Forum menu
If the friction is insufficient to stop the part moving, as you seem to suggest, it will move, and then the shear strength of the bolt comes into play.
exactly, except you realise that the shear strength of the bolt will not help you if you are trying to stop rotation..
I like the crows in the vid sounding sad cos they didn't get any dead meat 🙂
Epoxy will not bond properly to curved, shiney Ti. You'll need to flatten and key the surfaces to get a decent bond and this probably (certainly) won't be enough to stop the shear that is induced by the rotating brake caliper. Doing this will also certainly fubar the seat stay.
The brake caliper will, at some point, rotate around the mounting bolt as you only have the tightness of the bolt to stop it (friction). If you carry on tightening the bolt to stop the caliper rotating, you'll reach it's elastic limit and it'll snap. You might get lucky by using higher grade bolts (e.g. 8.8 and above) but I wouldn't bet the crows dinner on it 🙂
Of course it broke; the CF epoxy joint could not resist the thrust forces from the rotation of the brake calipers. I wasn't having a joke with a P clip - I have far more faith in that solution than the rough epoxy joint you made. It will work, but I wouldn't trust it long-term. Prove me wrong. Your problem is really that you have no effective means (short of welding) to resist the thrust along the short tangential bar. Make a longer one and fix it to the existing brake bosses (assuming you didn't grind them off). Or go and buy an adjustable tie rod for the purpose,as already mentioned. That is the solution listed in most of the examples on the the thread I linked to - commercial and otherwise.
PS, I hope the expoxy comes off nicely, and get some 3M Scotchpad to clean up the mess you've made.
toys19 - Member
exactly, except you realise that the shear strength of the bolt will not help you if you are trying to stop rotation..
Eh? There are 2 bolts attaching the lower mount, which is what I am talking about.
Thansk for your concern dj, but I've know about the Scotch 3M thing for decades.
Playing adjudicator here re employment tribunals ... you're both right 🙂
Lawyers wont get out of bed for £££, and typically their £££ are so high that their fees are met by an award made by the courts as part of the settlement (hence the rampant no win no fee culture).
Given that the employment tribunal was set up with the intention of being a mediation service as a last resort they don't award costs (including legal fees) etc. Guess the intention is to keep is simple, and accessible to all (and less threatening and complicated).
Hence any solicitors / barristers that are retained are done so out of the pocket of the individual, and as any pecuniary awards are typically pre-set makes the cost / benefit argument of using a solicitor / barrister less effective. Hence they are a rarity.
In larger case trails, or larger collective suites then yes, they do warrant their inclusion. The majority of companies (mine included) also retain legal insurance (Mentor Services in my case) so when involved do have legal representation, although typically are not necessarily members of the bar nor solicitors (as was my case).
Some household policies do now also include legal representation for employment tribunals so there are a few more about (but again not necessarily solicitors / barristers).
In fact in a lot of instances if you rock up with a solicitor in tow, the adjudicating panel (made up of both a judge as well as representatives from a trade union and business organisation) will frown upon it as it goes against the intention of the tribunal.
So to paraphrase, they do appear in the employment tribunals, but not very often and rarely on the behalf of the claimant.
Now ... ding ding round two.
CA, yes it has 2 but unfortunately you've designed the lower one as a pivot...
BTW Employment tribunals was another much duller thread. This is DIY engineering please stop polluting it with Lawyerly guff 🙂
boblo, how?
so to paraphrase as i dont need to spend my lunch reading al v TJ part Yawn] I assume it broke very quickly when you first braked
You are clive sinclair and I claim my useless underpowered electrical vehicle
I'm sure it came up in the earlier thread(s), but that frame looks like it might take an A2Z adaptor - have you tried it to see, al ?
Sorry to say, this is bang on:
[img] http://www.flickr.com/photos/25846484@N04/5686208299/ [/img]
The lower bolt (red x) is the pivot as there's nothing between the top bolt and the stay to stop the 'spoon' from closing on the stay. As it does this, the Spoon anchor point (black scab) travels up the stay delaminating the epoxy bond. Hard to describe, hope this makes sense.
<edit> can't get my plagiarised photo to show but it's TJ's phot below.
Indeed al - look at your picture that I modified and posted. The bolt marked with a red cross will act as a pivot and the calliper will rotate towards the seatstay -
If you are adamant about continuing with this I suggest you listen to what folk are saying.
You want positivity? You didn't listen to any of the advice you were given previously but try this
What you need is a single plate bolted to both calliper mountings, both bolt holes in teh drop-out and preferably to the axle as well IMO and to the seatstay. If you want to glue it ( and I don't understand why not use the v brake mount) then you need the area to be glued to match the curve of the seat stay
something like this
[url= http://farm6.static.flickr.com/5264/5686936132_7dec98232d_b.jp g" target="_blank">
[url= http://www.flickr.com/photos/25846484@N04/5686936132/ ]Image1[/url] by [url= http://www.flickr.com/people/25846484@N04/ ]TandemJeremy[/url], on Flickr
Then the glued area will only be in compression (ignoring flex in the plate) and you will have a large area glued that might hold
[i]Can I ask what was wrong with well set up 'non-spoon' v-brakes?
They don't work with sti levers[/i]
Nope but a set of mini-vees would.
boblo - this one?
[url= http://farm6.static.flickr.com/5253/5686208299_3d76fc3bd7_b.jp g" target="_blank">
[url= http://www.flickr.com/photos/25846484@N04/5686208299/ ]Image1[/url] by [url= http://www.flickr.com/people/25846484@N04/ ]TandemJeremy[/url], on Flickr
TJ. Yes. Ta.
OK ta boblo, gotcha.
You didn't listen to any of the advice you were given previously
No-one actually [i]knew[/i] whether the epoxy would hold it - and what I was seeking to do in the last thread is exactly what you have proposed BTW (and I have tried that without glue and it works fine) - and you said it wouldn't work on that thread.
So in effect I was right in the last thread and you were wrong, which your post above now concedes.
THREAD CLOSED.
Nope but a set of mini-vees would.
Yeah, but they're awful things IME.
Better. Whatever you do shirley the weld at the bottom of the seat stay would be a weak point as it will be taking loads it hasn't been designed for
No al - what you proposed is not what I have drawn- the critical difference is that I suggest the glued mount should be semicircular wrapped around the seatstay to give a large area of coverage and it still has large doubts about it - that it will be loading stresses into the frame that it was not designed for - some frames have a brace between the seatstay and chainstay to spread these forces and also that the two mounting bolts are m5 and were not designed to take the level of force that you will be putting in them. I also suggest ( as I did before) using the axle as one mount
I knwew it would be a waste of my time trying to help as for reasons of your own if I say it you think it must be garbage and you never actually take a moment to think about it before dismissing it out of hand
j_me - Member
Better. Whatever you do shirley the weld at the bottom of the seat stay would be a weak point as it will be taking loads it hasn't been designed for
Yes, ultimately, that would be my concern. If the epoxy did hold or if you redesigned the support as a triangle to stop the rotation, you'd then be inducing a bending moment into the lower part of the stay.
I'm no frame designer but that stay is not designed to take the induced load and is pretty thin there. I wouldn't be surprised if it would result in a bent or badly dinged stay. With the present set up, that's not a concern as the epoxy will fail at low loads saving the stay from any grief.
Have a go at copying (or buying) the commercial one that picks up the canti boss. That's been properly engineered and the canti boss (and surrounding stay) is designed to take the loads you'll be introducing. It would be a shame to knacker a nice frame unless it's disposable to you.
No-one actually knew whether the epoxy would hold it
I told you it would not hold it you got shitty as you did not want to listen/hear anything critical 🙄
This is brilliant,
We have legal eagle/expert engineer and mechanic Al being slated by NHS/health related desk jockey/renowned multi-discipline expert TJ who is trying to tell these guys
where, why and how the engineering is flawed.The funny thing is everyone in the room (2 x phds, me an MSC and a recent grad)
Absolutely brilliant 😆
And it's just as funny that if Al and TJ actually listened to each other between them they may well be able to come up with something that worked.
As it is, if one says do this the other one decides to do the opposite. Eventually Al will end up with the design originally suggested by TJ by which time TJ will be arguing for Al's original design.
Woody - apart from toys and I were in agreement about the actual engineering. 🙂 Just he was trying to put a positive gloss on it and I was not.
Cue 'Our Tune' theme.....
Love and Hate are such close emotions... I'm expecting them to elope soon and never to be seen again...
Can I ask what was wrong with well set up 'non-spoon' v-brakes?
They don't match the forks. 😆
Have TJ and Cynic-al ever met?
You guys are both in or around E/burgh, right?
cynic-al - trying to even defend that gluing on brake brackets is a good idea is just plain stupid mate. Don't know why others are kidd gloving this, you are a bam for even trying it!
7hz -yes. We used to be friends until al decided to continually make personal attacks on me and refused to stop when asked.
I refuse to believe that either of them exist. They can't be real people, surely...
I will also say that Al is a decent bloke in the flesh - like many of us becomes a complete male chicken behind a keyboard
But sometimes people just get on each others tits as you two obviously do. Why not just invest the energy in something else?
You're both clearly not going to become bosom buddies and the constant sniping and 'he started it' is just a little demeaning for a couple of mature, intelligent (ish 🙂 ) blokes.
Just saying like...
you are right boblo and I should know better.
Anyway, I think Al is in the shed mixing some more epoxy 😆
al for the love of god man dont use that.
ssshhhhhh !Why not just invest the energy in something else?
What else are we all going to watch ?
boblo - MemberYes, ultimately, that would be my concern. If the epoxy did hold or if you redesigned the support as a triangle to stop the rotation, you'd then be inducing a bending moment into the lower part of the stay.
I'm no frame designer but that stay is not designed to take the induced load and [u]is pretty thin there[/u]. I wouldn't be surprised if it would result in a bent or badly dinged stay. With the present set up, that's not a concern as the epoxy will fail at low loads saving the stay from any grief.
It's plain guage ti, of a similar guage to stays used on mtbs. They are never butted by the brake boss.
TandemJeremy - Member
No al - what you proposed is not what I have drawn- the critical difference is that I suggest the glued mount should be semicircular wrapped around the seatstay to give a large area of coverage and it still has large doubts about it - that it will be loading stresses into the frame that it was not designed for - some frames have a brace between the seatstay and chainstay to spread these forces and also that the two mounting bolts are m5 and were not designed to take the level of force that you will be putting in them. I also suggest ( as I did before) using the axle as one mountI knwew it would be a waste of my time trying to help as for reasons of your own if I say it you think it must be garbage and you never actually take a moment to think about it before dismissing it out of
hand
The only difference is your metal c-shape whereas mine is carbon. 2 M5 bolts vs 1 M6 (at the calliper) - a significant difference? Plenty of frames - in fact the majority - have no brace.
I can't take you seriously on many topics because you continually offer advice on matters you have no experience of, come out with guff like the Employment Tribanual thing (and then for reasons best known to yourself refuse to admit anything was wrong when you even changed your statement in the original thread). I have been seriously holding back and let you off with many examples of both since Flounce-gate, as you asked me not to challenge you anymore. If you don't come out with guff, I won't.
Junkyard - MemberNo-one actually knew whether the epoxy would hold it
I told you it would not hold it you got shitty as you did not want to listen/hear anything critical
Lots of people said that - it was the easy answer. Few, if any, had or demonstrated the credentials to back it up.
scaredypants - Member
What else are we all going to watch ?
Indeed, it's a larf...coming soon: al vs TJ 17 - after flounce-gate - Flame-ageddon!
Cynic al - why you have to do this I don't know. You make personal attacks not when I am wrong but when you are unable to understand - as you have done consistently. Examples on this thread. Your desire to attack blinds you to what you are doing
I shall just go back to ignoring you. It seems best.
That's not how it looks to me, you just can't admit that you are or have been wrong to me.
As for "personal attacks", how you can bring that up after your recent efforts beggars belief.
Al - just look back thru this thread about the lower bolt holding the caliper to the mount. Teh one I marked with a red X
It was clear and obvious the calliper would rotate around this. I drew diagrammes to show it. you denied it point blank until others backed me up. You still could not bring yourself to admit I was right and I bet you don't now. even tho the failure was because of this
just go away and have a think about it.
As for my personal attacks on you? you did it to me and thought it acceptable. You don't like it when its done to you nad what I have done is a tiny fraction of what you did.
I will simply ignore all comments from you in future nor will I commnet on your threads.
I have admitted that I got it wrong re. what bolt you lot were on about, and I understood from day 1 why it failed, not my fault you don't make yourself clear.
And I give you 2-3 months 😛
Al - is black white in your world?
My first post
........Even if the lower mount stays rigid the calliper will rotate around lower mounting bolt, clash on the disc and just push the glued on top mount straight off..........
Which is exactly what happened
Your answer
I truly am sorry that I appear to have sufficiently upset you to make you act like a crying schoolboy and type without thinking.Here's a clearer pic, have a think about what you see and see if you want to revisit any of the above before I destroy it.
Dunno what you were going to destroy - what I said would happen is exactly what did happen as you now appear to admit despite
Of course I understand it. If the friction is insufficient to stop the part moving, as you seem to suggest, it will move, and then the shear strength of the bolt omes into play.
In any event I made sure the plate was rotated as far as possible in teh direction it wants to rotate under braking forces before I tightened the bolts up - or I should say nyloc nuts
where again you were shown to be wrong byu toys and boblo as well as myself and others
toys19 - MemberIf the friction is insufficient to stop the part moving, as you seem to suggest, it will move, and then the shear strength of the bolt comes into play.
exactly, except you realise that the shear strength of the bolt will not help you if you are trying to stop rotation..
etc etc
I've come to the party late. I have read some although not all of the thread so may have missed some information, anyone fancy summarising it for me?
It looks interesting.... I am guessing it failed, how did it fail?
What did you use to bond the CF to the frame? Did you do any surface prep before applying the bondage stuff?
TandemJeremy - MemberI shall just go back to ignoring you. It seems best.
*cough*
after one last post chunky 🙂
8)