How would a hollow cue ball play?

Patrick Johnson

Patrick Johnson

Fish of the Day
Silver Member
Compared to a normal, solid cue ball, what differences would there be in the way a hollow cue ball of the same size and weight plays? Would the thickness of the hollow ball’s shell matter?

Thanks for your insights.

pj <- just curious
chgo
 
G

garczar

AzB Silver Member
Silver Member
Patrick Johnson said:
Compared to a normal, solid cue ball, what differences would there be in the way a hollow cue ball of the same size and weight plays? Would the thickness of the hollow ball’s shell matter?

Thanks for your insights.

pj <- just curious
chgo
Click to expand...
Is this a serious query or are you just chummin' the waters?? ;) I would think the thickness of the shell would be critical in getting the weight/sound/feel right.
 
xXGEARXx

xXGEARXx

AzB Silver Member
Silver Member
Patrick Johnson said:
Compared to a normal, solid cue ball, what differences would there be in the way a hollow cue ball of the same size and weight plays? Would the thickness of the hollow ball’s shell matter?

Thanks for your insights.

pj <- just curious
chgo
Click to expand...

It would have to be made out of different material then, unless there was a way to compress the cue ball material to get the same density - being that an unknown amount would be missing internally.

As a guess, I would say the resonance would be different and the feedback one would get would probably be different too after impact.

It would probably also matter how hollow it was.

We can fill it with foam and make it a low swerve cue ball, LOL.
 
dr_dave

dr_dave

Instructional Author
Gold Member
Silver Member
Patrick Johnson said:
Compared to a normal, solid cue ball, what differences would there be in the way a hollow cue ball of the same size and weight plays? Would the thickness of the hollow ball’s shell matter?
Click to expand...
What would be different is the mass moment of inertia (MMI), which would change with shell thickness. The MMI would be greater with a thinner/denser shell. Changes in MMI would affect anything involving changes in spin (e.g., the amount of spin delivered to the CB with an off-center hit, the rate of backspin loss with a drag shot, the curve shape of a masse shot, the natural-angle of a follow cut shot, spin transfer, etc!). A larger MMI would slow down all changes in spin. Many things would not change (e.g., cut angles, 90 degree rule tangent line, etc!). Basically, anything containing the variable "I" in the final results of any of my Technical Proofs would change.

Regards,
Dave
 
Last edited:
Patrick Johnson

Patrick Johnson

Fish of the Day
Silver Member
dr_dave said:
What would be different is the mass moment of inertia (MMI), which would change with shell thickness. The MMI would be greater with a thinner/denser shell. Changes in MMI would affect anything involving changes in spin (e.g., the amount of spin delivered to the CB with an off-center hit, the rate of backspin loss with a drag shot, the curve shape of a masse shot, the natural-angle of a follow cut shot, spin transfer, etc!). A larger MMI would slow down all changes in spin. Many things would not change (e.g., cut angles, 90 degree rule tangent line, etc!). Basically, anything containing the variable "I" in the final results of any of my Technical Proofs would change.

Regards,
Dave
Click to expand...
Thanks, Dave.

I imagine that:
- side spin shots would have fewer RPMs
- side spin would last longer
- the cue ball would “play heavier” (easier follow, harder draw)

How’d I do?

pj
chgo
 
336Robin

336Robin

Multiverse Operative
Silver Member
Probably not a lot to it. ;)


Patrick Johnson said:
Compared to a normal, solid cue ball, what differences would there be in the way a hollow cue ball of the same size and weight plays? Would the thickness of the hollow ball’s shell matter?

Thanks for your insights.

pj <- just curious
chgo
Click to expand...
 
dr_dave

dr_dave

Instructional Author
Gold Member
Silver Member
Patrick Johnson said:
dr_dave said:
What would be different is the mass moment of inertia (MMI), which would change with shell thickness. The MMI would be greater with a thinner/denser shell. Changes in MMI would affect anything involving changes in spin (e.g., the amount of spin delivered to the CB with an off-center hit, the rate of backspin loss with a drag shot, the curve shape of a masse shot, the natural-angle of a follow cut shot, spin transfer, etc!). A larger MMI would slow down all changes in spin. Many things would not change (e.g., cut angles, 90 degree rule tangent line, etc!). Basically, anything containing the variable "I" in the final results of any of my Technical Proofs would change.
Click to expand...
Thanks, Dave.
Click to expand...
You're welcome.

Patrick Johnson said:
I imagine that:
- side spin shots would have fewer RPMs
Click to expand...
Yep.

Patrick Johnson said:
- side spin would last longer
Click to expand...
Yep.

Patrick Johnson said:
- the cue ball would “play heavier” (easier follow
Click to expand...
Yep.

Patrick Johnson said:
harder draw)
Click to expand...
... less backspin off the tip, but it won't wear off as fast on the way to the OB.

Patrick Johnson said:
How’d I do?
Click to expand...
A. It could have been A+ if you had commented more on the draw.

Regards,
Dave
 
Cuebuddy

Cuebuddy

Mini cues
Silver Member
I decided to run a few test on this. I used a Christmas ornament that was close to the 2.250 mark.

This sphere played surprisingly bad.
Things learned
Safety glasses were needed.
New cloth is in my future.
I need to work on my break.
It is very important to position the hanging nub to the side on most shots.
 
R

Rickhem

AzB Silver Member
Silver Member
I think this is an interesting discussion topic. It's probably not something that would ever be implemented, but makes for an interesting idea.

Assuming that you could get a sphere with the exact same surface composition, texture, "hardness", and the like, I think that the size of that hollow core (or worded another way, the thickness of the outer shell) would have an effect on the way the cue responded to both impact with other balls, and most definitely with how cut tip position on the cue would create varying cue movement after impact.
Assuming that you could remove the possibility of a trampoline effect, with the shape of the cue ball not being altered at all by any impact, then the fact that the weight of the cue is distributed circumfrentially would certianly aid in having the cue ball conserve and retain whatever spin is applied by the tip of the cue. So imagine that you shot a draw shot which generated 500rpm of backspin on the cue, the cue ball would act much more like a flywheel in that the rotational energy would not bleed off as quickly as with a solid cue ball, where the weight is distributed evenly (or more evenly than in a hollow cue ball) thoughout the cue ball.
I'm thinking that the larger the hollow area, or the thinner and more dense the shell area is on such a cue ball, the more that ball would react to any kind of english, draw, or follow, and the further it would roll in general due to the weight being farther from that center point in the cue ball.
And like any other of the slight variations that we deal with, the player that would benefit most from that is the one that adapted faster to those differences.
 
dr_dave

dr_dave

Instructional Author
Gold Member
Silver Member
Rickhem said:
I think this is an interesting discussion topic. It's probably not something that would ever be implemented, but makes for an interesting idea.

Assuming that you could get a sphere with the exact same surface composition, texture, "hardness", and the like, I think that the size of that hollow core (or worded another way, the thickness of the outer shell) would have an effect on the way the cue responded to both impact with other balls, and most definitely with how cut tip position on the cue would create varying cue movement after impact.
Assuming that you could remove the possibility of a trampoline effect, with the shape of the cue ball not being altered at all by any impact, then the fact that the weight of the cue is distributed circumfrentially would certianly aid in having the cue ball conserve and retain whatever spin is applied by the tip of the cue. So imagine that you shot a draw shot which generated 500rpm of backspin on the cue, the cue ball would act much more like a flywheel in that the rotational energy would not bleed off as quickly as with a solid cue ball, where the weight is distributed evenly (or more evenly than in a hollow cue ball) thoughout the cue ball.
I'm thinking that the larger the hollow area, or the thinner and more dense the shell area is on such a cue ball, the more that ball would react to any kind of english, draw, or follow, and the further it would roll in general due to the weight being farther from that center point in the cue ball.
And like any other of the slight variations that we deal with, the player that would benefit most from that is the one that adapted faster to those differences.
Click to expand...
It would be a good "gimmick CB" to replace out on somebody before (our during) a game, especially if you have practiced enough with it to already know how to adjust.

Regards,
Dave
 
iusedtoberich

iusedtoberich

AzB Silver Member
Silver Member
Interesting topic. Maybe an original one? Almost nothing is original anymore...

I do think a ball like this already exists that you can buy and try to detect any real world differences. The Aramith magnetic CB that has a metal sphere near the outer surface. There were some pictures floating around of some that cracked a while back. I believe (but may be wrong) that this CB is same mass and same diameter. If so, then the density of the phenolic they use must be less, to allow for the higher density of the metal. The effect won't be as great as a hollow ball, but it would still be a higher moment of inertia compared to a regular ball.
 
iusedtoberich

iusedtoberich

AzB Silver Member
Silver Member
Here is the thread from years ago discussing the cracked magentic CB. Unfortunately, all the pictures are gone:
https://forums.azbilliards.com/showthread.php?t=168677

Here is a picture on google I just found:
Screen Shot 2020-10-24 at 12.41.50 PM.jpg
 
iusedtoberich

iusedtoberich

AzB Silver Member
Silver Member
Well actually looking at the picture, I think my prior assumption that Aramith used a lower density material for the core of the ball to make up for the magnetic layer's presumed higher density is incorrect. It looks like they just use regular balls for the core, probably the ones that come in undersize due to manufacturing variations.
 
justnum

justnum

Billiards Improvement Research Projects Associate
Silver Member
lets up it a little

and say the hollow cue ball can carry an electrical charge and be magnetized

and magnetize the table.

is it possible to approximate traditional ball dynamics with a hollow ball set and some computing device to make the adjustments in ball motion.

a pool table in space would have to simulate some things.

I don't think NASA or spaceX would put billiards equipment in the payload for free.

maybe China or UAE
 
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