Results 1 to 17 of 17
  1. #1
    mtbr member
    Reputation:
    Join Date
    Jul 2008
    Posts
    145

    How to bend the top tube

    Hi everyone, I'm designing my own 29er frame but I've got a problem.
    My ideal frame will have a curved top tube, I'm talking about a steel frame, but my builder and every builder who I've spoked with says that's impossible to bend the top tube because of its fragility. Even if I tell they to use a straight 1mm tube they say it's impossible.

    So, how do you bend your top tube? What tube do you use? Actually I'm in california but I live in Italy, so i can easily found dedacciai or columbus tubes.

    Thank you.

    Ps.: any framebuilder in the north of CA?


    Tapatalk from iPhone

  2. #2
    mtbr member
    Reputation: adarn's Avatar
    Join Date
    Aug 2009
    Posts
    280
    this guy is in norther CA and will bend all the tubes you want:
    Inglis & Retrotec Cycles | Quality Bicycles Handmade in Napa, California

  3. #3
    mtbr member
    Reputation:
    Join Date
    May 2007
    Posts
    1,835
    I think you need to speak to some more builders.
    Oh noes. I'm going to drink the Kool-Aid.

  4. #4
    mtbr member
    Reputation:
    Join Date
    Dec 2012
    Posts
    52
    Coconino does it on all his frames. Just sayin'. No big thing. Roll former, tube filled with sand.

  5. #5
    mtbr member
    Reputation:
    Join Date
    Jul 2008
    Posts
    145
    Ok, but what kind of tube? 0.8mm? 1mm? 1.2mm?

    I suppose you cannot use a variable tube like 0.8-0.4-0.8 or things like that...

  6. #6
    mtbr member
    Reputation: adarn's Avatar
    Join Date
    Aug 2009
    Posts
    280
    no, you can definitely bend thin wall or butted tubes if you are good at it.

  7. #7
    mtbr member
    Reputation:
    Join Date
    Dec 2012
    Posts
    52
    Give Steve Garro on Velocipede Salon a shout out, he's usually pretty good with advice.

  8. #8
    Moderator Moderator
    Reputation:
    Join Date
    Jan 2004
    Posts
    3,952
    You can bend all sorts of stuff. The thinner the walls/larger the diameter, the harder it gets to bend without causing problems, but it's doable for even very thin, pretty big stuff (I've bent 8/5/8 heat treated butted tubes up to 32mm, for example).

    If you want to do this yourself, spend some more time searching the archives. This has been discussed a lot. If you are having someone else build you a bike, and they say they can't/won't do what you want... sounds like it's time for a different builder.

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

  9. #9
    Nemophilist
    Reputation: TrailMaker's Avatar
    Join Date
    Sep 2007
    Posts
    1,697
    Easy;

    How to bend the top tube-fatbikeradiuseddowntube.jpg

    How to bend the top tube-kroozerframedone5.jpg

    You've obviously been talking to the wrong people.
    Most people ply the Well Trodden Path. A few seek a different way, and leave a Trail behind.
    - John Hajny, a.k.a. TrailMaker

  10. #10
    mtbr member
    Reputation:
    Join Date
    Jul 2008
    Posts
    145
    If that a Columbus/Dedacciai tube?

  11. #11
    The cat's name is jake
    Reputation: BungedUP's Avatar
    Join Date
    Aug 2003
    Posts
    221
    Some tubes are more challenging to roll than others, and one problem becomes length, with bike-specific tubing.

    I have successfully bent butted tubing. If I remember, the butt profile was in the neighborhood of a .9mm/.7mm sort of thing. This was with a shop built roller:

    How to bend the top tube-tube-bender-1.jpg

    The issue of length is this: Often, there is not enough length to both roll the tube, and have a safe exit when the tube comes off the roller. This is more of a challenge with butted tubing. One way to get around it is to use tandem specific tubing, if you can get it. I've also considered adding sections of tubing onto the ends, as sacrificial pieces via welding or mechanical internal connection somehow. Using straight gauge material makes this easy - it usually comes in the 0 heat treat state, so is easy to bend, and you can just get it with plenty of extra on the ends.

    This brings me to another variable, which you sort of get at with you question of tubing type: Not all bike tubing has the same hardness. TT OX Platinum/S3, Reynolds 853/725, etc., are too hard to roll bend easily in their out-of-box condition. Maybe someone has a way around this, but I have never been able to get that stuff to budge in a roller. I tried with a piece of 1.5" Reynolds (725 IIRC), and it actually polished my roller dies from the pressure - I've never seen anything like it. It changed the shape of the tube a little bit, but did virtually nothing like bend it.

    TT Verus, and Verus-like tubes are great tubes for building bikes (as far as I'm concerned), and are soft enough that they will roll fairly well. Reynolds 500 series tubes, and possibly 631 would be rough equivalents. I think much of the Fairing tubes (Nova generics) would also probably fit in this category.

    I'm not as familiar with the Columbus alloys, but I'm sure they have a similar tube type which could be rolled.

    There are other forming processes that might work as well - There are many ways to bend a tube, and rolling is just one of them.
    How to bend the top tube-complete-frame-5.jpgHow to bend the top tube-complete-frame-2.jpg

  12. #12
    Nemophilist
    Reputation: TrailMaker's Avatar
    Join Date
    Sep 2007
    Posts
    1,697
    Hey;

    Of course Peter is quite right, and you will never get better advice on bikes than he will offer, regardless of topic. My answer was a bit short on specificity. My example was using generic non hardened 4130 ChroMo straight .035 wall. It was easy in terms of setup, but it was NOT a gimme. It was quite physical to bend that 1.5 tube to the radius required. The 1.375 TT was a piece of cake by comparison. I've never tried any other types of tubing, mostly because tubes long enough for my bikes are not very common.

    The Harbor Freight bender I have is pretty crude, but up to the task for occasional use like it will see with me. It will vary due to distance between rollers on different benders, but with mine there was 6" of waste on each end. This goes to what Peter was talking about regarding trying to bend production length butted tubes.
    Most people ply the Well Trodden Path. A few seek a different way, and leave a Trail behind.
    - John Hajny, a.k.a. TrailMaker

  13. #13
    mtbr member
    Reputation:
    Join Date
    Apr 2012
    Posts
    197
    I bend non-heat treated tubes like TT versus without too much difficulty on a harbor freight roller with swagoffroad dies. The heat treated ones like OxPlat and S3 are not going to bend easily. Having good tight dies that prevent wrinkling help.
    SWAG Tubing Roller Dies Compatible With Harbor Freight Tube Roller
    Non ht-------------------------------------Ht
    Name:  12142812255_aa98058f1a_m.jpg
Views: 419
Size:  23.3 KBName:  8473787863_8c0898d00e_m.jpg
Views: 412
Size:  23.3 KB
    and that was packed with sand.
    cheers
    andy walker
    Flickr: afwalker's Photostream

  14. #14
    The cat's name is jake
    Reputation: BungedUP's Avatar
    Join Date
    Aug 2003
    Posts
    221
    Quote Originally Posted by TrailMaker View Post
    Hey;

    It was easy in terms of setup, but it was NOT a gimme. It was quite physical to bend that 1.5 tube to the radius required.
    I know, right? Compared to a rotary draw type bender, even using hand operation, it always seems AMAZING how resistant that little thin section of tubing can be in a roller. I guess it comes down to leverage, but still...

    I think that bending tubing is really interesting. I have such a different sense of metal alloys before and after bending them. Just yesterday I was bending 6061 and 6063 pipe. I thought there was NO WAY that the 6061 was going to bend in 6.5" radius. I was shocked when not only did it do it, but it was super smooth, and without and visible cracks (even upon close inspection of the surface). I had always been a little nervous to bend 6061 previously.

  15. #15
    mtbr member
    Reputation: Meriwether's Avatar
    Join Date
    Jul 2007
    Posts
    340

    How to bend the top tube

    I've got the cheap Harbor Freight roller with Swag dies and bend OX plat/Supertherm seat tubes with a lot of effort, but it's pretty easy once you figure out the method, all things considered. The Verus 9/6/9 top tubes I've done a few of too. Longevity? No clue yet.

    Bending butted tubes is seemingly a new thing though that many builders stay away from until more "testers" are out. Retrotec has been bending straight gauge for decades. Coconino bends 0.8 wall custom drawn tubing (I think that's right?).

    I think you may want to consider a US custom builder if you're set on that look of the frame.

  16. #16
    mtbr member
    Reputation:
    Join Date
    Jul 2008
    Posts
    145

    How to bend the top tube

    Thank you for all this advices, very apreciated!


    Tapatalk from iPhone

  17. #17
    Nemophilist
    Reputation: TrailMaker's Avatar
    Join Date
    Sep 2007
    Posts
    1,697
    Quote Originally Posted by BungedUP View Post
    I know, right? Compared to a rotary draw type bender, even using hand operation, it always seems AMAZING how resistant that little thin section of tubing can be in a roller. I guess it comes down to leverage, but still...

    I think that bending tubing is really interesting. I have such a different sense of metal alloys before and after bending them. Just yesterday I was bending 6061 and 6063 pipe. I thought there was NO WAY that the 6061 was going to bend in 6.5" radius. I was shocked when not only did it do it, but it was super smooth, and without and visible cracks (even upon close inspection of the surface). I had always been a little nervous to bend 6061 previously.
    Hey;

    What tube specs, and did you anneal the 6061 first? I've bent it before - 1" x .095 - but after annealing. I didn't think it would bend at all in its hardened state.
    Most people ply the Well Trodden Path. A few seek a different way, and leave a Trail behind.
    - John Hajny, a.k.a. TrailMaker

Similar Threads

  1. Seat tube, top tube, head tube deal
    By calstar in forum Frame Building
    Replies: 0
    Last Post: 08-29-2013, 10:12 AM
  2. S-Bend Steel Down Tube: Good Idea Or No?
    By Kiwi19 in forum Frame Building
    Replies: 3
    Last Post: 08-02-2013, 01:58 AM
  3. fargo down tube bend
    By bnelson in forum Salsa
    Replies: 3
    Last Post: 12-23-2012, 05:26 AM
  4. Bend 2 versus Bend 3
    By klydesdale in forum Salsa
    Replies: 19
    Last Post: 12-29-2011, 05:18 PM
  5. How to add flare bend to curved top tube?
    By jocko in forum Frame Building
    Replies: 2
    Last Post: 09-07-2011, 03:22 AM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •