seat stay boss broken - can it be repaired?

[therevd]

Apologies if this has appeared many times before.
I was fitting a Topeak rear rack yesterday on my daughter's 13.5" Scott Aspect 630 bike.
It has seat stay bosses, so I thought it would be a piece of cake fitting it.
I had the extra long brackets but thought I could get away with using the standard mounting brackets - so I could use the long brackets on my wife's similarly petite bike.
It worked okay on one side but when I tried to finish the job on the other side, I managed to break the boss, which now revolves.
"Argh"* (Not my actual words.)
Is there any way of re-securing the boss to the frame. In the past I have used araldite or something like it to fix a bottle cage boss.
The problem I see with trying to use glue for this is how to get the glue to the right place to fix the boss.
Any advice on solutions to this problem, gratefully received.
I do have the alternative clamp-type fittings, so all is not lost but even if it's just for aesthetic reasons, I'd like to be able to get the bolt back into the boss.
Are there any kinds of adhesive that would work better than superglue for this? Would there be any way the boss could be welded back without causing a lot of cosmetic damage to the aluminium frame?

[tim-b]

Hi

Is it welded in?

Some of these are Nutsert/Rivnut (insert your own tradename) and are fixed into position like a rivet... http://www.biketuna.co.uk/wiki/images/c/c3/Rivnut9.jpg
In the absence of the insert tool you might be able to GENTLY tweak it like this http://www.wranglerforum.com/f19/creating-your-own-nutsert-installation-tool-for-about-2-in-any-size-202021.html It might be a two-person job, one attempting to stop the insert revolving.

Your next stop might be the proper tool, which once threaded in, pulls rather than turns

Make sure that the rackbolt is long enough to use all of the threads in the insert, they can strip.

You really don't want to weld an alu bike frame because they are heat-treated and you could affect its strength

Regards
tim-b

[Brucey]

if you want a nutsert tool which will do the job without rotation, you can improvise one using a QR lever from a hub, a few washers and a suitable hollow axle.

cheers

[therevd]

Many thanks for these suggestions. While waiting for an answer, I tried "trusty" superglue and it seemed to work, until I applied that bit too much pressure on the allen key. I think I've now knackered the thread, so I decided to beat a strategic retreat from the problem. lest I do further damage I hope to regroup my brain cells for another go, using a different approach, so I will see if what you have thus far come up with is within my (limited) skill-set and endeavour to proceed with caution.

[CREPELLO]

Try using a new screw. Also, Brucey's tip on using the QR skewer sounds like it will work well to me.

[Brucey]

if is any consolation the worst case from where you are now is to drill out the extant nutsert (or simply file the top off it) and fit another one. Normally you are left with part of the old nutsert trapped inside the frame which won't come out. This can usually be captivated (to stop it from rattling) by using some wax or similar.

It probably doesn't seem that way to you right now, but this is a five-minute fix if you have the right tools. Given that you can make an M5 nutsert tool using a QR skewer and axle, and the insert itself costs pennies, it isn't even a very expensive fix.

Also, there are worse situations; for example what if you have an (almost undrillable) stainless steel bolt which is well and truly seized (by corrosion) in an aluminium nutsert? If this is stuck in (say) a seatstay, it mightn't easily drop out of the way, into the frame, even when the top is cut off.

cheers

[therevd]

Thanks Brucey and others.
Please accept my apologies for not being the most technically-minded of cyclists.
To be honest, I found the link to the Jeep website, slightly intimidating but was brave enough to revisit it.
As I understand it, the tool suggested was for inserting a "nutsert". The suggestion seems to be that if I can use the tool to insert a "nutsert", I can use the same tool in reverse to remove the one that is currently rotating on my seat stay. Is that the idea?
I don't think I understand the bike tuna link. There aren't enough labels on the diagram for me to know what is what. What is a pullup stud? (Sounds like someone who demonstrates his prowess at the gym with the intention of gaining attention and attendant favours. I am certain that this is not the meaning of the term in the diagram but thought I should preempt any replies in a similar vein.)
The other thing I would appreciate would be a drawing showing how the tool can be made with the QR skewer, washers and axle.
Thanks too for the worst-case scenario. I do hate it when things go wrong but i take comfort that on a world scale knackering a nutsert is annoying, rather than life-threatening. I take confidence from this and am determined to prevail and fix that pesky Topeak carrier, particularly, as it seems the plan B of using the clamp brackets is a non-starter, as the tubes are too fat / clamps are too short.
The threading in the existing nutsert seems completely wasted now, however I will try to ascertain the situation more accurately with a torch to see what the extent of the damage is, rather than waste any more time, simply twiddling the screw at various angles, all to no avail.
Cheers,
Tony.

[tim-b]

Hi Tony

The idea of both the Jeep tool and Brucey's QR refinement is to gently tighten the existing RivNut so that it works as originally designed.
If you have stripped the threads then this won't now work

Please don't take this the wrong way, but if you didn't quite get the suggestions made then I would advise a trip to either a local bike shop (LBS) or an engineer to have the pesky thing replaced, or ignore it and ask the LBS for a suitable P clip

Regards
tim-b

[therevd]

Thanks Tim,
Do have a LBS in Vientiane, Laos. However the one I use is owned by a road race fanatic - hard work finding the shop open - and although he does repairs, and I had intended buying the bike from him, my patience eventually wore out and I bought the bike from a not so LBS in Thailand. So I am little reticent about taking the bike to him. It is a bit of a hassle taking the bike back to Thailand but that might be my best option, if it is something your average bike shop should be able to do.
Having said all that, having had a closer look at the thread, with the aid of a torch, it may not be as bad as feared.
If you or Brucey could send a picture of the QR refinement, I would be grateful. I'm not totally useless when it comes to most routine stuff, this was just beyond my usual scope.
Cheers,
Tony.

[Brucey]

the QR lever approach for M5 rivnuts (nutserts) is detailed here;

http://www.parktool.com/blog/repair-help/water-bottle-fittings

To the astonishment of a very experienced mechanic (who had just shelled out £££ on a special tool for this very job, and had insisted that what I had suggested wouldn't work...) I first used this method to reattach the fittings for wing mirror onto a 1987 Mini, about 25 years ago.

You can exert a load over 1/2 tonne very easily using a bicycle QR, but the stroke is small; you usually need to compress the fitting in three or four goes, tightening everything up each time before the next stroke.

cheers

[therevd]

Many thanks Brucey.
Tony.

[Trigger]

Great tip RE: QR skewer and axle as makeshift rivnut gun, every day is a school day on here which is why I love it!