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Old 10-15-11, 01:01 PM   #1
Monster Pete
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Building a plywood frame

I'm considering building a frame for a short wheelbase recumbent bike out of wood. I'd use two plywood side sheets incorporating the rear 'triangle' and the basis of the seat. The main panels would be held apart by spacer blocks at regular intervals, cut from either timber or plywood laminations at right angles to the sides. One of these would be drilled to hold the head tube, and in front of that a narrower extension (sandwiched inside the main side sheets) would similarly contain the bottom bracket.

Is there anything especially 'wrong' with using plywood as a base material? I'm fairly confident in my ability to manufacture such a frame, and by not cutting it from a solid piece it should be lighter than other wooden frames I've seen (basically a big timber beam.)

I think it would be a very cool machine to ride around, while also challenging conventional ideas of what a bicycle should look like and be made from.
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Old 10-16-11, 02:45 AM   #2
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Durability when exposed to the elements.. would be the biggest detriment I can think of. High humidity / rain could cause eventual delamination. If you do decide to do it make sure its sealed well may even expoxy coated.
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Old 10-16-11, 07:19 AM   #3
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I'm going to have to give this a go sometime! I figure if they managed to make bits of various World War Two aircraft out of various types of wood, including, if memory serves, plywood, then it ought to be possible to make a bike from it that will perform fairly well. What sort of thickness of plywood were you thinking of using?
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Old 10-16-11, 07:20 AM   #4
garage sale GT
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Quote:
Originally Posted by Monster Pete View Post
I'm considering building a frame for a short wheelbase recumbent bike out of wood. I'd use two plywood side sheets incorporating the rear 'triangle' and the basis of the seat. The main panels would be held apart by spacer blocks at regular intervals, cut from either timber or plywood laminations at right angles to the sides. One of these would be drilled to hold the head tube, and in front of that a narrower extension (sandwiched inside the main side sheets) would similarly contain the bottom bracket.

Is there anything especially 'wrong' with using plywood as a base material? I'm fairly confident in my ability to manufacture such a frame, and by not cutting it from a solid piece it should be lighter than other wooden frames I've seen (basically a big timber beam.)

I think it would be a very cool machine to ride around, while also challenging conventional ideas of what a bicycle should look like and be made from.
I am not so sure you want to use plywood as a material for spars or beams.

The boom of a typical recumbent needs mostly longitudinal strength, but the layers in which the grain runs at right angles to the spar will mainly contribute resistance against splitting lengthwise. Imagine a seatstay made from only the layers of plywood which run across the length of the seatstay. Think of how easy it would be to break it over your knee. Those layers don't give you the strength you need.

I think you should use ordinary wood. You can still use a built up design. You don't have to carve it out of one piece.

The Mosquito and other aircraft were built of plywood but they probably laminated the layers in a way that was specific to the airframe rather than buying sheets of plywood in which each layer was placed at right angles to the last.
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Old 10-18-11, 02:17 PM   #5
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Charlie and Pearl the Unicorn Bikes are made from plywood. It is a medium grade from Home Depot, not as bad as CDX, but not as good as baltic birch either. The legs form the forks and triangles, and they seem plenty strong. Charlie has a problem with chain falling off under high torque, but he lacks Pearl's chain tensioner.

I also thought plywood would be a great medium to dial in a geometry before committing to cutting and welding tubes.
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