Gotte

I had this idea to make a frame cooapsable (I'm no frame builder, btw, just a happy amateur).
The idea was this, cut the bottom tube and the cross bar maybe three inches from the down tube, insert into both tubes a piece of smaller tubing or lathed rod of maybe 6 inches length so as it fits tightly and protrudes an equal distance as is inserted. Drill through tubes and inserts, bolt together to hold.

I'm looking at it as a bike youcan take apart and fit in a suitcase for taking on planes.

My main question is, will drilling the tubes weaken them so much as to make them unsafe, or will the insert give enough rigidity?

Cyclist0094

Nothing new under the sun, Rene Herse did it over 40 years ago


I have a similar project sitting on the shelf. I am taking the easier route of using short lengths of tubing the next size up in .058 wall to make external collars. For instance I have a 1.25 down tube, by using a length of 1.375 x .058 wall tubing as the collar ( 1.375 -.058 -.058 =1.259) I have .009 clearance , I am using a 2 seat collar binders for each joint.

NoReg

You can see from the Hearse approach that it takes some careful planing to create the right angles so that you don't end up with a demountable bike that won't come apart.

In my usual role of releasing bad smells among the congenitally conventional over on the Frameforum, I started a row a while back about the non-availability to amateurs of S&S couplers, that appear to be a better solution that the Hearse solution, though who knows, they might be heavier. It was speculated or claimed at the time that an amateur could get S&S couplers if he asked nicely, only wanted a pair, and swore never to sell the coupled bike, or some such non-commercial plans. Nobody could really substantiate that this was on offer, but it might be worth investigating.

More radically, one could investigate the possibility of making one's own bike friday, which does not seem too impossible, in fact probably cheaper that the coupled regular frame.

Velo, what kind of frame this time, what are the specs?

Dubbayoo

Ritchey sells 3 models like that already.

https://breakawaytoday.blogspot.com/

Gotte

Thans for the input, chaps. I have an old frame I might try it on. I like the slip coupling on the Herse.
My main problem is I can;t braze or weld, so everything has to be boltable. I quite like the idea of giving it a go, though.

Gotte

Hey, that's great.
I was wondering myself about a rid inside the tube that can be slid up and down so as to let the frame break. I'd cut a line like that on the seat tube to allow it to be moved.

kraftwerk 

Gotte You should get a frame builder to help you with this project, unless you have several frames to practice on and the desire to learn how to braze... Let us know how it turns out?

Gotte

I have a real urge to learn how to braze, or rather relearn. I did some a long time ago - about 25 years. but it was so long ago, I might as well have not done it.
I have got a few old frame. I cut one up recently to see if I could put it together, and you know what, I can. I found an MTB stem will fit both the top and the downtube. and will clamp so tight that I can;t get it to move, not even flex. It's an old fram though, just carbon tubing, which is good in that it's tough, but bad in that it's heavy (thinking about flying with it).
I found that a steerer fits perfectly into the downtube, so I can reinforce it that way, and I'm thinking af experimenting with the cut on the top tube. I figure a sideways v (if you can imagine it, will hold together quite nicely - can;t use a tuvbing insert here without either the frame not fitting together, or there needing to be a bolt type action worked out so as to relese it.
Anyways, I'm still trying, and may even get there.

Any links to brazing technique would be appreciated.

Gotte

Well, I took the bike out today, and it feels fine to me. No more flex than I would expect (and that with me putting my feet on the down tube, one hand on the seat post and one on the stem and pushing and pulling like mad.
I even rode it with the bolts loosened, just to see.
I decided to add frame clamps either side of the main clamps (the kind that hold brake cables onto frames - but I will try and go for something more sturdy - I have some old parts from a triple crown suspension fork that fit perfectly - ahh, standardization). I was also riding without an insert, which I will add for peace of mind to the downtude.
All in all, It rode well.
I have to strip the frame and build it up again with beter parts to get a true feel, but so far, I'm happy with it.

I was going to ask whether it would be possible to do the same thing to 531, though, when I weighed the bike, it was actually lighter than my 531 tourer, and by about 6kg. Bizarre. Maybe its becasue it's a smaller frame and had no rack, but then again, it has, at present all steel everything - wheels, chainring, stem, so depending on the ride, I may just stick with this.

SamHall

Cool, sounds like a fun project.
Where's the pics?

Gotte

Let me neaten it up - looking pretty rough at the minute.

oldokie

Another source is at https://www.davidsonbicycles.com/html/frames.shtml
Note the use of S&S couplings to take the bike apart.