• Quite a few years ago now, @Cycliste bought me a frame kit so I could build my own frame. I've not yet got around to building it. I did build my niece a balance bike for Christmas last year (TIG welded Columbus steel with unicrown forks):

    However, I've never done any brazing before, and the kit @Cycliste got me has lugs which need to be brazed. So rather than just getting an oxy-acetylene kit and giving it a go, I thought I'd do a frame-building course so I could learn to do things properly. I looked at various places, but ended up picking Enigma because I've got an Enigma titanium frame which is rather lovely, and I liked the idea of being taught by Geoff Roberts of the Roberts frame-building family.

    The week-long course started today. My fellow student framebuilder is an English teacher living in Italy called Josh. He's building a road/cyclocross bike with road geometry but Mini-V brakes, while I'm building a winter training bike with road geometry but clearances for mudguards. After getting the frame designed, it was time to start mitering the tubes for the main triangle. I finished that task mid-afternoon, so got to this point:

    I've also cut and mitered the chainstays. Next job is to mitre some tubes to use during my first attempts at brazing, and then it's time to start brazing. @Cycliste assures me it's very easy. Here's hoping she's right.

  • Subbed!

  • Enjoy the course. I'm pretty sure you'll find brazing lugs far easier than tig welding.

  • Ha, been waiting for you to start this.

    Hope you enjoy it as much as I did.


  • Day 2

    Day 1 didn't really feature anything I hadn't done before. I've made my own suspension arms for my race cars, which involves tube mitring, albeit with rather thicker tubing. But day 2 involved the thing I was really waiting for - brazing. I've done plenty of electric arc welding - lots of MIG and quite a bit of TIG in both steel and ali, but I've never used an oxy-acetylene torch before or done any brazing. And day 2 was all about brazing.

    We started off by just laying down some brass blobs on a length of spare tube, which was a bit like TIG welding just rather less precise and a lot slower. I got on reasonably well with that, and Geoff got me trying some lines of braze using a thicker bit of brass rod, like you'd use with fillet brazing. So far, so good. Next up, having mitred some practice pieces, was making tacks between a tube and a lug. We used a small torch tip for this, and it was reasonably straightforward. I did have a few issues in that I was trying to use the torch like a TIG welder, and aiming it at the joint between the lug and the tube, rather than concentrating the heat on the lug. But I got a few tacks made eventually.

    Then it was time to switch to a larger torch tip and a much bigger albeit softer flame to braze the joint properly. On the first one I had a few problems. The first was that I melted a bit of the lug, once again concentrating the heat too much on the shoreline rather than the lug. You can just about see the melted bit of the lug here:

    Also, my TIG experience played against me in that with the larger torch tip and larger flame, the idea is to heat the lug and the tubes generally, rather than focusing the heat in a particular place, something I had difficulty with. I kept moving the torch too close to the workpiece, and overheating it, as I was trying to get the heat more concentrated than was appropriate with the larger flame.

    So Geoff suggested I switch back to the smaller torch tip we'd used for tacking, albeit with a bigger and more powerful flame. This was much better, as I felt I was able to control the heat more effectively with the smaller and more focused flame. My second test piece was still pretty rough, but went a lot better than the first.

    After the two test pieces we were let loose on the real items. The first job was to put some tacks on the bottom bracket and seat tube, which was tricky as the tack was to go on the inside of the bottom bracket. I got it done at last - I kept on trying to add the brass before the bottom bracket shell was hot enough, but got there eventually. Then we fitted the bottom bracket onto a post on a surface table and made sure the seat tube was straight. Then it was time to start brazing the lugs on the head tube properly. I did the top one first, and then the lower one. By the time I was doing the lower lug, I started to feel I was getting the hang of it. I was able to insert the brass at one side of the lug, and pull it through to the other side using the heat from the torch. Obviously, I still have a lot to learn, and lots of practice ahead of me, but it seemed to go reasonably well.

    The seat tube lug I found a lot harder. The seat tube lug has a lot more material in it than the head tube lugs, as it includes the seat binder. I think using the smaller torch tip played against me here, as I simply couldn't get enough heat into the joint quickly enough - I was moving the brass around from place to place, but found it difficult to get it right through from one side to the other, round the back of the seat binder. In hindsight I should have used the larger torch tip for this, but I got it done eventually, albeit with quite a bit of burnt flux.

    So the currently position is that the BB shell is tacked into place, and the other three lugs on the front triangle are in place. Next job tomorrow is to get into the shot-blasting cabinet to clean up those lugs, before fitting the chainstays.

    Today did feature one rather pleasant surprise. I'd been discussing TIG welding with Geoff in the morning, and he'd asked whether I'd ever welded titanium. I'd said no, and observed that learning the TIG titanium was a rather expensive process given the price of titanium tubing, and the fact I was reluctant to spend a lot of money on practice tubing. So at lunch time Geoff turned up with an armful of scrap titanium tubing (mostly bits of scrap frames) for me to practice TIGing titanium when I get home. And apparently there's more to come. I also got the opportunity to have a chat with James Walker, Enigma's specialist titanium welder, who gave me some useful tips on welding titanium (what tungsten to use, the need for a pedal for the welder, prep and back-purging).

    And this evening I did a quick 36km night ride up a hill or two, as my first TT of the year is on Sunday. It was dark and it was raining, but it was rather enjoyable apart from the impatient artic driver.

    All in all, a good day. I've popped my oxy-acetyle and brazing cherry, and feel like I made real progress on the brazing front. Back tomorrow...

  • Good stuff. Looking forward to the updates.

  • Looking good, and a great write-up.

    I wish I'd thought of this as a birthday pressie for myself; oh well, next year...

  • This is the current stash of titanium scrap tubing for TIG practising. Hoping to add to it on Friday when I next drive in...

  • Looking good.

    A bit shocked that you were able to melt the lug though - how close by was the tutor when that happened? It must have had some fair heat in the flame to let that happen...
    Should easily be fixed with a bit more brass or silver and some clean up with the files though.

    I've had similar issues with getting flow at the seat lug (exact same LongShen as yours) and I have wondered if it's also a bit down to tight tolerance too... I prefer using slightly smaller flames than normal like you.
    I'm going to drill a couple of holes in the next one I use - or use a different seat lug. As you say it's a fair chunk of metal by the binder bolt.

    Any progress on the back end?

  • Cheers.

    The melted part on the lug was just on a practice piece, so I'm definitely not going to be spending time fixing it! I suspect Geoff was off dealing with Josh at the time - he's letting me get on with things by myself for long periods, which to be honest I prefer anyway. It was only the edge of the lug which melted slightly, largely I suspect because I was using the large flame and keeping it much too close to the lug. Plenty of progress today - details to follow...

  • Day 3

    Having done the main triangle on day 2, day 3 was all about doing the rear triangle. But before dealing with that, here's a quick action shot courtesy of Geoff. I think he took this while I was brazing the seat lug. Happily, you can't see what a Horlicks I made of it from this shot.

    I'd already cut and mitred the chainstays, so the first job was to fit them in the jig with a dummy bottom bracket shell, and tack the chainstays into the rear dropouts. Once they were tacked into place, we inserted the chainstays into the bottom bracket shell on the front triangle, and tacked them into place. After we'd done that, we went back to the front triangle and cleaned up the seat lug in the shot-blasting cabinet and then polished the seat lug using emery paper so that the lug was nice and clean and we could braze the seatstays into place.

    In order to braze the seatstays into place, we had to fit top eyes onto the ends to close off the tubes. According to Geoff until now he'd used cast top eyes, which you simply braze into the end of an open tube, but he decided that we should try plated top eyes. With these, you cut the end of the seatstay at an angle, then braze a thin plate over the end, and file back the plate so it is flush with the outside of the seat say. Here's me brazing the plate into place on the seat stay.

    I decided to leave a bit of the plate top eye extending beyond the end of the seatstay, so that I could bend it over the top of the seatstay. Utterly pointless, but hopefully it'll look good when its finished. Once the plates were in place and shaped, we had to fit the seatstays onto the seat lugs. This needed silver brazing, at a lower temperature than brass brazing, so that we didn't affect the brazing in the seat lug and the brazing attaching the plate onto the end of the seat stay. This was the first time I've used silver braze, and I rather liked it. It flows much more quickly than brass, which means you have to move quickly, but it suited the smaller flame which I seem to get on better with. The flux still needs to be cleaned off, but here are the tops of the seatstays brazed into place.

    Having checked the alignment of the rear triangle using build wheels, and in my case tweaking the tacks on the dropouts to get the wheel straight, we then brazed the seatstays and chainstays into the rear dropouts.

    At the end of the day we also cut the brake bridges and brazed them into position between the seatstays, although I didn't get a picture of that. First job tomorrow is to braze the bottom bracket (at the moment it's only held in place using tacks) and then start on the braze-ons.

    After a day's framebuilding I went off for a ride in the evening, and got a puncture just short of the halfway point. Unfortunately I didn't have a pump with me, so had to ride home on a flat rear tyre. Rather ominously, the Powertap hub stopped working 5 miles from home. Here's hoping it's just a flat battery rather than damage to the hub caused by riding on a flat tyre. Fingers crossed.

  • Day 4

    The first thing to do today was to braze the bottom bracket. Given the difficulties I'd had getting enough heat into the seat lug, and given the sheer amount of steel in the bottom bracket shell, I invoked Rule #5 and went back to using the big torch and the big fiery flame to do this. I erred on the side of caution when it came to adding the brass, and I suspect I added rather too much in a few places. And some in the wrong places too. But it was definitely penetrating through the lugs into the BB shell, so hopefully it's strong enough, and I can tidy up the shorelines in due course. Here's a piccy of it after I'd finished:

    With the bottom bracket finished, all that was necessary to add to the frame were the small braze-ons for cables and bottles cages and the like, together with a chainstay bridge to bolt the rear mudguard to. I did the chainstay bridge first. This was just a length of mild steel, cut to shape with the ends mitred to fit the chainstays, and a hole in it for a bottle cage boss so I could bolt the mudguard directly to the bridge. I also drilled a hole in the bottom of the seatstay brake bridge, and brazed a bottle cage boss into that, again for mounting the mudguard. No picture of the boss in place, just the hole, which isn't that exciting.

    Next up were the cable stops:

    and STI stops:

    and the bottle cage bosses, all of which were silver-brazed into place.

    With all the bits attached to the frame, I had to take the frame off to the shot-blasting cabinet to get rid of the flux and most of the excess brass around the lugs. This is the frame after blasting:

    Before I left today I started filing and polishing the lugs to clean up the shorelines and remove the remains of the excess brass. It's going to be a long job to finish it all off.

    Tomorrow will feature more polishing and filing, some tweaking of alignment on the surface table, and then hopefully a bit of fillet brazing practice.

  • Lovely work. Been toying with the idea of going on one of these courses rather than having somebody (talbot or rourke) build a frame for me, I don't suppose you know if Enigma let 'students' build lugless frames? A couple of courses I've read about only do lugged frames for novices, and I don't fancy a lugged frame.
    Keep up the great work, an excellent write up, look forward to seeing it finished. Jon

  • Lugged frames only at Enigma, certainly on the 2 person course which I'm doing. I'll try to remember ask Geoff if he'd do a fillet lugged frame on a single person course.

  • Thanks. I'm not planning on doing it for a few years ( next big birthday) , so may get some tubes and have a practice.

  • As long as you've got access to oxy-acetylene kit, that sounds like a reasonable plan.

  • Yep got access to flamey stuff, and the head mechanic does quite a bit of work on his kid's scrambler, so he may be able to show me the basics.

  • That looks great, what sort of money is the course?

  • 1200 pounds for a two person course, 1500 if you want to be the sole student.

  • Thanks, That's not bad I suppose.. you obviously get a frame at the end of it? is it painted etc? forks?

  • You have to pay for your materials too. I'd imagine forks and painting are extra.

  • Dan, are you staying in a hotel or comutting?

  • Yep, you get a frame. Painting is extra (I'm doing mine myself) and normally no fork, although I think you can make a fork on the solo course as long as Geoff brakes the fork crown.

  • Staying in a hotel. The daily commute from the Fens would be a bit too much. I'm staying in the Priory Court Hotel in Pevensey. It's very nice. I have a suite...

  • How long is the course?

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Geoff Roberts Framebuilding course - first and second, and third frames. And fourth (now finished). And fifth.

Posted by Avatar for Brommers @Brommers