Throw - Snooker balls vs. Pool balls

[BC21]

The cloth (or force between the ball and cloth) has nothing to do with throw. The throwing force pushes the ball in the thrown direction during impact, before the ball has any time to interact with the cloth.

..........

Really? You must mean for this particular study. I see where you are coming from....if the cloth is the same, it makes no difference in throw comparisons here . But normally, cloth condition can affect the amount of throw that occurs between the balls.

I mean, with a table surface of ice, instead of cloth, there would be very little friction between the OB and the surface when the CB comes along and forces it to move, pushing it over the ice until it finds its path. The amount of throw would be extreme on the ice compared to cloth because the OB would slide in the thrown/pushed direction with very little frictional opposition. If the table surface were rough like 80-grit sandpaper, there'd be more friction trying to keep the OB from being pushed by the cb, and it wouldn't move as far offline.

Frictionally speaking, there is more to consider than just the surface condition between the balls when it comes to collision-induced throw. If we could increase the friction between the table surface and the OB so that it exceeds the friction between the CB and the OB, then the amount of throw that occurs should be smaller. The ob will resist being pushed too much by the cb. If we could reduce the friction between ob and table surface, then we'll get throw dominated by the friction between the two balls.

I understand the proportional effects of friction and force, and with ball surface and table suface conditions being equal, pool balls and snooker balls should have equal amounts of throw at proportional speeds. But if you stroke a pool shot with a 10mph stun stroke, will the same shot using snooker balls and the same 10mph stun stroke produce the same outcome as far as throw? Or would you have to ensure the speed is proportional to ball size/weight, and not equal?

 

[pvc lou]

Hey Dave,

I've been playing caroms lately, and I think there's a big difference in the reactions of carom balls and pool balls. The carom balls have significantly more rotational inertia.

Why would you or others think ball size and weight would make a difference? And would you expect throw to be even more with carom balls, which are larger and heavier than pool balls (I still plan to do the test today)? If so, why?

Concerning equipment differences, the snooker world certainly seems to keep things newer and cleaner than some pool halls and bars in America. Old and dirty balls can definitely result in more throw and more-frequent cling/skid/kick. And as documented on the ball treatment resource page, the choice of ball cleaning product can also make a big difference.

Regards,
Dave

 

[dr_dave]

The cloth (or force between the ball and cloth) has nothing to do with throw. The throwing force pushes the ball in the thrown direction during impact, before the ball has any time to interact with the cloth.

Really?

Yes.

You must mean for this particular study.

Nope.

cloth condition can affect the amount of throw that occurs between the balls.

Nope. Cloth condition has many effects (see the cloth effects resource page), but throw direction is not one of them (although, there are some possible indirect throw effects related to cloth condition based on discussions on the cling/skid/kick resource page).

I mean, with a table surface of ice, instead of cloth, there would be very little friction between the OB and the surface when the CB comes along and forces it to move, pushing it over the ice until it finds its path. The amount of throw would be extreme on the ice compared to cloth because the OB would slide in the thrown/pushed direction with very little frictional opposition. If the table surface were rough like 80-grit sandpaper, there'd be more friction trying to keep the OB from being pushed by the cb, and it wouldn't move as far offline.

The OB starts off in the same direction regardless of the surface it is sitting on. Only once it starts moving across the surface (after CB impact) does the surface have any effect. The surface affects how the OB speed and top/bottom spin change during motion, but it does not affect the straight-line direction of motion (assuming there is no masse spin on the OB).

Frictionally speaking, there is more to consider than just the surface condition between the balls when it comes to collision-induced throw. If we could increase the friction between the table surface and the OB so that it exceeds the friction between the CB and the OB, then the amount of throw that occurs should be smaller.

Not true. The friction between the OB and table does affect OB speed (and how it changes during the shot), but not OB direction. The OB direction is a direct result of the forces (impact and throw) acting during the incredibly-brief ball contact time. The amount the OB moves during CB impact is negligible. The OB acquires its speed and direction immediately (for all practical purposes).

I understand the proportional effects of friction and force, and with ball surface and table suface conditions being equal, pool balls and snooker balls should have equal amounts of throw at proportional speeds. But if you stroke a pool shot with a 10mph stun stroke, will the same shot using snooker balls and the same 10mph stun stroke produce the same outcome as far as throw? Or would you have to ensure the speed is proportional to ball size/weight, and not equal?

If the ball speeds are the same, the throw should be the same. Throw changes based on the relative speed between the ball surfaces at impact. For more info, see the throw speed effects resource page.

Please take some time reviewing some of my throw resource pages. You might find some of them helpful. I would recommend starting with the following:

tutorial covering the basics of throw

answers to questions about CIT, SIT, and OE

And for the complete story, see all of the other sub topics of interest on the throw resource page.

Enjoy,
Dave

 

[dr_dave]

Hey Dave,

I've been playing caroms lately, and I think there's a big difference in the reactions of carom balls and pool balls. The carom balls have significantly more rotational inertia.

I agree, but throw direction is not affected by this stuff. If the balls are homogeneous spheres, everything scales with weight and size.

Regards,
Dave

 

[BC21]

Yes.

Nope.

Nope. Cloth condition has many effects (see the cloth effects resource page), but throw direction is not one of them (although, there are some possible indirect throw effects related to cloth condition based on discussions on the cling/skid/kick resource page).

The OB starts off in the same direction regardless of the surface it is sitting on. Only once it starts moving across the surface (after CB impact) does the surface have any effect. The surface affects how the OB speed and top/bottom spin change during motion, but it does not affect the straight-line direction of motion (assuming there is no masse spin on the OB).


Not true. The friction between the OB and table does affect OB speed (and how it changes during the shot), but not OB direction. The OB direction is a direct result of the forces (impact and throw) acting during the incredibly-brief ball contact time. The amount the OB moves during CB impact is negligible. The OB acquires its speed and direction immediately (for all practical purposes).


If the ball speeds are the same, the throw should be the same. Throw changes based on the relative speed between the ball surfaces at impact. For more info, see the throw speed effects resource page.

Please take some time reviewing some of my throw resource pages. You might find some of them helpful. I would recommend starting with the following:

tutorial covering the basics of throw

answers to questions about CIT, SIT, and OE

And for the complete story, see all of the other sub topics of interest on the throw resource page.

Enjoy,
Dave

Thanks. I just couldn't help but think of those hockey pucks, and how much different the throw was between light and heavy pucks. But of course the weight differences were extreme, and pucks cover a much larger area of table surface, so much that at the point of impact the friction between puck and cloth is many times greater than the friction between the pucks. Whereas with pool balls only a very small area of a ball is actually touching the cloth, and what little bit of static friction there is, well, it's just not enough to make a difference compared to the frictional force between the balls at impact.

 

[Imotv8u]

I play a lot of pool and snooker(10 ft, American snooker, 2 1/8” balls, 760 Simonis cloth). I’m with Dr. Dave on this. I can’t tell any significant difference in the amount of throw.

 

[Straightpool_99]

After all that sciency stuff, here are my observations regarding throw on snooker vs. pool tables.

The throw is more or less the same. The exception being when the balls are on their spots on a very worn table. They tend to sink in, causing all kinds of weird reactions, especially jumping on hard shots. Otherwise, I use pretty much the same compensations on pool and snooker tables.

 

[jsp]

The friction between surfaces during impact depends on the absolute speed of relative motion between the surfaces. That's what my current model assumes; and again, the model matches real-life results over a wide range of shot angles, speeds, and spin types/amounts. The speed of relative motion between ball surfaces is independent of ball size or weight.

I understand.

So for the hypothetical example that I presented in my previous post in which everything is scaled by 2x, including the velocity, then your friction model would predict that the throw angle would be less than the 1x case. Is this correct? To me this counter-intuitive.

Going to an extreme, if the balls were as big as bowling balls and they were hit at the same absolute speed as pool balls, my intuition is that the bowling ball-sized balls would throw more.

 

[jsp]

I just did my test, comparing pool ball throw to carom ball throw, and I found no measurable difference.

Here is what I did:
1.) Cleaned 3 fairly new Aramith Red Measles CBs and a set of 3 fairly new carom balls (from the same set) with Aramith ball cleaner.
2.) Set up a frozen-combo 1/2-ball-hit shot straight up table (like in my recent small-gap-combo throw video) with the pool balls, carefully tapping and marking (with donuts) the balls into place.
3.) Hit the shot numerous times with a consistent slow speed (judged based on ball travel distances) to see how much throw I got, measured by placing a golf tee on the rail where the OB was arriving. After many shots (and adjustments of the tee position), I hit the tee fairly consistently when the same speed was used.
4.) Set up the same frozen combo with the carom balls, with the thrown ball on the same spot, but the other balls shifted slightly (and re-tapped and marked) due to the ball size difference. I did make sure a straight hit sent the ball straight up table as was the case with the pool ball.
5.) Hit 1/2-ball-hit shot numerous times with a consistent speed as with the pool balls, and the thrown ball headed straight for the tee fairly consistently.

For those interested, I also weighed the balls and calculated the density difference. Here's what I got:

pool ball:
diam = 2 1/4" = 2.25 in
weight = 0.166 kg = 5.855 oz
density = 1698 kg/m^3

carom ball:
diam = 2 7/16" = 2.438 in
weight = 0.208 kg = 7.337 oz
density = 1674 kg/m^3

density difference: pool ball is 1.5% denser than the carom ball (although, I didn't have a vernier caliper handy to measure the ball sizes carefully, so it is possible they were slightly out of spec).

Regards,
Dave

PS: Again, I would expect snooker balls to also throw the same amount, if also fairly new, and cleaned with Aramith ball cleaner, and hit with the same ball speed.

Thanks a lot for doing this. I can't argue with experimental data.

One question I have is how exactly did you control the speed of both types of balls? You said you based it on ball travel distances, but can you please elaborate more.

 

[jsp]

I can't comment to a scientific certainty, but I compensate about the same between both games.

I don't know much about physics, but living in the UK (snooker is massive here) and playing both games I'd say that there is little to no difference in throw. I definitely dont adjust between games. I would think that any differences would be fromexternal factors (the cleanliness of the balls etc) rather than because of inherent differences in friction.

I play a lot of pool and snooker(10 ft, American snooker, 2 1/8” balls, 760 Simonis cloth). I’m with Dr. Dave on this. I can’t tell any significant difference in the amount of throw.

After all that sciency stuff, here are my observations regarding throw on snooker vs. pool tables.

The throw is more or less the same.

Thanks all for the input. I guess my intuition has always been wrong.

 

[dr_dave]

I understand.

So for the hypothetical example that I presented in my previous post in which everything is scaled by 2x, including the velocity, then your friction model would predict that the throw angle would be less than the 1x case. Is this correct? To me this counter-intuitive.

Going to an extreme, if the balls were as big as bowling balls and they were hit at the same absolute speed as pool balls, my intuition is that the bowling ball-sized balls would throw more.

The size and weight should not matter, assuming the relative sliding speed between the surfaces is the same in any comparison. The friction force is always proportional to the impact force, so the throw angle should be the same.

Regards,
Dave

 

[dr_dave]

Thanks a lot for doing this. I can't argue with experimental data.

One question I have is how exactly did you control the speed of both types of balls? You said you based it on ball travel distances, but can you please elaborate more.

I watched how far the OB traveled (by checking where it came to rest after rebounding off the cushion). If it didn't travel the same distance as my reference shot, I would consider it a bad shot, and the throw would be different than with the reference shot, because throw does vary with shot speed (sometimes).

Regards,
Dave

 

[dr_dave]

Thanks all for the input. I guess my intuition has always been wrong.

Many things went against my intuition when I started doing all of the throw research, analysis and experimentation in the past. For example, my intuition found it difficult to accept the following facts at first:

- CIT is less at faster speeds at large angles but not at small angles.
- CIT is largest close to a 1/2-ball hit (i.e., more angle does not create more throw).
- SIT is maximum at close to 50% of maximum sidespin with a direct hit (i.e., more spin does not create more throw).

After doing all of the research, analysis, super slow-motion video, and experiments, all of the squirt, swerve, and throw effects are now "intuitively obvious."

Good thread,
Dave

PS: Convincing resources (videos, articles, and other info) documenting all throw effects are available via the supporting links listed with items 16-37 in the numbered list beneath the videos and illustrations on the squirt, swerve, and throw effects resource page. Throw is complicated, with 22 different effects listed!

 

[jsp]

I watched how far the OB traveled (by checking where it came to rest after rebounding off the cushion). If it didn't travel the same distance as my reference shot, I would consider it a bad shot, and the throw would be different than with the reference shot, because throw does vary with shot speed (sometimes).

Thanks for the replies.

I was asking how you maintained the same speed between the pool ball and carom ball. Given the same initial speed, wouldn't the heavier carom ball roll farther than the pool ball?

 

[dr_dave]

Thanks for the replies.

I was asking how you maintained the same speed between the pool ball and carom ball. Given the same initial speed, wouldn't the heavier carom ball roll farther than the pool ball?

I used the same travel distance for both.

I think rolling resistance is directly proportional to weight, so the balls should slow at the same rate (neglecting air resistance, which does scale non-linearly with size).

Regards,
Dave