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  1. #1
    650b me
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    Sleeving a seat tube

    The post about the warped seat tube got me thinking. One reason I have only used externally-butted seat tubes so far is that I have questions about the sleeving process. Do you treat it like a lug and try to get the silver to flow all the way though? That's a long length of tubing to draw silver through, seems to me. Do you just hit it from each end and not worry if the middle isn't filled with silver?

    Also, for a 27.2 seatpost, what source/tubing do you use for the sleeve?

  2. #2
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    coconino cycles custom bicycles 928 774 7747 www.coconinocycles.com: preskit matt's bike in progress / what's up with seattube sleeves??

    Edit: Actually, I just realized that's not all that informative.

    -Use .058" tubing that is 1/8" larger in diameter than what you are sleeving.
    -The sleeve does not need to be fully filled with silver/brass/whatever like a lug. I just use a little in the top and the bottom to make sure I don't get weird air bubbles during powdercoating.
    -For 27.2, all you need is 28.6x.6mm tubing with some thicker wall at the bottom (most single butted seat tubes are .9/.6) for the BB joint. This is a loose slip fit for a 27.2 post prior to joinery and usually requires a slight ream afterwards, depending on your heat control and luck. Using a different post size? Just figure out what diameter and wall thickness you need.

    -Walt
    Last edited by Walt; 04-01-2013 at 05:19 PM.
    Waltworks Custom Bicycles
    Park City, UT USA
    www.waltworks.com
    waltworks.blogspot.com

  3. #3
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    Lately I've been securing the sleeve with bronze (I hate spending for silver.) I like to drill the clamp hole only through the sleeve, and leave half an inch or so of the ST sticking out of the top. That gives three spots to add filler. I like to add flux when the sleeve is in place so there isn't a bunch of extra being left behind (although it's not supposed to be corrosive according to the 'Dunk Tank' thread from a year ago.)

    I normally use the plain old 28.6 seat tube w/o the external butting, and .058 aircraft cromo from Wicks or Aircraft Spruce for a perfect slip fit. As Walt noted, the .058 - 1/8" thing works very well. If you aren't sure, the folks above normally list the ID of the tubes as one of the measurements.

    I typed most of this before noting Walt updated his reply, so I'm leaving it.

  4. #4
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    Quote Originally Posted by Walt View Post
    coconino cycles custom bicycles 928 774 7747 www.coconinocycles.com: preskit matt's bike in progress / what's up with seattube sleeves??

    Edit: Actually, I just realized that's not all that informative.

    -Use .058" tubing that is 1/8" larger in diameter than what you are sleeving.
    -The sleeve does not need to be fully filled with silver/brass/whatever like a lug. I just use a little in the top and the bottom to make sure I don't get weird air bubbles during powdercoating.
    -For 27.2, all you need is 28.6x.6mm tubing with some thicker wall at the bottom (most single butted seat tubes are .9/.6) for the BB joint. This is a loose slip fit for a 27.2 post prior to joinery and usually requires a slight ream afterwards, depending on your heat control and luck. Using a different post size? Just figure out what diameter and wall thickness you need.

    -Walt
    Walt,

    Do you weld the ST to the sleeve then braze? Or braze first?

  5. #5
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    I just tack the sleeve (at the top) to hold it where I want it, then braze in the bottom with brass, build the rest of the frame, and seal up the top (fuse with TIG) last.

    Basically the order doesn't matter much and you don't need full penetration of the sleeve. It's a very difficult thing to screw up in my experience. And trust me, if it's possible to screw something up, I've done it.

    -Walt
    Waltworks Custom Bicycles
    Park City, UT USA
    www.waltworks.com
    waltworks.blogspot.com

  6. #6
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    Walt and Smudgemo,

    Does the +1/8" .058 rule apply across the board to all sizes of tube used for bicycles? What about head tubes (31.8mm or 36mm)- say for an extension to a HT-TT lug?

    Thanks.

  7. #7
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    I could make a very snarky comment here but instead I'll just say you may want to spend a little time with a calculator, or failing that, paper and pencil.

    -Walt
    Waltworks Custom Bicycles
    Park City, UT USA
    www.waltworks.com
    waltworks.blogspot.com

  8. #8
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    I'll be slightly more helpful by saying, yes, it does apply across the board, but good luck finding 36mm + 1/8".

  9. #9
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    The standard slip-fit formula only works if you can divide the OD of your tube by .125 evenly. 1", 1 1/8, 1 1/4, etc.
    31.8 should work, 36 would not.

    Beaten to the explanation again.
    Last edited by Smudgemo; 04-02-2013 at 04:05 PM. Reason: I was scooped.

  10. #10
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    Quote Originally Posted by Walt View Post
    I could make a very snarky comment here but instead I'll just say you may want to spend a little time with a calculator, or failing that, paper and pencil.
    Low Hanging Fruit, Walt;

    One resident snot per forum is the rule, isn't it? Besides, as I've read in someone's MTBR sig line; There are three kinds of people. Those who are good with numbers, and those who are not.

    I myself don't happen to be any of the three! All help with anything math related is most appreciated.
    Most people ply the Well Trodden Path. A few seek a different way, and leave a Trail behind.
    - John Hajny, a.k.a. TrailMaker

  11. #11
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    You do not even want to know what, er, certain people would write if they saw this kind of question!

    -Walt
    Waltworks Custom Bicycles
    Park City, UT USA
    www.waltworks.com
    waltworks.blogspot.com

  12. #12
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    To re-direct attention back to the O/R, I like the Steve Garro method as he is a brazer and I know Golden Boy is braze orientated. With brazing, you need the whole sleeve filled, so pre-drilling the seat slot and breather hole for the TT are neccessary, as Smudgemo also attests.

    Walt, I read some time ago where you said that you brazed a sleeve on a seat tube, then Tig'ed a joint to it. At the time I wondered the wisdom of doing such, in context of a lower temp task done first, then hitting it with white fusion. Now that you have let us know how you do it I understand better and am satisfied that it works this way - I mean, no breakages - right? 0.058" = 1.5mm tacked to a much thinner seat tube that could be between .6 to .9mm top and bottom and there is no movement?

    OK, we learn new things everyday....I suggest a lug like pointed and thining taper shape on the BB side of this sleeve, less stress this way.

    Eric
    If I don't make an attempt, how will I know if it will work?

  13. #13
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    I just braze the bottom in (no attempt whatsoever to flow anything through the entire joint) because I can clean up the shorelines more easily before the seat tube has anything else attached to it. It's not structural. You could certainly just skip brazing in the sleeve at all and distortion from joining the toptube and seatstays would hold it all together just fine - but it would be hard to make it look nice under paint/powder that way.

    I've never seen a sleeved seat tube of mine have a problem. That's not to say it couldn't happen, of course, but I'd estimate I've done 300 or so this way with no problems.

    -Walt
    Waltworks Custom Bicycles
    Park City, UT USA
    www.waltworks.com
    waltworks.blogspot.com

  14. #14
    650b me
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    Thanks for the comments, everyone. More info to stash away in the archive.

  15. #15
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    Ream a 27.2mm sleeve to 30.9mm?

    I have a Lynskey Pro29 frame. While having identical seat tubes, some of these Pro29 frames shipped with a 27.2mm aluminum reducer sleeve insert and others shipped without the sleeve and take a 31.6mm post. My particular frame has the 27.2mm sleeve but I want to run a 30.9mm or 31.6mm post.

    I can either attempt to ream the aluminum insert from 27.2 out to 30.9mm, or attempt to remove the insert.
    I would guess there should be a local shop with reaming tool such as:
    Chadwick Adjustable Reamer 25 4 28 6mm | eBay
    I was told by the manufacturer that removing the insert sleeve from the frame would require heating the seat tube.
    Any advice as to which is best or easiest (less risky) solution... reaming or trying to remove the insert?
    Last edited by cratercraver; 04-04-2013 at 08:29 AM.

  16. #16
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    Is the insert bonded in there? I would think you could just pull it out and get another one. Might try asking Lynskey. I would think what you suggest would be fine, but like you say, it's a $3k frame so you should probably make sure. Assuming it's okay, those reamers would work, but you'll also need a handle. By the time you spend all that money, you'd probably be better off paying someone whose done it before. Again, assuming Lynskey thinks it's okay.

  17. #17
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    It's not *quite* as straightforward as you might think because the aluminum shim is very, very soft and doesn't really like to be cut with hand tools at low RPM - so it will tend to gall and clog up the cutter, then jam and gouge big chunks out of the shim, and you'll end up (maybe) with a bit of a mess unless you make about 100 passes and take of a TINY amount of material each time.

    I have only done something similar once, though, so maybe my experience was the exception. I was only trying to ream .2mm and it was, shall we say, a bit of an excrement show.

    I would contact Lynskey and see if you can just swap shims. Alternately, GravityDropper, KS, and Thomson all make 27.2 droppers.

    _Walt
    Waltworks Custom Bicycles
    Park City, UT USA
    www.waltworks.com
    waltworks.blogspot.com

  18. #18
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    Quote Originally Posted by cratercraver View Post
    I was told by the manufacturer that removing the insert sleeve from the frame would require heating the seat tube.
    Any advice as to which is best or easiest (less risky) solution... reaming or trying to remove the insert?

    Sounds like maybe it's been bonded in with red Loctite, hence the heat required to free it.

    Reaming it out would take a long time. It would be best to bore it out, if you know someone with access to the right equipment. Here is an example, not my set up, a friend here in town,


    Stuck Seatpost Boring by Haulin' Colin, on Flickr

  19. #19
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    Cratercarver-
    Try first using a hacksaw blade to cut a slot through the aluminum insert (but not into the frame tubing). Once you get a slot through the insert, it will not be as tight of a fit in the tube and you can then bend it inward with a screwdrive then easily pull it out.

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