Righto –

I’ve got an old commencal frame on my wall thats got a cracked front end. old so single pivot with linkage. I loved the frame. easily the most fun bike ive ever owned and perfect for the local terrain just a bit old skool now (and broken!)

After i’ve fixed welding the van i’m toying with teh idea of making a new steelfront end for it just to see if; A: i can; and B: to make a frame i’d like to ride

Now while i can weld steel (its not pretty but it works) and i’m pretty practical i’ve never made anything quite like this.

I dont fancy throwing loads of money at it so for a test of principle would cutting u an old steel frame for parts be practical? (thinking head tube and BB here) Given its steel i’m assuming i can just grind/ cut off off the bits i dont need!? as i’ve got the old frame i can use that as a guide to get these bits in the right place.

Obviously i neeed a jig and thats probably gonna take more time than the frame to build and get right! Any tips/pics of homemade jig for bodging somehing together to make sure my new front end is mainly straight?

I’m assuming i will probably have to buy a tube for the down tube, seat tube and top tube?

realistically i’m probably 6 months from starting but i recon its worth a try! i have nothing to lose apart from time, a few quid and some teeth when the head tube falls off! – haha.

cheers, mark

Just commenting to follow. Love ideas like this. No matter how it turns out the journey will be brilliant.

If you’re not planning to build more frames, the easier and quicker (and cheaper) way would be to make some kind of rigid rack with fixed geometry rather than fully funcional frame jig.

This guy has some great ideas that you could apply.

If I were you (and could weld or have any kind of framebuilding skill 😉 ) I would copy everything reg mounting points and BB area from the old front triangle and just play with angles and length. Everythung you change around seattube, has to be double checked, beceuse squish and clearance.

Good luck, I’m already jealous!

I have only stick and mig welded on a few occasions in an agricultural manner and certainly never a bicycle, so take this fwiw.

First, can you TIG weld (GTAW)? I believe mig, stick etc are not suitable. Small Inverter welding machines have made tig much cheaper but it’s still expensive, argon is not cheap. The main alternative is fillet brazing.

Can you weld very thin metal? Bike tubing will have walls about 1mm thick.

Cutting through an old frame for practice prices is often recommended to those thinking about welding a frame. Cutting up a frame for parts is not common because plain gauge 4130 tubing is relatively cheap.

Mitering tubes is one of the other main skilsl you will need to develop.

You are very likely to need to buy or make some sort of jig/fixture to makes sure everything is properly aligned.

oh yea i’m just making it 2 inches longer and a bit slacker. i’m keeping teh rear end and suspension linkage as standard. the bearings are all in teh linkage and rear end which helps loads. everything else would be the same for v1!

i think just making a straight jig will probably be harder than the frame!

Watch Paul Brodie’s videos. He’s a real master but a great teacher.

CeeWay for frame tubes and stuff.

Ceeway does various plain gauge Columbus cromo tubes for about £12 per 1.5m length. Butted Zona tubes are about £25 each. Plain bb shell is £7.50. 44mm head tubes £15. Shipping £10. All plus Vat. Plain cromo Gara tubes here:

https://www.framebuilding.com/Spare%20Tubes.htm

A scrap frame cut back to a bb attached to a seat tube will be a good place to start and help with initial alignment (bb already square to the St).

A flat surface is the minimum you need. Think thick mdf, plywood, kitchen worktop etc. Bolt bb and sus pivots to that surface. Hold other tubes at height using blocks of wood, vee blocks or whatever you can bodge.

Brazing is more forgiving than welding but you need access to bottles (but can be done with oxy propane as acetylene is a no no for home use.

just found ceeway – looks ideal!

I’ll bodge something together at some point. should be good for comedy value if nothing else!

i’ll try MIG first (as its what i have) i think a buddy has a tig (as hes been welding stainless) if all else fails! i`m not after looks at this stage.

plenty of practice welding thin steel – i’m currently working on a 1972 vw bay and all the thick bits of steel disappears years ago… 🙄 🤣

if, by some fluke, it looks and works OK i might get it made properly.

You can bodge a “one use” jig together out of MDF like the ones used in bamboo bike kits.
Bamboo are thread

Use another frame to get the geo correct….

As Mick says, get new bits from ceeways rather than cutting up old frames. Peter at ceeways is very helpful and great to deal with.

Don’t use MIG, it just doesn’t work for building bikes. You will be wasting your time and money. If a welded frame is what you want then TIG is really the only option.

Don’t use MIG, it just doesn’t work for building bikes. You will be wasting your time and money. If a welded frame is what you want then TIG is really the only option

i keep seeing that but i’ve not really read a good reason why not? surely if MIGs good enough to stick cars together a few tubes would be fine?

it’ll be fiddly admittedly but even i can get really nice mig welds on new clean metal. (admittedly less so on crusty campervan metal!)

Atomic zombie is the only place I’ve seen using mig or stick – but that is mostly thick mild steel tube and gas pipe donor bikes.

https://www.atomiczombie.com/

Generally mig and stick are too hot for thin tubes (burn through and loads of distortion). Car repairs tend to be a load of joined up tacks of poop or short runs that then get ground off. Access into tight corners is also tricky (but not too bad if only a front triangle). Your old VW isn’t made from posh cromoly. Loads of heat, wrong filler wire and shielding with co2 not argon is just sending fancy tubes back to mild steel at the joints.

But do have a go – it sounds like a fun project. Just do it with cheap donor bikes or erw tube if going the mig / stick route.

i keep seeing that but i’ve not really read a good reason why not? surely if MIGs good enough to stick cars together a few tubes would be fine?

Cars aren’t really mig welded together though, they’re spot welded mostly by robots. There’s very few mig welds in a modern car and only on heavy steel parts.

Repairs are done using mig probably because any idiot can do it but even then no doubt you’ve seen all kinds of horrendous damage and and shady bodges done by mig welding patches into cars.

Anything that has to be strong and look half decent like roll cages, wishbones etc are all Tig welded.

Sounds like a cool project though, I’d love to try something similar. Post up the results.

Again, mostly what Mick says. 🙂

Regarding Mig – most car bodywork is 1-1.2mm thick. Bike tubing is generally 0.7 – 0.9mm. For cromoly that thin you would need about 15A weld current. The vast majority of mig machines do not go below 20A and mosy hobby machines will not go below 35-40A. You could try just joining up tacks as per car bodywork but you will almost certainly blow holes and have a poor weld if you do manage not to. Please don’t take this as a criticism of your welding ability, many have tried it before you including me. Unfortunately it just doesnt work.

Add to that the filler should be matched to the tube material. Bodywork is plain old mild steel. Tubes will be at the least 4130 cromoly. You need a filler such as er-70s2 or weldmold 880 (316ss also works). It is hard to get these as 0.6 or 0.8 mm mig wire. Likely damn expensive if you can get it.

I’m not trying to put you off, just trying to save you time and money attempting what other have tried before. The more people riding home made frames the better!

the mechanic in one of the shops local to me cut up old steel bikes to build himself a full suspension frame. he’d never built a frame before and it’s holding up well.

he brazed, rather than welded. the hardest part to salvage was a tapered head tube.

Tapered headtubes are a pain to mitre. 44 is much easier but I haven’t found a cheap source other than that £15 one at Ceeway.

Don’t try and freehand mitre or you will get very frustrated. Plenty of online things for printing off paper templates. Mark a good straight line down the tube so you can align the templates on each end.

I’ve been trying to upload some photos but postimage keeps freezing. Grrrr.