Math Questions For Pool Players:

gerryf

Well-known member
He is the only to point out the ball could've be following a hidden deformation in the cloth creating the track like motion. The same phenomena for gutter balls on a pool table.

Your post on the other hand was empty criticism.
Similar to when people notice other players for the wrong reasons.
See following diagram.
Ha! Ha! Where did Danny say anything about a hidden deformation in the cloth? You should read his post again.
 

Pin

Registered
Reminded me of this article .
The problem with saying anything at all about pool is that if people scrutinize it closely enough, you're always wrong.

Here's Joe Hood from 1908, time traveler from another dimension:
1622844837371.png
 

Pin

Registered
I am not sure if this is possible or not, but its possible a curve would twist onto itself, but why?
I have heard about DrDave and his so called swerve theory.
Are you suggesting a ball shot with side and a level cue could curve, because of the rotation of the ball?

I read something, I think by Roberts Jnr, saying that a particular shot could be played along the rail against the nap of the cloth, and would hold to the rail due to side. But played with the nap of the cloth, the same effect wouldn't occur.

Which sounds like the same thing, on equipment that brought out the effect to a noticeable level.

It might have been in Modern Billiards (the British version, there's an American one with the same title). But I'm not desperate to read the whole thing again to find it!
 

justnum

Principal Investigator of Magic Trick Shots
Silver Member
Are you suggesting a ball shot with side and a level cue could curve, because of the rotation of the ball?

I read something, I think by Roberts Jnr, saying that a particular shot could be played along the rail against the nap of the cloth, and would hold to the rail due to side. But played with the nap of the cloth, the same effect wouldn't occur.

Which sounds like the same thing, on equipment that brought out the effect to a noticeable level.

It might have been in Modern Billiards (the British version, there's an American one with the same title). But I'm not desperate to read the whole thing again to find it!

No the math question is to generalize the statement DrDave made.
There are only two contact areas, cue to cue ball and cue ball to cloth.

Instead of asking for if "swerve is possible" I am doing the measured and calculated analysis to determine if his theory is worth investigating.
So far I got it up in a computer simulation, the first problem I had was placing the sphere on the surface, I have doubts about it touching at the plane tangentially.

Are there forces acting and which are negligible and which are worth noting. I suspect DrDaves theory is rooted in seeing, not calculating.
The problem with seeing is the explanation can be whatever you want it to be.
 

PoolStats

Pool Stats LLC
Silver Member
No the math question is to generalize the statement DrDave made.
There are only two contact areas, cue to cue ball and cue ball to cloth.

Instead of asking for if "swerve is possible" I am doing the measured and calculated analysis to determine if his theory is worth investigating.
So far I got it up in a computer simulation, the first problem I had was placing the sphere on the surface, I have doubts about it touching at the plane tangentially.

Are there forces acting and which are negligible and which are worth noting. I suspect DrDaves theory is rooted in seeing, not calculating.
The problem with seeing is the explanation can be whatever you want it to be.
In my professional opinion, my advice to you is to get into contact with Lawrence Berkeley National Laboratory and see if you can borrow their TEAM 0.5 half an angstrom microscope and count using your fingers and toes the number or electrons it takes to make up the rectangular surface area of various types of pool balls that touch the table. Using the following diagram and surface integration to complete your results.

Guide:

ZN02qFhm.png



I would like it to be done on DynaSphers, Predator Arcos and Arcos II, your local pool hall billiard balls, and the pool table and balls found here:

2wJUw8ml.png


Do this for a minimum of 30 balls. The more balls the better my mom always used to say.
 

rostym

AzB Gold Member
Gold Member
I haven't been reading these forums for long, but this is the strangest that I have seen. I'm not sure that anyone here is really interested in how the area of contact is calculated but here is my take. I've been a student of pool all of my life and a decent but certainly not great player ( I was a 7 in Busch league pool and was collegiate champion at Tulane University for three years in the 60"s and 70's). I practiced engineering for 40 years and was in college for 7 prior to that getting BS and Masters in mechanical engineering/thermodynamics so I have some mathematical cred, although I've probably forgotten more of what I learned than what I remember. So, unless one is trying to obtain the answer to 5 (maybe more) significant digits/figures ( Significant figures - Wikipedia ) the contact area due to the compression of the ball and slate are negligible. If we remove that from consideration, the contact area would be the area of the cap of the sphere (ball) calculated with r as the radius of the ball and h as the depth of the depression/compression. See this Wiki site for equation Spherical cap - Wikipedia Of course, to actually make that calculation, one would need to calculate the compression of the cloth based on the physical characteristics of the cloth and the weight and radius of the ball. I expect we could determine how that calculation could be made, but I doubt that getting the characteristics of the cloth for any given situation to make that calculation would be possible. One could probably determine the compression (h in the calculation) of the cloth by the ball by measuring it if one had the proper instruments.
 

Chili Palmer

AzB Gold Member
Gold Member
Silver Member
I haven't been reading these forums for long, but this is the strangest that I have seen. I'm not sure that anyone here is really interested in how the area of contact is calculated but here is my take. I've been a student of pool all of my life and a decent but certainly not great player ( I was a 7 in Busch league pool and was collegiate champion at Tulane University for three years in the 60"s and 70's). I practiced engineering for 40 years and was in college for 7 prior to that getting BS and Masters in mechanical engineering/thermodynamics so I have some mathematical cred, although I've probably forgotten more of what I learned than what I remember. So, unless one is trying to obtain the answer to 5 (maybe more) significant digits/figures ( Significant figures - Wikipedia ) the contact area due to the compression of the ball and slate are negligible. If we remove that from consideration, the contact area would be the area of the cap of the sphere (ball) calculated with r as the radius of the ball and h as the depth of the depression/compression. See this Wiki site for equation Spherical cap - Wikipedia Of course, to actually make that calculation, one would need to calculate the compression of the cloth based on the physical characteristics of the cloth and the weight and radius of the ball. I expect we could determine how that calculation could be made, but I doubt that getting the characteristics of the cloth for any given situation to make that calculation would be possible. One could probably determine the compression (h in the calculation) of the cloth by the ball by measuring it if one had the proper instruments.


Justnum is our resident odd duck and this question is not out of the norm for him. Some people bash him, some people ignore him, and some people just brush him off.

Knowing this, and being the type of guy who follows the "The more you know" philosophy, I tend to read his posts but, with skepticism. At the end of the day he's either the best troll EVER or he's just trying to be inquisitive and learn new things but doesn't quite have the English language down. I lean more towards the latter so generally don't razz him too much ;)

That being said - excellent response. I work in the A/E industry (accountant), I should send the question to our structural/mechanical subs and see what they say.
 

boogieman

It don't mean a thing if it ain't got that ping.
You can lay down a sheet of carbon paper on top of the cloth, and if you roll a ball over it, you'll see the contact area.
Some pool book used carbon paper between balls to see how much they flattened when struck at various speeds. I forget who's book it was but it was pretty interesting. I suppose you could just set a ball on the paper and tap it ever so lightly to see the result. Might be better to do it on a non clothed hard surface.
 

Chili Palmer

AzB Gold Member
Gold Member
Silver Member
Its all fun and games until somebody takes a shot to the eyes.

Since we're already in a strange thread I'll throw in a funny story.

My son started playing in league with me about 6 months ago and on his first night we played at a bar that has 4 tables going north/south and two tables going east/west - if you're breaking and look past the rack you would be looking at the left side of a player breaking on the table next to you (hope that makes sense and keep it in mind).

My son goes to break and does the 'ole clip the 1B and send the CB flying. Well, it took off like lightning and went directly at the other table and smacked the girl breaking right in the side of the head. By the time I realized what happened the ball was falling out of her hair (she had a lot and I'm sure it saved her from excruciating pain) and dropped onto the concrete floor and bounced around. The only person that really knew what happened was my son. Once we realized the girl was ok the whole bar was laughing.

If she was pointing the other way she easily could've lost an eye or had a broken nose.
 

Chili Palmer

AzB Gold Member
Gold Member
Silver Member
Some pool book used carbon paper between balls to see how much they flattened when struck at various speeds. I forget who's book it was but it was pretty interesting. I suppose you could just set a ball on the paper and tap it ever so lightly to see the result. Might be better to do it on a non clothed hard surface.

How thick is the carbon paper?
 

boogieman

It don't mean a thing if it ain't got that ping.
How thick is the carbon paper?
No idea but it would be a variable. The stuff I've seen is basically a sheet of normal paper with a thin sheet of carbon on it, like the old hand written receipts. It might not be exactly precise but it would give you a good quick and dirty answer.
 

Chili Palmer

AzB Gold Member
Gold Member
Silver Member
No idea but it would be a variable. The stuff I've seen is basically a sheet of normal paper with a thin sheet of carbon on it, like the old hand written receipts. It might not be exactly precise but it would give you a good quick and dirty answer.

That was point, the variables within that are way too large for it to be accurate. You could easily double or even triple the actual number you're trying to reach simply because of the different types of carbon paper you can buy.
 

justnum

Principal Investigator of Magic Trick Shots
Silver Member
Here is a diagram.
A good place to start the measurements are to find the smallest possible cue width.

As for the deformation in the cloth, I'd rather use a sand measurement system like those used in track and field events.

A more general question of what I stated earlier is what is the smallest possible cue width that provides as much control as with the standard cue?
Saving money on material is a common concern in engineering.

I layer the sand based on different depth, then perform the rolling motion. I have a good idea of what will happen.

What I don't know is the precision measurement of the cloth fibers?


sphere.png
 
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