because they're too tight yet, should i worry too? Or maybe i supose to take big pipe and get in on my 8mm allen key and push it to the end? titanium thread in axle is weaker than steel, isn't it?Cranks generally loosen a fraction so you can tighten it on further after a few rides, so it should be fine - just keep them tight. Quote Link to comment Share on other sites More sharing options...
Ben John-Hynes Posted December 7, 2009 Report Share Posted December 7, 2009 so if i was to put spacers on 3mm thickness, id snap my bb?It's not certain that you'd snap it, but it's a lot more likely. Quote Link to comment Share on other sites More sharing options...
Ashley-Wood Posted December 7, 2009 Report Share Posted December 7, 2009 It's more where the crank sits relative to the lip on the spindle rather than how spaced out your pedals are or whatever...yeah but surly having longer and wider pedals, is going to cause more force than a 3mm spacing... Quote Link to comment Share on other sites More sharing options...
Ali C Posted December 7, 2009 Report Share Posted December 7, 2009 its different Quote Link to comment Share on other sites More sharing options...
Matt Vandart Posted December 7, 2009 Report Share Posted December 7, 2009 (edited) As it goes I havn't seen it Mark.Adam your drawing skills are marvelous but tell us nothing.There are no force values shown, no distance values just a bunch of lines.As stated in my above post, the force is applied to the axle can be considered a point load at the end of the axle.There is a corresponding and opposite force reacting at the plane on the bearing face.This distance is fixed no matter how far off the axle you space the crank.The shear force (and I am assuming it sheared at the bearing I really havn't seen it) is highest at the bearing and lowest at the end of the axle.This force applied at the end of the axle would be the same. It would not be significantly increased by spacing it out 3mm, It's just the same as having a crank + pedal offset of +3mm or a big fat git riding the bike.I can see why you think this it seems logical to blame the spacer but shear forces work to set rules.I'm sorry but it just doesn't work out.It's more where the crank sits relative to the lip on the spindle rather than how spaced out your pedals are or whatever...BolloxThe axle has been designed to resist the load at the resisting plane, this is dependent on the length of the axle not on how far out your cranks are spaced, the calculation is made with the load as a point load at the end of the axle Edited December 7, 2009 by Matt Vandart Quote Link to comment Share on other sites More sharing options...
Mark W Posted December 7, 2009 Report Share Posted December 7, 2009 As it goes I havn't seen it Mark.It wasn't just the BB you've missed then. Quote Link to comment Share on other sites More sharing options...
AdamR28 Posted December 7, 2009 Report Share Posted December 7, 2009 Adam your drawing skills are marvelous but tell us nothing.There are no force values shown, no distance values just a bunch of lines.Sorry, I thought it would be obvious, both circumstances are identical in terms of force and distance - apart from the addition of the spacer (red bit) on the axle.The crank stop (alloy sleeve, grey on my image) on the axle is 15mm long. Adding a 2mm spacer (red bit) means the force is applied at a point which is 2mm further away from the bearing, right? Therefore a higher bending moment on the axle, as the force (which remains identical for the sake of argument) is being applied further from the pivot (bearing).Increasing the width of the pedal is pretty much irrelevant as this will only increase the (vertical/horizontal, whichever you want to use) component of the force a tiny amount? The maths could be done but nobody knows the exact foot position Dave uses so...Edit: Had yet another look at the BB, looks like it's broken at the end of the crank bolt, which ends at almost exactly the same distance from the crank stop as the thickness of the spacer used. There is of course a stress riser from the bolt anyway (solid to hollow section change), but combined with the crank being in the 'wrong place' and not covering over this stress riser... you get the idea. Looks like more of a torsional failure, doubt it would have happened if the crank was up to the stop as designed... Hence Reset not replacing it. Quote Link to comment Share on other sites More sharing options...
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