All these bloody framebuilders eh

jealous of the space! so good.

Certainly! Happy to build anything!

Yeah it is really great, im feeling super lucky to have come across it!

I have made progress on the MTB! I welded the front end a few days ago however I'm waiting for a rear wheel to continue. It'll hopefully come early in the week then I can weld the rear end out.

After that I have a track frame for a friend back in London lined up. I think it'll be really cool, it's gonna be all large diameter life tubing.

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I have decided to swap to a different filler metal for Tig welding. I used to use stainless filler, er312l. It's a filler that is used widely across the framebuilding world, it's a good option and is very nice to weld with however it is not the "technically" correct choice according to welding handbooks. The technically correct application for 312 (and similar filler 309) is for joining dissimilar metals, mainly stainless and non stainless. A lot of notable framebuilders (44bikes,chumba, btr) use it and I have no doubt it's just fine but I'd like to change.

I've decided to swap to er70s2, which is a more standard filler metal that is used for a very wide range of steels, it is the go to filler metal for chromoly and the technically correct choice for these alloys so I'm going to use it in the future. It's marginally more difficult to weld with and doesn't have as pretty colours because it's not stainless, but it is the better choice in my opinion.

Ultimately er70s2 is a tried and tested filler that has been used with chromoly steel in a range of safety critical applications (aerospace, rollcages etc) for decades. Er312 is well evidenced to be effective but there's no reason to use it over er70s2.

Gripping stuff I know

Workshop photos. Hopefully the MTB will be done in the next week or so, really excited to finally see it finished.

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Lots of interesting things going on here. Good work!

Nice new workshop and work! Could be a fun experiment to try TIG Silicon Bronze brazing

Very jealous of this space! Would you share what settings you use on the R-tech welder for thin wall frames? I've been messing with settings and think I've come up with something that works, but intrigued by what others are doing.

it is the better choice in my opinion.

I'm curious why you've reached this conclusion. I'm not saying you're wrong, I'd just be interested to know what benefits er70s2 will have over er312.

Thanks! I have never used silicon bronze tig rod but it looks fun id like to give it a go at some point. I think BTR uses it for braze ons

Never mind commissions, when are you taking bookings for week-long Provençal frame building holidays?

@liam-h Sure! I dont use any machine pulse, I find it a bit stressful. So i use straight current, generally between 45 and 75 amps depending on the wall thickness. I have about 0.5s of preflow, i use a #8 gas lens most of the time. I have reasonable postflow of a good few seconds, I cant remember exactly how long ill have a look next time im near the welder. The ramp up on the amps is quite short to keep heat input low, its nice to get started quickly. The ramp down is about 0.7s, its good to have a reasonable taper as well as taper off at the pedal to avoid creating craters when the arc terminates.

I generally pulse using the foot pedal to keep the heat down, sometimes i don't though, it depends on the joint.

@Brommers Its a complex topic with a lot of opinions etc. Id hesitate to say one is better than the other i don't think its easy to draw a conclusion like that. I think there's a lot of evidence to show that stainless filler is fine, clearly people have used it a reasonable amount and the frames are fine. Certainly stainless filler generally will have a higher yield strength and greater elongation than er70s2 or 6, which is nice. However this doesn't really help in any meaningful way, if you crash your frame hard enough to push things at the weld, filler choice is unlikely to affect the outcome.

Most bicycle frames fail from fatigue, which is where stainless filler has the potential to cause a problem. Most stainless steels have a reasonable amount of chromium in them, this is an alloying element that gives stainless its properties of not staining as much as other steels. However chromium is susceptible to carbide precipitiation, which is where the chromium bonds with carbon in the presence of air and leads to localised embrittlement within the weld, because carbides are much harder than steel. Another famous carbide is tungsten carbide, which is very hard and used to create cutting tools for machinery. Small hard bits in a weld are bad and lead to failure as they act as stress risers which can form cracks. Carbide precipitation is much more likely in 312 because of the amount of chromium it contains.

Another reason that i would like to change is simply based on precedent, there is endless data out there on the metallurgy of chromoly welded using er70s2, its a very well understood combination. There isn't that much on stainless filler in the same application, because people dont generally use it. Reynolds/Columbus/everyone technically specify er70s2 or equivalent alloys to join their tubes as the best method.

So long story short, stainless filler is fine and i may use it every so often for things, but i'm going to switch to er70s2 as the perceived benefits don't outweigh the drawbacks for me. I started using stainless because it does weld easier, and it looks nice. I felt that i could lay better welds with it and that would be ultimately better. Nowadays i can do good welds with any filler and the stainless felt like a crutch that is no longer needed.

Ultimately i think it just boils down to best practice, the difference is likely to be marginal but it makes me feel happy about my process because I feel like I do everything I can to produce a great frame, by following the best practice possible, whether its filler metal selection, acetoning the daylight out of things before welding or spending ages making the mitres really nice. Even if its a negligible difference.

Haha that would be fun, ill let you know! Im getting the worrying urge to open a bike shop as well...

This is the track frame up next, standard but cool, were going with a nice paintjob from Jack Kingston as well so i think it'll be a very tidy build. Tubes are on the way!

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I managed to leave the charger for my drill in England, also the battery is ancient and no longer used by makita so i dont think i can buy a charger that readily. Turns out it works fine with a power supply tho!

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There's adapters out there for old makita power tools

Oh nice! thats very handy thanks!

Nice one, cheers!
I've been playing around with some super slow pulse settings -- 1/sec roughly, with really low background amps, its made it less stressful but less beautiful in my view.

Interesting, I’ve only used Er70s2 and s6. I think the s6 has a bit more silicone in it, and potentially flows better. S2 is the one they code out here for all the airframe and race car stuff for 4130 tubing.

Workshop looks fantastic.

Awesome, Ive played around a bit with that kind of thing, i think a lot of people like it and you can make nice beads like that for sure! Only thing to be wary of is underfilling the bead, when the pulse on time is very low there isn't much time to fill the puddle with filler. So i know some people who use that technique tend to use a larger filler to be able to add more metal while the pulse pulses.

Yeah s2 and s6 are fairly similar although the extra silicon in s6 makes it feel like it flows more for sure, i find it a bit more difficult actually as the puddle can be a bit more squirrelly. Hard to put into words. The purpose of the silicon is to bond to contaminants in the weld and then rise to the surface, so i think the s6 is intended for slightly dirtier things.

Makes sense. I can't say I've really noticed much difference between the two. I've only ever gas welded though, so my puddles and HAZ are a lot larger. I'd love to have a go with Tig one of these days.

Tig is very fun! Certainly recommend giving it a go at some point. Its maybe kinda frustrating at first, but once you've got a bit under your belt its very satisfying