Does speed effect deflection?

switching to the voice of Festus from Gunsmoke...

I read this again and it looks like you are saying your units are in degrees, but this confuses me... wish I were better at fancy book-learnin'
 
Not sure if this will help....there is a area on the OB that the the CB can impact and the ball will go in the pocket. For a centerball hit, the CB contacts the OB in the center of that area. Cheating the pocket, the CB contacts the OB other than the center of the impact area. If you are cheating to the right in a pocket, the CB will impact to the left of a center ball hit in that area.

Phil Chapelle calls this margin of error. I call it the impact area.

The size of the impact area is determined by, the distance the OB is from the pocket and the OB approach angle.

Approach angle is the angle the OB will be approaching the pocket. For what I consider a true center pocket shot, the OB is on a line that is the center of the pocket. This line would be 90 degree on a side pocket and 45 on corner.

Move the location of the OB in realtion the pocket and the size of the impact area changes.

The angle of the CB to the OB determines how much of that area you can use if needed.

Trying to accuratly measure deflection in order to use this measurement as a constant will never work because of the wide variety of playing conditions. It is better to understand this concept as you play and you will get a feel, over time, for it.

FWIW
 
hunger strike said:
Jim, I appreciate very much the offort you have put in your post. But to use it and understand it fully I need to know what units your numbers refer to. What I am looking for is variance in millimeter (distance) measurement of contact points for given distances. For example, if the cueball squirts .2 degrees, and you are aiming at the rail from 3 feet away, how many millimeters of error do you hit on the rail from your intented target? This information might verify what I have taught people all these years, that for each cue you play with, it is nice to find a speed that gives you a predictable amount of squirt so that aiming can be trusted with english. And if your speed is too low the tip won't grab the ball whereas if your speed is too fast the cueball may be pushed out of the way enough to cause a squirted, missed ball.
What are the units of the numbers you are giving me? Thanks so far....
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Hunger, the units for every number (except the 3' CB-OB separation) are degrees. For example, if you need a three-quarter ball hit to bring the OB to exact center-pocket, but instead the cueball squirts 0.3 degrees off the exact line needed to accomplish this (i.e., your squirt compensation is off by 0.3 degrees), the OB's direction will be off by 4.72 degrees if the "excessive" squirt is to the outside, or -4.60 degrees if to the inside.

But to answer your question directly, 1 degree of error is equivalent to being 1" (25.4 mm) off line (to the side) after traveling 57.3 inches in the forward direction. So an error of 0.3 degrees over 3' of travel results in the CB being off line by:

d = (36"/57.3) x (0.3 deg/1 deg) = 0.19" or 4.8mm

You can do the same to figure how far the object ball will be off line after traversing some distance. In the first example, with a 4.72 degree error in direction, after the OB travels 2', it'll be off by:

d = (24"/57.3) x (4.72 deg/1 deg) = 2.0"

So if the pocket is 2' away, instead of hitting center-pocket, it'll be off to the side of center-pocket by 2.0". These numbers aren't exact, but very close for smallish angles (i.e., the method of calculating doesn't work very well when you get to angles of several tens of degrees).

To calculate the error in OB direction from some error in CB direction, as in my earlier post, requires a bit more math.

Hope that's what you're looking for.

Jim
 
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Switching to the voice of Poindexter from Felix the Cat

Yes, this topic can actually be funny if you think of it in Poindexter's voice.
I, for one, am actually going to take advantage of your data and Dr. Dave's graphs to add some consistency to my game. At this point I am not so sure that ^speed=^squirt is a big myth. That does not mean that scientifically minded people cannot still appreciate each other, and Dr. Dave's work is a great gift to us all if we choose to analyze it and use it. Thanks Jim, and Thanks Dave
 
Tennesseejoe said:
I've read several articles about deflection but still do not know if cue speed increases deflection. Any opinions?
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My "opinion" is inline with the "facts." Squirt (AKA "cue ball deflection") does not change with shot speed. For video demonstrations, illustrations, and detailed articles showing actual experimental data, see:

However, "effective squirt" (the combined effects of squirt and swerve, AKA "squerve") does change significantly with shot speed, cue elevation, amount and type of English, and conditions. FYI, the following video summarizes squirt and swerve effects fairly well:

Enjoy,
Dave
 
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From what I have observed I have formed the opinion that the tip can have a definite impact on Cueball squirt at different speeds. During contact the tip will compress, deform and spring back into shape. Different tips have both different hardness ratings and different CORs (ie. elasticity ratings).

I think that COR has to vary based on speed because of the changes in compression. If Dr. Dave used a medium hard tip I would expect the results shown in the graph. At slow speed there would be little compression of the tip material so the radius of the tip would induce a force slightly off in direction to the cueing line. At medium speed compression will occur and the force vector from the tip's shape will minimize. At high speed you would reach maximum compression and the tip's shape would again lend itself to creating a force askew to the cueing line.

I think this is why we have so many different tips on the market. Most players have a certain goto speed they consistently hit the cueball. If they select a tip that over compresses or under compresses through there normal speed range their game could suffer slightly.
 
The Renfro said:
From what I have observed I have formed the opinion that the tip can have a definite impact on Cueball squirt at different speeds.
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Squirt does not depend on shot speed; although the combination of squirt and swerve (squerve) does. For more info, and experimental proof, see:


The Renfro said:
During contact the tip will compress, deform and spring back into shape. Different tips have both different hardness ratings and different CORs (ie. elasticity ratings).

I think that COR has to vary based on speed because of the changes in compression. If Dr. Dave used a medium hard tip I would expect the results shown in the graph. At slow speed there would be little compression of the tip material so the radius of the tip would induce a force slightly off in direction to the cueing line. At medium speed compression will occur and the force vector from the tip's shape will minimize. At high speed you would reach maximum compression and the tip's shape would again lend itself to creating a force askew to the cueing line.

I think this is why we have so many different tips on the market. Most players have a certain goto speed they consistently hit the cueball. If they select a tip that over compresses or under compresses through there normal speed range their game could suffer slightly.
Click to expand...
A tip compresses more with more speed, but the contact time does not change significantly with speed. For more info, see:

If the contact time did change with speed, then the amount of squirt would vary with speed, which it doesn't. With longer contact time, the effective endmass (and squirt) increases per the effects described here:

Now, tip hardness does have an effect on tip contact time, and this does have a slight effect on squirt amount. For more info, see:

But again, this effect doesn't change with speed.

Regards,
Dave
 
I'm also in the "squirt isn't affected by speed" camp. The thing that does change is the amount of swerve.
 
I use squirt on some shots. Mostly where the CB is close to the OB. It easy to do the more you jack up your cue cause now the OB is kinda between a rock and hard place so to speak where as when the cue is level, that is not the case.
 
dr_dave said:
Squirt does not depend on shot speed; although the combination of squirt and swerve (squerve) does. For more info, and experimental proof, see:


A tip compresses more with more speed, but the contact time does not change significantly with speed. For more info, see:

If the contact time did change with speed, then the amount of squirt would vary with speed, which it doesn't. With longer contact time, the effective endmass (and squirt) increases per the effects described here:

Now, tip hardness does have an effect on tip contact time, and this does have a slight effect on squirt amount. For more info, see:

But again, this effect doesn't change with speed.

Regards,
Dave
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Dr. Dave,

You seem to have reached the conclusion that the slight dependency of squirt on cue speed shown in your Feb. 08 Billiard Digest article (see post # 11 and Hunger Strike's and my subsequent comments), is an artifact of the test equipment or procedures and not a true variation. Is that so?

I ask because if it is a real variation, albeit only a few tenths of a degree, that's enough to make it something that has to be compensated for.

Jim
 
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Jal said:
dr_dave said:
Squirt does not depend on shot speed; although the combination of squirt and swerve (squerve) does. For more info, and experimental proof, see:


A tip compresses more with more speed, but the contact time does not change significantly with speed. For more info, see:

If the contact time did change with speed, then the amount of squirt would vary with speed, which it doesn't. With longer contact time, the effective endmass (and squirt) increases per the effects described here:

Now, tip hardness does have an effect on tip contact time, and this does have a slight effect on squirt amount. For more info, see:

But again, this effect doesn't change with speed.
Click to expand...
Dr. Dave,

You seem to have reached the conclusion that the slight dependency of squirt on cue speed shown in your Feb. 08 Billiard Digest article (see post # 11 and Hunger Strike's and my subsequent comments), is an artifact of the test equipment or procedures and not a true variation. Is that so?

I ask because if it is a real variation, albeit only a few tenths of a degree, that's enough to make it something that has to be compensated for.
Click to expand...
Jim,

Honestly, I don't think the one set of data shown in my February '08 article is enough to make any strong conclusions, other than: "squirt doesn't vary much with speed." The curve does seem to suggest a slight decrease in squirt with speed on the low end and a slight increase in squirt with speed on the high end, but I'm not sure if this effect is significant, meaningful, repeatable, or explainable. FYI, I have some additional data in my September '07 article, and it didn't seem to show the slight dip in squirt at medium speeds.

Regards,
Dave
 
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