cue to ball energy transfer

evergruven

AzB Silver Member
Silver Member
I'm curious about energy transfer in general, but especially wonder how cue aspects affect it?

cue length, weight, taper, shaft/butt diameter, balance point...

I've heard that a harder tip will transfer energy better than a softer one.

etc.

beuller?

cheers-
 

HawaiianEye

AzB Silver Member
Silver Member
I'm curious about energy transfer in general, but especially wonder how cue aspects affect it?

cue length, weight, taper, shaft/butt diameter, balance point...

I've heard that a harder tip will transfer energy better than a softer one.

etc.

beuller?

cheers-

Uh, oh!

You just opened the floodgates for the pool scientists.

I have my "ideas", but I'm keeping them to myself.

I think certain things "affect" the playing characteristics of the cue, but others will say "it is all in your head".

I think a "soft" tips dampens the energy transfer and a harder tip will cause the cue ball to rebound off the cue faster.
 

Patrick Johnson

Fish of the Day
Silver Member
I'm curious about energy transfer in general, but especially wonder how cue aspects affect it?

cue length, weight, taper, shaft/butt diameter, balance point...

I've heard that a harder tip will transfer energy better than a softer one.

etc.

beuller?

cheers-
Weight: a heavier cue delivers more force at the same speed (but takes more force to move it).

Tip: a harder tip absorbs less (transfers more) of the cue’s Energy.

Taper: a stiffer shaft might absorb less (transfer more) of the cue’s energy.

I don’t think anything else matters. Weight is by far the biggest factor.

pj
chgo
 

S.Vaskovskyi

AzB Silver Member
Silver Member
If to keep it simple and the technique of the player is not the part of the discussion than in my humble opinion in all the equation materials and construction used are those two quantities which seem to have the biggest influence at the end. Than the rest are coming...if the technique is the part than for me it is definitely on the first place.
 
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nataddrho

AzB Silver Member
Silver Member
Tips only affect friction and feel (the vibrational harmonics they create). Other than that, physically there isn't much difference tips make.

The only thing that can be done to a cue ball is the application of an acceleration vector upon a small area on the surface of the ball for about 1 millisecond, and there is not much a human can do to affect what happens during this short time. Everything else is faith and religion, which can be important if it helps you feel happy and be consistent.
 

mikepage

AzB Silver Member
Silver Member
I'm curious about energy transfer in general, but especially wonder how cue aspects affect it?

cue length, weight, taper, shaft/butt diameter, balance point...

I've heard that a harder tip will transfer energy better than a softer one.

etc.

beuller?

cheers-

A softer tip might take almost twice as long to compress and decompress against the ball than a hard tip. And this, by itself, doesn't affect energy transfer at all. But there is some empirical evidence hard tips tend to be a little more elastic (have less energy loss). Also, this is going to be a tip-to-tip thing. It is not like here is anything automatic about softer tips that make them less elastic.

For the cueball to "feel" the entire weight of the cue, the tip-ball collision has to last long enough for the signal the collision is in progress to travel back and forth across the stick a sufficient number of times. So at some point as we get harder and harder tips, the cueball might not feel the full weight of the cue.

This is a little like a fast-moving train hitting a car that is on the tracks. The car will be launched with a speed characteristic of being hit by just the engine or the engine plus the first couple of cars. The collision time would have to be longer for the car to feel the weight of the rest of the train cars as they crush across the couplings.
 

ChrisinNC

AzB Silver Member
Silver Member
I'm curious about energy transfer in general, but especially wonder how cue aspects affect it?

cue length, weight, taper, shaft/butt diameter, balance point...

I've heard that a harder tip will transfer energy better than a softer one.

etc.

beuller?

cheers-
I would assume the energy transfer from the cue ball to object ball has nothing to do with the tip of the cue - which is energy transfer from the tip to the cue ball. I'd assume the energy transfer is most entirely related to how full the hit angle on the object ball is (straight on vs 90% feathering cut), and possibly slightly related to the spin on the cue ball at the moment it contacts the object ball.
 

Bob Jewett

AZB Osmium Member
Gold Member
Silver Member
... I think a "soft" tips dampens the energy transfer and a harder tip will cause the cue ball to rebound off the cue faster.
In general that's true and it's why break cues have phenolic tips, but as Mike mentioned it could be possible for a soft tip to transfer energy very well. None has been found yet or you would see them on break cues. Phenolic tips are nasty.

I tried a super ball as tip material but it didn't stay on well and it fractured.

One of the reasons for Predator building Iron Willie was to test tip efficiency.
 

ceebee

AzB Silver Member
Silver Member
One other thing about energy transfer. When the cue ball hits an object ball at half ball, the distance both balls travel is about the same, When you cut an object ball on the 1/4 object ball hit, The cue ball generally runs about 3 times the distance of the object ball. Practice these hits to learn about the cue Ball & object ball's travel after impact. Some of this info will change, when spin is applied to the Cue Ball, i.e follow, draw & side spin.
 

Bob Jewett

AZB Osmium Member
Gold Member
Silver Member
One other thing about energy transfer. When the cue ball hits an object ball at half ball, the distance both balls travel is about the same, When you cut an object ball on the 1/4 object ball hit, The cue ball generally runs about 3 times the distance of the object ball. Practice these hits to learn about the cue Ball & object ball's travel after impact. Some of this info will change, when spin is applied to the Cue Ball, i.e follow, draw & side spin.
The numbers you quote are for a smoothly rolling cue ball. For a stun shot, a quarter-ball hit (45-degree cut, more or less) will have each ball go the same distance.
 

ceebee

AzB Silver Member
Silver Member
Thanks Bob for that info. I'll have to try out that stun shot info, to see if it is true...
 

dr_dave

Instructional Author
Gold Member
Silver Member
The numbers you quote are for a smoothly rolling cue ball. For a stun shot, a quarter-ball hit (45-degree cut, more or less) will have each ball go the same distance.
Thanks Bob for that info. I'll have to try out that stun shot info, to see if it is true...
It is good to see it for yourself, but it can also be proven with physics analysis. The results of the analysis provide several useful speed-control "rules of thumb" or principles. For more info, see:

ball speeds and travel distances for different types of shots

Enjoy,
Dave
 

Hits 'em Hard

AzB Silver Member
Silver Member
I'm curious about energy transfer in general, but especially wonder how cue aspects affect it?

cue length, weight, taper, shaft/butt diameter, balance point...

I've heard that a harder tip will transfer energy better than a softer one.

etc.

beuller?

cheers-

Simplifying a bunch, but a cue weighs about 3x the weight of a cue ball. In a perfect world where maximum energy transfer occurs, the cue will make the cue ball gain speed at 3x the rate. So a 5mph cue speed will create up to a 15mph cue ball speed.

Now we are not in a perfect world. Cues do not transfer energy at 100%. The best break cue is only in the lower 90% range. Playing cues can vary from 50% to 90%. And rarely anymore do people play with cues that weigh 3x as much as the cue ball. A 19oz cue is only 2.75x as heavy. So basically if we take an arbitrary 75% energy transfer(Coefficient of Restitution) and put that as a starting point. We then have a basic formula ((input speed x ((cue weight/cue ball weight)x .75CoR)) = output speed). Since the CoR of each cue is different, that’s really an approximation.

A perfect hit with a playing cue will transfer approximately 2x of its input speed. Generally speaking.
 

Bob Jewett

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Silver Member
Simplifying a bunch, but a cue weighs about 3x the weight of a cue ball. In a perfect world where maximum energy transfer occurs, the cue will make the cue ball gain speed at 3x the rate. So a 5mph cue speed will create up to a 15mph cue ball speed.

...
That's false. You have to go deeper into the equations.

The results are on Dr. Dave's website and in Byrne's books somewhere, but the basic result is that the cue ball will ideally be going 150% of the cue stick speed just before contact and the cue stick will slow to 50% of its previous speed.

A.D. Moore measured the actual speeds almost 60 years ago and published the results in a paper. He got about 135% for the cue ball speed over a range of stick speeds which tells you how much is lost in the collision (mostly in the tip). Here is the description of Moore's setup from his paper:

The cue and ivory ball were hung by light steel wires beneath a
horizontal 10-inch board. String was wrapped around the ball, and
held in place with Scotch tape. Loops in the string permitted two
wires to be attached. The wires went to screw-eyes put in the edges
of the board, across from each other. Similar pairs of wires (two
pairs) suspended the cue for direct central impact, The vertical
radii were all 20 inches. When both bodies were at rest, they grazingly
touched.
 

Chili Palmer

323
Gold Member
Silver Member
Uh, oh!

You just opened the floodgates for the pool scientists.

I have my "ideas", but I'm keeping them to myself.

I think certain things "affect" the playing characteristics of the cue, but others will say "it is all in your head".

I think a "soft" tips dampens the energy transfer and a harder tip will cause the cue ball to rebound off the cue faster.

LOL, I like the way you keep things to yourself :)

Tips only affect friction and feel (the vibrational harmonics they create). Other than that, physically there isn't much difference tips make.

Take a CB and drop it from 12" onto a soft tip and see how far it rebounds, now do that with a hard tip and then a phenolic tip. I'd bet money the soft tip will not rebound as much, that's a loss of energy. When you hit with a soft tip it compresses, that takes energy which is then NOT transferred to the CB.
 

dr_dave

Instructional Author
Gold Member
Silver Member

Hits 'em Hard

AzB Silver Member
Silver Member
That's false. You have to go deeper into the equations.

The results are on Dr. Dave's website and in Byrne's books somewhere, but the basic result is that the cue ball will ideally be going 150% of the cue stick speed just before contact and the cue stick will slow to 50% of its previous speed.

A.D. Moore measured the actual speeds almost 60 years ago and published the results in a paper. He got about 135% for the cue ball speed over a range of stick speeds which tells you how much is lost in the collision (mostly in the tip). Here is the description of Moore's setup from his paper:

The cue and ivory ball were hung by light steel wires beneath a
horizontal 10-inch board. String was wrapped around the ball, and
held in place with Scotch tape. Loops in the string permitted two
wires to be attached. The wires went to screw-eyes put in the edges
of the board, across from each other. Similar pairs of wires (two
pairs) suspended the cue for direct central impact, The vertical
radii were all 20 inches. When both bodies were at rest, they grazingly
touched.

“Simplified” and “perfect world”. My statement is actually true, much to your dismay. Sixty years ago does not apply to today. There is not one public pool hall that uses ivory cue balls, so why even bring up a statement so blatantly misleading? Ivory has a lower CoR than phenolic, which kind of proves my napkin match there. Will we ever see a cue that imparts 3x speed to a cue ball, no. But it’s easier to start there and then explain the rest, than starting at the right answer and explain it incorrectly. I don’t think there’s a single cue out there that performs at a 1.35x level anymore due to proliferation of the use of phenolics.
 

Bob Jewett

AZB Osmium Member
Gold Member
Silver Member
... My statement is actually true, much to your dismay. ...
If what you said was true, a ping pong ball struck by a locomotive going five miles per hour would break the sound barrier. That doesn't happen. The maximum speed a light object can go when set in motion by being struck by a much heavier object is twice the speed of the heavy object.
 

mikepage

AzB Silver Member
Silver Member
Simplifying a bunch, but a cue weighs about 3x the weight of a cue ball. In a perfect world where maximum energy transfer occurs, the cue will make the cue ball gain speed at 3x the rate. So a 5mph cue speed will create up to a 15mph cue ball speed. [...]

We have to conserve momentum and energy

momentum before: 18oz*5mph = 90 oz-mph
momentum after: 18oz*?? + 6oz*15mph = 90 oz-mph ONLY if the stick stops completely.

But the stick can't stop completely because that violates the conservation of energy. That is, the 1/2 m * v^2 terms don't add up.
 
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