Cracked Ali frame

Yak

Pedelecer
Mar 20, 2020
80
33
It’s a very sad day. My beloved 1997 Carrera Vanquish has a big crack in the frame, and knowledgeable TIG welders have said a fix is one of their trickiest tasks due to the required heat treatment/curing to make a strong weld. They have suggested it is time to retire the old girl. The problem was probably caused by the need to spread the stays wide enough to fit the Yose rear hub wheel, which was wider than the original hub. I struggled fitting the kit and have posted previously on having to dish the wheel to get any clearance with both chain and seat stays on the motor side.

So, my question is, does anyone know what aluminium road bike frames have sufficient rear hub width that this won’t happen again??
44344
 

Andy-Mat

Esteemed Pedelecer
Oct 26, 2018
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The welders gave you good and valid advice.
Till you get your new frame, why not do a good and easy fix on the crack.
Clean off all paint, slightly rough up the surface for some good distance, 2 inches, will be good.
Clean the whole area with methylated spirits. Do not touch with your fingers as sweat and grease will halve or more the strength of the resin to metal bonding..
Wear clean nitrite medical gloves, that you have also cleaned with Meths. You may need a dozen pairs of gloves handy.....
Get some thin fiber glass or carbon fibre bandage, paint the whole area of clean metal, back to the paint, with Epoxy resin and just before it hardens, but still tacky, wrap the bandage, also soaked in resin, tightly around the break.
One layer at a time.
Leave to just "go off" and slightly tacky again, and add some further layers. Make it as thick as you can go. The more the merrier!.
Round off with a further painted on layer of Epoxy resin, sealing to the edge of the old paintwork. Leave no gaps or holes.
Clean tools and skin with meths, before the resin hardens. Your gloves too if you do not have a fresh pair handy....
Leave the bike in a warm room for at least twice the recommended hardening time from the manufacture of the epoxy resin, before using the bike again.
For the first week or so, check the state of the repair before riding.
It may not be pretty, but it should hold for a very long time.
It will look better still if you can match the frame colour!
Polyester and vinyl ester resins are simply not good enough for such a repair, and may break loose under stress.
regards
Andy
PS. Read up on such repairs before starting!!
 

Yak

Pedelecer
Mar 20, 2020
80
33
Thanks for that Andy. A guy in my bike club suggested this but I was a bit doubtful…now I have looked - amazing stuff, epoxy! I’m hoping to get a replacement bike next week, so the e-conversion kit will go onto the wife’s hybrid and my old frame will become art, in some way. I greatly appreciate the time taken for your response though. This is an incredible forum.
 

JPGiant

Esteemed Pedelecer
Sep 3, 2017
346
165
West Yorkshire
How's about this...
 
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Nealh

Esteemed Pedelecer
Aug 7, 2014
14,632
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West Sx RH
Personally any damaged frame I would scrap or not use.
 
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Tony1951

Pedelecer
Mar 27, 2016
202
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Personally any damaged frame I would scrap or not use.
Too true.

The idea of bodging the thing up with fibre glass or carbon fibre is mad. Who wants the back wheel of their bike to suddenly steer them into the path of a truck after going over a bump because a ridiculous bodge repair let go?
 
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Nealh

Esteemed Pedelecer
Aug 7, 2014
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West Sx RH
I had a cube fs bike and scrapped it, somewhere I picked up large full width dent on the underside of the down tube. I decided not to continue using the bike as the chance of the frame giving in wasn't worth the risk esp of road going quickly.
I still have the rear frame and suspension pivots along with the shock and front air forks. The brakes I sold on ebay as they were Hope and not compatible with all my others.
 

Andy-Mat

Esteemed Pedelecer
Oct 26, 2018
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Too true.

The idea of bodging the thing up with fibre glass or carbon fibre is mad. Who wants the back wheel of their bike to suddenly steer them into the path of a truck after going over a bump because a ridiculous bodge repair let go?
You obviously have never used Epoxy or any similar derivatives, not your fault, but you are letting your bias affect your judgement.
A properly made repair will be stronger than the aluminum tubing.......maybe not quite as pretty though!
Think of all the cars, boats, fishing rods and planes that use such products as the main building material! You may have used or been driven in a glass fiber or carbon fiber vehicle, maybe at very high speeds!!!
The fishing rods made from carbon fiber are almost impossible to break, unless you go at them with a heavy hammer maybe, and they are thin walled tubes for lightness!
Even some top quality racing bikes are made from Carbon fiber, not forgetting all F1 cars nowadays!!

Carbon fiber:-

It is a very strong material that is also very lightweight. Carbon fiber is five-times stronger than steel and twice as stiff. Though carbon fiber is stronger and stiffer than steel, it is lighter than steel; making it the ideal manufacturing material for many parts.

Fiber Glass:-

While the exact number for the specific strength of fiberglass varies depending on the specific composite, a good average is about 1,307 kN m/kg. For comparison, stainless steel's specific strength is 63.1, and titanium is 260. That's a massive difference in favor of fiberglass.


Maybe you understand better now?
Have a great day!
regards
Andy
 

Ocsid

Esteemed Pedelecer
Aug 2, 2017
317
210
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Hampshire
The issue here is nothing to do with the strength of the epoxy carbon fibre composite material, I think we all realise that, but its bond to the aluminium, particularly here in this application.
 

Nealh

Esteemed Pedelecer
Aug 7, 2014
14,632
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West Sx RH
Carbon doesn't take much to give way in a crash, It was SW who posted a clip a couple years back of a bike snapping during an off road race.
 

Tony1951

Pedelecer
Mar 27, 2016
202
97
70
Quite a few carbon frames get scrapped every year because they have taken a fall. To need to scrap a steel framed bike it would need to have been run over by a tank.

I actually don't like aluminium frames. They are only repairable when injured if you can access a large oven so it can be cured for about 24 hours. This involves real expense. Any decent welder can fix a steel frame. I wouldn't try it myself, having dabbled with amateur welding and burned holes in plate a sixteenth of an inch thick. I'm no welder.
 

Tony1951

Pedelecer
Mar 27, 2016
202
97
70
The issue here is nothing to do with the strength of the epoxy carbon fibre composite material, I think we all realise that, but its bond to the aluminium, particularly here in this application.
Yes - I'm ignoring that patronising shyte you were responding to. I agree with you - the issue is not whether it is safe to factory produce a carbon fibre air frame or a racing car part after detailed engineering calculations and expert application of fibre reinforced epoxy mixtures, but whether an ordinary chap is likely to make a safe, successful repair to a frame that already failed, by daubing it with epoxy and trying to lay on a fibre cloth to a stump of a tube in his garage, or even in his back yard.

There is a good chance I was using epoxy resin before Andy was even born.

The fact that the frame as already snapped there, implies that the area is under high levels of stress.
 

AndyBike

Pedelecer
Nov 8, 2020
186
88
Can I point out if I may, a fact that if you epoxy a wrap of carbonfiber over an alloy frame the alloy will likely corrode beneath it.
I had a similar query on another well regarded bike forum, and was put straight by someone who works in these materials.
Plus, just wrapping a bit of cloth tape around the stay, cf or no, all you are doing is introducing air bubbles into the 'fix'. You would likely need to a vacuum to make sure the bond is bubble free. CF is strong, but its not a magic material that provides a star trek level bond that is stronger than anything else, and there are criteria in using the stuff.

I wish a simple wrap would solve the ills of the problem, but it just isn't that type of material.
Even some top quality racing bikes are made from Carbon fiber
Indeed they are, but they're not just wrapped around a model and left to set, they are directionally laid up in a mold and then cured under pressure.
 

soundwave

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May 23, 2015
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Andy-Mat

Esteemed Pedelecer
Oct 26, 2018
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The issue here is nothing to do with the strength of the epoxy carbon fibre composite material, I think we all realise that, but its bond to the aluminium, particularly here in this application.
When the metal is lightly roughed up, and properly cleaned with Meths or similar, and then not touched with fingers, the bond is unbelievably strong, even when large temperature changes are experienced..
I have been using epoxy for metal, glass and other items, since I was in school, though it took 24 hours to harden in the early 60s.
When, on an aircraft carrier in the mid 1960s, the air conditioning pumps, huge steel pumps, got attacked/corroded by the icy salt water we used to carry cooling into all spaces requiring it, we simply cleaned the corrosion off down to bare metal, and using huge amounts of epoxy, we "replaced all the corrosion", and isolated the steel from the cold water to prevent further corrosion.
They were then machined to get mating surfaces flat, to prevent any leaks, and they lasted till the carrier was broken up for scrap some 15 years later!!
Furthermore, epoxy resins in those days, would not stick to plastics (as long as I have known them, but they always stuck to properly prepared metal and glass!), and that has been fixed a great many years ago.
Also in the 1960's, it took days to fully harden, that has also been fixed, though even today, slow hardening makes an even stronger bond when required!

This is just one of many suppliers of epoxy talking about metal bonding:-
Everyone should try these the next time something is broken, you have nothing to lose and a lot to gain!

Anyone speaking with no personal understanding of the way such glues, when applied correctly, work nowadays, making impossible repairs possible, is missing out on some really remarkable stuff!

regards
Andy
 

smifee

Pedelecer
Feb 22, 2017
55
55
73
Chandler's Ford
Boxer cargo trike (tadpole type). Moved in close to a kerb to let a load of cars pass. Leaning into the camber. Hit a pothole. Now I'm leaning away from camber. Trike is tipping and I steer into kerb. Back end swings hard into the kerb as I come to a stop.

Brake caliper bracket on frame cracked & twisted.

Waiting on a reply from a mobile welder.


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