Pool ball cut-induced throw and cling/skid/kick experiment

[dr_dave]

I think the best way to test would be to repeat this test on top of a sheet of sandpaper and see if it makes any difference. A thin 800 grit would probably be perfect. Maybe sprinkle some chalk on there for good measure.

That's a great idea (especially if the sandpaper is taped down so it can't move). That would be a good extreme test to determine if cloth type could possibly have any significant effect (because if chalk-laden gritty sandpaper didn't make a difference in throw, then no reasonable changes in pool cloth could make a difference either).

There are countless things that could be tested that might be interesting: different brands of chalk at different places, different brands of balls, different levels of humidity, surface treatments done in different combinations and in different order, chalk on different surface treatments, etc., etc., etc.!!! Unfortunately, they all take time and motivation.

I was motivated by the tests I did because I'm writing a series of articles on this topic for Billiards Digest, and I knew the results would be interesting. Maybe I'll do more in the future, but I'm done with everything I had planned for now.

My guess would be that this could influence the gearing effect of the balls, as it would increase the rolling gearing of the balls to the point where they may slip on the ball to ball gearing (where that gearing would otherwise not be slipping). Something tells me this would reduce CIT a little, at least under those conditions.

The resistance to ball rotation at the ball-to-cloth contact point could have a slight effect as the throw force turns the balls. If there were any measurable effect, I would think that the amount of throw could actually increase (a very slight amount) since larger throwing friction forces might develop in response to the turn resistance. Regardless, I think this effect would be minimal because the forces involved with throw are so much greater than what is required to overcome spin resistance (even in your extreme sandpaper situation). Anyway, I would be interested to see the results if anybody (maybe you?) is willing to the do the tests.

Catch you later,
Dave

 

[dr_dave]

My thinking is how does this chalk affect the ball to ball throw?

That's a good question. It would be interesting to test different chalks with different ball surface conditions. Although, I would suspect that if the chalk is able to help the leather tip grab the CB, it probably will also help a ball grab another ball (but I could be wrong).

Also, if the chalk didn't stick to the CB as well as it sticks to the tip, maybe there would be less chance for cling.

Regards,
Dave

 

[swest]

So my own, small-scale experiment, with the same basic set up as Dr. Dave's:

OB1 at head spot.
OB2 frozen to OB1 on the long string.
CB at 45° from OB1.

New (previously unhit) Centennials.

I performed the shot 20 times, or so, and recorded where OB2 hit the foot rail on 90% of the shots (i.e., there was some variability... not sure why).

Then, I laid a piece of parchment paper over the original donuts (i.e., a surface that is much slicker than my Simonis cloth, but is thin enough to allow the donuts to telegraph through, hopefully guaranteeing the same ball placement).

I repeated the 20 shots, and I saw no significant difference in results... I still had some variability between shots, but the limits of throw, and the majority of shots, were the same in both instances.

FWIW (i.e., not much:grin-square

- s.west

 

[dr_dave]

So, I asked a question if cloth could or couldn't have an effect on CIT, gave my reasoning why it should.
...
I believe physics agree with me and you have to prove me wrong. So I won't do your test.

I am sorry if I offended you. That was not my purpose.

Let me try to explain my reasoning a little better.

When you hit an OB straight, it goes straight regardless of what type of cloth it is sitting on. Now, it might go more slowly, and it might not travel as far on different cloth, but it still goes straight (assuming the table is level and the cloth is not damaged, irregular, or littered with small debris).

With a straight shot, all of the force between the balls is straight, in the direction the ball heads. With a cut shot, there is still a force along the line of centers, but there is also a sideways force due to friction between the balls that creates CIT. These two forces act only during the incredibly brief time that the balls are in contact (see ball contact time). The two forces acting together are equivalent to a single force acting in the throw direction (which is off from the line of centers slightly). And if you just had a single force acting on the ball in this direction, the ball would head straight in this direction (just as with the straight-on shot), regardless of the type of cloth.

This is why I strongly believe that cloth type could not affect CIT in any noticeable way. The CB responds to two forces the same way it would respond to a single force that is the resultant of (or is equivalent to) the two separate forces, so the CB should head in the thrown direction, which is the direction the two forces push the ball together, regardless of the cloth type.

Again, I don't feel a need to test this, because I am fairly certain; but I didn't mean to discourage you or others from doing the test on their own. It's not that difficult.

Again, I am sorry if I offended you,
Dave

 

[Hits 'em Hard]

I am sorry if I offended you. That was not my purpose.

Let me try to explain my reasoning a little better.

When you hit an OB straight, it goes straight regardless of what type of cloth it is sitting on. Now, it might go more slowly, and it might not travel as far on different cloth, but it still goes straight (assuming the table is level and the cloth is not damaged, irregular, or littered with small debris).

With a straight shot, all of the force between the balls is straight, in the direction the ball heads. With a cut shot, there is still a force along the line of centers, but there is also a sideways force due to friction between the balls that creates CIT. These two forces act only during the incredibly brief time that the balls are in contact (see ball contact time). The two forces acting together are equivalent to a single force acting in the throw direction (which is off from the line of centers slightly). And if you just had a single force acting on the ball in this direction, the ball would head straight in this direction (just as with the straight-on shot), regardless of the type of cloth.

This is why I strongly believe that cloth type could not affect CIT in any noticeable way. The CB responds to two forces the same way it would respond to a single force that is the resultant of (or is equivalent to) the two separate forces, so the CB should head in the thrown direction, which is the direction the two forces push the ball together, regardless of the cloth type.

Again, I don't feel a need to test this, because I am fairly certain; but I didn't mean to discourage you or others from doing the test on their own. It's not that difficult.

Again, I am sorry if I offended you,
Dave

So the CIT will only throw so much regardless of the cloth. Are you will to put money on the line the the object balls will contact a different point on the end rail with varying types of cloth? I am. I already know that I will win. Want to know why I am so certain? All you got to do is watch your video again, and look at EVERYTHING happening during the shot. Just not where the ball is hitting the end rail.

 

[dr_dave]

My takeaway from all this is that it would be incredibly prudent to check the amount of throw before starting a match so as to be mentally prepared for it when shots come up where it is a factor.

Good advice, and well stated.

I would also recommend cleaning chalk marks off the CB every chance you get with ball in hand and between games. And if you spot any chalk marks or other spots or dirt on the OBs, also clean those off between games.

Also, if you ever end up playing under extremely clingy conditions (e.g., in a league bar with filthy conditions, where the cloth and balls are never cleaned, and the balls are very old and beat up and have lots of chalk marks and chalk dust on them), use gearing outside english whenever possible (based on CB control limitations) if you want to the ball where you expect it to go under normal conditions (... and/or play for straight shots where possible).

Regards,
Dave

 

[swest]

All you got to do is watch your video again, and look at EVERYTHING happening during the shot. Just not where the ball is hitting the end rail.

I'm not sure I get that. What else matters?

The experiment measures the throw, and the throw is defined as some quantity of deflection of OB2 from the idealized path defined by the line through the centers...

??

 

[dr_dave]

So, I asked a question if cloth could or couldn't have an effect on CIT, gave my reasoning why it should.
...
I believe physics agree with me and you have to prove me wrong. So I won't do your test.

I think the point is that the vector that represents the resistance of the cloth to OB sliding comes into existence at the moment the OB begins to move, and the direction of that motion is already established...

But, having said that, I think the experiment would be simple enough to perform.

Well stated. Thank you for helping to make the physics more clear.

Good job,
Dave

 

[dr_dave]

Thank you very much for the video. That really opened up my eyes on how much an OB can change from 2.2 to 6.5 to 13.6. No wonder why I have problems making balls that were cleaned with Windex. I bet 90% of the players that watch that video are somewhat amazed at some of those results. you must love your job to do all that, and you do it well. Johnnyt

Thank you for your supportive remarks.

I was also a little surprised by some of the results.

I wish I would have tried Windex also ... I had some in the house. Maybe next time.

Catch you later,
Dave

 

[dr_dave]

So my own, small-scale experiment, with the same basic set up as Dr. Dave's:

OB1 at head spot.
OB2 frozen to OB1 on the long string.
CB at 45° from OB1.

New (previously unhit) Centennials.

I performed the shot 20 times, or so, and recorded where OB2 hit the foot rail on 90% of the shots (i.e., there was some variability... not sure why).

Then, I laid a piece of parchment paper over the original donuts (i.e., a surface that is much slicker than my Simonis cloth, but is thin enough to allow the donuts to telegraph through, hopefully guaranteeing the same ball placement).

I repeated the 20 shots, and I saw no significant difference in results... I still had some variability between shots, but the limits of throw, and the majority of shots, were the same in both instances.

FWIW (i.e., not much:grin-square

- s.west

Thank you. I was hoping somebody would do something like this.

BTW, possible sources of inconsistency are differences in shot speed or not having the balls frozen perfectly and in the exact same spots every time. There could also be slight differences between the portions of ball surfaces that are at the contact point. I was very careful to place the balls as consistently as possible before each shot, and when I tapped down on the balls to train the table (before placing the donuts) I made sure the balls would lean against each other to make sure they would always be frozen. I also discarded any shots that didn't have the desired speed (based on both OB travel distances).

Thanks again,
Dave

 

[Hits 'em Hard]

Well stated. Thank you for helping to make the physics more clear.

Good job,
Dave

So the spin induced onto the object ball from the CIT will remain constant? How ignorant to make statements regarding the coefficient of friction where you haven't tested.

 

[swest]

Yes, my experimental method was quite weak . I mainly wanted to just walk through a sort of proof-of-concept of the steps.

Thank you. I was hoping somebody would do something like this.

BTW, possible sources of inconsistency are differences in shot speed or not having the balls frozen perfectly and in the exact same spots every time. There could also be slight differences between the portions of ball surfaces that are at the contact point. I was very careful to place the balls as consistently as possible before each shot, and when I tapped down on the balls to train the table (before placing the donuts) I made sure the balls would lean against each other to make sure they would always be frozen. I also discarded any shots that didn't have the desired speed (based on both OB travel distances).

Thanks again,
Dave

 

[jtaylor996]

Swest or Dave:

With the amount of $$ I just spent rehabbing my (new to me) diamond pro, there's no way in hell I'm running the sand paper test myself. If I had some spare balls, maybe. But I don't right now.

I think it's the perfect compliment to the parchment paper test, though.

 

[JayKidd]

I got that. I was wondering how much it goes up with super chalk vs regular chalk. Since various other substances were checked I thought maybe Kamui vs masters would be worth testing.

As long as the tip grab the ball right after the first contact, the friction between the tip and the ball surface is considered static friction, the static friction coefficient only means the upper bound of the maximum static friction force this contact area could provide, it doesn't mean the actual friction force will go that high. The actual friction force is generated on a kind of "as much as needed" basis to counter the moving tentency of the two surfaces.

So even if Kamui chalk demonstrate higher friction coefficient that of Master's, it won't affect the actual friction force the way their marketing diagram shows.

That's just my 2 cents.

 

[3kushn]

Lou, I don't think its so obvious that Aramith Cleaners leave something (wax)on the balls. IMO the mild abrasives in the product burnish the micro scratches, leaving a more perfect surface. The effect is similar to wax but balls cleaned with Aramith and played on a reasonably clean table the balls stay consistent for a very long time compared to balls polished with car wax. More proof there's no wax in the Aramith product. Play on a typical public table and bets are off.

Interesting stuff.

So, it makes me wonder about a couple of things or three: if the Aramith polish is leaving behind a residue on the balls, what would be a better product to use? Perhaps something like Novus plastic cleaner? And, if you use Aramith or another wax-type product, are you inpregnating your tip with wax over the course of play? Lastly, while the frozen shots are interesting I would love to see an experiment where the setup is just a normal cut shot with follow. (I know, i know, ain't nobody ever happy

Lou Figueroa

 

[lfigueroa]

Lou, I don't think its so obvious that Aramith Cleaners leave something (wax)on the balls. IMO the mild abrasives in the product burnish the micro scratches, leaving a more perfect surface. The effect is similar to wax but balls cleaned with Aramith and played on a reasonably clean table the balls stay consistent for a very long time compared to balls polished with car wax. More proof there's no wax in the Aramith product. Play on a typical public table and bets are off.

3kushn (is this Tom?), I have noted than fresh out of the Diamond ball polisher and a dose of Aramith Billiard Ball Cleaner the balls will stay consistent for about 30-45 minutes of 14.1 practice. The balls in the stack come apart well and the CB draws easily. Then not so much as the practice session goes on. Soooo, my experience correlated along with Dr. Dave's video leads me to believe something is wearing off the balls rolling over the cloth.

Yesterday for the first time in over a year I cleaned the balls with Novus Plastic Clean & Shine and felt that the balls behaved much more consistently for most of a three hour practice session. I'll try again today and pay more attention.

Lou Figueroa

 

[Dopc]

3kushn (is this Tom?), I have noted than fresh out of the Diamond ball polisher and a dose of Aramith Billiard Ball Cleaner the balls will stay consistent for about 30-45 minutes of 14.1 practice. The balls in the stack come apart well and the CB draws easily. Then not so much as the practice session goes on. Soooo, my experience correlated along with Dr. Dave's video leads me to believe something is wearing off the balls rolling over the cloth.

Yesterday for the first time in over a year I cleaned the balls with Novus Plastic Clean & Shine and felt that the balls behaved much more consistently for most of a three hour practice session. I'll try again today and pay more attention.

Lou Figueroa

Lou.
You keep talking like this and you're going to force me to try Novus. .:thumbup:

Dopc. Time to start researching this Novus product....

 

[dr_dave]

As long as the tip grab the ball right after the first contact, the friction between the tip and the ball surface is considered static friction, the static friction coefficient only means the upper bound of the maximum static friction force this contact area could provide, it doesn't mean the actually friction force will go that high. The actual friction force is generated on a kind of "as much as needed" basis to conterbalance the moving tentency of the two surfaces.

So even if Kamui chalk demonstrate higher friction coefficient that that of Master's, it won't affect the actual friction force the way their marketing diagram shows.

That's just my 2 cents.

If a chalk did create a larger COF between the tip and the CB, it is possible that the miscue limit would be further out on the ball. That would be interesting to test out.

Concerning cling, if the chalk did in fact have a higher COF, it could definitely increase the amount of cling for shots where the balls are sliding during the entire contact period (i.e., when they don't gear together).

Good points,
Dave

 

[dr_dave]

Lou, I don't think its so obvious that Aramith Cleaners leave something (wax)on the balls.

To me, it is fairly clear that something is left behind that creates the shine and less friction.

Here's the reason I think the Aramtih cleaner leaves a wax-like substance on the ball surfaces.

1.) If you clean the balls with the Aramith cleaner, the amount of throw decreases (and the balls are shiny).
2.) if you then clean the balls with alcohol, which is a solvent that helps remove substances on the ball, the amount of throw increases (and the balls are less shiny).
3.) If you then use the Aramith cleaner again, the amount of throw decreases again.

What do you think?

Dave

 

[dr_dave]

3kushn (is this Tom?), I have noted than fresh out of the Diamond ball polisher and a dose of Aramith Billiard Ball Cleaner the balls will stay consistent for about 30-45 minutes of 14.1 practice. The balls in the stack come apart well and the CB draws easily. Then not so much as the practice session goes on. Soooo, my experience correlated along with Dr. Dave's video leads me to believe something is wearing off the balls rolling over the cloth.

Yesterday for the first time in over a year I cleaned the balls with Novus Plastic Clean & Shine and felt that the balls behaved much more consistently for most of a three hour practice session. I'll try again today and pay more attention.

Lou Figueroa

Lou,

Are you sure you aren't a Novus sales representative?
... because you sure make their product sound good.

I plan to try it out.

Catch you later,
Dave