Cue Tip Contact Myth-Busting Truths in Super Slow Motion

[WobblyStroke]

I don't think I am entirely wrong, if we are using the edge of the stripe on a striped ball as the miscue limit there is far more than the edge of the tip contacting the cue ball. In fact if its a hard tip I would be willing to bet the the edge of the tip doesn't even contact with the cue ball.

Bad bet. Check out the pic on Dr. Dave's video in OP. The top of the ball is being struck to impart topspin, only the bottom edge of the tip is in contact with the ball. Similarly, when shooting with sidespin, only the center-side portion of the tip will make contact with the ball.

 

[buckshotshoey]

One thing we can all agree on is the cue ball comes off a hard tip quicker then it does off of a soft tip.

With that in mind, wouldn't an off center hit also impart a quicker spin (because the cue ball reacts faster) then a soft tip struck at the same speed? Visualize that before you respond.

 

[L.S. Dennis]

Typical cue tips have contact times in the 1-2ms second range, where differences do not have any important effects. But if you change the contact time significantly (e.g., by using a soft rubber tip instead, which is not suitable for playing pool), the physics is very different.




I was simply stating that if you want to be skeptical and propose alternative theories that go against current knowledge and understanding, you need to convincingly justify and test your claims. This is how science works. I won't do it for you because I don't believe the time would be well spent. This isn't spite, just honesty.




Mike Page has correctly pointed out that it might be possible to create a soft tip suitable for playing pool that might have a better hit efficiency than a typical hard tip also suitable for pool. I have not seen one yet, but I agree with him that it might be possible.




The statement is very much on point, because several people have suggested doing comparisons with the same cue speeds. This could give misleading results.

Dave above you referenced a rubber tip not being suitable for pool, I have a short story on that.
Back in the mid 90's I used to work for United Airlines here in SF and had access to a lot of scrap aircraft tires that were constantly scattered on the ramp. You can probably guess where I'm going with this, yes one night I took a piece home and fashioned a 13mm tip out of it. I put it on my cue lathe using one of my spare shafts that I had. Yes, you're right rubber is not meant for a cue tip but what crazy ball action I got on it! True story.

 

[Patrick Johnson]

One thing we can all agree on is the cue ball comes off a hard tip quicker then it does off of a soft tip.

With that in mind, wouldn't an off center hit also impart a quicker spin (because the cue ball reacts faster) then a soft tip struck at the same speed?

Yes, and quicker speed too - same spin/speed ratio. About like hitting a little harder with a softer tip.

pj
chgo

 

[VTEC John]

Dave above you referenced a rubber tip not being suitable for pool, I have a short story on that.
Back in the mid 90's I used to work for United Airlines here in SF and had access to a lot of scrap aircraft tires that were constantly scattered on the ramp. You can probably guess where I'm going with this, yes one night I took a piece home and fashioned a 13mm tip out of it. I put it on my cue lathe using one of my spare shafts that I had. Yes, you're right rubber is not meant for a cue tip but what crazy ball action I got on it! True story.

I was witness to this experiment. Hopes were high. Results were low. Real low. Incomprehensible. L.S. Dennis did a great job of mounting and shaping the aircraft rubber into a cue tip with a perfect dime curve, but the hit was disastrous. (Rome wasn't built in a day.)

 

[justnum]

All these so called experiments are based on cue tips that are shaped in the traditional way.

I've been experimenting with cue tips of various shapes. The logic that less contact time causes less miscues is a narrow minded study of one variable.

A researcher with significant math training would consider at least bivariate relationships or multivariate relationships.

I support and promote DrDave's work with no condition it is ideal for the specific applications of selling hard cue tips.

For billiard players that want a significant edge over the standard and widely available equipment, then they will have to think like Corey and find innovations that have not been outlawed.

If you are familiar with my posts, all I can say is if you want an edge you have to be willing to try what no one else has. The classified research being performed at the Harriman Academy, is where you can learn more about developing an edge. An edge as defined by legal equipment that no one else has access to with performance ratings well above standard equipment.

 

[Patrick Johnson]

For billiard players that want a significant edge over the standard and widely available equipment, then they will have to think like Corey and find innovations that have not been outlawed.

I'd think an innovator like you would be more impressed with Earl's beekeeper's suit and assweights*. Corey's a traditionalist compared to him.

pj
chgo

*credit: Joe Rogan

 

[justnum]

I'd think an innovator like you would be more impressed with Earl's beekeeper's suit and assweights*. Corey's a traditionalist compared to him.

pj
chgo

*credit: Joe Rogan

Here is a hint at the innovation, a self leveling cue. Imagine a cue that can adjusts its balance point, all a player has to do is apply force and the cue will ensure it translates the force linearly with minimal deviation.

The short name is the cue on invisible rails.

Let's respect DrDave and support his research. Hard tips are better than soft tips for traditional tip shapes.

 

[Patrick Johnson]

Let's respect DrDave and support his research. Hard tips are better than soft tips for traditional tip shapes.

It’s no surprise that’s all you get from Dave’s voluminous work. Or that you got it wrong.

pj
chgo

 

[justnum]

It’s no surprise that’s all you get from Dave’s voluminous work. Or that you got it wrong.

pj
chgo

Other researchers on the forum have argued that its the "Indian not the arrow."

 

[straightline]

I was witness to this experiment. Hopes were high. Results were low. Real low. Incomprehensible. L.S. Dennis did a great job of mounting and shaping the aircraft rubber into a cue tip with a perfect dime curve, but the hit was disastrous. (Rome wasn't built in a day.)

JFTR, any video with this?

 

[telinoz]

If you are familiar with my posts, all I can say is if you want an edge you have to be willing to try what no one else has. The classified research being performed at the Harriman Academy, is where you can learn more about developing an edge. An edge as defined by legal equipment that no one else has access to with performance ratings well above standard equipment.

Yep.
Familiar with your posts and the ability to try and derail every thread on here with more gibberish than drunk irishman with a lisp and missing teeth.

 

[pvc lou]

Thank you for being honest.

Please do your homework first. You seem to be capable of it. A conversation on a technical subject is difficult if one party has none of the standard knowledge of the subject and is just winging it.

I must say that I am disappointed that both of you have decided to be evasive, dismissive, and condescending in response to the questions put to your "myth-bust" claims.

Oh well...I guess I should have known better than to challenge the wisdom bestowed down to the commoners from the high priests of pool physics.

 

[buckshotshoey]

Here is a hint at the innovation, a self leveling cue. Imagine a cue that can adjusts its balance point, all a player has to do is apply force and the cue will ensure it translates the force linearly with minimal deviation.

The short name is the cue on invisible rails.

Let's respect DrDave and support his research. Hard tips are better than soft tips for traditional tip shapes.

Imagine this.... you go through all the work to develop this, then you find out the cue is illegal to use. Cues with movable parts are, in general, illegal to use in just about all sanctioned events.

 

[Gary Jones]

Firstly, thanks to Dr Dave and Bob for indulging us all and everyone else for being mostly civil in the topic as I find -- despite the other thread about toxicity -- the forum to be on the whole fairly respectful.

I do have a question for Dave and Bob that I would like explaining.

Just so we are discussing the same thing, first let me accept a couple of things:
1. Let us ignore the speed / spin constant based on offset for now as it makes things more complicated and just accept what you said.
2. Discuss things in terms of forces on the cueball and ignore the varying efficiencies from the tip hardness (although they are important when choosing a tip as there is obviously a trade-off to be had).

So, here's the bit I'd love some correcting on:
Considering speed / spin being related, let's just talk about the change in velocity
Not using changes in momentum, let us use f = ma or rather f = m dv/dt
For simplicity sake, let us say the difference between two tips are 1ms vs 2ms contact time
Mass and change of velocity are equal so we have an average force being applied of half for the soft tip vs hard tip to achieve the same velocity.
I have bolded average on purpose as I know that the peak instantaneous change of velocity / acceleration / peak force applied is not half but it might be 80% or 95% for the soft tip compared to the hard tip but it is definitely less (smaller average force applied over a longer time -- area under the graph and all that).
Can we agree on this?

Now, the reason I think this is important is due to the miscue limit of soft vs hard tips. If the peak force is lower for a soft tip, and assuming the coefficient of friction is identical between soft and hard, even if we ignore the larger surface area of the soft tip, surely this means that a soft tipped cue can operate further from the center and as such be used to impart more spin for the same speed of cueball?

I am the first to accept that my maths and physics background is 30 years old and never to your level but I like a problem and I am in the crowd that think 'soft is good for spin' and went on a rabbit hole to try and work out why I think that.

The amount to which this is important can probably be debated (and I am sure it will) but does the physics / applied maths make sense?

Thanks!

 

[Texas3cushion]

Does all this mean that I can start playing one pocket with my phenolic break tip?

That way I don't have to have more than one cue. Would be pretty convenient.

I could rough up the tip really well and use toam chalk.

 

[dr_dave]

Firstly, thanks to Dr Dave and Bob for indulging us all and everyone else for being mostly civil in the topic as I find -- despite the other thread about toxicity -- the forum to be on the whole fairly respectful.

I do have a question for Dave and Bob that I would like explaining.

Just so we are discussing the same thing, first let me accept a couple of things:
1. Let us ignore the speed / spin constant based on offset for now as it makes things more complicated and just accept what you said.
2. Discuss things in terms of forces on the cueball and ignore the varying efficiencies from the tip hardness (although they are important when choosing a tip as there is obviously a trade-off to be had).

So, here's the bit I'd love some correcting on:
Considering speed / spin being related, let's just talk about the change in velocity
Not using changes in momentum, let us use f = ma or rather f = m dv/dt
For simplicity sake, let us say the difference between two tips are 1ms vs 2ms contact time
Mass and change of velocity are equal so we have an average force being applied of half for the soft tip vs hard tip to achieve the same velocity.
I have bolded average on purpose as I know that the peak instantaneous change of velocity / acceleration / peak force applied is not half but it might be 80% or 95% for the soft tip compared to the hard tip but it is definitely less (smaller average force applied over a longer time -- area under the graph and all that).
Can we agree on this?

Yes. If the contact time is longer, the average force during that time will be less.

Now, the reason I think this is important is due to the miscue limit of soft vs hard tips. If the peak force is lower for a soft tip, and assuming the coefficient of friction is identical between soft and hard, even if we ignore the larger surface area of the soft tip, surely this means that a soft tipped cue can operate further from the center and as such be used to impart more spin for the same speed of cueball?

But if there is more force, than the friction force is also greater by the same proportion, assuming the standard COF model of friction (F = mu x N) is valid for the dynamic event of tip/ball collision. If this is the case, then there should be no difference. The impulse (integral of force over contact time) and momentum change is the same for both tips, so the friction impulse is also the same. If you are curious, the basic math and physics related to this can be found here:

TP 2.1 – Minimum cue tip friction required for no-slip horizontal impact​

And a more-advanced analysis (also taking other things into consideration, including tip efficiency and cue weight) can be found here:

TP A.30 – The effects of cue tip offset, cue weight, and cue speed on cue ball speed and spin​

However, I am not sure the miscue limit is based solely on the effective COF of the chalked tip because for all the chalks I have tested, I was not able to find any differences in miscue limit. Honestly, I was surprised by this because I thought there would be a difference, assuming different chalks would have different COFs. I think the miscue limit is determined more by the complicated dynamics of a tip on a flexible shaft hitting the slanted surface of the CB. When the angle of the ball surface exceeds the angle at the typical miscue limit, I suspect no amount of added friction can prevent a miscue, maybe because the tip is being pushed away from the CB surface, so the friction isn't able to grab the surface.

 

[dr_dave]

Does all this mean that I can start playing one pocket with my phenolic break tip?

Probably not, but a good hard leather tip might be a good choice for all the reasons here:

why a hard tip is better than a soft tip​

 

[justnum]

Imagine this.... you go through all the work to develop this, then you find out the cue is illegal to use. Cues with movable parts are, in general, illegal to use in just about all sanctioned events.

It was intended to be used for trickshot exhibitions. However it can be used for other purposes. There is no current cue inspection and if it looks like a duck, talks like a duck, its a duck.

Drdaves research is a good study on limits for current equipment.

 

[buckshotshoey]

It was intended to be used for trickshot exhibitions. However it can be used for other purposes. There is no current cue inspection and if it looks like a duck, talks like a duck, its a duck.

Drdaves research is a good study on limits for current equipment.

If a tournament director suspects a Cue has moving parts, or is over 25 ounces, you can bet on it they will inspect it. Happened to our team in Vegas.