Sponge Posted October 13, 2005 Report Share Posted October 13, 2005 (edited) . Edited April 26, 2014 by Sponge Quote Link to comment Share on other sites More sharing options...
tipsy Jock Posted October 13, 2005 Report Share Posted October 13, 2005 So it was the noise and vibration and not the repetative on off frame flex caused by the brake that broke their frames? (Y) Quote Link to comment Share on other sites More sharing options...
Bionic Balls Posted October 13, 2005 Report Share Posted October 13, 2005 resonance....anyone bothered to work out the frequency required to resonate certain tubes? cba personally..but i can feel it too. adam Quote Link to comment Share on other sites More sharing options...
Sponge Posted October 13, 2005 Author Report Share Posted October 13, 2005 Well, I got this idea from a friend, who happens to be a trials rider, at the same time a bike mechanic and has studied all sorts of engineering and knows almost everything about bikes, metal properties exactly, and other forces (Physics).. I'm pretty sure that this won't affect many of you, but for Zoo bike 2005 owners such as myself, it could be worth noting about, as the brake mounts are just about the shoddiest design ever on a trials bike, and the vibration is likely to be most powerful there.. it'll probably contribute as well as frame flex in the whole process of brake mount crackage.. Quote Link to comment Share on other sites More sharing options...
Will Arnold Posted October 13, 2005 Report Share Posted October 13, 2005 a booster would help stop vibrations surely? also, get shittier brake pads - no vibration (Y) Will Quote Link to comment Share on other sites More sharing options...
JIX Posted October 13, 2005 Report Share Posted October 13, 2005 Probally not enough to worry about. Actually, not enough to worry about. Resume: Physics A-level Job: Engineer Bikes: 5 years (Y) Quote Link to comment Share on other sites More sharing options...
Luke Drewery Posted October 13, 2005 Report Share Posted October 13, 2005 I run heatsink blues with no tar and they lock like buggery! Loud sharp squeal and feirce lock! I can understand the brake mounts being fatigued by constant vibration and stretching but trials frames should be designed to take that kind of abuse. I for one would rather run a good brake that I can trust than worry about little cracks in my frame! Quote Link to comment Share on other sites More sharing options...
PaRtZ Posted October 13, 2005 Report Share Posted October 13, 2005 a booster would help stop vibrations surely? Would only stop sound coming from the noise the seat stays make when they bend like a bitch :P I think its bull to be honest (N) if it damages metals why isn't it damaging people, and thus we're going to die younger cos of noise. Or do people in night clubs or people who work in a pneumatic drill testing factory die younger? :P :D (Y) Quote Link to comment Share on other sites More sharing options...
Gandalf the Yellow Posted October 13, 2005 Report Share Posted October 13, 2005 i agree with ad101 with his physics-ness. but from physics point of view and a bit of common sense, the resonance from the vibration of the pads can never really cause crack unless there is a clear manufacturing defect. the resonance need to be pretty damn hardxcore to crack a T6 (the zoo's and echos?) or any other good quality alu frames.... we're talking about metals here, not a packet of crisps. steve (N) Quote Link to comment Share on other sites More sharing options...
quick_spider Posted October 13, 2005 Report Share Posted October 13, 2005 Probally not enough to worry about. Actually, not enough to worry about. Resume: Physics A-level Job: Engineer Bikes: 5 years (N) Are you an Engineer or an engineer? (Y) I'd hope you have more than an A-Level to call yourself and Engineer. Resonance wise, why do you want to know the frequency? It's obvious that resonance is occuring. As for the frames cracking? I agree with StinkEE - if it's going to crack, it's going to crack. Jon Quote Link to comment Share on other sites More sharing options...
dave33 Posted October 13, 2005 Report Share Posted October 13, 2005 i think this could contribute to fatigue as iv hear of a plane in the 1960's which was all aluminium and the resonace from flying fatigued the plain wings and body over a long time, they only found out when one of the plains crashed because of losing a wing, cant remember the name of the the plain though. Quote Link to comment Share on other sites More sharing options...
Tomm Posted October 13, 2005 Report Share Posted October 13, 2005 Yeah, but you are comparing the (massive) force of locking the brake and landing a big drop gap (for example) to some mincing little squeak. That's stupid. Quote Link to comment Share on other sites More sharing options...
Mark W Posted October 13, 2005 Report Share Posted October 13, 2005 Hi there, a friend told me recently about really loud rumbly rear brakes can cause eventual frame fatigue. By this I immediately thought of the brake mounts cracking on 2005 Pitbulls and a Python, I experimented in a way, and pulled the rear brake a bit so it howled really loud, I could definitely feel some vibration in the toptube and all the contact points on the bike. Then I definitely, thought, yes.. This in time, does contribute a bit to frame fatigue, and possibly one of the reasons to why those brake mounts on those Pitbulls and Pythons cracked, let alone brake booster, as the booster does nothing to totally stop vibration of a loud brake. Anyway, I'd just like to see other people's views on this topic. And I wonder if Dan and Ross had loud brakes on the rear , seeing as they fell victim to brake mount cracking.. (N) Are you sure the "Vibration" isn't due to the braking action on the rims though? It's not going to have a super consistent braking feel, so it will feel like it's jolting you. But either way, the tiny vibration from the sound of the brake locking, like Tomm said, is going to be nothing compared to the forces that's making the brake make that noise (e.g. gaps, ups, drops). Poor quality control and a faulty batch caused those brake mounts to tumble off, not C#. Quote Link to comment Share on other sites More sharing options...
dave33 Posted October 13, 2005 Report Share Posted October 13, 2005 Yeah, but you are comparing the (massive) force of locking the brake and landing a big drop gap (for example) to some mincing little squeak. That's stupid. yea the actual force of locking the brake will fatiuge the frame more x100(at a guess) but it will still contribute a small amount Quote Link to comment Share on other sites More sharing options...
Mark W Posted October 13, 2005 Report Share Posted October 13, 2005 yea the actual force of locking the brake will fatiuge the frame more x100(at a guess) but it will still contribute a small amount In the same way riding into a headwind will? (N) Quote Link to comment Share on other sites More sharing options...
dave33 Posted October 13, 2005 Report Share Posted October 13, 2005 correct (N) and what theair pressures like Quote Link to comment Share on other sites More sharing options...
RyanRs Posted October 13, 2005 Report Share Posted October 13, 2005 Resonance wise, why do you want to know the frequency? It's obvious that resonance is occuring. Jon different resonances effect materials in different ways.. a bit like a high ish pitched resonance (not sure the exact Hz) will smash a glass.... whereas lower Hz can moove objects ...like a powerfull car sub.. few years back, so a source of great knowledge told me, when suspension bridges wer built, they would construct a giant bass bin, and play a bass note of a very low resonance, to test the integrity of the structure. there is also that also that 'Brown noise' from brainiac.. aparently if you hear this brown noise....which iirc is a flat tone of a constant resonance , at the right volume level, it relaxes your bowl causing u to shit yourself?! duno if it works though?? Quote Link to comment Share on other sites More sharing options...
Mark W Posted October 13, 2005 Report Share Posted October 13, 2005 different resonances effect materials in different ways.. a bit like a high ish pitched resonance (not sure the exact Hz) will smash a glass.... whereas lower Hz can moove objects ...like a powerfull car sub.. few years back, so a source of great knowledge told me, when suspension bridges wer built, they would construct a giant bass bin, and play a bass note of a very low resonance, to test the integrity of the structure. there is also that also that 'Brown noise' from brainiac.. aparently if you hear this brown noise....which iirc is a flat tone of a constant resonance , at the right volume level, it relaxes your bowl causing u to shit yourself?! duno if it works though?? Yeah, riot police were going to use it, but they found it wasn't directional. So rioters would shit themselves, but so would the police, apparently. Quote Link to comment Share on other sites More sharing options...
mink Posted October 14, 2005 Report Share Posted October 14, 2005 Yeah, but you are comparing the (massive) force of locking the brake and landing a big drop gap (for example) to some mincing little squeak. That's stupid. Abso-bloody-exactly Check out the stress V cycles to failure graph. It shows that below a certain point (the rumble from your brake compared to the actual force required to hold your wheel will be below this point) the number of cycles the component is put through does not contribute (or contributes very little) to fatigue. Quote Link to comment Share on other sites More sharing options...
JT! Posted October 14, 2005 Report Share Posted October 14, 2005 (edited) I'll add my 2 cents. I thought this was one of sponges trademark "I'm thinking about it too much" thread. But the more I thought about it myself, it's quite a valid point. Resonance wise, why do you want to know the frequency? It's obvious that resonance is occurring. The reason we want to know the frequency is because if it matches the frames natural frequency (what it like to resonate at naturally) it will do damage. A few examples. That's the tacoma narrow bridge, basically the wind blew it down in the 1940's. This was because the wind (in to basic terms) had the right speed to make the bridge basically start swaying, like a biatch! After a while it dropped to bits, just because of the right speed of wind. A better example would be a glass, opera singers can shatter glasses just by singing the right note. To find the right note you flick the glass and get the note. The noise it makes is the glasses naturally resonating. If you then 'input' this frequency into the glass, it will start to resonate, the louder the note, the more it will resonate, and because glass is so brittle it will shatter. So as for brake mounts, and resonations from brakes, it could well be possible. But weather the frequency's match (which I doubt they will) it could crack the metal. In theory it's possible, but I doubt that is what is causing frames to crack. It's more likely to be the forces of the brakes pushing out. Edited October 14, 2005 by JT! Quote Link to comment Share on other sites More sharing options...
Will Arnold Posted October 14, 2005 Report Share Posted October 14, 2005 maybe this is one of the drawbacks of u6 aluminium :ermm: Quote Link to comment Share on other sites More sharing options...
Brian Bleech Posted October 14, 2005 Report Share Posted October 14, 2005 Yeah, riot police were going to use it, but they found it wasn't directional. So rioters would shit themselves, but so would the police, apparently. yeah haha they is some weird industrial band that did onstage once - glad i wasn't at that gig! the chances of your brake finding the right resonance frequency is slim and the time your brake is on wouldn't be long enough to cause any serious damage. would be an interesting warrenty claim though.... Quote Link to comment Share on other sites More sharing options...
deadly venom Posted October 14, 2005 Report Share Posted October 14, 2005 Trials forum member sponge made a comment saying that the 2005 Pitbulls had a bad brake mount design. Looking at the 2006 model, in the opinion of the people in this forum, do any of you think the 2006 Pitbull model has bad brake mounts? Ride on, Deadly venom Quote Link to comment Share on other sites More sharing options...
Mark W Posted October 14, 2005 Report Share Posted October 14, 2005 Trials forum member sponge made a comment saying that the 2005 Pitbulls had a bad brake mount design. Looking at the 2006 model, in the opinion of the people in this forum, do any of you think the 2006 Pitbull model has bad brake mounts? Ride on, Deadly venom In that they're generic as hell, and like I said it was a bad batch, I'd say you didn't have anything to worry about. If it was a shit design, would there not be more than a handful of frames breaking out of the hundreds and hundreds sold? Quote Link to comment Share on other sites More sharing options...
quick_spider Posted October 14, 2005 Report Share Posted October 14, 2005 The reason we want to know the frequency is because if it matches the frames natural frequency (what it like to resonate at naturally) it will do damage. It obviously doesn't though. Resonance causes vibrations with massive amplitutes. It occurs when there is little damping. I've yet to see a trials frame with a good timbre. If you think about the glass example - you're shaking the glass enough to break it at it's weak points, ie defects. These defectes are at a molecular level. How much energy do you think would be needed to vibrate a metal 'glass' enough to make it shatter? What sort of frequency do you think it's likely to need? Jon Quote Link to comment Share on other sites More sharing options...
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