Yes, here we go again.
When I hear snap-back this is what I picture: video link 1. See first video.
The back of the ball is clearly moving upwards in the snap-back direction after the bounce.
None of that is happening here: video link 2. See movie 2. Hold a ruler horizontally at the ball after the bounce and see that the back of the ball never moves upwards in the snap-back direction.
The same thing can be observed in in movie 1.
The thing I expect to see, if there was significant snap-back is not present so, I say there is no significant snap-back.
It is also evident by this video that the snap-back does not significantly spin the ball.
But it is proven that low friction strings and string movement does in fact increase the spin, so what is the explanation.
1) The string movement makes the felt and rubber core not skid over the strings thus giving the ball time to press into the string pattern and create more mechanical grip, bite.
2) The string movement decreases the ball's rolling resistance. When the ball flattens against the string bed the mid section of the contact patch is deformed and compressed laterally. When the ball rolls over the string bed different parts of the ball move in and out of the compressed region. Without string movement this deformation is restricted and the rolling resistance is larger.
3) The restricted ball deformation without string movement also makes the ball act stiffer, reducing contact time. With string movement the ball acts softer and flattens out more which increases contact time and the area of the contact patch.
4) As the ball rolls the compressed part will move outward and expand, the expansion happens more easily in the snap-back direction due to the string tension acting in that direction.
When I hear snap-back this is what I picture: video link 1. See first video.
The back of the ball is clearly moving upwards in the snap-back direction after the bounce.
None of that is happening here: video link 2. See movie 2. Hold a ruler horizontally at the ball after the bounce and see that the back of the ball never moves upwards in the snap-back direction.
The same thing can be observed in in movie 1.
The thing I expect to see, if there was significant snap-back is not present so, I say there is no significant snap-back.
It is also evident by this video that the snap-back does not significantly spin the ball.
But it is proven that low friction strings and string movement does in fact increase the spin, so what is the explanation.
1) The string movement makes the felt and rubber core not skid over the strings thus giving the ball time to press into the string pattern and create more mechanical grip, bite.
2) The string movement decreases the ball's rolling resistance. When the ball flattens against the string bed the mid section of the contact patch is deformed and compressed laterally. When the ball rolls over the string bed different parts of the ball move in and out of the compressed region. Without string movement this deformation is restricted and the rolling resistance is larger.
3) The restricted ball deformation without string movement also makes the ball act stiffer, reducing contact time. With string movement the ball acts softer and flattens out more which increases contact time and the area of the contact patch.
4) As the ball rolls the compressed part will move outward and expand, the expansion happens more easily in the snap-back direction due to the string tension acting in that direction.
