Mick wrote:gummidge wrote:I'm not sure I agree with that. If your skate only accelerated when you weren't pushing then wouldn't that mean that all of your acceleration came from pushing off from the skate rather than from pushing sideways?
Well, there are two ways of looking at the acceleration of the skater, either as the actual acceleration of the skater's centre of mass during a single stroke, or else as the average acceleration in the overall direction of travel. The actual acceleration will always be very close to 90 degrees to the fore/aft axis of the skate, so there can be no acceleration of the skate in the same direction as the momentary acceleration of the skaters centre of mass.
However it is possible to accelerate the skate in the average direction of travel by using a purely sideways stroke, but it's not necessary and it will vary depending on how far you let your foot fall behind you during a stroke. Because it's variable I don't think it's a useful measure of how much power assistance to supply.
If you did use just that acceleration to decide how much power assistance to provide then it might be possible to learn to control it, but you would no longer just be skating normally but more powerfully, you would need to learn a special technique. And I have a suspicion that it might be unstable. If you accidentally let a skate shoot out a bit too much the power assistance would try to accelerate it even more.
Yeah, what we really want is to somehow measure the force the stride is producing.