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

[dr_dave]

Couple of comments on this:

1. How is it you don't have a cueing robot by now?

... I had one many years ago, but I don't anymore. However, even with a pool robot, one must be very careful with setup and procedures. For more info, see robot test results.

Regardless, with careful procedures, the human results can be quite consistent and accurate (and in some cases, more meaningful than robot results).

2. Related to #1, are you verifying shot speeds with the video to remove outliers?

Yes. For the throw-vs-speed tests, I actually used the video to calculate the OB speed (with the video frame time stamps). With all of the other tests, I just observed on video how far the OBs traveled. If there was spin on the CB, or if the OBs did not travel the correct distance, I threw out the shot.

3. Where's a good place to get silicone spray?}

... at any hardware store. Walmart probably has it also. It is sold as a spray lubricant (like WD-40).

4. Why do we need chalk, again?

... to help the tip completely grab the CB during contact.

I'm thoroughly convinced the sport would be improved if a substitute tip with appropriate friction was produced that required no chalk at all.

I agree with you 100%. I suspect that if anybody ever invents or discovers a chalk-free material that works as well as or better than chalked leather, he or she will become very wealthy (if he or she has good business sense).

It seems chalk is the root of all evil when it comes to throw.

Chalk is only a problem when it happens to remain on the balls and end up at a contact point, creating cling. Luckily, this doesn't happen very often, especially when the balls are cleaned and wiped frequently.

Regards,
Dave

 

[dr_dave]

Well thought out and executed again.

Thanks.

Pictures are worth a thousand words.

... video, even better.

Regards,
Dave

 

[dr_dave]

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?

I think that if a "residue" (i.e., some form of "wax") is not left on the balls after cleaning, there will be excessive throw (as with the alcohol, acetone, and dish-washing-liquid tests, where the balls are left "squeaky" clean with no residue).

And, if you use Aramith or another wax-type product, are you inpregnating your tip with wax over the course of play?

I don't think this presents much of a problem, but I have not tested for it. Silicone spray is another story ... that stuff is nasty and gets all over everything.

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

I've done some limited tests comparing frozen-combo stun shots with small-gap-combo stun shots, and there was little difference. For more info, see: frozen-ball throw.

Concerning follow vs. stun, follow reduces throw, especially for cut angles in the 1/2-ball hit range. For more info, see effects of follow and draw on throw.

Good questions,
Dave

 

[dr_dave]

Dr. Dave, very interesting experiment!

I compared your experimental data http://i.pixs.ru/storage/2/9/2/davejpg_8520739_12290292.jpg with my measurements http://dbkcues.ru/articles-2/ball-motion-properties-in-stun-and-follow-shots/?lang=en

Results correlates very well http://i7.pixs.ru/storage/3/7/9/coefficien_5543822_12290379.jpg

Sorry my english

Thank you for sharing the links again. That's good stuff.

Best regards,
Dave

 

[nobcitypool]

Were there a tip material that "gripped" the CB adequately without chalk, that means there would be friction. Subsequently, there would be wear. I cannot imagine there is a material that would provide that "grip" that is harder than the CB, therefore, that wear would occur on the tip. Therefore, the tip would wear out rather quickly compared to a leather tip with chalk.

 

[dr_dave]

Were there a tip material that "gripped" the CB adequately without chalk, that means there would be friction. Subsequently, there would be wear. I cannot imagine there is a material that would provide that "grip" that is harder than the CB, therefore, that wear would occur on the tip. Therefore, the tip would wear out rather quickly compared to a leather tip with chalk.

Ideally, the tip would grab the CB so well, that there would be no slipping or rubbing at all during contact, so maybe there would not be much wear. When using chalk, it is rubbed against the leather often, which contributes to wear.

Honestly, it baffles me that we haven't found a material better than chalked animal skin in the roughly 200 years since the leather tip was invented.

Regards,
Dave

 

[CreeDo]

Dave this is so good. It dispels some myths and shows some unexpected results.

I love that you humored the static electricity people,
and I think you're right... static doesn't increase or decrease throw,
your slightly reduced throw is probably just the polishing effect.
Still, if you wanted to really be thorough, you could get them charged without rubbing I guess.

So, a few questions...

1. The stuff that you'd think cleans super well, rubbing alcohol... somehow results in more throw.
So your theory is that normally cleaned balls have residue that makes them slippery,
and if that residue is minimal or evaporates (as with rubbing alcohol),
you get a lot of throw because the microscopic roughness of the balls
allows them to rub against each other without any lubricant?

It looks like the max difference between peaks and valleys on a decently-treated ball
is about 1 micron. Is that enough to explain the difference between 6.6 degrees
(used balls that have been cleaned) and 7.1 degrees (the balls that have rubbing alcohol)?
Or could that be experimental error?

How did you clean the balls in the baseline test, just going over them with a cloth?
If so, any chance of residue on the cloth?

2. If a totally clean ball throws more due to the friction of the ball's microscopically rough surfaces,
doesn't it seem like the sandpaper-roughened ball (especially with chalk) would have thrown even more?

3. Is it possible the sandpaper is... I dunno, 'shearing the peaks' of those microscopic peaks 'n' valleys,
thus creating a relatively smoother surface? And can chalk particles fill in valleys,
making it effecively smoother yet? What if you had used a coarser grit?

Last but not least, as Lou pointed out... this illustrates how cleansers affect throw,
but can we set up a good "skid simulator" using wired balls that are some distance from each other?
Can we experimentally wire up a cue ball that is several inches from a lone object ball,
using donuts for positioning, and consistently get the cue ball's chalk mark to rotate
just right into the object ball and create an intentional skid?

Showing how different products (especially different brands of chalk) affect skid
would be extremely interesting, and you could prove whether only chalk causes a kick,
or both chalk and certain cleansers.

 

[dr_dave]

Dave this is so good. It dispels some myths and shows some unexpected results.

I love that you humored the static electricity people,
and I think you're right... static doesn't increase or decrease throw

... unless you sprinkle the balls with "pixie dust" before the shot (which I did not test).

your slightly reduced throw is probably just the polishing effect.
Still, if you wanted to really be thorough, you could get them charged without rubbing I guess.

There is a lot more I could do, but I won't (in the near future, anyway).

So, a few questions...

1. The stuff that you'd think cleans super well, rubbing alcohol... somehow results in more throw.
So your theory is that normally cleaned balls have residue that makes them slippery,
and if that residue is minimal or evaporates (as with rubbing alcohol),
you get a lot of throw because the microscopic roughness of the balls
allows them to rub against each other without any lubricant?

I think really clean and smooth phenolic surfaces have more friction than desireable at the pool table. I believe the waxy "residue" ball cleaners (like the Aramith product) leave behind help reduce the friction to acceptable levels.

It looks like the max difference between peaks and valleys on a decently-treated ball
is about 1 micron. Is that enough to explain the difference between 6.6 degrees
(used balls that have been cleaned) and 7.1 degrees (the balls that have rubbing alcohol)?
Or could that be experimental error?

I think this difference is significant because the results were very consistent, and I was very careful with the procedure. The balls were placed very consistently and frozen every time, and only shots with no sidespin and of consistent speed were kept. Having said this, I could believe there might be up to a 1/2 degree in possible experimental error (e.g., due to slight differences in speed and ball-surface properties over an area).

How did you clean the balls in the baseline test, just going over them with a cloth?

When the baseline was "used balls," I did not clean them at all ... I used them as is (and it had been a while since I had last cleaned the balls). When the baseline was "used and clean," I cleaned them with the Aramith ball cleaner, and buffed them with a dry and clean cotton cloth.

2. If a totally clean ball throws more due to the friction of the ball's microscopically rough surfaces,
doesn't it seem like the sandpaper-roughened ball (especially with chalk) would have thrown even more?

I was honestly a little surprised at first when the sandpaper-roughened surfaces didn't throw more; but as I tried to describe in the video, I think it is because the amount of throw was already close to the maximum possible throw corresponding to the balls gearing together during contact. In this case, added friction has no effect because the balls are already gearing together during contact.

3. Is it possible the sandpaper is... I dunno, 'shearing the peaks' of those microscopic peaks 'n' valleys,
thus creating a relatively smoother surface? And can chalk particles fill in valleys,
making it effecively smoother yet? What if you had used a coarser grit?

I actually used a coarser-grit sandpaper too, but the results were no different, that's why I excluded it (along with other non-interesting tests) from the video which is already a bit long.

Last but not least, as Lou pointed out... this illustrates how cleansers affect throw,
but can we set up a good "skid simulator" using wired balls that are some distance from each other?
Can we experimentally wire up a cue ball that is several inches from a lone object ball,
using donuts for positioning, and consistently get the cue ball's chalk mark to rotate
just right into the object ball and create an intentional skid?

I have done some limited tests with a small-gap combo vs. a frozen combo, and the results were very similar (see frozen-ball throw).

There are many things that can be done, but to simulate cling, it is much easier to put the chalk mark on the OB, where it is guaranteed to be exactly in the right place at contact.

Showing how different products (especially different brands of chalk) affect skid would be extremely interesting, and you could prove whether only chalk causes a kick, or both chalk and certain cleansers.

There are many things that could be done, with enough time and motivation. However, I'm fairly confident chalk will cause cling regardless of the surface conditions (unless the balls already have enough friction to create gearing during contact resulting in the maximum possible throw already, in which case the chalk should have no addition effect).

Good questions,
Dave

 

[DRW]

I think you should also try the new cyclops balls in this experiment.

 

[oshua86]

@DrDave

Great video and info. I got a question. How about table cloth? Would the quality, condition and age of the table cloth have any effect on CIT or SIT?

 

[dr_dave]

I think you should also try the new cyclops balls in this experiment.

I didn't have a set handy to test, but I would expect the results to be similar for the different surface treatments tested.

Actually, it is not that difficult for others to do similar tests. You don't even need a camera, the donuts, or the ruler on the rail. Just tap the balls into place, and observe where the OB hits the cushion. Then switch ball brands and see if there is any difference (for shots of the same speed with no sidespin).

I would be curious to see what people find in a comparing different ball brands.

Good idea,
Dave

 

[dr_dave]

@DrDave

Great video and info. I got a question. How about table cloth? Would the quality, condition and age of the table cloth have any effect on CIT or SIT?

The table cloth should have absolutely no effect on the results. The cloth properties have no direct effect on throw.

Now, if the cloth is really filthy with chalk dust and the balls are dirty, the balls might tend to pick up more chalk and result in cling more often (although, I'm not sure).

Also, if the cloth is really slick, it might not rub chalk marks off the CB as easily (e.g., with draw shots, where the CB slides against the cloth), so there might be a greater chance for cling as chalk smudges remain on the CB more easily (but again, I'm not sure).

Regards,
Dave

 

[Hits 'em Hard]

What felt was being used?

 

[dr_dave]

What felt was being used?

The table cloth is Championship; but again, this is immaterial in these experiments.

Do you (and others) think a different cloth would produce different results in this experiment? If so, why?

Thanks,
Dave

 

[JayKidd]

I agree with you 100%. I suspect that if anybody ever invents or discovers a chalk-free material that works as well or better than chalked leather, he or she will become very wealthy (if he or she has good business sense).

I think chalkless tips would create a healthier playing environment for pool too. Even without the possible heavy metal component int he chalk, inhaling dusty cloud of chalk day in and day out wouldn't be too good to one's lung.

Not to mention how much longer the table cloth and balls will last with out the leftover chalk dust.

 

[row21097]

great work!

thanks
bert

 

[AngryTurtle]

The Aramith cleaner is definitely leaving something behind on the phenolic surfaces to reduce friction and throw a reasonable amount (unlike the hard-shell Turtle wax which reduces it too much, IMO).

Hi Dr Dave, a couple of questions:

Why do you think the Turtle wax is too much? From a theoretical perspective at least its removing a side effect that needs to be compensated for. Does removing throw make things too simple?

Also would you expect the non Phenolic balls (Polyester I think) to behave similarly?

 

[dr_dave]

Hi Dr Dave, a couple of questions:

Why do you think the Turtle wax is too much?

You have a great user name ("AngryTurtle") for asking this question. :wink:

From a theoretical perspective at least its removing a side effect that needs to be compensated for. Does removing throw make things too simple?

If there were no throw, shot making would be easier because you could aim every shot, regardless of angle, speed, and spin, to hit at the ideal ghost-ball position along the "line of centers." However, as I pointed out earlier, throw shots and spin transfer shots would no longer be possible. Also, as the wax wears off with use, the conditions could change significantly. Also, if everybody didn't use the same wax and clean balls frequently, conditions could be very different from one place to another, from one day to the next, and from one ball to the next.

Also would you expect the non Phenolic balls (Polyester I think) to behave similarly?

I don't know, but that's a good question. As with the phenolic balls, I would expect them to have low throw with the Turtle wax and/or Silicone spray. I would also expect them to have similar cling with a chalk mark. I'm not sure how they might respond to Acetone or alcohol cleanings.

Regards,
Dave

 

[JB Cases]

Ideally, the tip would grab the CB so well, that there would be no slipping or rubbing at all during contact, so maybe there would not be much wear. When using chalk, it is rubbed against the leather often, which contributes to wear.

Honestly, it baffles me that we haven't found a material better than chalked animal skin in the roughly 200 years since the leather tip was invented.

Regards,
Dave

Maybe it's because leather is so well suited the the task. Could you try this with different brands of chalk?

Kamui says that theirs reduces deflection. Would that then mean that it increases friction?

 

[jtaylor996]

I get that leather is well suited, but it's the chalk dust getting everywhere and wearing everything down that bothers me.

Maybe leather with a thin layer of natural rubber on the end would work. The rubber should flex and not wear too fast (well, I'm guessing here, to be honest), and should provide plenty of grip. Maybe a soft tire compound. I can't believe nobody has tried a rubber tip up to this point.

In Renfro's thread there was talk of an "ideal" chalk, and one of my main criteria was that it would stick to tips and not to the balls, or get on everything else.

Maybe Dave's got some tip measurements that could help us define from a physics perspective what the critical functions of the tip/chalk actually are. That would be amount of friction, energy absorbed, etc...