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Old 09-17-11, 12:12 PM   #1
Bloodshot
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Making a take-down bike and need some input.

Hi everyone. I am sick of the ridiculous prices airlines charge to transport bikes and decided it would be a good idea to make one I can stuff in my luggage.
I was thinking of taking an old road frame I have and chopping it in 2 at the top tube and down tube maybe 5" or so from the seat tube. Then to fasten them together again, I'd have a couple of rods turned down on a lathe to the exact inside diameter of the tubes and use these inside and run bolts though them. I hope I described that sufficiently.
My only concern is if this will be a strong enough joint or will the bike be flexing all over and unrideable? I'm hoping all the chopping experience here can help me out.
Thanks
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Old 09-17-11, 02:30 PM   #2
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Here's another option that you may want to consider, a coupled frame O.o




http://www.thirdraildesignlab.com/fo...p?f=55&t=20931
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Old 09-18-11, 01:13 AM   #3
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Bloody hell, that's awesome. I thought about that but didn't think I could get the couplers I needed. nice to see it can be done. thanks for the inspiration.
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Old 09-18-11, 09:17 AM   #4
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it's hard to get couplers. S&S will only sell to pro framebuilders. I never did figure out how to get Ritchey's couplers, but I am not a big fan of them anyway. I think the best solution for a home build is to copy the Rene Herse demountable
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Old 09-18-11, 11:17 AM   #5
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Quote:
Originally Posted by Bloodshot View Post
... I was thinking of taking an old road frame I have and chopping it in 2 at the top tube and down tube maybe 5" or so from the seat tube. Then to fasten them together again, I'd have a couple of rods turned down on a lathe to the exact inside diameter of the tubes and use these inside and run bolts though them. I hope I described that sufficiently.
My only concern is if this will be a strong enough joint or will the bike be flexing all over and unrideable? I'm hoping all the chopping experience here can help me out.
Thanks
I haven't done this myself, but anyway.

There's no way you could get a decent slip-fit to work. You would need some kind of coupling that works by screw compression.

I would use two clamping collars over the ends.
Something like a two-bolt pipe repair clamp, but I wouldn't use an actual pipe repair clamp, I 'd make something similar:
http://www.google.com/search?hl=en&s...og&sa=N&tab=wi

The pipe clamps would be too soft & thin (I'd think), since they are only for holding lower pressures.

---------

It is easier to make these clamps if you make them closed and then cut them open at the last step.

See below:
1) get the main tube you want, with the ID, overall length and wall thickness you need
2) cut two rounded grooves into one side of it, perpendicular
3) weld/braze two smaller tubes into the rounded grooves. These are the tubes that the clamping bolts will go through. Make sure that the ID of the small tubes does not intrude into the space of the ID of the larger tube.***
4) cut through that side with a cutoff wheel or saw.



If you make tube clamps this way, the little bolt tubes are always aligned correctly.

***I have also seen clamps like this, where the bolts intrude into the larger tube's inner diameter. The tubes to be joined (that fit inside the BIG tube) have notches in them, so the clamp bolts hold the clamp tight, plus they mechanically "lock" the other two tubes inside the clamp as well. I don't think that would work well with bicycle frame tubes though, because they're so thin.
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Old 09-18-11, 11:37 AM   #6
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look at my link, that's essentially the same as the proven Rene Herse design. You don't want to cut the clamp tube all the way through, it's not as strong that way. Just make it like two seat post clamps back to back.
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Old 09-18-11, 11:38 AM   #7
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More great info and another practical solution. The clamps would be easier to use since I'm dealing with an aluminium frame. And its definately cheaper.

Thanks again.
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Old 09-19-11, 06:47 PM   #8
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depending on the thickness of the tubing, an aluminum frame might not be appropriate for this treatment
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Old 09-21-11, 12:16 AM   #9
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I came across an early '70s Peugeot frame. It would be an ideal candidate for a coupler conversion. It's not a racing frame. It's fairly heavy, has a light kit on it and it looks stock. Everything says made in France. If I get some couplers, should I chop it, or is this a found treasure?
edit: I'll try to get around to taking and posting pics.

Last edited by Bloodshot; 09-21-11 at 10:04 AM. Reason: actions to be taken
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Old 09-21-11, 06:43 AM   #10
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need more info. If it's a PX10 or closely related, you have a quandary. If it's anything else, you might as well cut.
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Old 09-21-11, 11:23 AM   #11
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I missed these post that I should have seen before I cut my bike in half. No matter the deed is done and mine works well for my needs. Won't get my bike on the airline but all I needed was to put beast in the back of my wifes car. After looking through these post here I found ways I'm willing to try on a diamond frame.
My breakdown frame is here http://www.bikeforums.net/showthread...=#post13254850 post #948

The good thing about my type of frame the lower and upper tubes are parallel and the go together like a trombone before bolting. What ever you do in setting up for the joints is remember the lowest tube will take the most strain. Before I bolted mine up it was the lowest joint that was walking away while the top joint hung tight. What I'm going to try (when I get the time) is make my lowest tube on the diamond frame up as I did on my recumbent and the top tube like Doug5150 suggested with unterhausen's input by not cutting all the way through. Seems to me that would work and at least I'd give it I try on one of my bikes. This may not work for you on your high end high tech bikes but the older stuff I work with I don't see a problem. This is DIY stuff anything else you might as well get a pro to do the work for you or buy a bike that was intended to meet your transporting needs. Good luck.

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Last edited by Sculch; 09-26-11 at 02:36 PM.
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Old 09-25-11, 01:19 AM   #12
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Ok, here are the bike pics. I'm sure these should be in the "what the hell do I have" forum thread, but I started the post here and figured I'd finnish it here.
thanks for everyones input. Now what the hell kind of bike do I have here? thanks
Attached Images
File Type: jpg P2130107.jpg (94.0 KB, 12 views)
File Type: jpg P2130106.jpg (91.2 KB, 9 views)
File Type: jpg P2130103.jpg (92.8 KB, 9 views)
File Type: jpg P2130105.jpg (92.9 KB, 13 views)
File Type: jpg P2130108.jpg (93.6 KB, 12 views)
File Type: jpg P2130104.jpg (93.6 KB, 16 views)

Last edited by Bloodshot; 09-25-11 at 01:22 AM.
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Old 09-26-11, 02:42 PM   #13
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Bloodshot.......that I would cut that in a second......French made is not a favorite of mine to work on.....looks like a 70's bike but cool just the same.
I doubt it's aluminum it could be CroMo. I've hacked tubes off some French bikes and they weld up nicely. Looks like a project bike for you.

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Old 10-01-11, 11:21 PM   #14
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Quote:
Originally Posted by unterhausen View Post
it's hard to get couplers. S&S will only sell to pro framebuilders. I never did figure out how to get Ritchey's couplers, but I am not a big fan of them anyway. I think the best solution for a home build is to copy the Rene Herse demountable
Did not know that. Thanks
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Old 10-02-11, 12:04 AM   #15
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I suspect if there was some other way to make a strong reliable stiff joint like that, then S&S couplers wouldn't exist.

I would hate to have a frame come apart under me.

One other option is folding bikes, which come in some fairly pricey and functional designs.
Another option in some cases might be bike rentals.
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Old 10-02-11, 01:16 PM   #16
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the demontable is a proven design, and does provide stiffness. Jan Heine has said they are better than S&S, deciding if that is true is left as an exercise for the reader.

S&S can come decoupled, it's up to the rider.
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