I haven't run 50 either, so my take on this is prolly worthless, but here goes:
- I've read that the maximum amount of sidespin you can impart to an object ball is only about 2% of the spin on the cue ball. So the idea that spin helps spread 'em better doesn't seem correct to me for a few reasons...
1. after the CB hits the OB, some of that CB's inside spin will be killed. The collision induced throw as the CB scrapes across the face of the OB will work against the inside spin. So by the time the CB arrives at the rack, it isn't even at full spin.
2. What little spin there is will barely transfer to the ball in the rack you hit first... 2% or so, right? Not sure what such a tiny bit of rotation can accomplish even if you assume rotation helps.
3. ... and I'm not convinced rotation helps. If the first ball in the rack gets a piece of the cue ball's sidespin, how would that translate to shoving the surrounding balls with more force? That tiny bit of spin doesn't seem like it would add speed or distance to any of the splattering balls.
If the extra spread theory is true at all, it's for the reason steve said: You can cut the OB a tiny bit thinner, therefore the CB keeps a tiny bit more speed.
But I don't think this is right either. At low speed you get max effect from throw. At high speed, the effect is negligible... you can cut a ball with as much inside as you want, but at very high speed you're only going to throw off the cut angle a little bit. You can get the same benefit by just cheating the pocket a bit more, if you've got godly accuracy. Or by hitting just a little bit harder.
To be fair a lot of pros you see in "watch me run 100 balls" videos don't use anywhere near max speed, so their typical break speed might be affected a bit more by sidespin than Joe Barbanger, who just hits as hard as he can. Note: some guys like Pat Fleming seemingly hit this way to good effect, so maybe that's the real secret.
Other things I think are myths:
That outside spin will help the CB somehow climb up the side of the rack and help it dig its way out of the rack... many a time I have seen the CB hit a ball in the rack dead square, and then just spin in place. A clearer example: set up a short stop shot, but put lots of side on it. Make sure you account for deflection. If the CB hits the OB dead center, the result is still a stop shot. Left sidespin doesn't make the CB whirl away to the left, it just sits in place and spins.
Sidespin isn't controlling the direction the CB takes after colliding with the rack... that direction is determined by how fat it hits the first (and second) object balls in the rack.
Sidespin isn't helping the CB fight out of a rack, only top or bottom can do that, combined with the fatness of hits on the various balls you run into. See the stopshot example.
I'm still up in the air on the theory that it's better to put a little outside english on a ball to cancel out the tiny bit of collision induced throw. At this kind of speed I'd think the effect is so small that the outside won't change anything.
I'll admit that the physics here are subtle, and the physics for hitting a full rack is a lot more complex than for hitting just one ball, so maybe the transferred sidespin matters after all. Or maybe there's some other factor that helps the spread, but not because the first ball you contact in the rack gets some of the CB's spin.
From my experience, for getting maximum "fight out of clusters", and for maximum "making the shot as easy as possible on myself" pure top or bottom gets much better results shooting with added sidespin. I can see the use of side for position play though. There's a cool shot in Joe Tucker's video where he uses inside and a bit of draw when he can see the CB will hit more or less between 2 balls. The draw causes it to hit the side rail only a little lower than the point where it touches the rack... and the inside causes it to spin back uphill towards the shooter. I think inside draw feels unnatural and is tough to aim though, so I never try it. But it looks pretty on tape.
