I agree that hard tips hit harder. These tests show that hitting harder doesn't matter for spin effectiveness.
By the way, that's a good idea.
pj
chgo
Last edited:
Speed and Spin and the Cues That Make Them
- Thread starter Patrick Johnson
- Start date
I agree that hard tips hit harder. These tests show that hitting harder doesn't matter for spin effectiveness.
By the way, that's a good idea.
pj
chgo
That's right, and it helps prove my point. Even with my imperfect stroke, even letting other people take the shots, the results remain remarkably consistent. So long as tip placement is the same, stroke doesn't matter either.
pj
chgo
Patrick Johnson said:
Sheesh, I've only got a couple of test grippers built and already people are saying "the machine proves me right, the machine proves me right"
There are many tests to perform in a controlled environment before I'll take sides.
Dave, a patient man ... or is that slow
Yes but I would think it should, shouldn't it?Patrick Johnson said:
On the softer shots, where the ball had time to develop considerable topspin enroute to the cushion, the spin/speed ratio should have been significantly altered - multiplied by as much as 7/5'ths. This is because of the slowing effect of the cloth friction. Of course I don't know what you mean by "soft", but with anything less than lag speed the ball should have acquired full roll before reaching the first cushion.
There should also have been about 3/4 degree of swerve, given that the minimum cue elevation is about 1-1/2 degrees (shaft rubbing on top of cushion). If you hit any as slow as half of lag speed, this should have produced about a quarter inch of sideways displacement by the time the ball reached the rail (the ball would have reached full roll and ceased swerving in only about 5-6" from its starting position).
I'm not trying to be anal here and appreciate you sharing this. But I'm a little mystified by the spin/speed ratio thing.
Jim
Last edited:
Well, I can only measure the results if I hit at least hard enough to hit the next rail, but that's pretty soft (soft enough to include the vast majority of shots). I do try softer shots out of curiosity, but haven't been able to see the difference, if any, and haven't tried to measure them yet. However, if I *try* to increase the spin/speed ratio by hitting slowly with drag draw (and with the butt elevated more), I can get a visible difference, so I understand and agree with the principle.Jal said:
I do shoot with the shaft rubbing on the rail, and I correct my aim so I'm hitting the same spot on the first rail with every shot.
I understand your concern, but it's a concern about the test setup and eliminating the "noise" of swerve, not about the central conclusion, which remains unchanged: changing only the speed of the shot (unless it introduces swerve) doesn't change the speed/spin ratio and therefore doesn't change the effectiveness of spin. In particular, shooting softer doesn't seem to increase the cueball's "grab" on the rail and shooting harder (increasing RPMs) doesn't seem to increase the amount of spin effect.
pj
chgo
Last edited:
Patrick Johnson said:
So does this follow that buying custom cues for better playability is over-rated?
The only times I see a player doing what you describe has to do more with their aim and set up than the cue. I assume you are playing a non-LS/LD shaft. So you are changing your point of aim to make the shot? That will change the angle of entry of the CB to the first rail. I would recommend setting a very easy to make shot where you can spin in the same spot repeatedly with various spins and still make the shot without compensating for english.
As was said earlier, try changing the speed of your stroke. I remember a match where Earl hit a great slow spin to pull the CB past the side from the short rail one diamond and the announcer made the comment that the shot was successful because Earl understood the correct spin AND the importance of speed.
Creating reliable and repeatable spin off the rails takes practice and knowledge. The knowledge you need is best described by Dr. Dave (AZ member) when he speaks of the 90-30 rule and tangent lines. When you understand the tangent line you can best predict the CB path to the rail and the subsequent result of any applied spin. The entry angle is just as important as the spin applied.
Just my 2 cents.
As was said earlier, try changing the speed of your stroke. I remember a match where Earl hit a great slow spin to pull the CB past the side from the short rail one diamond and the announcer made the comment that the shot was successful because Earl understood the correct spin AND the importance of speed.
Creating reliable and repeatable spin off the rails takes practice and knowledge. The knowledge you need is best described by Dr. Dave (AZ member) when he speaks of the 90-30 rule and tangent lines. When you understand the tangent line you can best predict the CB path to the rail and the subsequent result of any applied spin. The entry angle is just as important as the spin applied.
Just my 2 cents.
I think custom cues are overrated as far as improved "objective playability" is concerned, but there's another playability factor that I'll call "subjective playability", which includes how much you like the hit of your custom cue, how much confidence you have in your equipment and even how much you enjoy playing with something so beautiful. These things aren't objective, but they're important to many players.
pj
chgo
I don't know what you mean by "doing what you describe".
My playing cue has a custom hollow-tipped, small-diameter (10mm), straight-tapered shaft with a hard Moori on it - it's very low-squirt. But I compare lots of other cues too when I do these tests, including everything from one-piece house cues with cheap tips to fiberglass WalMart specials to high-end custom cues. That's the whole point of doing these tests: to see if the cue or the speed makes a difference.
I shoot from the same spot every time and reject any shot that doesn't hit the same target - so what you suggest isn't happening. I do have to adjust my aim for the difference in squirt from various cues I test, but that's so the angle of entry *won't* change.
This does bring up a difference that I expected to see but don't: a higher squirt cue needs more aim adjustment to hit the same target on the first rail, so in effect I'm hitting farther offcenter with higher squirt cues (by contacting the same CB point at a greater angle). So I'd expect to see more spin effect with higher squirt cues - but I don't, so the increased effect must not be as high as I expected - or maybe the difference in squirt just isn't enough over that short shot distance to matter.
pj
chgo
Thanks for your earlier response. Still mulling that spin/speed thing over. But this one has an easy enough answer.Patrick Johnson said:
Changing the angle of the cue to adjust for squirt didn't change the net direction of the force applied to the cueball. So your effective offset didn't change even though the apparent offset was larger for the higher squirt cues. Like this (ignore the math):
The effective offset is b' in the diagram (blue), while the apparent offset is b (black).
Jim
It appears to me that your diagram shows the "adjusted aim" offset being more in the same way as if you simply moved the stick sideways more without adjusting the aim. Why wouldn't that produce greater spin/speed?Jal said:Thanks for your earlier response. Still mulling that spin/speed thing over. But this one has an easy enough answer.
Changing the angle of the cue to adjust for squirt didn't change the net direction of the force applied to the cueball. So your effective offset didn't change even though the apparent offset was larger for the higher squirt cues. Like this (ignore the math):
The effective offset is b' in the diagram (blue), while the apparent offset is b (black).
Jim
pj
chgo
The black arrow emanating from the center of the cueball (labeled v) is the direction you want the cueball to go. The blue arrow at the bottom represents the direction of the stick for a perfect compensation, given the anticipated squirt angle gamma (the small "y" ...don't mean to be insulting, you probably know more Greek than I do.)Patrick Johnson said:
Since the cueball is driven in the direction indicated by v, that's the overall direction of the force applied at the contact point, despite the direction of the cue. It's the direction of the force, not the aim line of the cue that determines the effective offset. So it's as if you initially lined up in the direction of v (with offset b'), then made the squirt adjustment by pivoting about the contact point and ending up in the blue arrow's direction. You now have a greater apparent offset (b), but the same working offset b'. In your particular case, b' is (1/2)R, although the diagram was not drawn with this offset in mind.
The torque, b' x F, puts the spin on the ball. (F is not shown, but as just mentioned, it points in the same direction as v, and extends from the contact point.)
Is the rebound angle shown in your diagram a fairly accurate representation of the actual angle, say within a degree or two? I suspect it is, but ask anyway because I want to see how well a simple friction model of the cushion does in predicting it.
Jim
Last edited:
That brought it home to me - thanks. The effective distance from center is determined by the effective direction of the combined forces, which of course doesn't change because that's what we're preventing with the aim adjustment. Duh.
Is there any change in the amount of force in the effective direction (for the same cue at the same speed)?
pj
chgo
Yes, directly in front of the 1st diamond from the near corner pocket (on new Granito over new rubber with a clean Centennial ball). I go to more than one pool hall with different conditions, so I'll try to remember to take a few measurements and notes about conditions if that would help.
pj
chgo
You guys will not figure out the answer since you don't know the coefficient of friction of the tip and the cue ball, and the tensile properties of the stick and the cue ball.
Yes there is if I understand you to mean as compared to a squirtless cue stroked in the direction of v. I don't know how big a change though, as this depends on how great of an energy loss takes place. It can be worked out, but I haven't attempted it.Patrick Johnson said:
(Been having some phone line problems.)
Jim
Thanks a lot Patrick. So the rebound angle is about 33 degrees by my reckoning. A very simple "theoretical" calculation based on assumed values for some parameters, predicts an angle of 25 degrees.Patrick Johnson said:
To pin down the source of the discrepancy would require some data that would be tedius for you to acquire, and would probably require video (high-speed all the better). Dr. Dave has a few examples at his site, which if I ever get really serious about it, could help.
I really appreciate the offer to continue your measurements, and I would be happy if you did so - they might be very useful in the future. But at this time I couldn't promise that they would be put to good use by me.
Jim