The Miff of Topspin (Simpson chimes in)

overspin thoery

I was at first a tad skeptical after reading the ?myth of top spin? ? so I did a little experiment.

I froze the cue and the OB on the head rail at the center dot and kept the cue parallel to the table while executing a firm stroke through the two frozen balls. Hitting this shot, I cannot make the cue outrace the OB. Hence the claims of over-spin with parallel top English seems confirmed.

If I jack up on the cue ball and stroke through with top English (and a small amount of left or right to keep from colliding with the OB), the cue ball will outrace the OB to the end rail consistently. I believe this may indicate an ?over-spin? condition that can only be achieved by using a high downward angle on the cue.

Does the experiment relate to the ?over-spin? myth/fact or are there other factors I am not considering?
 
DWoods6354 said:
...

I froze the cue and the OB on the head rail at the center dot and kept the cue parallel to the table while executing a firm stroke through the two frozen balls. Hitting this shot, I cannot make the cue outrace the OB. Hence the claims of over-spin with parallel top English seems confirmed.
...
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I suspect that the fact that the CB is frozen to the OB and you're hitting straight through them adds a little more friction and makes it even harder to get any overspin from the tip/ball collision. Frozen balls are going to behave a little differently. So, it might not be a fair experiment.
 
DWoods6354 said:
...I froze the cue and the OB on the head rail at the center dot and kept the cue parallel to the table while executing a firm stroke through the two frozen balls. Hitting this shot, I cannot make the cue outrace the OB. Hence the claims of over-spin with parallel top English seems confirmed.
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Possibly only Bob Jewett understands these frozen ball situations. But if I get what you're trying to do, I would think your test would be evidence against it? I think Tom's remarks are to the point.

DWoods6354 said:
If I jack up on the cue ball and stroke through with top English (and a small amount of left or right to keep from colliding with the OB), the cue ball will outrace the OB to the end rail consistently. I believe this may indicate an ?over-spin? condition that can only be achieved by using a high downward angle on the cue.
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This one I definitely don't understand. Is this the trick shot where the cueball curls around the object ball and outruns it?

DWoods6354 said:
Does the experiment relate to the ?over-spin? myth/fact or are there other factors I am not considering?
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Obviously, I'm not the one to judge.

If you want to clarify and perhaps modify your tests, maybe someone here can help. Here is another test.

CueTable Help



The 1-ball and 2-ball are frozen together with their line of centers parallel to the end-cushion. Their anticipated contact points with the cueball are moistened to minimize throw and spin loss.

Shoot to split them with the cueball, favoring the 1-ball slightly. Try hitting several shots with a rolling cueball, contacting the cueball about 2/5'ths of its radius above center to get it to roll within a short distance, and then as high as possible to overspin it. There should be about an 8 degree difference in the cueball's final roll direction if maximum overspin is achieved. Since the cueball's speed is reduced to 1/4'th of its original speed during the double-collision, the shots have to be fairly brisk.

The setup produces a precise and repeatable contact on the 2-ball. Sans throw, it is driven at virtually 30 degrees from the long direction of the table despite variations of several degrees in the cut on the 1-ball. It does the same for the cueball's initial tangent line direction off the 2-ball, but the less than perfectly elastic collision does alter it a little. However, it should remain consistent with similar cueball speeds.

In theory, if the cueball is moving at 10 mph (about twice lag speed) with max overspin, the overspin won't be completely rubbed out until it has traveled about 30" in a straight line - the distance where natural roll sets in. So if the cueball is set up about 6" from the two object balls when attempting to superspin it, not much spin should be lost along the way.

I can't say I've tried the test yet - the numbers are calculated values.

Jim
 
Jal (on the Wei table):
If it has a spin/speed ratio of 1.25 when contacting the 1-ball...
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Jim, you suggest that maximum cueball overspin is 1.25:1, and I notice that maximum tip offset (1/2R) is 1.25 x "natural roll" tip offset (2/5R). Does this mean that spin/speed ratio increases linearly with the amount of tip offset?

pj
chgo
 
Patrick Johnson said:
Jim, you suggest that maximum cueball overspin is 1.25:1, and I notice that maximum tip offset (1/2R) is 1.25 x "natural roll" tip offset (2/5R). Does this mean that spin/speed ratio increases linearly with the amount of tip offset?

pj
chgo
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Yes it does Patrick. But as with all things, it's an approximation. Squirt reduces the effective offset, but the cueball's rotation during contact increases it. You thus get a certain amount of mutual cancellation.

Squirt seems to be nearly independent of shot speed, while the amount of rotation during contact does depend on it. So the amount of mutual cancellation is likely not the same at different speeds. But these are details and fairly small effects. The linear relationship should hold for the most part, I think.

And of course you're right about the 1/2R --> 1.25 ratio.

Jim
 
DWoods6354 said:
I was at first a tad skeptical after reading the ?myth of top spin? ? so I did a little experiment.

I froze the cue and the OB on the head rail ...
Does the experiment relate to the ?over-spin? myth/fact or are there other factors I am not considering?
Click to expand...
I think the issue is clouded. As I understand it: the cue ball will start with a certain speed and some top spin. The object ball will start with the same speed and no tip spin. That's immediately after tip-ball contact which will only last over a half-inch or so. The follow will keep the cue ball rolling at more or less the same speed, but the object ball will be skidding at the start and will slow down as it slides on the cloth. The cue ball will likely repeatedly bump into the object ball if you shoot straight along the line of the balls but this will be hard to see.

I don't expect the rubbing of the cue ball on the object ball during tip-ball contact to cause any particular problem or change in behavior.

I would try the "two times fuller" system with a center ball hit and with a high hit. I think you will see the cue ball with relatively faster forward motion compared to the object ball when you shoot with follow.

One last point is that if you play a frozen ball straight-on with follow, you should be able to get "excess" follow on the cue ball because the object ball has held the cue ball against the tip -- kind of like the table holding the cue ball against the tip on masse shots.

There is a standard trick shot in which the cue ball is played against a whole line of frozen object balls. The spin is amazing to see.
 
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Tom Simpson said:
Hi Everyone,

I've pretty much been off the forums for about 10 years now. Someone gave me a heads up about the Myth of Top Spin?? thread that's underway, so I thought I should visit and read it.

I'm now more convinced than ever that this myth needs to be cleared up. My next column (September issue) will address this in a little more depth. A lot of players have a mistaken idea of how follow works, and it's related to this issue.

For those who don't get Inside Pool, I've attached a pdf of the original article, so you can see what the fuss is about.

I think poster 3andstop did a nice job in post #34. Thanks to you and the various other physics fans for helping.

What I feel is really going on is that our adoption of the term "topspin" has led most players to a mistaken idea of how balls behave. It's easy to see how players assume that hitting above center causes overspin. Before I started reading pool physics, I thought so too. I can also see how playing with that mistaken notion can still produce terrific results. I believe that the clearer your grasp of this stuff, the better and smarter you will play. Just as you can learn to pocket balls perfectly without knowing anything about throw, you can play perfect follow without understanding how follow actually works. But I think the truth helps us learn more quickly and helps us better solve new game situations.

My experience is that most players have trouble at first believing that what they've always assumed was overspin in the CB is nothing more than roll - and that "force follow" is merely fast roll. As we hit higher above center, the skidding of the CB decays to full natural roll sooner in the shot. As we hit harder, the skidding zone lengthens.

Other than the special cases of masse and the fleeting overspin it's possible to get, hitting in the last 1/8" of CB before the miscue boundary, what we refer to as "topspin" is roll. Overspin is what you see in the CB after a collision has removed some or all of its linear force. What was, prior to the collision, a rolling CB, now is a stopped or slower moving CB with overspin. That overspin was not there when the CB left the tip.

Please consider that maybe the physics guys are correct (and maybe I'm not nuts). :)
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Welcome back Tom

Here's my attempt at generating overspin

http://video.google.com/videoplay?docid=-46117048581594236
 
that's a great video and this is a great concept. But how do you square the fact that overspin is very hard or impossible to produce, with force follow? there used to be some videos of Buddy Hall on YouTube, where he demonstrated some awesome follow shots, where the path of the cueball totally changed due to "topspin." (I put that in quotes since we don't know if it really exists.) Or how do you square this notion with the shot we are all familiar with, where you shoot the cueball with "follow" into the short rail, and it bounces back and then reverses course and goes back to the rail? Remembering the movie Philadelphia, please explain this to me as if I were a 6 year old. Thanks.
 
Chesscat said:
that's a great video and this is a great concept. But how do you square the fact that overspin is very hard or impossible to produce, with force follow? there used to be some videos of Buddy Hall on YouTube, where he demonstrated some awesome follow shots, where the path of the cueball totally changed due to "topspin." (I put that in quotes since we don't know if it really exists.) Or how do you square this notion with the shot we are all familiar with, where you shoot the cueball with "follow" into the short rail, and it bounces back and then reverses course and goes back to the rail? Remembering the movie Philadelphia, please explain this to me as if I were a 6 year old. Thanks.
Click to expand...

See post # 43, referencing post # 41.

Also see Mike Pages, video, Ref post # 57
http://www.youtube.com/watch?v=XI-NMgYbMyA
 
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Chesscat said:
that's a great video and this is a great concept. But how do you square the fact that overspin is very hard or impossible to produce, with force follow? there used to be some videos of Buddy Hall on YouTube, where he demonstrated some awesome follow shots, where the path of the cueball totally changed due to "topspin." (I put that in quotes since we don't know if it really exists.) Or how do you square this notion with the shot we are all familiar with, where you shoot the cueball with "follow" into the short rail, and it bounces back and then reverses course and goes back to the rail? Remembering the movie Philadelphia, please explain this to me as if I were a 6 year old. Thanks.
Click to expand...

The thing to recognize is that a fast rolling cueball has much more topspin than a slow rolling cueball (just like a fast car has faster spinning wheels than a slow car).

So when a fast rolling cueball strikes an object ball, losing much of its speed, it find itself with "extra" spin. So overspin is ubiquitous once another ball is involved.

this video shows the effect near a rail

http://www.youtube.com/watch?v=XI-NMgYbMyA
 
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