New/amateur/garage/kitchen framebuilding discussion

maybw more refined like a chapman bi plane

obviouslyt custom to your bike. but bi plane concept.

or maybe a bit hunter ish

I want to practice tig welding tubing as I assume welding thin wall stuff is an entirely different ball game than plate steel. Does anyone know anywhere to buy steel tubes that will go some way to mimicking the experience of welding 4130 without the cost?

Ceeway sells practice tubes I believe

Also I think quite a few people pick up junk / broken / cheap frames to cut up and practice on

Just buy some bottom end plain gauge top or down tubes from Ceeway.

Cutting stuff up and cleaning paint/powdercoat/rust off is more hassle than it’s worth.

Here’s what Peter offered for anyone wondering. Presumable 28.6 is top tube diameter and 31.8 is down tube/sea tube?

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The 28.6 will be the seattube, 28.6 - 0.8 x2 = 27.0 seatpost or ream it out a bit for 27.2mm.

poifect i'll order one of those, and start welding it together!

What filler rod do people use for 4130? Miller recommends ER70S-2. It is mad expensive though

Er70s2 and er70s-6 are the go to industry standard rods for joining chromoly. A good bet and cost effective. Well understood metallurgy in that combination

Many framebuilders use stainless filler. Er312 for chromoly, some use a proprietary filler called weld mold 880t which is very similar. Stainless filler flows differently and can be nice to weld with but really should be purged as best practice. Certainly in my opinion on thin wall tubing. I use a mix of the two depending on how I feel/the joint and materials used.

For joining chromoly to stainless (usually dropout joint) use 309

Best bet I reckon just use an er7o. Get used to it and at some point in the future try out stainless. I use 1mm dia, occasionally thicker can be handy but I do all of a frame with 1 u just need to feed a bit more consciously in higher fill areas

Prior to seeing this I ordered some a15 in 1.2mm which I understand to be the British Standards equivalent. My tubes appeared to average at about 1.2mm thick and I understood a filler rod of <= the size of the tube to be best practice. Going the whole hog to produce a few frames, expecting to get the bug and Building a frame fixture so I should definitely consider integrating back purging into the fixture.

I use ER70s6. That’s what all the airframe guys use here. I have a big roll of 30thou mig wire for thin stuff (like 20ga) but you don’t really need filler if the fit is good. Even tiny gaps are a bastard to bridge on thin stuff. Might be easier with Tig but I’ve never tried it.

Not a frame but there is no filler in this bit - 20ga mild steel.

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For practice, I use regular mild steel. It welds just like 4130 and is a fraction of the price. I started on 20ga sheet but any old tubing will do. The technique is a bit different for mitred corners as you bridge across and need to modulate the heat as you go around.

I’m pissing around with Aluminium now which is a bit of a bugger…

Slow progress but I only started in May. OA with an old Smith AW1 torch. Lightweight hoses made a big difference for me.

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Oh, final ramble…welding brackets or anything onto thin tube is a total bastard with OA, same for welding to a thicker section. I’ve been welding two stroke pipes but the spring clips and brackets I braze on - you can weld, but it’s SO easy to blow holes. Imagine this would be the case for cable hangers and stuff on bike frames. Brazing is probably stronger for lap joints like that anyway.

These are looking OK. Decent fillet, could probably get them a bit more attractive with some practice. I want to make a swingarm for a motorbike project. Next step, making a jig. It will be in 1 1/8in, 16ga 4130 for the main arm with a triangulated mono shock mount in 3/4in.

The only annoying thing is that my el cheapo notcher is pretty dubious. Very tricky to make repeatable notches, particularly off 90degrees.

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Pissing around with some scrap tubing, trying to tweak my notcher as much as anything. This is 16ga mild steel in 1 1/8” and 3/4”. Interestingly, even though the tubing is the same thickness, I needed two different torch tips. The cluster was at the limit of an AW205 which is it the biggest I have at the moment. Lot of gas and heat required.

Also, very minimal warpage, considering I didn’t clamp anything. Tacked and then ran little beads like you’d tighten a cylinder head. A little bit on opposing sides at a time.

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I’ve got better at welding brackets to thinner wall tube. If you use a slightly larger filler rod than usual for the tube thickness, you can take some heat out of the puddle with a quick dip just as it starts to pool. Saves having to swap tips and dig out the brazing rod.

These are spring clips made from 3/32 rod, welded to 20ga. Works just as well on 22ga. I’ve not tried it on anything thinner, so might still be an issue on the thinnest butted sections of bike tubing.

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Trying to get hold of a fork jig, anyone know of anything that won't break the bank?

A local engineering workshop has been kind enough to offer to teach me to braze for gas money and beers. So thought I'd take advantage of @M_V 's ‘no question too dumb’ policy in the opening post...

The guy at the workshop says he has experience of brazing frames and recommends rods with flux in them. Just wanted to question this as always remember seeing framebuilders slapping flux everywhere. What would people recommend?

I don't think any framebuilders use flux coated rods. You need to really cover the whole joint in flux and at that point, any extra on the rod is pointless.
I think the reason most don't use them is because as I say, you have to flux the joint and I think you can have a lot of trouble with the two fluxes being different and incompatible and some chemical nastiness happening.
If the flux doesn't react badly, I'm sure it would work though. I think you'd want more precise control over your rod by using bare rods but for a quick and dirty job, it would work I'm sure.
Where are you based? I've got a bunch of brazing rods and maybe a pot of flux that you could borrow

Thanks for confirming. From my in-depth research of following framebuilders on Instagram I can't remember any not using lots of flux. Good point on different types of fluxes reacting, hadn't considered that.

That's very kind thank you. I'm based in Bedfordshire but don't mind investing in consumables. Any flux/brass rods you can recommend I'm all ears to repair/further ruin a damaged 531c frame.

Ooof that's not going to be an easy repair.

Sif Bronze no 101 is the rods I've got. 1.5mm dia. And Cycle Design Low Fuming Bronze flux paste.
You can get both from Ceeway.

The Sif rods may be cheaper from a regular welding supplies place. Look around. Usually sold by the kilo which is far more than you're likely to use practicing at home

Thanks for all the help, will get searching on rods but sure the workshop should have them. Just don't want to take the piss and turn up empty handed.

If the frame isn't repairable that's fine, just wanted something to cut up and practice really.