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By ChiefHoser (Wed Jul 14, 2004 at 10:50:12 AM EST) (all tags)

...bike!

During my lunch break today I began to wonder about the homemade construction of a bicycle. I began to think of materials that one could use in the frame and about how one would get around certain design issues dependent on the material of choice.

I have decided on trying to make a bike out of PVC tubing. It is relatively strong (bike not for non-road use) for its mass and easy to work with (no welding required). The bonds in the joints between pipes are quite strong also if one uses the correct adhesive.

The problem is settling on a design and then hammering out some of the problems. Hence the problem. Being some what limited in the pipe coupler's that are available I am going to have some problems mounting the front forks (although I think I have a good solution to this problem) and a bigger problem with the rear part of the diamond, as it is doubled on either side of the rear wheel.

Just using one side support for the rear wheel doesn't seem to be strong enough, and might cause minor balance issues so I tossed that idea. Another problem with the rear end is mounting the breaks and rear derailer. This could be avoided by going with a single speed bike, but I have a rear derailer already and want to do this bike on the cheap.

I was wondering if anybody has any experience with designing their own bike frames or has any suggestions or just things to keep in mind that they have come across in their biking. It should be a good project and relatively easy to construct so I am getting excited about the prospect of driving my pvc bike to work in the near future.

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Make Your Own... | 7 comments (7 topical, 0 hidden) | Trackback

PVC is not strong enough by zantispam (5.50 / 2) #1 Wed Jul 14, 2004 at 11:05:25 AM EST

Take whatever tubing you were going to use, hold one end in one hand and the other end in the other hand. Bend tube using your knee.

Imagine this piece of tubing being your down tube. Every pedal stroke will do that to the down tube (and the seat tube and the top tube and the rear frame stay, etc). Sooner, rather than later, it will break. Spectacularly.

re: headset - the steer tube and neck of the fork need to be stiff enough that the bearings don't wear out after ten minutes of operation. Also, forget about speeds greater than 15 mph; I'll bet the shimmy will render the bike uncontrollable (read: you'll have to bail).

re: bottom bracket - same problem as above multiplied by about a thousand.

re: rear triangle - the most difficult part will be to prevent lateral torsion from ripping the wheel out. Reference what Colnago, Cannondale, and others have done on this front.

re: rear derailleur - if it's index you'll have to mount it on something metal. If it's not you should still mount in on steel, unless you have a whole lot of chainrings and sprockets lying around.

rere: rear derailleur - it it's index I would suggest finding a friction one instead. For the most part, indexed derailleurs are designed to work with a specific frame geometry. Meaning that it has to be in such and such a place in reference to the freehub and the shift lever. This is why indexed jobbies are so much more difficulty to dial in correctly than friction ones.

rerere: good luck. I applaud your initiative, but as a cyclist who has broken a couple of frames, I say there's a reason bicycles are made of metal.

Yeah, you better run before LiaD stabs you with his shiny metal cock! -- theboz

: Yes, that's true. by ti dave (5.50 / 2) #2 Wed Jul 14, 2004 at 11:16:44 AM EST

however, if he does it, he stands a good chance of skewering his 'taint.
That might fix his "girl trouble", IYKWIM.
I don't care if people hate my guts; I assume most of them do.
The important question is whether they are in a position to do anything about it. --W.S. Burroughs
[ Parent ]

PVC is such not a good idea. by LinDze (3.00 / 0) #3 Wed Jul 14, 2004 at 11:22:08 AM EST

If you did manage to build it up, fit the kit, and get on it your first hammering pedal strokes will snap the top/down tubes and probalby impale yourself.

For tubing the easiest possible way would be some thin wall steel. Something like a cruiser/pixie bike, or even BMXish geometry would be simplist*.

Good luck though, the more bikes the better!

*read: actually possible

-Lin Dze
Arbeit Macht Frei

My brother did this in high school by Greener (3.00 / 0) #4 Wed Jul 14, 2004 at 12:55:19 PM EST

Designed, cut and welded the frame himself. If you've got any specific questions I can pass them along. I'll ask him if he still had any design/build notes lying around that I can send to you. It was a self directed school project so it should be very well documented.

I doubt you'd be able to build a ridable frame using existing pipe couplers due to the angles involved but it sounds like a fun project anyways just to see if it can be done.

omfg what a dumb idea by Bob Dog (6.00 / 1) #5 Wed Jul 14, 2004 at 01:22:00 PM EST

make it out of bendy straws instead.
--

: Cheese straws by Rogerborg (6.00 / 3) #6 Wed Jul 14, 2004 at 01:42:45 PM EST

That way he'll have something to eat while waiting for the ambulance.

-
Metus amatores matrum compescit, non clementia.
[ Parent ]

don't listen to these guys by tps12 (6.00 / 1) #7 Wed Jul 14, 2004 at 02:29:09 PM EST

I made a piccolo out of PVC and it works fine. Never come close to impaling myself, though the range is only an octave and a half or so.

Make Your Own... | 7 comments (7 topical, 0 hidden) | Trackback