I am a frame builder AMA

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  • You'd be better off getting whatever Genesis's geared equivalent is. If you don't want a single speed any more it'll be cheaper in total to sell your SS frame and buy geared. By modifying it you're turning it from a rare-ish frame into just another steel hardtail, but modified so some buyers won't want it.

  • Both sensible comments, I'm not desperate to keep the frame as geared - ideally would want something lighter but thought it was worth considering.

    It does a good job as a SS commuter so in no hurry, probably end up with a whole new frame...as usual.

  • I’ve used the DMR version of what @Colonel_of_Truth suggests. Worked fine for me but I was using friction shifters and like 8 (I think) speed components. Modern stuff might be more sensitive.

  • Im thinking of building a lugged frame but using a combination of tubing diameters which is not catered for by available lugs (28.6mm st/31.7mm tt).

    I figure I could pretty easily sleeve the seattube out to fit a 31.7/31.7 lug and could even make it into a decorative feature but I wonder if anyone would have a recommendation of whether I solder the sleeve to the lug first, the tube first, or do both at the same time?

  • Rough cost to get some braze-ons welded onto an old steel frame so I can mount a rack?

  • Dimpling chainstays on a Ti frame to increase tyre clearance. Yay/nay? Rough cost if possible?

    Edit: Enigma says no. Ti tubes can't be crimped once they have been welded. Didn't understand why but it had something to do with stress release.

  • Seat tubes with 27.4 ID are gonna fit a 27.2 post after brazing right?

    All the 28.6mm seat tubes I'm seeing have a 0.6mm wall thickness

  • I used a Deda replacement for one of the Cromor externally butted tubes (not in stock) from Ceeway that had an internal diameter of 27.4 (1.2 wall and 29.8 external dia) pre-brazing that just needed a light reaming to fit a 27.2 post nicely. I'd guess the 28.6 with 0.6 wall would be the same.

  • I asked about this on that facebook framebuilders group and someone replied saying that 27.4 id seat tube was for 27.2 od seat post.

    Doesn't seem to make sense but there you go!

    I'm using the same 27.4 id Zona tube you used on my next frame.

  • You need .1 of clearance for the seat post to actually slide in, otherwise it’d be a press fit

  • Seems like I've been sticking verniers down seattubes and measuring a 27.2 tube and fitting a 27.2 post for years?

    The 2 frames I've built so far have had seat tubes that worked out to 27.0 id (28.6 od minus 2x 0.8mm wall thickness), 27.0 seat posts have been a nice slip fit in the bare tube pre brazing so post brazing I've reamed to the point where the 27.0 post would fit in again.

    You reckon I'd have been better with 26.8 posts in these seat tubes?

  • I've a seat lug that takes a binder bolt with a 6mm shaft and 10mm head.

    Seems like 99% of binders have an 8mm shaft. The one I have also has 12mm heads.

    Ceeway do a binder with 10mm heads (article 444 and 445) but they look like they step down to 8mm not 6mm.

    Before I chuck this binder in the lathe and go at my lug with a drill, anyone know where I could get the correct binder?

  • Email Peter and tell him what you need.

    I'm sure he will have it in stock, but he just doesn't list it on his website.

  • Cool, I have dropped him an email but they (or is it just ‘he’?) are shut for the week.

  • Am I correct in thinking this seattube (SLFM13635) can be reamed to 30.9mm?


    1 Attachment

    • slfm13635.jpg
  • No. It'll need a 30.6mm seat post or require shimming to 27.2. Reaming it out to fit a 30.9mm seatpost will leave the walls to thin and cause a stress riser at the end of the reamed section.

  • Makes sense. This one can't be reamed beyond the external taper, then?

    http://www.henryjames.com/Cpdf/seat-tube­s/ZON113550001.pdf

  • Reaming should really only be for getting rid of lumps, bumps and distortion from brazing or welding, not changing the internal diameter of the tubing. Reaming that tube back to 31.7mm at any point would be fine. Trying to ream it out further to fit a bigger seat post is asking for trouble though.

    On Brommers Bike no. 3 I used a 31.7mm external seat tube, because that fitted the lugs I was using. I bonded a 30.6>27.2mm shim in place to allow me to use a 27.2mm seat post.

  • Aha, I had gotten to the understanding that the tubes warp during welding / brazing and are therefore sold with an ID slightly smaller than the intended seat post. And I got my logic backwards with the Zona tube, seems to fit the bill. Thanks!

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I am a frame builder AMA

Posted by Avatar for coldharbour @coldharbour

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