Bamboo Bike Frame.

Step 2 Design!

I CAD'ed my bike in SolidWorks, to make sure that I had clearance for everything. You can try to copy a bike you particularly like, or draw something out on paper. Then set up your jig according to your design. Simple, yet very important.

I don't actually know much about frame design. I did a little bit of Googling, a lot of looking at pictures of bikes, and a bunch of poring over the geometry charts published by bike companies. Then I used SolidWorks to check for clearance. You don't want to finish your bike to find that your pedals almost scrape the ground, or, worse yet, hit your rear triangle!

I "tested" my bamboo for strength by stacking bricks on it, sitting on the bricks, and then leaning to one side. It was so rigorous. My bamboo withstood about 300 ft-lbs of torque.

I found a picture online that has the names of the tubes of a bike frame. It may be useful to you.

Comments

[khan0000]

Just a question about the "test" weight. Wouldn't velocity increase your actual weight through force/speed? I wouldn't know how to accurately figure that, something along the lines of weight x speed = force/perceived weight at contact point. I'm showing my calculative ignorance here but, just wonder how that all plays out? Great idea though and looks like a fun ride.

[LaFeev]

I've used a flexural strength testing apparatus (a machine that does pretty much what you were trying with the bricks) on different frame materials, including bamboo aluminum and steel. The machine wasn't calibrated, so the readouts were essentially unitless, however the results of each material could be compared with each other. The bamboo withstood the most amount of force out of all of the materials, which was impressive. It also sprung back into shape when the weight was removed (unlike the other materials). So not only would I not worry about the crash safety of bamboo, but I'd actually prefer it over the other materials. It deserves way more credit than most people give it.
And as an aside, acceleration does not increase force. Rather force causes acceleration. Further if the force is constant the acceleration will be constant, not increasing. But if you're worried about crashes you should actually be looking at inertia, and more specifically inelastic collisions.

[Kryptonite]

Depends how the seat is, and the g forces wouldn't be enough to increase his weight by all those bricks.

[baslisks]

velocity increases I rather than F, acceleration increases F. So initially you will have an increase in F but in a static system you have the exact same F as you do in any other static state. The only change you should really worry about is when your acceleration is sharp. That could cause problems.

[xman]

When moving on a bike, your only acceleration is parallel to the ground (unless you hit a curb or a pothole), so I doubt that the perceived weight/normal force increases. I'm not so hot on the physics either.

[khan0000]

I was thinking in reference to impacts (which I apologize for not making clear). Potholes (big and small) and other road imperfections might cause quite a beating on the joints.