Spin vs deflection.

Jodacus

Jodacus

Shoot...don't talk
Silver Member
There have been similar threads to this in the past but I have a very specific question.

I believe the laws of physics say x amount of off center hit with x amount of cue speed and x amount of shaft deflection will cause y amount of cue ball spin. If this is accurate then shaft deflection becomes the critical factor in how much spin can be induced given constants in the other variables

IMO LD shafts really due reduce cue ball deflection. I'm reminded of this every time I play with a non-LD shaft.

My question is not about cue ball deflection but rather cue ball spin.

Is there really enough variation in spin caused by shaft deflection to really be apparent to anybody?

Not that opinions based on experience are not important but I am really looking for a science based answer.

Thanks
 
Jodacus said:
I believe the laws of physics say x amount of off center hit with x amount of cue speed and x amount of shaft deflection will cause y amount of cue ball spin.
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We have to be careful with terminology. "Cue ball spin" can mean either RPM (Revolutions Per Minute, regardless of cue ball speed) or RPD (Revolutions Per Distance of CB travel, regardless of time - also known as "spin/speed ratio").

You can increase RPM simply by hitting the CB harder, but to increase RPD you must hit farther from center. In pool, the important one is RPD (spin/speed ratio) because that's what determines how much effect the spin has on the shot. For instance, more RPM without more RPD (simply hitting the CB harder) doesn't by itself change the angle of rebound off a rail.

Is there really enough variation in spin caused by shaft deflection to really be apparent to anybody?
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There is some, but I don't think it's a noticable amount.

I am really looking for a science based answer.
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I'll bet Dr. Dave has the scientific answer on his website.

pj
chgo
 
Patrick Johnson said:
You can increase RPM simply by hitting the CB harder, but to increase RPD you must hit farther from center. In pool, the important one is RPD (spin/speed ratio) because that's what determines how much effect the spin has on the shot. For instance, more RPM without more RPD (simply hitting the CB harder) doesn't by itself change the angle of rebound off a rail.


I'll bet Dr. Dave has the scientific answer on his website.

pj
chgo
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I know that if you hit harder you close the exit angle, so you can change the angle by hitting harder..
 
Me:
...more RPM without more RPD (simply hitting the CB harder) doesn't by itself change the angle of rebound off a rail.
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Slh:
I know that if you hit harder you close the exit angle, so you can change the angle by hitting harder.
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Yes, you can change the angle of rebound by hitting harder, but not because of increased sidespin RPM. That's why I said "doesn't by itself change the angle".

pj
chgo
 
Jodacus said:
There have been similar threads to this in the past but I have a very specific question.

I believe the laws of physics say x amount of off center hit with x amount of cue speed and x amount of shaft deflection will cause y amount of cue ball spin. If this is accurate then shaft deflection becomes the critical factor in how much spin can be induced given constants in the other variables

IMO LD shafts really due reduce cue ball deflection. I'm reminded of this every time I play with a non-LD shaft.

My question is not about cue ball deflection but rather cue ball spin.

Is there really enough variation in spin caused by shaft deflection to really be apparent to anybody?

Not that opinions based on experience are not important but I am really looking for a science based answer.

Thanks
Click to expand...


You can get all the science feedback you want but, unless you are a machine and can use the exact(I mean exact) force on any given shot, science is almost useless. More force will equal more deflection...period.

This is what separates the average Joe from a really good player. Getting a "feel" for how much force to use on any given shot.

I know this is not the answer you are looking for. But if you chase the Holy Grail, you will never find it. Practice, practice, practice.....
 
Several things can alter the spin speed ratio..... Given a set speed you need either more friction or a tip with a high COR....... Energy transfer can be rotational of linear..... Kamui chalk will increase the friction and the right tip can impact the COR.... While spin and deflection are cousins..... Enough generations have passed that they are merely distant cousins.....

You did ask for science in the OP and if you search on predator they showed a 10% in english using their shafts... they had numbers that backed the claim up....
 
The Renfro said:
Several things can alter the spin speed ratio..... Given a set speed you need either more friction or a tip with a high COR.......
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Spin/speed ratio is determined by the tip offset, i.e., how far from center you make contact. COR has little to with it. I agree that with a higher friction tip/chalk combination, you would be able to hit a little farther from center, but not much. As you get beyond one-half a ball radius of offset, the possibility of having the tip strike the ball again as it vibrates laterally, looms large. (The separation speed between the tip and ball deceases as you move out from center. A better COR would help there, but we're talking about rather smallish gains, and then only if you're willing to seriously flirt with a miscue.)


The Renfro said:
You did ask for science in the OP and if you search on predator they showed a 10% in english using their shafts... they had numbers that backed the claim up....
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Even if they reduced squirt to zero, you wouldn't see anywhere near that much of an increase in spin/speed ratio....unless they were using a lead shaft as a reference. The squirt measurements they themselves supplied belie that claim, if they ever made it. I'm basing this on data many years old, but even if they somehow completely eliminated squirt, as I said, you wouldn't see that sort of gain. Squirt typically reduces the ratio by only a few percentage points and you can always make up for that by hitting farther out. (At extreme offsets, a lower squirt shaft should have a smaller miscue limit than a higher squirt shaft, so there really isn't anything to be gained with the LD shaft. Dr. Dave actually has a demonstration of this.)

Jim
 
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:confused:
Patrick Johnson said:
Yes, you can change the angle of rebound by hitting harder, but not because of increased sidespin RPM. That's why I said "doesn't by itself change the angle".

pj
chgo
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so you are saying if speed is a constant the cue ball spinning more doesnt rebound more that the slower spinning cueball???


so how do explain the concept that one tip english gives you one extra diamond and 2 tips gives you 2


you start at one diamond up from corner pockect and shoot at the opposite 2nd diamond
ball should go to the third diamond with no english
1 tip goes to 4th diamond
2 tips 5th diamond
 
tucson9ball said:
You can get all the science feedback you want but, unless you are a machine and can use the exact(I mean exact) force on any given shot, science is almost useless. More force will equal more deflection...period.

This is what separates the average Joe from a really good player. Getting a "feel" for how much force to use on any given shot.

I know this is not the answer you are looking for. But if you chase the Holy Grail, you will never find it. Practice, practice, practice.....
Click to expand...

Amen you are right on the money.
Ray
 
bbb said:
...so you are saying if speed is a constant the cue ball spinning more doesnt rebound [at a different angle] that the slower spinning cueball???
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No, I'm saying the opposite: changing the ratio of speed to spin does change the rebound angle. Changing speed and spin "equally" (in the same ratio) by hitting the CB on the same spot but simply harder or softer, does not change the rebound angle.

The ball's rebound angle is the ratio of its speed away from the rail (caused by how fast it's moving) to its speed along the rail (caused by how fast it's spinning). If they're equal we get a 45-degree rebound. If speed away from the rail is greater the rebound angle is steeper than 45 degrees. If speed along the rail is greater the rebound angle is shallower than 45 degrees.

If we increase or decrease both of these speed components in the same ratio to one another ("equally") the ball's rebound angle doesn't change. This is what happens when we hit the CB harder or softer but at the same distance from center.

If we change one of these speed components more than the other (in a different ratio) the ball's rebound angle does change. This is what happens when we hit the CB closer to or farther from center (at any speed).

pj
chgo

P.S. Hitting the same distance from center on the CB only guaranties the same spin/ratio as the ball leaves the cue tip. If not hit with "natural roll topspin" the spin/speed ratio may change on the ball's way to the rail because of friction with the table's cloth.
 
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Jal said:
Spin/speed ratio is determined by the tip offset, i.e., how far from center you make contact. COR has little to with it. I agree that with a higher friction tip/chalk combination, you would be able to hit a little farther from center, but not much. As you get beyond one-half a ball radius of offset, the possibility of having the tip strike the ball again as it vibrates laterally, looms large. (The separation speed between the tip and ball deceases as you move out from center. A better COR would help there, but we're talking about rather smallish gains, and then only if you're willing to seriously flirt with a miscue.)


Even if they reduced squirt to zero, you wouldn't see anywhere near that much of an increase in spin/speed ratio....unless they were using a lead shaft as a reference. The squirt measurements they themselves supplied belie that claim, if they ever made it. I'm basing this on data many years old, but even if they somehow completely eliminated squirt, as I said, you wouldn't see that sort of gain. Squirt typically reduces the ratio by only a few percentage points and you can always make up for that by hitting farther out. (At extreme offsets, a lower squirt shaft should have a smaller miscue limit than a higher squirt shaft, so there really isn't anything to be gained with the LD shaft. Dr. Dave actually has a demonstration of this.)

Jim
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COR has a little more impact than you think because it's measurement is the basis for energy transfer and loss at impact..... A leather tip with a COR in the 70s vs a phenolic in the 90s will produce less spin for a given offset because of the leather tip being less efficient at energy transfer. The leather tip can produce the same spin as the phenolic but not at the same stroke speed..... Since the question was about spin/speed ratio that was where my answers were based.....

Friction plays in this ratio as well... we all know that if the tip slips you will get linear energy but likely the rotational energy will be lost... With the 100x magnification shots of Kamui compared to both masters and Blue diamond along with using it on my phenolic playing tip I have no doubt that friction from the Kamui does indeed increase the spin to speed ratio....

As fa as the LD shafts are concerned your observation may be correct in that it simply allows for a further offset than standard.... The marketing of the predator shafts allowing for 10% more spin may be based on this aspect of the shaft... I do know originally they said it came from the fact that the tip stayed on the ball slightly longer but would a 1000th of a second be worth 10% or merely a percentage point or 2.....

I love DR Dave's stuff but I don't always put full stock in everything his site offers... Much of it was done prior to many of the tip and shaft break thrus so I am of the belief that shafts and tips can possibly have an impact greater than 1000th of a second or 2.......
 
The Renfro said:
A leather tip with a COR in the 70s vs a phenolic in the 90s will produce less spin for a given offset because of the leather tip being less efficient at energy transfer.
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Again, we have to be careful with our terminology. Hitting the CB the same distance from center, a greater COR may produce greater RPM, but not greater RPD (revolutions per distance traveled).

It's the same effect as simply hitting harder.

pj
chgo
 
Patrick Johnson said:
Again, we have to be careful with our terminology. Hitting the CB the same distance from center, a greater COR may produce greater RPM, but not greater RPD (revolutions per distance traveled).

It's the same effect as simply hitting harder.

pj
chgo
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Patrick that is an astute observation...

Without a high speed camera I am not sure how I'd test this but A higher COR tip would indeed be equivalent to hitting a lower COR tip harder.......

I am unsure if this aspect of the differences in travel based on COR lend themselves to increased spin as well but my suspicions, intuition and observations have me leaning towards a belief that it does....

Of course playing 3 years with a phenolic tip may have my observations skewed but you have given me a little more food for thought......

edit.... BTW Welcome back... glad to see you here =)
 
Patrick Johnson said:
No, I'm saying the opposite: changing the ratio of speed to spin does change the rebound angle. Changing speed and spin "equally" (in the same ratio) by hitting the CB on the same spot but simply harder or softer, does not change the rebound angle.

The ball's rebound angle is the ratio of its speed away from the rail (caused by how fast it's moving) to its speed along the rail (caused by how fast it's spinning). If they're equal we get a 45-degree rebound. If speed away from the rail is greater the rebound angle is steeper than 45 degrees. If speed along the rail is greater the rebound angle is shallower than 45 degrees.

If we increase or decrease both of these speed components in the same ratio to one another ("equally") the ball's rebound angle doesn't change. This is what happens when we hit the CB harder or softer but at the same distance from center.

If we change one of these speed components more than the other (in a different ratio) the ball's rebound angle does change. This is what happens when we hit the CB closer to or farther from center (at any speed).

pj
chgo

P.S. Hitting the same distance from center on the CB only guaranties the same spin/ratio as the ball leaves the cue tip. If not hit with "natural roll topspin" the spin/speed ratio may change on the ball's way to the rail because of friction with the table's cloth.
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thanks for the clarification...:thumbup:
 
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