Originally Posted by
Falanx
Wooden 'tube'?. Do you mean 'bar'?
No, I mean tube as in hollow cylindrical structure. The hardest part of this has been making the mandrels on which the tubes are formed.
Originally Posted by
Falanx
That's not toughness. In fact, it's the opposite of it. Toughness is the ability of a material to undergo plastic work to prevent failure, not the resistance to deformation, and it is quantified by the energy absorbed in propagating a fracture. Seeing as you've not fractured anything yet, you've not actually tested toughness in a measurable way.
That's strength you've just tested, and not in an ubiased way. You've dented a hollow shape with a solid one, which is unsurprising. I wonder how many cracks run down the grain of that wood.
Well, I did say it was a rough guide....
As you point out, this is impact strength rather than toughness. Maybe there's a bit of crossover: there's an awful lot of kinetic energy in the "hammer" tube when it strikes the "anvil" tube and this energy is going somewhere. Some of it goes into my hand, there's an interesting difference between the sting when holding the Ti tube vs the wooden one.
The test is not as biased as you assume: the two tubes were of equivalent diameter and weight per unit length. Of course this means the wood one has thicker walls, but that's part of the advantage of working with wood.
I seem to have hijacked this thread which was not my intention, I was just offering some observations of what I have found worked.
I'd like to repeat what I started with: my primary interest is not in constructing a wooden bicycle, it is in investigating the acoustic properties of frames and frame materials. That has lead me to the use of woods, specifically tonewoods, but they are a means to an end.