Quote:
Originally Posted by jyl
You're right, I was confused.
Aaschen's comment that the drive could hold the weight at any point on the rim is interesting and, I think, disproves my assumption that the drive must produce a constant 20 N of force. If the weight is parked at 5 oclock it will produce less force (tangent to the rim). If it is parked at 6 oclock it will produce no force (tangent to the rim).
It also seems that, if the weight has very low friction to the rim, then it might not require much energy to hold it at 6 oclock. So maybe it could remain in this "idle" low energy state for most of the race, then switched to 3 oclock for the key attack or sprint or climb.
Yes, this whole discussion has emphasized how pathetically weak the human engine is.
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A minor interjection then I can let it die, I promise.
If the weight is at 5 o'clock it still exerts a 20N force. It just does not create as much torque on the wheel, which is the important aspect here. Only a component of the force is orthogonal to the wheel so less torque is created on the wheel and less power will be required of the device to keep it steady.
You can imagine in our example of coasting along at 6 oclock, the device creates no torque and would require no force to keep in place (with the hypothetical frictionless conditions).
This follows intuition as if you made a completely dumb and passive device to ride in the wheel on rollers it would "want" to stay at the bottom. IT would require more and more torque to have it advance along the wheel, until it maxed out at 3 oclock
sorry, I like to think about this sort of stuff