Originally Posted by Martin Bell
Sorry, BigE, perhaps what I should really have asked is "How do they exert an external force upon their bodies to begin their rotation, and which fixed point do they use as a fulcrum?"
The turn I'll describe is an inclined park and ride carved arc, one foot in front of the other, because it's probably the turn most similar to skiing that makes people go "hmmmm.....".
The key elements are:
3) Balance centered between the feet.
4) Turn radius
Inclination helps to set the edge, but it's mainly to resist the centrifugal force... the one that wants to tip you over to the outside of the turn.
Edging: outside edge forefoot, inside edge aft foot.
When the balance is centered between the feet, the tendency is for the front blade to run on the rear rockered part, the rear blade on the front.
Without inclination, you glide straight. Basically, as you have the front skate on the rear rocker, it's easy to pivot it to point to the direction you want to go. Point the toe -- you can't push the heel. Is that the answer you wanted?
The turn radius is set by the difference in direction of the front and rear skates. This is not the same at all as in skiiing. View your blades as tangents to a longer virtual edge. It is the radius of the virtual edge that determines the radius of the turn. In otherwords, the more you point your front blade away from the direction of the rear blade the more you will turn. Keep in mind, the front blade runs on the outside edge, so left in front to turn left....although you can do it with right foot in front, but it's much harder...
It all happens very fast. Inclination leads you into the turn, you feel for a moment, like you are falling, but the pivot of the front blade creates the virtual edge that engages and provides a centrifugal force that catches you and stops you from falling over. The turn completes, as the inclination decreases.
The move looks very skier like, but the important difference is the creation of the platform with fore and aft blades, that define the virtual edge the skater follows. Making this platform simply with a "scissor-like" opening of the legs is possible because of the rocker.
Hope this helps!