Originally Posted by Nessism
The only way energy could be lost is if it's converted to another form of energy such as heat. Simple physics.
If you are flexing the frame, you ARE creating heat. Like you said, simple physics. I don't know how significant the heat created is, but it's there.
Another way to look at it is as though your chain were made out of rubber. The chain would stretch when you applied force and return that energy when the force was less. Yes, that would even out the force distribution, but it would also cause the power portion of the stroke to go faster and the dead portion to go slower, kind of the opposite of Bobby Julich’s oval chain rings. I don’t think that would be desirable.
Bottom line, materials aren’t flexy, frames are. After all, aluminum has the lowest modulus of elasticity of the three materials, yet frames made from aluminum are generally considered stiff.
Here’s an article on the subject:
http://www.sheldonbrown.com/frame-materials.html
-murray