The Straighten

If the nock end of the arrow continued to bend away from the bow then eventually the arrow would snap. What limits the amount of this arrow bending? The best way to look at this is to regard the arrow as a spring with a weight on the front end being pushed from the rear. When the arrow is released the nock end of the arrow accelerates forward faster than the pile end which is heavy and has high inertia. The gap between pile and nock reduces and this reduction goes into spring compression of the arrow (it bends). The acceleration of the pile comes from shaft forces on it which comprise the string force through the shaft and also from this spring compression (bending) of the shaft. As the arrow bends more the pile acceleration keeps increasing until it exceeds the nock acceleration. At some point the pile forward speed catches up with the nock forward speed at which point the arrow stops bending. The pile is still accelerating faster than the nock (string force + spring force) so the pile now travels faster than the nock and the spring compression comes out of the arrow i.e. it straightens up. As the rear of the arrow straightens the force with which the pile end of the arrow is pressing against bow/button from torque reduces and so the bend in the front part of the shaft reduces. As the arrow straightens the pile acceleration decreases. You end up with a more or less straight arrow with the pile and nock travelling forwards at the same speed.

The differences between this 'straight' arrow and the one at full draw is that in addition to the arrow being further forward and so the string force and direction to the brace height position being different the arrow shaft has a lateral velocity profile. Not all the spring energy goes into pile acceleration, much of it has gone into a lateral shaft acceleration.

Дата добавления: 2015-07-11