I am a frame builder AMA

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  • I saw someone recently on mtbr saying that its best to place dt holes in the upper half of the tube.

    Their reasoning was that in general the forces acting on the dt/tt/ht assy are working to pull the ht off the other two. So the underside of the dt is in tension and the upper parts are in compression, as the heat tube levers off the top of the mitre.
    They said holes are more likely to fail in tension and so the best bet was to put them in the top of the tube where the stresses are best suited to a hole. IDK how true this is, but it makes sense.

    I think its still wise to reinforce it a fair bit as there's alot of stresses up there. And to make sure to not put it in the butt transition zone.

  • I did mine under the DT but I did braze a stainless washer around the hole

  • What tubing is it? Waffer thin Spirit or True Temper S3, or Gas Pipe Special?

  • Zona, so it’s on the lighter side of things.

    Hmmm.

    Go in the back of the headtube and through the breather into the dt?

  • Still relatively sturdy compared to others. I'd just do it, but I'm a bit blasé about such things.

  • I’d also just do it but I’m not known for sensible life choices

  • Just realised that it's a lugged frame so if I can put the hole within the lug then it's like a massive reinforcement innit.

  • This might generally be true for MTB, but on a front brake only, dynamo equipped fixie I would imagine there will be lower tensile stresses on the DT as you won't be schralpin rad drops n shit. For instance ISO 4210 fatigue tests road bike headtubes with a symmetrical rearward and forward force, but doubles the forward force for MTB.

    I would say go for it through the lug, but make the effort to deburr properly and seal it with paint and a grommet.

  • What is the reason for not putting in the butt transition zone?

  • This one was reported to be in the butt transition zone...

    More details in the framebuilders fb group


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  • The thinner section in the middle flexes more than the heavier gauge ends, works to distribute stresses over the tube/away from the welds.

    The transition zone can be a focus of those stresses afaik.

  • I can see that makes sense.

    Just measured my last frame and I have banged my holes right in the transition 😬

  • How much heat does it take to distort a tube?

    Less than I thought it seems.

    I’m doing a top tube replacement on an S&S couplered Thorn Nomad. Im only replacing from the coupler forward.

    Did the fillet brazed joint between the top tube and headtube the other day and with the coupler half just slid (but really snuggly) onto the other end of the toptube the frame fit together super nice.

    Silver brazed the coupler half and the cable guides along the bottom of the toptube today and when I undid the couplers to pull it apart to soak the flux off, it pinged.

    The ends of the tubes had moved closer together. Still horizontally aligned but vertically out by around 3-4mm.

    I can’t see that brazing the coupler half onto the end of the tube could have caused this so it must have been putting the cable braze-ons along the under side of the tube that did it.

    Holding a 6” steel rule along the top of the tube does maybe show a slight convex distortion at the point of one of the braze-ons. I might just be looking at it too hard though!

    Its not a problem, I’m certain I can cold set it out but it was just really interesting that the heat from attaching braze-ons could do this. I suppose this will be happening in normal frames too it’s just that the couplers make it much more noticeable.

    Explains why every single frame I’ve ever cut up (and I’ve cut up quite a few) has done that ping.


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  • wow thats pretty crazy, i never really realised!

  • Going back to my dynamo wire routing issue, I used di2 guides but I’m repainting the frame now so thought I’d run the cable through the toptube.

    I’ve silver on some washers but haven’t drilled it yet, anyone got an opinion of my positioning?

    Should be well within the thicker section of the tube.


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  • Any opinions on R-tech tig welders for bike tubing? Specifically this one... https://www.r-techwelding.co.uk/tig-weld­er-240v-dc-160amp/

    I’ve been learning to tig at college but it looks like that’s going to be off for a while so I’m looking to get set up independently. I’ve got a big ol bottle of argon not doing anything so it should be a case of plug an play. I’m liking the look of their 3 year warranty too.

    I can’t really see me using it for much more than bike tubing tbh. I have a mig and oxy/propane setup for bits and bobs. I certainly don’t plan on doing any aluminium so given the thinness of tubing i’m hoping 160amp dc 240v will suffice. Am I on the right track with this?

  • I have one on Biggles's recommendation and I like it. I believe Matt from Talbot used one for years as well.

    Good company to deal.with

  • I only hear good things about them, and great customer service. My friend just bought one and I'd consider one too if my expensive one ever broke.
    I would also definitely consider going for the AC/DC version for aluminium, you won't regret it and aluminium isn't harder to weld. Otherwise you'll find people asking you to do it in a few months time and won't have the kit.
    Aluminium picture frames are always in demand and are fairly simple to churn out 👍
    If you can go for 180amps or more it'll be worth it, especially for aluminium where it needs the extra punch because it conducts alot away to begin with.

    Otherwise 160 covers most bits and bobs in steel.
    You won't look back, loads of work out there for TIG welders it seems 👊

  • Aluminium picture frames are always in demand and are fairly simple to churn out

    How do I get in on this swim? I need more income streams

  • Go round and make friends with the picture framers. They supply the galleries etc. Take a sample.
    Then they can do all the fitting, glass and other faff. You just do the metal
    I did some for a bit, but it can be fairly repetitive.
    Nice mitres and filed perfectly flat/square. Frames and aluminium painting panels too.

    If you don't mind cutting glass and making subframes, loads of artists prefer aluminium frames. But I wouldn't want to be handling paper/canvas artworks to be honest, it raises insurance costs too. Haha.

  • @fizzy.bleach - Awesome, cheers

    I hear you, but I think an AC/DC 200+ looks more like a company purchase further down the line. I’m happy to be limited to mild and stainless for now. Thanks for the advice. Picture frames, who knew!

  • Yeah get an rtech theyre awesome, the warranty is handy and they honour it without question. Last week my pedal was doing some wierd stuff, didnt stop working, but occasionally would blast a load of current at random times. I rang them to see if they had any suggestions, i thought it might be metal dust in there shorting it out somehow. I mentioned that to them they just sent me another one, im not even sure it was in warranty anymore. I really rate them as a company, ive only ever had excellent interactions with them.

    I have the digital verson of the machine you linked, same thing tho, 160a dc. I really like it definitely fine for framebuilding. Mine has barely seen 100amps hah

  • my ac/dc tig recently broke so just bought an rtech tig welder but not used it yet. worth haggling as I got over £100 off mine. its the 160 digital tig.

    also the pedals are hella basic, I'm making my own, in case anyone wants to make one its just about £10 worth of parts; 47k pot, 2 capacitors, cable, plug and a pedal. don't spend £150 or whatever it is, crazy.

    https://www.mig-welding.co.uk/forum/thre­ads/foot-pedal-wiring-pinout.30824/page-­2

    the pot resistance on the new pedals are 47k.

  • I managed to haggle a bit on mine as well, same welder in fact, plus some PPE

  • also the pedals are hella basic

    Yeah i pulled mine apart the other day to give it a clean and see if it helped and there is almost nothing in there. Kinda bollocks they cost 100 quid but they sent me a free one so i dont care

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I am a frame builder AMA

Posted by Avatar for coldharbour @coldharbour

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