Steve Davis and a sport scientist on ball spin on snooker!

[nrage]

have you watched the video where steve uses the striped balls? clear from the video that when there are no other balls or cushions involved very very little or no side is transferred. When the object ball is locked against other balls or a cushion then the amount of friction generated will be massively increased, in this situation i think a certain amount of side can be transferred.

I think the friction is the key. Any time there is an increase in friction, or contact time between the balls, there may be more side transferred. So, a bit of chalk on the object ball or cue ball at the contact point. A ball sitting in a slight dent in the table, or on top of some chalk accumulation. Or, thicker cloths and/or heavier balls perhaps?? Likewise in a pack/rack, or against a cushion will increase contact time and allow more side to transfer.

That said, these guys reckon it happens:
http://www.billiards.colostate.edu/b...les/index.html

The 2 pdfs in particular:
http://www.billiards.colostate.edu/b...07/march07.pdf
http://www.billiards.colostate.edu/b...07/april07.pdf

and the list of videos referred to in those pdfs:
http://billiards.colostate.edu/normal_videos/index.html
http://billiards.colostate.edu/high_...eos/index.html

It seems to me that the absolute hardest part about proving or disproving this by experiment seems to be guaranteeing the contact between the white and object ball is exactly center/full ball and not to one side or the other due to swerve induced by side spin and the nap (as shown in the original videos linked in the OP).

[02aleric]

good videos. They don't really disagree with what i've said though in my opinion. Yes, the effect the running side has on the object ball going down a rail is smaller when playing from a shallower angle, but it is still this running side effect, not spin transfer! One thing the chap on the video does say is that running side causes a ball to speed up off a cushion. This is wrong. I'm sure the laws of physics prevent this. the ball can certainly 'lose' less speed off a rail than it would with plain ball striking but i'm sure it can not actually gain speed.

[nrage]

good videos. They don't really disagree with what i've said though in my opinion. Yes, the effect the running side has on the object ball going down a rail is smaller when playing from a shallower angle, but it is still this running side effect, not spin transfer!

I wasn't suggesting it was "spin transfer" instead, just that the effect of the side (running side) is negligible/zero in this case.

One thing the chap on the video does say is that running side causes a ball to speed up off a cushion. This is wrong. I'm sure the laws of physics prevent this. the ball can certainly 'lose' less speed off a rail than it would with plain ball striking but i'm sure it can not actually gain speed.

It does happen. The reason is that side spin is being transferred into forward roll (aka speed) off the cushion. Remember the white is both rolling forward and spinning like a top at the same time, then it hits a cushion and if hit slow enough the forward roll rotation is completely stopped by the friction/contact with the cushion, the ball is shoved off the cushion, slides and then at a point immediately re-develops forward roll. Only this time that forward roll is partially in the same direction as the side spin, so the side spin "adds" some energy to the forward roll, resulting in an increase in "speed".

[02aleric]

I wasn't suggesting it was "spin transfer" instead, just that the effect of the side (running side) is negligible/zero in this case.
.

i completely agree and always play these shots plain ball regardless as i think this is the easiest way.

regarding the ball gaining speed of a cushion i'm unsure. I see the reasoning and it makes sense. i always thought it was possible myself until a thread on here around a year ago. Thinking about it now though, it may have been about springy cushions being unable to add speed to a ball. The ball has to lose energy to

a) the cushion deforming (bending in)
b) the sound the ball makes when it hits the cushion
c) heat caused by friction from the cloth and the cushion

however i do think it could be possible that as you say the side spin that almost becomes forward spin could add pace to the ball. Afraid to say i'm sitting on the fence with this one!

[nrage]

i completely agree and always play these shots plain ball regardless as i think this is the easiest way.

regarding the ball gaining speed of a cushion i'm unsure. I see the reasoning and it makes sense. i always thought it was possible myself until a thread on here around a year ago. Thinking about it now though, it may have been about springy cushions being unable to add speed to a ball. The ball has to lose energy to

a) the cushion deforming (bending in)
b) the sound the ball makes when it hits the cushion
c) heat caused by friction from the cloth and the cushion

however i do think it could be possible that as you say the side spin that almost becomes forward spin could add pace to the ball. Afraid to say i'm sitting on the fence with this one!

I am almost 100% certain that rubber cushions cannot add energy to the ball, for all the reasons you have above. The ball has a certain amount of kinectic energy, the cushion has/stores none, the contact simply converts the available energy, but cannot add more, and does lose some due to conversion to other sorts of energy.

But, in the side-spin to forward roll theory new energy does not need to be added, we just convert what is already present from side-spin to forward roll. Assuming this theory holds we should see an additional effect, the amount of side-spin should decrease.

I haven't looked for this myself and I suspect it will be hard to be sure whether we're seeing this or not, because the effect we do see will always be a result of both the amount of side spin on the white and also the angle into/off the wall.

I have tried is playing a ball slowly, straight into a cushion with maximum side spin you really can 'see' it come off noticeably faster. I'm going to have to try it again and look to see the effect off the following rail too..

[PatBlock]

have you watched the video where steve uses the striped balls? clear from the video that when there are no other balls or cushions involved very very little or no side is transferred. When the object ball is locked against other balls or a cushion then the amount of friction generated will be massively increased, in this situation i think a certain amount of side can be transferred.

Yes, that piece of video shows that for a medium paced, dead straight shot, without bottom or top spin, very little effective side is transfered to the object ball. But that alone doesn't convince me that under different circumstances, with variations of pace, angle, and top or bottom spin on the cueball, the results would always be the same.

However, I was wrong when I said that the slo-mo split pack video implied transfer of spin, because there was probobly very little or no side put on the cueball by Steve, so I think that the spin picked up by the ball directly under and to the left of the apex red, was aquired because the cueball struck it somewhere near half/quarter ball, rather than full on, and it's this glancing blow which made the object ball spin like it did.

As for what you said about the pack increasing the friction, I can't make up my mind whether being in a pack helped or hindered the spin. In effect, the rest of the pack is holding our OB in place, so when it's hit by the white, this holding effect may increase the amount of friction between it and the CB, but at the same time, it must also be restricting/resisting that aquired spin to some degree due to its contact with the other reds.

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[sydneygeorge]

Thank you for posting !!!