Arc welding a bicycle frame

[GeorgeB]

I can almost guarantee when you fit your cable guides you will fit them too close to the steerer head and end up woth horrible kinks etc. Unless you read this first.

I'm pleased I have read the above first. Thanks very much. I'm sure I would have made that mistake. I've now fitted the rear panel, using a plug weld.

Previously, I've thought plug welds were a great technique and so easy. Today, the weld kept sticking to the plate, rather than the crossbar. Eventually, I managed to sort it out but an enormous amount of heat must have been involved.

I think the secret with plug welds is to make sure you drill a large enough hole in the top piece.

 

[Alfaman]

XTR gear cables are the only bike tart components I have ever bought, wonderful things.

XTR cables ROCK! The one thing on my Giant I don't need to worry about getting clagged up with sh*t, they just keep on working faultlessly, bloody brilliant invention.

 

[Alfaman]

drill a large enough hole in the top piece.

you've got it in one, George. Wee holes almost always cause grief & cack spot welds

 

[GeorgeB]

I ended up using a central plug weld and then filled in gaps around the edge with filler. The plate seems very unlikely to fall off but time will tell as to whether I've damaged the crossbar to my potential detriment.

 

[GeorgeB]

I just discovered welded (OEM) tacks on the underside of my donor bike frame. I don't think they're brazed spots because the colour is steel and there are signs of rust. I hope it bodes well for my welding on a similar frame, i.e. that welding is probably OK for this type of steel frame. If there's a danger of heat damage, why would Raleigh or their frame suppliers have used even a few spots of weld?

 

[Windy Miller]

I just discovered welded (OEM) tacks on the underside of my donor bike frame. I don't think they're brazed spots because the colour is steel and there are signs of rust. I hope it bodes well for my welding on a similar frame, i.e. that welding is probably OK for this type of steel frame. If there's a danger of heat damage, why would Raleigh or their frame suppliers have used even a few spots of weld?

Are you sure that's not MIG?

 

[GeorgeB]

Are you sure that's not MIG?

It may well be! I didn't say it's not.

Arc, Mig, Tig - they all produce welding levels of heat.

 

[wyn]

Would that spot weld have been there just to hold things in position for it to be brazed when the frame was made?

 

[GeorgeB]

Would that spot weld have been there just to hold things in position for it to be brazed when the frame was made?

I don't know, but if welding was such a no-no for these steel bicycle frames, I wouldn't have thought they would have risked as much as those simple spots.

 

[gavuk]

I don't know, but if welding was such a no-no for these steel bicycle frames, I wouldn't have thought they would have risked as much as those simple spots.

The original manufacturer has the advantage of knowing the exact composition of the steel they were using ,had probably carried out extensive testing of the joints,and may have employed some form of normalising or heat treatment ,its because of these unkowns ,that most welder's on here have expressed concerns,brazing is not the quickest production technique,but it does use less heat than arc.why braze for no good reason?..We all hazzard our best guess's ,most of us air on the side of caution ....can you take a slice out of that joint and see if its brazed?

 

[GeorgeB]

can you take a slice out of that joint and see if its brazed?

I can but I don't know if it's worth it because I have no doubt the main joint is brazed. My guess is that the spot of weld is there to provide extra strength (not less) in a zone of high tension.

But when I added welding to the brazed joint on the tubes, the general feeling was that it's likely to have weakened the original tube. I accept your point that the manufacturer has the facts and I'm clueless as to the type of steel.

 

[gavuk]

I would tend to agree with Wyn,more likely to aid location for speed of assembly than there for added strength,a brazed slip over joint like that relies on the material strength not really the braze strength.The tack was prob placed there before the brazing took place...I don't know for sure ,i know i would be careful with the fork ends the rest wouldn't worry me,apart from the handlebar stem !

 

[Wozzaaah]

I expect you'll find Wyn's spot on (no pun intended ).
The frame would have probably been jigged up, mig spotted to keep everything in place then passed to the brazing station.
There's no way they'd do those spots after brazing as it would likely compromise the joints.
No need to remove the spots afterwards as they're out of sight.

 

[Alfaman]

George, remember to put a nut on that cotter pin...

Anyway guys, I'm off out of the forum. Good luck with the bike George!
Cheers

 

[Chickenjohn]

I've just read through this entire thread with bemusement- I'm not entirely sure if the original posters and many of the replies are serious or not.

If so and you are risking your life by intending to ride a bike with welded frame and forks in such a manner, then please do ride out to Margate to show the result to me, and if you make it alive a nice cup of tea and a slice of cake will be on offer.

 

[GeorgeB]

I've just read through this entire thread with bemusement- I'm not entirely sure if the original posters and many of the replies are serious or not. If so and you are risking your life by intending to ride a bike with welded frame and forks in such a manner, then please do ride out to Margate to show the result to me, and if you make it alive a nice cup of tea and a slice of cake will be on offer.

I'm serious and I'm sure the responses are sincere. I started gluing together the handlebars with resin this morning and time will tell if the joint holds. The photo with the cotter pin is from the donor bike but I rode that bike for hundreds of miles with no nut on the cotter pin because the cotter pin is seized solid. Any ideas for how to get it out?

Margate is too far, otherwise I'd take you up on your offer.

When I see some of the DIY frames with extreme geometry and weird shapes, I reckon my small project is low risk, unless those bikes and tandems are only intended for exhibition use.

 

[Chickenjohn]

Yes, heat it (blow torch may be enough0 put a nut on the thread and hit it with a big hammer to get the cotter pin out.

I'm a bit worried about fibreglassed handle bars!!!!

 

[chunkolini]

I have always been very suspicious of comosite materials in bikes.
I saw a carbon frame fail once, amazing. Matey got on his bike, clipped his pedal in a cracl, the whole frame shattered, he was left standing there with the bottom bracket and pedal clipped to his foot. 5 minutes we were hitting 50mph down massive hills in the Cotswolds.

Carbon Fibre? burned toast and glue. Dodgy stuff.
Fibre glass? string and glue.

Chunko'.

 

[hotrodder]

With regards to bars/stems/seatposts i am too. With highend lightweight kit some components are going to have a limited lifespan regardless of what they're made from but composites fail in a very different way in a crash. Metal bends some before it snaps. FRPs don't they just snap or shatter.

Been out riding in a group before when one of the guys went down after losing the front. With metal bars he would likely have been able to ride home with just some road rash and bent bars. As it was his carbon bars snapped into several pieces making the bike unusable but that didn't matter too much as he had several carbon splinters pushed quite deeply into his wrist as well as the road rash

 

[GeorgeB]

I used aralidite to glue together the split. I also spread some resin around the handlebars, to see if it prevents them turning. The existing bolt now provides insufficient pressure to stop rotation. Once it's set, I'll use wire and/or fibreglass to lash together the handlebars and the main part of the broken stem.

I was going to try TIG welding until someone said it's the wrong type of aluminium.