Cracked chainstay bridge weld

Bodhbh

Guru
I was spreading the dropouts on my Raleigh Twenty 'ala Sheldon' from 120mm to approx 135mm to take a Nexus 8-speed hub and managed to partially crack the chainstay bridge weld. I knew this was a risk, but didn't have the gear to stop it happening (i.e. a couple of clamps and few of lumps of drilled out pine). The rear end is now 135 and aligned fine (again checked ala Sheldon), but I'm stuck with a cracked bridge.

Questions -

a) is this a big deal in terms of riding it?
b) it's gonna bug me even if it's fine, so I'd like to get it fixed - where's the best place to get a quick weld? Car mechanic? Correct me if I'm wrong - as it only needs a few globs of weld so far as I can see - but I can't see it's worth the attention of a frame builder.
 

screenman

Legendary Member
Where are you? a car mech could do it, I would prefer a bodyshop tech though. Personally I would find a frame builder or a welder.
 
OP
Bodhbh

Bodhbh

Guru
Where are you? a car mech could do it, I would prefer a bodyshop tech though. Personally I would find a frame builder or a welder.
Salisbury, afaik the nearest framebuilders that'll take on odd jobs are London (Roberts) and Bristol (Argos). Might be wrong on that tho. It's also the fact they tend to have a couple of weeks backlog. I'd post a photo, but tbh, it's hardly visable. I very clearly heard it go tho when I did it.
 

screenman

Legendary Member
Salisbury, afaik the nearest framebuilders that'll take on odd jobs are London (Roberts) and Bristol (Argos). Might be wrong on that tho. It's also the fact they tend to have a couple of weeks backlog. I'd post a photo, but tbh, it's hardly visable. I very clearly heard it go tho when I did it.
Bit too far away for the guys I know to do it then. The reason I said bodyshop guy over mechanic is they tend to be a bit more delicate.
 
OP
Bodhbh

Bodhbh

Guru
Its not welded its BRAZED take it to a cycle shop FFS
tbh I never understood the difference, as I've never been in a situation where I had too. Guess I need to get on Google. I was just hoping to take it somewhere who know's what they're doing to fix it by whatever's the most appropriate technique.
 
I don't know what axle was there before, but you presumably now have a solid 15mm nut one with the hub.

Seems to me the chain stay bridge is now less critical.
 
OP
Bodhbh

Bodhbh

Guru
I don't know what axle was there before, but you presumably now have a solid 15mm nut one with the hub.

Seems to me the chain stay bridge is now less critical.
Yup it's one of those. And yes, quick bit of googling brings up a few posts questioning if they're even needed, bar something to attach the mudguard too. I know my Roatrat only has half a bridge - just long enuff for the mudguard to mount too.
 

Andy_R

Hard of hearing..I said Herd of Herring..oh FFS..
Location
County Durham
tbh I never understood the difference, as I've never been in a situation where I had too. Guess I need to get on Google. I was just hoping to take it somewhere who know's what they're doing to fix it by whatever's the most appropriate technique.
Welding is where you make two or more parts of the SAME metal into one by using heat. Brazing is where you make two or more parts of different or the same metal into one common piece by using a lower melting point metal as a glue.
 
Location
Loch side.
The chainstay bridge is not a structural element of the frame and a crack there is neither here nor there. I don't know if that bike is alu or steel, but welding/brazing the crack involves a repaint as well. If it is aluminium, just leave it. If it is steel, you want to rust-protect it somehow. If it is cracked through and causes noises when you pedal hard, you will want to consider a repair.

You don't say whether you re-aligned the drop-outs. If you didn't, you may have premature hub failures as the hub axle now has to bend into a slight bow when you tighten the QR. Further, tightening the skewer/nut on such a frame with non-parallel dropouts alters the rear derailer alignment. You can see this happening as you tighten. Get yor drop-outs sorted. You get special frame alignment tools for the job but since this is a DIY job, do it by eye. Use a large shifting spanner to slightly (do the math and you'll see it is slight) end the drop-outs inwards. Now use the wheel as a guide - fit the wheel and start to clamp it with the QR whilst watching the gap between the drop-out and the hub's jamb nut. The space should be parallel and there must be no movement as you tighten the QR. If you can achieve that, you've done a perfect job on the frame.

I love the euphemism for "bending the frame open" namely "cold setting". I used to have "Cold Setting" as a labour item on my workshop invoicing system. Somehow I didn't like the term "Frame Bending". You can charge much more for a Cold Set than a Frame Bend.
 
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