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  1. #1
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    Breakaway 29ers?

    Hey Guys -

    I've run into an interesting problem and wondering if anyone has some experience with this. I have a customer who wants a breakaway (the Ritchey system) coupled 29er. I figured, no problem, called up Ritchey, and got the stuff. Much cheaper/lighter, etc than S&S, seemed like it would be no problem. Admittedly, I've never seen a breakaway steel mountain bike, but I assume they exist.

    I've run into a major problem, though - the lower portion of the downtube coupler is a mitered tube with a built-in lip for the collar/coupler. I imagine it works great for most road bikes, and even most mountain bikes, but I'm trying to do a 29er with a reasonably long (100mm travel) fork. Big problem: there isn't room to miter the downtube to the seat tube (or alternately weld the seat tube onto the downtube) without making it impossible to use/destroying the coupler.

    I've thought of several mediocre solutions:
    -Offset the seat tube *backwards* and put a bend or kink in it a few inches up. It would need to be a LOT of offset, though, in order to get enough room for the seat tube and the saddle where I need it. The seat tube *has* to be 28.6 and take a 27.2 post in order to work with this system, so anything crazy in the bending realm is out - at most, I'd have ~6" of .9mm tubing to work with before the thinner section, which I'm not willing to bend.
    -Weld a piece of 1.5x.058" tubing over the lower coupler, leaving room for the lip/clamp area, then miter that to the BB shell. Downside is I'd be a bit worried about distorting or damaging the lip of the coupler, given how little distance there would be between the weld and the lip. Maybe not a big deal.
    -Twin seat tubes ala Wolfhound? I've never done it, think it makes zero sense functionally or aesthetically, and would probably rather not. But I guess it would solve the problem.

    You guys are much more creative than me. Ideas?

    As an aside, does anyone have any idea why the canti hanger appears to be backwards (note the vent holes for the seatstays) on the seat tube lug/sleeve assembly?

    Yours in cluelessness,

    -Walt

    EDIT: Figured out the cable stop (it's for a road brake, not a canti). Feel free to mock me anyway...
    Attached Thumbnails Attached Thumbnails Breakaway 29ers?-coupler.jpg  

    Breakaway 29ers?-coupler2.jpg  

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

  2. #2
    WIGGLER
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    Walt how about turning the coped end (fish mouth) 90* you could still attach it to the seat tube and down tube and with the fish mouthing you have more weld area and
    its probably still in the thickest part of the butt for both pieces.
    PAYASO 36er.....Live the Circus

  3. #3
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    Roll your own with sanitary ferrules and clamps?

    And they're stainless! I know you love stainless!

  4. #4
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    Bigger BB shell? EBB/American?

  5. #5
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    s-bend the downtube so it comes out to the bottom bracket at a lower angle? with the nova pre-bent ones, you'd just have to bend one end...

  6. #6
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    can you turn it around and use the (now) bb end as a lug/sleeve to catch the down tube and use another piece of dt welded to the bb but a little longer to get the joint away from the bb just enough?
    does that make sense?

  7. #7
    RCP Fabrication
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    Can you remiter it to sit lower on the bb, and offset the seat tube miter to push it back slight?

  8. #8
    Eric the Red
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    You could silver braze the extension, that might keep distortion to a minimum.

  9. #9
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    I bet you can weld the piece of 1.5 .058 on distortion free maybe heat sink it if you want. That was the solution that popped into my head first. This is a positive solution that adds strength.
    Last edited by vulture; 02-29-2012 at 08:58 PM. Reason: spelling.

  10. #10
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    1. Get one of the hydroformed Nova downtubes and run it backwards, which will give you an extra 15 degrees or so on the DT/ST junction.
    2. Weld the .058 extension onto the cast Ritchey section.
    3. Make the bottom 3" of the seat tube out of 1.25" .058 with a big notch in the front and some offset, then slip the 1.125" seat tube into your sleeve and braze it.

  11. #11
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    The steel version of the Ritchey Break away is sold by Dahon as the Flo X20
    (Flo X20 | Dahon Global)

    Ofcourse it's a 26er (which makes sense for packing). The third picture kind of shows how tight the coupler is on that frame. How much strength would you loss if you welded or brased a notch in the seat tube?

  12. #12
    Shamisen Appreciator
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    have you called Ritchey to see if they have a longer option? I had to send some parts back when I built one of these a few years back.
    Sean Chaney :: Owner/Builder :: Vertigo Cycles LLC
    flickr :: www.vertigocycles.com

  13. #13
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    Roll your own with sanitary ferrules and clamps?

    And they're stainless! I know you love stainless!
    We have tons of them at my day job and I always wondered if they would be strong enough to use on a bike. Maybe if I added something that would act as a torsion stopper between the ferrules inside...

    Well if you want some, let me know, I can dig in the recycling bin. The sizes available are a little awkward for bike tubing though.
    Guillaume

    Cycles Golem

  14. #14
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    Quote Originally Posted by Golem builder View Post
    Well if you want some, let me know, I can dig in the recycling bin. The sizes available are a little awkward for bike tubing though.
    I own a dairy, so I have plenty of them too!

  15. #15
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    Quote Originally Posted by dr.welby View Post
    I own a dairy, so I have plenty of them too!
    Nice!

    Where are you located? What's the name?

    Are you doing cheese? I like cheese a lot!

    We are doing a lot of work for dairies at my day job.
    Guillaume

    Cycles Golem

  16. #16
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    Quote Originally Posted by Golem builder View Post

    Where are you located? What's the name?

    Are you doing cheese? I like cheese a lot!
    Cozy Cow Dairy in Windsor, Colorado.

    We make a bunch of different cheeses, ice cream, milk, chocolate milk, eggnog (in season), butter, etc...

  17. #17
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    Use an S&S coupler on the downtube and keep that bit for later.
    No longer member of the bike industry nor society, so don't hassle me.

  18. #18
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    That was what I suggested...

    ...but he is dead-set on the Ritchey system.

    BTW, for those who are curious, I ended up making a slip-fit "extension" and welding it on. Doesn't look too ghetto, plenty strong, all in all not bad.

    The cast/stamped/whatever lug things from Ritchey are horrible. They are full of voids and impossible to get clean without resorting to a belt sander due to their uneven surface. The stamped "TR" logos are going to get melted unless you use like a 25.4 toptube, too. Lame. Next time I will make my own.

    IMO a hybrid S&S and custom lug/binder system for the seat tube would be the ideal way to go if someone asks me for this again in the future.

    -Walt

    Quote Originally Posted by Thylacine View Post
    Use an S&S coupler on the downtube and keep that bit for later.
    Waltworks Custom Bicycles
    Park City, UT USA
    www.waltworks.com
    waltworks.blogspot.com

  19. #19
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    Super nice Dr Welby!
    Guillaume

    Cycles Golem

  20. #20
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    ...

  21. #21
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    Guillaume!!

    Nice to see you on MTBR! You bikes are looking great! and thanks for offering an English version of your site,too.
    (sorry for the hi-jack, Walt)

  22. #22
    Stokeless Asshat
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    Quote Originally Posted by dr.welby View Post
    Cozy Cow Dairy in Windsor, Colorado.

    We make a bunch of different cheeses, ice cream, milk, chocolate milk, eggnog (in season), butter, etc...
    Your products rock!!!
    Sent by a Ft.Collins cheese freak.
    J
    Zip ties? Not on my bike!

    Want:
    650B rims or wheel set. 80's vintage 32 or 36 x 135mm

  23. #23
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    Ironically enough I"m building a similar bike now as well. I opted to just purchase the bottom clamp and machine the rest out of some 4130 stock. Took a little time, but worth the effort.


  24. #24
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    Quote Originally Posted by Cracked Headtube View Post
    Guillaume!!

    Nice to see you on MTBR! You bikes are looking great! and thanks for offering an English version of your site,too.
    (sorry for the hi-jack, Walt)
    Hey Jeremy,

    Thanks! My english is not perfect but I think it's good enough so you guys can understand what I mean.

    We went to UBI together, right?
    Guillaume

    Cycles Golem

  25. #25
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    For the sake of the lineage of this thread, I'll also put in my preference for an interlocking bottom coupler a la S&S. The Ritchey bottom coupler is too simple and does not resistant enough to torsion. When I built my coupled bike I opted for a breakaway seat cluster like Ritchey but built my own interlocking coupler (S&S is an easier solution).
    Too many bikes, not enough time.

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