Agreed.
:grin-square:Does anyone here have a sufficiently large vacuum chamber?
Throw - Snooker balls vs. Pool balls
- Thread starter jsp
- Start date
As for the effect of an air cushion, if that does exist I would expect it to be less important for denser balls or for thinner air. Does anyone here have a sufficiently large vacuum chamber?
https://xkcd.com/669/
So, if anyone here is in New Jersey, would you please click on add to cart? I'll see about reimbursing you after the experiment. We will also need to get a volunteer to do the shooting. Evidently physics professors don't work as well as expected.
![CropperCapture[76].png](https://forums.azbilliards.com/data/attachments/352/352785-29b14e253a6eab62a1ef38b51f9a5786.jpg?hash=KbFOJTpuq2 "CropperCapture[76].png")
I think there a difference
I bought a 5 by 10 1943 Brunswick snooker table, after playing pool for 68 years. I bought aramith snooker balls and aramith pool balls. I had 760 Simons installed. I could not get use to the pool balls because I could not transfer English or throw the ball I know the 760 was part of the problem, but I have a stroke and can spin snow.
I bought a 5 by 10 1943 Brunswick snooker table, after playing pool for 68 years. I bought aramith snooker balls and aramith pool balls. I had 760 Simons installed. I could not get use to the pool balls because I could not transfer English or throw the ball I know the 760 was part of the problem, but I have a stroke and can spin snow.
Curious. What did you use for a stick?
A few weeks ago I did a related experiment using pucks -- 2 official ice hockey pucks and 2 smaller and much lighter air hockey pucks. For each set of pucks I shot a few pool shots. The lighter pucks, naturally, had much more throw upon impact. They are smaller in diameter, which means less frictional contact against the cloth. The lighter weight also reduces sliding friction. So I would expect a lighter and smaller sphere to throw more than a heavier, larger sphere.
I recorded my puck shots and will try to find the video and post it if anyone is interested.
I recorded my puck shots and will try to find the video and post it if anyone is interested.
Thanks for the reply.
I looked at your analyses, and the resulting equations hinge on the experimental friction data used to model the relationship between coefficient of friction and relative surface speed. But is it not reasonable to question whether this coefficient of friction model remains constant for all ball masses and radii? In other words, if the coefficient of friction itself is a function of the ball's mass, diameter, or density then so too would be the amount of throw.
Is the above a typo? Did you mean you couldn't get used to the snooker balls?
As for the effect of an air cushion, if that does exist I would expect it to be less important for denser balls or for thinner air. Does anyone here have a sufficiently large vacuum chamber?
I can make a wind tunnel.
The model of friction and my analysis results have been well tested, and the theory matches reality very well over a wide variety of shot angles, speeds, and spin types/amounts. I can think of several reasonable physical explanations for why friction varies with relative surface speed, but I can’t think of any for how it might vary with ball weight or size (assuming the surface properties and treatments are the same in the comparison).
I don’t have a set of snooker balls; but I do have a set of carom balls, which are much larger and heavier than pool balls. I’ll try to compare their throw to pool ball throw tomorrow. I suspect they will be very similar.
Regards,
Dave
There are far more situations in pool where throw is a factor. Cuts, banks, grouped balls - where you would take another option in snooker and not even consider using (or countering) throw.
My understanding of physics says it's the same for both sets of balls but that same physics along with my intuition tellls me that the combination of physical factors including ball size and equipment differences leads to more throw in pool than in snooker.
My understanding of physics says it's the same for both sets of balls but that same physics along with my intuition tellls me that the combination of physical factors including ball size and equipment differences leads to more throw in pool than in snooker.
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
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I think it's possible that friction could have a radius component to it, considering we know that friction is dependent on surface speeds. Maybe friction is dependent not on the absolute speed of the surface but the "relative speed" of the surface, which I will define here as the ball's absolute speed divided by its radius (units in radii/second). The friction data/model doesn't differentiate between the two because the size of the pool ball never varied for the experiments (my assumption, I could be wrong), so there was no need to differentiate between the ball's absolute and relative speeds.
So if friction is actually dependent on the speed of the ball relative to its radius, then the size of the ball would factor in the amount of throw.
Let me attempt to explain further. Take balls with radius r and absolute velocity v. For a given cut angle the throw angle is T. Now scale every dimension by 2x, keeping the ball material exactly the same (as if visually you simply zoomed in by a factor of 2). That means the radius is now 2r and its velocity is now 2v. What would be our guess for the throw angle given the same cut shot? A reasonable guess is that it would still be T, since everything simply scales by a factor of 2 and the 2x factors cancel out on both sides of the equation.
But if throw is still T in the 2x case, doesn't that violate our friction model if the CB's speed is now 2v? Doesn't our model say that the coefficient of friction goes down with increasing ball speeds? It does violate the model if friction is dependent on the CB's absolute speed. However, if friction is actually dependent on the CB's relative speed (its speed relative to its radius), then it does NOT violate the model since the CB's relative speed remains constant for both cases. In the 2x case both the radius and velocity doubles, keeping the relative speed the same.
Now, assuming the above is true and friction is actually dependent on the CB's relative speed, then for the same absolute CB velocity (which was the condition of my OP), the size of the ball does factor into the amount of throw. Given the same absolute ball speed, the smaller the ball the smaller the throw, since the relative speed increases as the radius decreases.
Is my thinking reasonable?
That would be great if you try that experiment. I look forward to your results. :thumbup:
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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'll post the results as soon as I finish the test. I should be able to get to it soon.
Regards,
Dave
I'm curious and look forward to your findings if you get a chance to test it out. I tend to believe the smaller and lighter ball will slide easier upon impact due to having a smaller static frictional force between ball and cloth. But the impact force would also be smaller with the smaller/lighter balls, so it may turn out that equal amounts of throw occur for snooker and pool balls.
With my puck experiment I was simply showing how aiming a shot in pool is not a complicated process involving spheres, but that we aim using the equators of the balls. I shot the cylindrical pucks into pockets like they were balls, using a 1/2 ball aim (center of cue puck to edge of object puck). Anyway, I had to stroke the heavy hockey pucks very hard to get the object puck to travel 2ft to the pocket. I also had to strike the lighter air hockey pucks very firm to get the object puck to the pocket. Naturally, once the heavy puck gets sliding it slides farther than the lighter puck, but the light puck was always pushed/thrown off the shot line by several degrees and I had to overcut it in order to pocket it, where the heavy puck went just fine with a straight 1/2 puck aim.
This is what makes me think a lighter ball will be knocked/pushed farther offline before it begins to roll. I did have to use a faster stroke speed on the lighter puck shot in order to get the object puck to the pocket. So maybe the extra speed caused the increased throw. With snooker balls vs pool balls, and using the same cue and stroke speed for each shot, the snooker cb will have more speed, so maybe it'll push/throw that ob more also..???
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.
With friction and throw, everything changes in equal proportions. If the balls are heavier, they result in large impact forces, but the throwing friction force increases in a proportional amount. Friction force is always directly proportional to the "normal" impact force. That's why the throw angle should be the same with balls of different weights (assuming the surface properties are the same in the comparison).
In any comparisons, the ball speeds should be the same, because throw does vary with ball speed (for certain shots). For more info, see throw speed effects.
Regards,
Dave
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 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.
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