- #71
EM_Guy
- 217
- 49
jbriggs444 said:Again, you come back to the model with tennis shoes on spokes. If that is the model you want, just say so.
That is not the model I want. How did I "come back" to this model?
jbriggs444 said:Again, you come back to the model with tennis shoes on spokes. If that is the model you want, just say so.
You have mass units on the end of spokes supporting shear stresses and unaffected by the rim. That is precisely the situation for tennis shoes on spokes.EM_Guy said:That is not the model I want. How did I "come back" to this model?
jbriggs444 said:You have mass units on the end of spokes supporting shear stresses and unaffected by the rim.
But you do not seem to want to accept that the rim does anything. If it does nothing, it might as well not be there.EM_Guy said:I didn't say that they are unaffected by the rim. Can you not have mass units on the end of spokes supporting shear stresses that are also affected by the rim?
jbriggs444 said:But you do not seem to want to accept that the rim does anything.
jbriggs444 said:If we take a model where each spoke transmits part of the torque from hub to rim and where the contact force from the ground exerts a force at a single point, what can we say about the change in tension or compression of the rim across the point of contact with the ground?
EM_Guy said:It still remains true that T = ma.
That is also my interpretation. Although I would rather say "determines", instead of "causes".EM_Guy said:The summation of forces causes acceleration.
It doesn't "turn out". You simply choose to decompose a physical force such that one component is equal to the net force. There is nothing significant about the fact that you can find such a decomposition, because as you correctly noted yourself: Any given vector (representing a physical force) can be decomposed into any number of components..EM_Guy said:It turns out in this case that ∑F=T
A.T. said:That is also my interpretation
A.T. said:It doesn't "turn out". You simply choose to decompose a physical force such that one component is equal to the net force. There is nothing significant about the fact that you can find such a decomposition, because as you correctly noted yourself: Any given vector (representing a physical force) can be decomposed into any number of components..
Yes, we agree.EM_Guy said:First, it is not clear to me - even in free space (no ground) whether the torque on the axle causes the rim to be in greater compression or tension? On one hand the torque transmitted through each spoke would seem to compress (push) the section of rim ahead of it, while also pulling the section of rim behind it. Therefore, without considering the ground, I don't think the torque on the axle changes the compression / tension of the rim.
If there are (for instance) 24 spokes attached to the rim, what fraction of the total torque from the hub would you expect the spoke nearest the bottom to be applying to the rim?But for the section of wheel touching the ground, right as that section starts to touch the ground, I think that there is increased compression (torque through spoke pushing the rim, while static friction is pushing the rim in the opposite direction).