setting cue ball in motion

Cdryden said:
I gotta ask because of previous experience, are you an engineer? I worked as a machinist for years and we had a few engineers that meant well but had a tendency to over engineer everything! It got to where it became a bit of a problem. I got a kick out of it, but the boss got a bit angry when the budgets got out of whack from needless spending.

I once had a engineer who was designing a clean air system for our building ask me how much air was in the clean room. I looked at him and said "All of it?" He was not amused. I eventually got to where I answered all his questions with one standard answer, 4.
He would ask me something like "how did you figure the circular interpolation for milling that sphere?" and I would answer "I divided it by 4". He would walk away and work on it for a few hours and be completely confused. Another time he asked me how much Carbon is in 316 Stainless steel, I said "4".
After a while he quit asking me to do his work. He didn't last long after that.


I think you had a neat idea but it was maybe a bit over engineered, but you never know. It's people like you that sometimes come up with the best stuff. Without people thinking out of the box and improving on existing ideas we would still be in the dark ages.
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I'm glad to say that of the hundreds of engineers I've had to deal with in my career, a very small percentage would fit such a stereotype.
 
Cornerman said:
I'm glad to say that of the hundreds of engineers I've had to deal with in my career, a very small percentage would fit such a stereotype.
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True, He was not a typical engineer. But I have found that the difference between a good and a bad one is that the good ones tend to do more with less.
 
Sloppy Pockets said:
No, I understood what you meant, I just wanted your opinion on the mass at the grip end. What you say is what I figured, although I've seen the opposite argument coming from many learned pool experts.

However, regarding the speed of sound, it travels through maple at about 4000 FPS, so a hard tip coupled with a fast stroke speed that created only a 1/1000th second impulse would not allow for much or any contribution from hand mass if the cue is more than four feet from the tip. Is that correct?
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Check your units. Make sure were are... international.
 
Bob Jewett said:
Cornerman said:
... Now if you can change tip contact time, then you can change effective end mass ...
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You can change tip contact time by using a harder or softer tip. The time goes as roughly the the square root of softness, so a tip that's twice as hard will have a 30% shorter contact time.
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Several tip properties affect play:
- tip efficiency (related to "coefficient of restitution" or "elasticity")
- tip weight (affects squirt, potentially a lot)
- tip shape and size (affects squirt a little)
- tip hardness (affects contact time, and affects squirt a little)

The links above have detailed information, illustrations, articles, and demonstrations dealing with many of the effects.

Bob Jewett said:
The theory says, however, that contact time has no big effect on squirt. I think Predator may have done some experiments on this. I know they tested various hardnesses for break cues but I'm not sure they looked at squirt at the same time.
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I did some tests with a cue-testing robot a while back and did a limited tip-hardness study. The results are describe in the following article:
"Return of the squirt robot" (BD, August, 2008)​

Tip hardness did seem to have a small effect. A softer tip will generally create slightly more squirt (due to the longer contact time), unless the hard tip it is being compared to is much denser and heavier, in which case it could create much more squirt (due to the increased endmass).

Regards,
Dave
 
Cornerman said:
I'm glad to say that of the hundreds of engineers I've had to deal with in my career, a very small percentage would fit such a stereotype.
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I agree. I have lots of friends who are engineers, and they always have very precise ways to explain why my thinking is incorrect. lol

Not the same for scientists, however. In one lab I worked at, the lead researcher showed me a what he considered to be a highly engineered piece of aluminum that he used to open the tops of the tiny molecular biology plastic vials we used for doing PCR. He was very emphatic that I take good care of it as it was specially designed for him by the machinists at his previous job and was irreplaceable.

It consisted of a 6" section of round aluminum rod with a notch cut out of the end, leaving an overhang that extended into a recessed cut that was the same size as the lids on the vials. It actually worked quite well, but I've seen beer bottle openers that were a lot more complicated.

I took a few measurements and went home that weekend and made a copy. Two cuts with a slotting saw of the proper thickness is all it took. It was so much fun I made him six more. Then I did seven out of aluminum hex stock, because these wouldn't roll off the lab bench like the round one did. I even chamfered the ends for him so they didn't dig into your palm, a nicety that his original didn't have.

I bundled them up (seven rounds or hexagons make a nice, nested bundle) and handed them to him. He looked stunned.

"How did you get these?", he asked.

"I made them at home this weekend.", I replied.

He gave me a real long look, and I swear to God he had a tear in the corner of his eye. He said, "I don't know what to say, except I think I'm just beginning to realize how much potential you have here with me."

Two weeks later I got let go. I'll bet he never runs out of vial openers, though.
 
Didnt read the last page so I don't know if this was covered but the Jim Rempe Training Ball has a coating on it that hold chalk marks so you can see where you hit it.
 
dr_dave said:
Several tip properties affect play:
- tip efficiency (related to "coefficient of restitution" or "elasticity")
- tip weight (affects squirt, potentially a lot)
- tip shape and size (affects squirt a little)
- tip hardness (affects contact time, and affects squirt a little)

The links above have detailed information, illustrations, articles, and demonstrations dealing with many of the effects.

I did some tests with a cue-testing robot a while back and did a limited tip-hardness study. The results are describe in the following article:
"Return of the squirt robot" (BD, August, 2008)​

Tip hardness did seem to have a small effect. A softer tip will generally create slightly more squirt (due to the longer contact time), unless the hard tip it is being compared to is much denser and heavier, in which case it could create much more squirt (due to the increased endmass).

Regards,
Dave
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Good info Dave. Good because it goes with my current thinking of squirt. If it didn't jibe with my thinking, it would be bad info. j/k

I need crib notes, but I swear I'll read these articles.
 
Sloppy Pockets said:
I agree. I have lots of friends who are engineers, and they always have very precise ways to explain why my thinking is incorrect. lol

Not the same for scientists, however. In one lab I worked at, the lead researcher showed me a what he considered to be a highly engineered piece of aluminum that he used to open the tops of the tiny molecular biology plastic vials we used for doing PCR. He was very emphatic that I take good care of it as it was specially designed for him by the machinists at his previous job and was irreplaceable.

It consisted of a 6" section of round aluminum rod with a notch cut out of the end, leaving an overhang that extended into a recessed cut that was the same size as the lids on the vials. It actually worked quite well, but I've seen beer bottle openers that were a lot more complicated.

I took a few measurements and went home that weekend and made a copy. Two cuts with a slotting saw of the proper thickness is all it took. It was so much fun I made him six more. Then I did seven out of aluminum hex stock, because these wouldn't roll off the lab bench like the round one did. I even chamfered the ends for him so they didn't dig into your palm, a nicety that his original didn't have.

I bundled them up (seven rounds or hexagons make a nice, nested bundle) and handed them to him. He looked stunned.

"How did you get these?", he asked.

"I made them at home this weekend.", I replied.

He gave me a real long look, and I swear to God he had a tear in the corner of his eye. He said, "I don't know what to say, except I think I'm just beginning to realize how much potential you have here with me."

Two weeks later I got let go. I'll bet he never runs out of vial openers, though.
Click to expand...

Priceless, great story.
 
Sloppy Pockets said:
Like I said:

"I have lots of friends who are engineers, and they always have very precise ways to explain why my thinking is incorrect.":embarrassed2:
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I think I've gotten a lot better in realizing when I engineer just to engineer. But I still am always inventing excuses to make something. I don't think that will ever go away. As long as my idea success rate is greater than 5% I'm happy, lol.
 
Cornerman said:
nrhoades said:
Dr. Dave showed that squirt changes as you move the pivot point.
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I think you are misreading what Dr. Dave is saying about the pivot point.
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Freddie is correct. The natural pivot length of a shaft determines the amount of squirt (cue ball deflection) the shaft creates, but bridge length (AKA "pivot point") usually has absolutely no effect on squirt; although, bridge length does have a major affect on pivot-based aiming systems, BHE/FHE, and swooping strokes.

Cornerman said:
Be that as it may, unless your bridge hand is supremely rigid (like made of metal, then the bridge hand has little influence on the effective mass in the collision. (bridge length is not the same thing as the pivot point, no matter how many people try to redefine the terms).

The human hand has too much compliance to add mass to the collision.
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Actually, even if the bridge were perfectly rigid, it would still have absolutely no effect for bridge lengths beyond about 6-7 inches. The following video shows and explains why visually (at the 2:32 point point in part 2):
Here's a direct link to the pertinent point in the video.

And Diagram 4 in the following article gives some additional experimental proof related to endmass:

Enjoy,
Dave
 
Sloppy Pockets said:
There was a recent thread where the idea of using a 1oz cue to achieve great break speed was brought up. Someone with an engineering background made the point that the cue speed would have to be about 50 MPH in order to move the CB at 20 MPH.

I'm not an engineer, so I don't know exactly how to calculate such things
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For the engineers and physicists out there who are interested, the full analysis for any cue weight and any tip offset can be found here:

However, optimal break cue weight is not based just on simple physics like this. For more info, see:


Regards,
Dave
 
Knowing the theory of how things are and why does not help you become consistent with precise tip/ball placement.

The key learning process is still shooting a shot, observe the CB action, make necessary adjustments, and repeating - until you can achieve consistent and constant trustworthy and dependable results.
 
allanpsand said:
Knowing the theory of how things are and why does not help you become consistent with precise tip/ball placement.

The key learning process is still shooting a shot, observe the CB action, make necessary adjustments, and repeating - until you can achieve consistent and constant trustworthy and dependable results.
Click to expand...
Well, yes, but.... Sometimes knowing the why of things leads you to what you have to adjust and in which direction. Adjusting randomly until things work better is what a lot of people do, but it's not very efficient. An example would be the beginner who doesn't even notice which side the shot just missed on. If you understand how fullness of hit is linked to cut angle of shot, the adjustment can be faster.
 
That is true. Having at least a vague understanding of the physics of the action does help in the understanding.
 
allanpsand said:
Knowing the theory of how things are and why does not help you become consistent with precise tip/ball placement.

The key learning process is still shooting a shot, observe the CB action, make necessary adjustments, and repeating - until you can achieve consistent and constant trustworthy and dependable results.
Click to expand...

Yes, though physics tells us that we should be focusing on consistent tip placement, regardless of how you look doing it.


Sent from my HTC6435LVW using Tapatalk 2
 
Bob Jewett said:
Well, yes, but.... Sometimes knowing the why of things leads you to what you have to adjust and in which direction. Adjusting randomly until things work better is what a lot of people do, but it's not very efficient. An example would be the beginner who doesn't even notice which side the shot just missed on. If you understand how fullness of hit is linked to cut angle of shot, the adjustment can be faster.
Click to expand...

I agree, however, it is reserved to those that reached very high advance level and can distinguish between the many contributing errors, and also for those that have the luxury of owning a table at home, and got a LOT of time on their hand.
 
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