Cue Tip Contact Myth-Busting Truths in Super Slow Motion

[ShootingArts]

The one's he used when i saw him were milk-dud elks.

Milk duds can be all over the place in hardness, I have even seen people crush them down until they destroy the integrity of the leather fiber. While most crush the duds down some for a harder tip I always just returned mine to roughly the same height as a new Elkmaster. I felt they held shape a little better and lasted a little longer.

Last few years I have been playing with a plain Elkmaster after I sorted them and find it plays very well. However, there were nine culls in that box of fifty. If an installer doesn't test their tips there is a roughly one in five chance of getting a lemon according to that, too high. Elkmaster is now offering presorted tips. That makes me wonder if the percentage of culls in the main channel has went up or if they are tossing culls as they go improving all Elkmasters?

Hu

 

[pvc lou]

So, you don't buy the "same lever arm" argument? If not, what is the relationship of spin/speed ratio for different tip hardnesses in your theory? Is the change in spin/speed ratio directly proportional to the amount of tip compression?

Hi Bob,

Thanks for engaging with me.

What is the "same lever arm" argument? Is it that the dominant effects are determined by the tip speed and its offset from the center of the cb?
I await your answer on this piece. Now for the "If not," piece...

Spin/speed ratio dependence on tip hardness:

My hypothesis is that the spin/speed ratio goes like tip softness; that is, a lotta spin and a little speed is had with a soft tip.

Whether the variation is a direct proportionality, I can't say by thought experiment. I would guess it's easier to measure first and then guess the relation a posteriori.

Looking forward to continued discussions.

Best,

Lou

 

[Bob Jewett]

... Whether the variation is a direct proportionality, I can't say by thought experiment. ...

Please do some testing. Be sure to document it well. Video would be good.

Coriolis gave us a pretty good theory in 1835. (There's an English translation if you are interested.) I have not yet seen an evidence that his theory -- the lever arm idea -- is wrong. I look forward to seeing your measurements.

 

[garczar]

Please do some testing. Be sure to document it well. Video would be good.

Coriolis gave us a pretty good theory in 1835. (There's an English translation if you are interested.) I have not yet seen an evidence that his theory -- the lever arm idea -- is wrong. I look forward to seeing your measurements.

You're a brave man Bob.

 

[garczar]

Milk duds can be all over the place in hardness, I have even seen people crush them down until they destroy the integrity of the leather fiber. While most crush the duds down some for a harder tip I always just returned mine to roughly the same height as a new Elkmaster. I felt they held shape a little better and lasted a little longer.

Last few years I have been playing with a plain Elkmaster after I sorted them and find it plays very well. However, there were nine culls in that box of fifty. If an installer doesn't test their tips there is a roughly one in five chance of getting a lemon according to that, too high. Elkmaster is now offering presorted tips. That makes me wonder if the percentage of culls in the main channel has went up or if they are tossing culls as they go improving all Elkmasters?

Hu

If you like soft try the Ultraskins. They make three: soft, ss and pro soft. I'm not a soft tip guy myself but they make great tips. Far more predictable/consistent than Elks i would venture. Price is great too here on AZ.

 

[Fatboy]

Yeah, players just don't realize how much slack the gods have allowed them.

They really don’t!

 

[pvc lou]

Please do some testing. Be sure to document it well. Video would be good.

Coriolis gave us a pretty good theory in 1835. (There's an English translation if you are interested.) I have not yet seen an evidence that his theory -- the lever arm idea -- is wrong. I look forward to seeing your measurements.

Je peux bien lire les oevres de Coriolis en français, Bob. J'ai eu ma thèse en france....pour eux je suis le cowboy du Texas qui fait sa recherche en écoulements diphsiques.


You somehow evaded the bulk of my response to you. This makes me triste (sad).

 

[WobblyStroke]

Milk duds can be all over the place in hardness, I have even seen people crush them down until they destroy the integrity of the leather fiber. While most crush the duds down some for a harder tip I always just returned mine to roughly the same height as a new Elkmaster. I felt they held shape a little better and lasted a little longer.

Last few years I have been playing with a plain Elkmaster after I sorted them and find it plays very well. However, there were nine culls in that box of fifty. If an installer doesn't test their tips there is a roughly one in five chance of getting a lemon according to that, too high. Elkmaster is now offering presorted tips. That makes me wonder if the percentage of culls in the main channel has went up or if they are tossing culls as they go improving all Elkmasters?

Hu

I'm no expert on the subject but will parrot one I came across a while back in a thread on here that I found interesting.

Guy was a milk dud guy and outlined his process for prepping the tips. He soaked them (I want to say in milk bc that just fits but I can't be 100% on that). Anyway, over the course of 48hrs, they soaked up some protein in the liquid (almost sure it was actually milk now) and grew in size.

By saturating the tips and getting this protein to fill in the widely varying gaps in the tips responsible for the variability in density/hardness, the batches would play much more uniformly than without this soaking step.

 

[Bob Jewett]

Je peux bien lire les oevres de Coriolis en français

There are multiple modern reprints in French available, but Ron Shepard's excellent paper on pool physics is quite readable even for people who's calculus is rusty. It covers the main points of interest.

Here you go: https://billiards.colostate.edu/physics_articles/Shepard_apapp.pdf

 

[pvc lou]

Thanks for that. I'll have a close look at it.

In the meantime, if you would reply to my initial response to you, it would be much appreciated.

Best wishes

 

[fastone371]

Anytime we talk about the interaction between tip and cue ball we accept a bunch of assumptions and conclusions are based on those assumptions. It is clearly shown that the contact time can be fifty percent or more longer depending on the tip, and the ferrule which escapes these discussions. We can argue that the absolute difference in time isn't significant but nobody can argue that a lot happens in a .001 of a second if we don't hit the cue ball dead center. Why shouldn't up to fifty percent more happen if we increase dwell time to .0015 second? Five ten-thousandths of a second doesn't sound like a lot, fifty percent more contact time sounds like a bunch!

Nowhere have I seen any information concerning the effectiveness of the interface between cue ball and tip. If we hit off center there has to be some slippage. Is that slippage 2%, 20%, more? We can discuss tips, chalk, even ferrules, shafts, and further back on a cue but if we don't know what we are dealing with to begin with, how can we say what is significant?

By eyeball we can double contact time and increase the contact patch many times, just for a number say twenty times although again by eye it looks more like fifty or a hundred times. The gut tells me there is the potential for a lot more transfer with a soft tip. If we have 80% slippage during a particular shot there is potential for a huge improvement. If we have 5% slippage then nothing we can do is going to increase the transfer more than 5% no matter how large the potential increase in transferred forces is. To nitpick there is always some slippage so we have less than five percent in play in this example.

Nowhere have I ever seen real numbers concerning the quality of energy transfer between tip and cue ball. Without a starting number, nothing else means much.

HU

One thing that I think is safe to assume happens with tip compression which usually means a softer tip is that as the tip compresses the tip will be touching more of the cue ball closer to center effectively reduce the amount of spin. For example if you are aiming for 2 tips of english you may end up with only 1 1/2 tips of english. The hard tip will maintain more of its contact farther from center creating more spin by comparison. There are so many ways to view the possibilities of what happens between tip hardness levels and spin that probably the only way to know for sure would be using a cue stroking machine and high speed video to actually observe cue ball revolutions. That's about the only way I see this theory being put to bed. I like hard tips because I like the feedback I get from my cue on shots, I despise soft tips because it makes the cue feel dead. I also don't understand why people think you cant play with a phenolic tip, I often run out out the table with my beak cue using english without suffering miscues and it has a phenolic tip.

 

[dr_dave]

Do you expect my thick rubber tip will impart (slightly) less spin than a hard plastic tip with a very thin coating of the same rubber?

First of all, a soft rubber tip would be useless because it would create far too much CB deflection because of the contact time being too long. For more info, see the info and links in the paragraph starting with "There are many ..." here:

cue tip hardness resource page​

You do the measurements, and I'll bet you $100 that it doesn't go that way.

I have done lots of testing of pretty much everything over the years. I have also done lots of math/physics analyses. If you want to claim my statements are wrong (which make sense and agree with accepted theory), it is up to you to do the tests to prove me wrong.

(Quick edit: I just noticed your caveat "for a given CB speed." Not sure if you meant to be slick, but I'll give you the benefit of the doubt. I'll assume you meant cue-stick speed. This is what the test is really about.)

I wasn't trying to be slick. A soft tip does not provide as efficient a hit, so more cue speed is required to get the same CB speed and spin. You can definitely get more effective sidespin with a slower-speed shot, especially with a below-center hit, either with a soft tip or a hard tip, using a drag shot, which intensifies the sidespin per the info and demonstrations here:

drag shot effects
​

That's why important variables (tip position, cue elevation, and CB speed) need to be the same in any comparison.

 

[Monti]

This is all very interesting and most of it is above by head! However it seems like you have some saying “this is what happens”, and any minute difference isn’t tangible so why bother with it.? And the other side saying, we need to have 100% accuracy to be sure

I am on the fence with these two sides but in regards to the argument denying that the softer tip staying in contact doesn’t create more spin. I seem to recall one of Dr Dav’es videos putting chalk on a ball to show cling? had the effect of the ball throwing more. If that is the case ,then isnt that similar to saying a soft one has more grip so spins it more as well

Interesting debate guys and agree it should stay cordial- it’s too easy to be insulting in a social media context, when you would never be so face to face.

 

[garczar]

This is all very interesting and most of it is above by head! However it seems like you have some saying this is what happens, any minute difference isn’t tangible so why bother with it. And the other side saying, we need to have 100% accuracy to be sure

I am on the fence with these two sides but in regards to the argument denying that the softer tip staying in contact doesn’t create more spin. I seem to recall one of Dr Dav’es videos putting chalk on a ball to show cling? had the effect of the ball throwing more. If that is the case ,then isnt that similar to saying a soft one has more grip so spins it more as well

Interesting debate guys and agree it should stay cordial- it’s too easy to be insulting in a social media context, when you would never be so face to face.

Again, tip-offset is what determines the spin amount.

 

[WobblyStroke]

There are multiple modern reprints in French available, but Ron Shepard's excellent paper on pool physics is quite readable even for people who's calculus is rusty. It covers the main points of interest.

Here you go: https://billiards.colostate.edu/physics_articles/Shepard_apapp.pdf

Thanks for the informative link Bob. At 107 pages, tho, this thing needs a table of contents.

 

[dr_dave]

The real physics would have to be tested with identical cues (one with a hard tip and one with a super soft tip). Both cues would have to strike the cb at the exact same offset and cue speed. Test results should clearly show which one actually creates more cb spin (sideways rotation). Until that's done, it's all speculation.

My guess is that the hard tip would produce slightly more spin, as well as slightly more cb speed, because the soft tip will absorb more of the impact and transfer less energy to the cb.

Has anyone done such a test?

If you use different CB speeds in any comparison, you would need to measure the CB speed and spin and not rely on any changes off a cushion to measure spin. A softer tip definitely creates less CB speed per the info and test here:

hit efficiency
​

And if there is slower CB speed (with a soft tip or hard tip) and any drag action, the sidespin/speed ratio changes during the shot per the info and demonstrations here:

sidespin intensification with a drag shot​

 

[dr_dave]

I am on the fence with these two sides but in regards to the argument denying that the softer tip staying in contact doesn’t create more spin. I seem to recall one of Dr Dav’es videos putting chalk on a ball to show cling? had the effect of the ball throwing more. If that is the case ,then isnt that similar to saying a soft one has more grip so spins it more as well

Ball-ball contact times are much shorter than tip-CB contact times per the info here:

ball-ball contact time​

A chalk mark causes more throw due to increased friction, not increase contact time. For more info, see:

cling/skid/kick​

Throw is also greater for slow-speed stun shots, again, not because the contact time is changing, but because the friction is greater at slower speed per the info and demonstrations here:

throw speed effects​

 

[ShootingArts]

If you like soft try the Ultraskins. They make three: soft, ss and pro soft. I'm not a soft tip guy myself but they make great tips. Far more predictable/consistent than Elks i would venture. Price is great too here on AZ.

I'm no expert on the subject but will parrot one I came across a while back in a thread on here that I found interesting.

Guy was a milk dud guy and outlined his process for prepping the tips. He soaked them (I want to say in milk bc that just fits but I can't be 100% on that). Anyway, over the course of 48hrs, they soaked up some protein in the liquid (almost sure it was actually milk now) and grew in size.

By saturating the tips and getting this protein to fill in the widely varying gaps in the tips responsible for the variability in density/hardness, the batches would play much more uniformly than without this soaking step.

One thing that I think is safe to assume happens with tip compression which usually means a softer tip is that as the tip compresses the tip will be touching more of the cue ball closer to center effectively reduce the amount of spin. For example if you are aiming for 2 tips of english you may end up with only 1 1/2 tips of english. The hard tip will maintain more of its contact farther from center creating more spin by comparison. There are so many ways to view the possibilities of what happens between tip hardness levels and spin that probably the only way to know for sure would be using a cue stroking machine and high speed video to actually observe cue ball revolutions. That's about the only way I see this theory being put to bed. I like hard tips because I like the feedback I get from my cue on shots, I despise soft tips because it makes the cue feel dead. I also don't understand why people think you cant play with a phenolic tip, I often run out out the table with my beak cue using english without suffering miscues and it has a phenolic tip.

I don't usually try to answer three posts at once but in this case the answer is the same to two of them and similar to the same in the third. I don't mean to be rude.

While dudding a tip might help some marginal ones that wasn't my intent. The casein was supposed to get in the quality leather and bind it a little tighter making it move less than it did before dudding. Also, nine out of fifty tips were extremely light, either made from rotten hides or leather damaged in the tanning process I believe. Nothing was going to turn these into quality tips. Four tips were very heavy. I lost these before I got to play with them. The remaining tips fell into two very uniform batches. All of these tips that I have installed played great without dudding. Not putting on tips for others and going through very few tips myself I think I have a lifetime supply.

About the soft tip giving less spin because of compressing, maybe it gives more spin because of rebounding and staying on the cue ball longer! All tips hit the cue ball the same distance from center on every shot. That kinda messes up a lot of explanations of what is happening. There are compensating factors that add to the conclusion. A simple question: Can we get more total spin on a cue ball with a hard tip or a soft tip? To consider the question say that the speed of impact is the same but both tips can hit at the optimum location for that tip. It is a simple question, it is the answer that is tricky!

If I still had a metal lathe and my mill I would have created a simple test fixture long ago. Unfortunately after losing one home too many I am now an apartment dweller for the first time in my life. I have a feeling that my neighbors and management would be less than thrilled to see me bringing in a J-head mill and forty inch metal lathe. That Mill would require a small hole in the ceiling too! I do miss my toys.

Hu

 

[BC21]

If you use different CB speeds in any comparison, you would need to measure the CB speed and spin and not rely on any changes off a cushion to measure spin. A softer tip definitely creates less CB speed per the info and test here:

hit efficiency
​

And if there is slower CB speed (with a soft tip or hard tip) and any drag action, the sidespin/speed ratio changes during the shot per the info and demonstrations here:

sidespin intensification with a drag shot​

A better test would involve a more accurate method of testing for spin, like using a tachometer, not simply observing cushion action. It would be interesting to see accurate RPM results between two different tips striking the cb at the same ccb offset and same stroke speed.

 

[pvc lou]

First of all, a soft rubber tip would be useless because it would create far too much CB deflection because of the contact time being too long. For more info, see the info and links in the paragraph starting with "There are many ..." here:

cue tip hardness resource page​

I have done lots of testing of pretty much everything over the years. I have also done lots of math/physics analyses. If you want to claim my statements are wrong (which make sense and agree with accepted theory), it is up to you to do the tests to prove me wrong.




I wasn't trying to be slick. A soft tip does not provide as efficient a hit, so more cue speed is required to get the same CB speed and spin. You can definitely get more effective sidespin with a slower-speed shot, especially with a below-center hit, either with a soft tip or a hard tip, using a drag shot, which intensifies the sidespin per the info and demonstrations here:

drag shot effects
​

That's why important variables (tip position, cue elevation, and CB speed) need to be the same in any comparison.

Ok Doctor Dave,

You gave me a lot of homework to do...I thought I was done with school. Gosh!

For your and the audience's convenience, I have color coded and enumerated my response. I hope that it is not made in excessive haste.

1) "because of the contact time being too long": already, it seems that you are conceding my point...that the contact time has an effect.

2) If you want to claim my statements are wrong (which make sense and agree with accepted theory): I feel that you are taking my skepticism of your claims personally. I hope I'm wrong, because neither a scientist nor a pool player should.

3) I wasn't trying to be slick: I believe you. I really do.

4) A soft tip does not provide as efficient a hit, so more cue speed is required to get the same CB speed and spin: Here, there is much room for discussion, as your compatriot and also resident scientist, Mike Page, has challenged you on this question. My response to this is: at the end of the day, the question is: what is the effect of the tip hardness on the amount of imparted spin?...all else being equal...i.e. cb speed and so on.

5) You can definitely get more effective sidespin with a slower-speed shot, especially with a below-center hit, either with a soft tip or a hard tip, using a drag shot: This statement seems to me to be beside the point. The question is: Is there a difference between what you get if the tip is hard or soft? Whether you hit high or low is irrelevant...the location is the same, the difference is the tip's material properties.


Ok. I gave you all that I've got Doctor Dave. I hope that you trust that my questions are posed in good faith.

Best wishes