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Hey all papier machist,
I am an avid bike nut and love using things for something completely different to what they were meant to be. Last year I built a bike out of bamboo and this year I want to make a bike out of, predominantly papier mâché. I have used papier mâché quite a bit in my life for many different craft and costume projects, so I know how to use it, but I need some advise.
I was thinking of making the frame first in polystyrene as a base structure, then wrapping half sheets of news paper in a thick water and pvc glue paste. The sheets would be overlapping like roof tiles and the tear direction will change every sheet to ensure the most strength.
For the main tubes (the front triangle, top bar bottom bar and seat tube) I will use about 1.5cm thickness on all walls and for the stays (rear forks) as they neqed to be thin, I was thinking about using dowel as the structural base instead of polystyrene. For all the joins, ie. The head tube, bottom bracket rear drop outs and seat post join I will use an old bike chopped up.
What I need to know is how ambitious is this, how will I waterproof it, what is the best glue to use (it needs to be rock solid and strong), what the best paper is to use (should i use another kind of paper for the rigidity then do the aesthetically pleasing newspaper Finnish) and has this been done before.
Thanks heaps, Franque.
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Are you wanting this PM bicycle to be usable, to carry a person's weight? If so, polystyrene wouldn't be strong enough.
Do you think a 'hard' type of paper, rolled tightly and glued into solid rods and then attached to your metal parts would work? I think hollow tubes would be too weak. Your dowel base sounds workable, and bamboo might be, too.
Jackie did some experiments with sealers and found that marine varnish worked the best against moisture.
Sue
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Yeah it would be completely ridable.
The polystyrene wouldn't provide any strength, purely a mould for the pm. But I think a bamboo base would be better and stronger.
I was thinking and hoping the papier mâché would work like ply wood after enough layers.
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Layered paper can be very strong but you would have to get the combination right. Use a good proportion of PVA in your paste. Bond (office) paper alternating with kraft (brown) paper makes a strong laminate.
I suggest doing some small trials before undertaking the project to see if it meets the strength you need.
If you made a batch of finely rolled tubes, for example, and joined them together, you can achieve amazing strength. It is the principle of the fasces - a group is stronger than any individual.
DavidO
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Thanks for that, that could be quite handy, i would had never though of using a bundle of papier mâché "sticks". I will definitely do a few some test runs, I learned form my last build when my bike broke and I destroyed my toe. Do you think if i made the tubes triangular as well it might make the tube strength increase? Do you suggest PVC as my strongest paste? It will need to be strong and non flexible and not shatter/fracture under stress.
Thanks again, you guys are helping me heaps.
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I don't think triangular in paper laminate would be good but in strong card juxtaposed so you have something like a honeycomb structure would be strong horizontally. Your problem, with all this stuff, would be lateral strength. As a simple experiment without any paste, try taking the cardboard tube from a toilet roll. Into that push another that you have squeezed in the sides to make it look like an 8 in cross section. Then test the strength.
DavidO
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Are you wanting technological innovation, or just a bike that looks highly individual? If the latter, why not just take a normal bike but build on the surface with pm to create the look you want?
DavidO
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Your requirements of being “non flexable but “not shatter/fracture" under stress are two opposite ways to deal with stress in materials and to eliminate both makes it nearly impossible to solve.. I would suggest a careful blending of both approaches.
For an example, rebar (flexible metal rods) are mixed in to “brittle" concrete structures to spread the load to add strength and fiberglass (flexible) is mixed in to “brittle" epoxy for the same reason. This is a variation of DavidO’s idea of finely rolled “tubes" and well worth considering.
My wife has been kind enough to begin to collect dryer “lint" for me because I want to increase the strength of my paper mache clay and I’m considering replacing paper with this dryer “lint" . I have read some people use wool for the same purpose. I have not yet tried this experiment.
I have had some experience with PVA based glue (4 parts PVA, 1 part Acrylic Paint 1 part water) for out door “yard art" toad stools because I didn’t want any flour in the mix to tempt insects or critters appetite’s . I then read PVA gets brittle when cold but I have no 1st hand knowledge of that but I did have my toad stools crack after the 1st season. After drilling a vent hole in each of them they all made it passed this record setting summer ( for number of days over 100º F) with no cracking from air expansion in a closed container (toad stool).
The stresses on the top tube, down tube and seat tube joints will be enormous so careful attention needs to be paid there. This is an engineering challenge as well as an artistic one. I think it can be a fun yet challenging project. I just would not attempt a century ride on it. Please keep us posted.
Bob C.
Last edited by Pelletor (2010-10-06 09:38:20)
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Pelletor, if you're looking for additional strength from fibers, you'll probably have to use longer fibers than what you'll get from dryer lint. Wool has a much longer length.
My short (very short) experiment with dryer lint proved that it sticks to everything (whether you want it to or not), it practically dissolves when mixed with water, and it takes a LOT to do anything with it.
I didn't have the patience, and didn't think it was very useful. But be sure to let us know if you find different, and tell us how you did it.
Sue
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