Table Difficulty Factor (TDF) for measuring table "toughness"

Mr. Bond said:

I know what you mean about the effort. Seems a little nitpickity even to me, but in all fairness, I have to say, I've seen a helluva lot of cushion facings that were dam near perfectly vertical. So there has to be lots of people out there getting rattled out of their shot, and they probably didn't know why.

I'm certainly not insisting that you need to follow my instructions, its just something that seems to need more attention.

A 2.25" ball is about 179.5mm in circumference?

So that means every degree around the ball = about 2mm ?

A facing tilted 10 degrees is making contact roughly 5mm higher on the ball than a facing that is perfectly vertical ?

12 degrees = 6mm higher
...
...
...
20 degree = 10mm higher

On slow moving balls the effects would be negligible, but on moderate to fast moving balls it would seem that the higher on the ball the impact occurs, the more downward force it would receive upon impact. Which seems like it would help more balls drop sooner, rather than rattle horizontally. But of course I don't have a super slo mo to show you.

Another theoretical benefit to a steeper angle would be a slight softening of the impact against the facings near the points. A steeper angle puts more distance between the point of impact and the subrail wood = slightly less violent rebound
= more likely to drop.


edited to add: i think i incorrectly used the word "steeper".
it was meant to indicate a cushion facing that was inclined or leaning further toward the pocket.

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Thank you for your insight. I think I agree with everything; although, it would be nice to actually test these effects with a controlled experiment (which would take a long time to do properly).

Regardless, I don't think I want to include a facing-vertical-angle factor in the TDF (at least, not yet). The angle is not easily measured with a single ruler, and the effect probably isn't as important as the others (especially if the vertical angle is within spec).

Thanks again for your input,
Dave

Sloppy Pockets said:

I think the PAF is by far the most important factor in hard-hit shots, and I agree with comments made Bob Dixon that it is not a linear relationship, and that there comes a go/no-go point for hard shots as the pocket facing angle increases. I suspect at angles over 145° that the effective pocket size would be reduced to that of the back of the throat because most hard shots that hit the facing will be rejected.

At the other end of the velocity spectrum, balls shot at pocket speed will be much more affected by shelf depth. They won't have enough energy to rebound off the facing and into the opposite facing. If the shelf is deep, they will hang. If it's shallow, gravity will assist it nicely as it rolls toward open space.

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Agreed. But remember, the TDF is an average for the complete range of shots typical in pool (at various angles, speeds, and pocket entry points).

Sloppy Pockets said:

I don't think you need to set up elaborate test machinery to figure this all out. You can use the old tried-and-true set up of five balls lined up at various angles. Fire away at the first ball in the line and see what happens to the ball of interest as it is either accepted or rejected. Of course, this won't tell how much spin might assist in pocketing balls for that particular pocket configuration, but as you stated on a few occasions already, this is definitely a work in progress.

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Bob Jewett and I have done tests for the effective size of a pocket at different angles and speeds. It takes a really long time to do these test properly to get useful and meaningful results over a wide range of shots. FYI, Bob is currently writing a series of articles for BD on this topic (with some experimental results for various tables). Bob, if you are listening, please post links to your articles when they are available online.

Sloppy Pockets said:

I think it would be helpful to consult Glen Hancock, Mark Gregory, and the Dominguez's regarding all this. They are the leading experts in rail and pocket optimization. They might also give their insight into how the pocket facing down angle affects all this.

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Great suggestion. I agree. I'll add this to my "list" (which is quite long at the moment).

Thank you for your input,
Dave

cigardave said:

Dae - All the rest of the corner pockets on my table have 4.5" mouths and 3.5" throats.

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Good. Now I'm glad I went with 1" on the (mount-throat) value.

Thanks for checking,
Dave

iusedtoberich said:

Hi Dr Dave,

I kind of think the table size should be weighted much more heavily than the pocket size. Going to a larger table not only requires greater accuracy in pocketing the ball, but it also requires greater accuracy in position play. Poor position play is what ends runs (forcing a hero shot, etc)

Right now, there are 3 pocket factors, and one table size factor.

The table size factor ranges from .85 for a 7' table, to 1.0 for a 9' table. (staying within the ranges 99% of us will ever play on)

A loose GC pocket (like my table) is 5 1/8 : 0.90 x 4 1/8 : 1.05 x 1 1/2 : 0.98 = 0.923
A tournament Diamond pocket from cigardave --4 1/2":1.00 -- 1":1.10 -- 1 3/4":1.00 = 1.10
(note, the above two lines are only pocket considerations)

These two ranges of pocket sizes are what "most" of us will encounter on a daily basis at our local rooms.

So from a loose factory (no shims added) GC we have the 3 pocket factors = 0.923
And a factory Diamond pro cut pocket = 1.10

That is a difference of 0.177

Contrast that with the max and min table sizes (again, for 99% of what we'd find in a local room) we have:
9' = 1.0
7' = 0.85

That is a difference of 0.15

I just can't see in the real world playing scenario pro cut Diamond pockets compared to standard non-shimmed GC pockets having more of the overall affect as a 9' table compared to a 7' table does. If anything, I think the above scenario should result in the table size maximum variation having twice the affect of the pocket maximum variation. Again, I'm using the word maximum here for what we'd typically find in a local room, not the super tight 3" pockets some people have, or the 10' table that is in 5 rooms around the country.

Thoughts?

Edit* I had the math wrong above, which had the 3 factors of the pockets contributing to twice the factor of the max table size difference. I corrected the math, and reworded the last paragraph. Its not near as severe as what I thought it was before. I will leave the post up with the corrections, as I still feel the argument is valid with the corrected numbers.

Click to expand...

Thank you for the input and your table specs (I've added them to the list). I think these conclusions will vary with the skill of the player and the game being played. For example for 8-ball, a top player would probably prefer a larger table with less clustering and traffic, and the size of the pockets is probably less a concern (as long as they are not too small). And for a mediocre player, 9-ball would be much easier on a smaller table; although, the size of the pockets is also a huge effect.

I think I like where the numbers stand for now, but I'm still open to revising them as we get more data and feedback. I also plan to do more analysis and testing in the future to provide more analytical and experimental justification. I've done some of this already, especially for table and pocket size, and the numbers I have now make sense so far.

Thank you for your input,
Dave

furryboffin said:

ok, just popping upstairs to take all the measurements...

Click to expand...

Please post them when they are available.

Thanks,
Dave

SloMoHolic said:

Dr. Dave,

I've heard back from a couple of friends that have played on my table, and they agree with the 1.00 TDF. We also agree that the old, slow cloth accounts for any additional perceived difficulty with this table.

It looks like your formula is coming along very nicely, and will be very helpful as a simple, yet effective way to compare table difficulty. Great job!

FWIW, I measured all four of my corner pockets and came up with the same dimensions on each one. I may take new measurements with the post-it notes, and use the new diagram to be sure the numbers are correct.

Thanks again,

-Blake

Click to expand...

Thank you for the positive feedback and validation.

Catch you later,
Dave

mamics said:

Revised measurements using the new improved method.

9 foot 50" x 100"
Mouth = 4 5/8"
Throat = 3 13/16"
Shelf = 1 1/4"

2.0 inch wide cloth section of rail (from nose to feather strip)

TSF = 1.00
PSF = 0.98
PAF = 1.05
PLF = 0.95

TDF = 0.98 by my calcs ?
Please update ur list Dave if u concur...
Cheers.

Click to expand...

Thanks for the update (and good math).

Here's the latest:

Data reported by AZB users in table difficulty factor (TDF) order, based on the table size factor (TSF), pocket size factor (PSF), pocket angle factor (PAF), and pocket shelf factor (PLF):

name -- TSF -- PSF -- PAF -- PLF -- TDF
tough 10' -- 10':1.10 -- 4":1.15 -- 3/4":1.02 -- 1 7/8":1.03 -- 1.33
example "B" -- 9':1.00 -- 3 7/8":1.20 -- 5/8":1.00 -- 1 7/8":1.03 -- 1.24
Bonus Ball -- 9':1.00 -- 3 7/8":1.20 -- 1/8":0.97 -- 3/4":0.98 -- 1.14 (Bonus Ball table)
rexus31 -- 9':1.00 -- 4":1.15 -- 3/8":0.98 -- 1":0.98 -- 1.10
cigardave -- 9':1.00 -- 4 1/2":1.00 -- 1":1.10 -- 1 3/4":1.00 -- 1.10 (typical Pro-Cut Diamond)
FatBoy -- 9':1.00 -- 4":1.15 -- 1/4":0.97 -- 1":0.98 -- 1.09
TATE -- 9':1.00 -- 4":1.15 -- 1/4":0.97 -- 7/8":0.98 -- 1.09
Qaddiction -- 9':1.00 -- 4 1/8":1.10 -- 5/8":1.00 -- 1 3/8":0.99 -- 1.09
SloMoHolic -- 9':1.00 -- 4 3/8":1.02 -- 5/8":1.00 -- 1 3/8":0.98 -- 1.00
"standard" table -- 9':1.00 -- 4 7/16":1.00 -- 9/16":1.00 -- 1 5/8":1.00 -- 1.00 ("standard")
Sloppy Pockets -- 8'+:0.95 -- 5":0.95 -- 1":1.10 -- 1 3/4":1.00 -- 0.99
JC -- 9':1.00 -- 4 7/16":0.98 -- 9/16":1.00 -- 1 3/8":0.98 -- 0.96
12squared -- 9':1.00 -- 4 7/8":0.95 -- 3/4":1.02 -- 1 1/2":0.98 -- 0.95 (typical Gold Crown)
mamics -- 9':1.00 -- 4 5/8":0.98 -- 13/16":1.05 -- 1 1/4":0.95 -- 0.98
rexus31 friend GC -- 9':1.00 -- 4 1/4":1.05 -- 1/4":0.94 -- 15/16":0.95 -- 0.94
Neil -- 7':0.85 -- 4 1/8":1.10 -- 5/8":1.00 -- 1 3/8":0.99 -- 0.93
iusedtoberich -- 9':1.00 -- 5 1/8":0.90 -- 1":1.05 -- 1 1/2":0.98 -- 0.93 ("loose" GC)
MSchaffer -- 9":1.00 -- 5 1/10":0.90 -- 3/4":1.02 -- 1 3/4":1.00 -- 0.92
BRussell -- 8':0.90 -- 5":0.95 -- 13/16":1.05 -- 1 1/2":0.98 -- 0.88
Dopc -- 8':0.90 -- 4 1/2":1.00 -- 3/4":1.02 -- 1 1/4":0.95 -- 0.87
dr_dave -- 8':0.90 -- 4 3/4":0.98 -- 5/8":1.00 -- 1 3/8":0.98 -- 0.86
example "A" -- 8':0.90 -- 5":0.95 -- 1/2":0.98 -- 1 3/8":0.98 -- 0.82
Valley "bar box" -- 7':0.85 -- 4 1/2":1.00 -- 0":0.94 -- 3/4":0.95 -- 0.76 (typical Valley/Dynamo "bar box")

Bob Jewett said:

The two articles I did on effective pocket size were in the May and June issues of BD. I included the effect of speed and spin on the object ball (get-in english). As you mentioned, it takes a long, long time to get complete, accurate measurements. To do a single corner pocket well would probably take a day or two. Maybe a couple of hours with a robot to shoot the shots and a couple of helpers.

Effective pocket size for a particular pocket is affected by:

• angle of approach
• speed of the ball
• side spin on the ball
• follow on the ball
• cleanliness of the ball

Different pockets don't react to those variables in the same way. For example, some pockets are real touchy (read: small) for power shots along the rail. For other pockets, shots along the rail are not much different from shots from other angles. The variability in pocket behavior means you can't measure just a few shots and completely describe the pocket.

Click to expand...

Please post your articles online and link to them here when you get a chance. I'm sure people would enjoy them.

Bob Jewett said:

I agree with Dr. Dave on keeping the measurement of TDF simple -- a perfect measurement will never get done.

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I'm glad to hear this from you. I agree completely.

Thanks Bob,
Dave

dzcues said:

I like this idea!

9' Diamond Pro with League Cut pockets

dzcues -- 9' -- 4 3/4":1.00 -- 4 1/8":.98 -- 5/8":1.00 -- 1 7/8":1.03 -- 1.01

IMO, this table plays EASY but then I'm comparing it to my old GC2 that had 4 1/2" pockets that were really screwed up. I wish I could check the measurements on that table but they would have been different at each corner. It was reassuring to find the Diamond was exactly the same everywhere.

My son has a Gandy Big G. I'll get measurements on his, too.

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Thank you for posting. I've added it to the list (see below). Please post the other table after you get the measurements.

Regards,
Dave

Data reported by AZB users in table difficulty factor (TDF) order, based on the table size factor (TSF), pocket size factor (PSF), pocket angle factor (PAF), and pocket shelf factor (PLF):

name -- TSF -- PSF -- PAF -- PLF -- TDF
tough 10' -- 10':1.10 -- 4":1.15 -- 3/4":1.02 -- 1 7/8":1.03 -- 1.33
example "B" -- 9':1.00 -- 3 7/8":1.20 -- 5/8":1.00 -- 1 7/8":1.03 -- 1.24
Bonus Ball -- 9':1.00 -- 3 7/8":1.20 -- 1/8":0.97 -- 3/4":0.98 -- 1.14 (Bonus Ball table)
rexus31 -- 9':1.00 -- 4":1.15 -- 3/8":0.98 -- 1":0.98 -- 1.10
cigardave -- 9':1.00 -- 4 1/2":1.00 -- 1":1.10 -- 1 3/4":1.00 -- 1.10 (typical Pro-Cut Diamond)
FatBoy -- 9':1.00 -- 4":1.15 -- 1/4":0.97 -- 1":0.98 -- 1.09
TATE -- 9':1.00 -- 4":1.15 -- 1/4":0.97 -- 7/8":0.98 -- 1.09
Qaddiction -- 9':1.00 -- 4 1/8":1.10 -- 5/8":1.00 -- 1 3/8":0.99 -- 1.09
dzcues -- 9':1.00 -- 4 3/4":0.98 -- 5/8":1.00 -- 1 7/8":1.03 -- 1.01 (typical League-Cut Diamond)
SloMoHolic -- 9':1.00 -- 4 3/8":1.02 -- 5/8":1.00 -- 1 3/8":0.98 -- 1.00
"standard" table -- 9':1.00 -- 4 7/16":1.00 -- 9/16":1.00 -- 1 5/8":1.00 -- 1.00 ("standard")
Sloppy Pockets -- 8'+:0.95 -- 5":0.95 -- 1":1.10 -- 1 3/4":1.00 -- 0.99
JC -- 9':1.00 -- 4 7/16":0.98 -- 9/16":1.00 -- 1 3/8":0.98 -- 0.96
12squared -- 9':1.00 -- 4 7/8":0.95 -- 3/4":1.02 -- 1 1/2":0.98 -- 0.95 (typical Gold Crown)
mamics -- 9':1.00 -- 4 5/8":0.98 -- 13/16":1.05 -- 1 1/4":0.95 -- 0.98
rexus31 friend GC -- 9':1.00 -- 4 1/4":1.05 -- 1/4":0.94 -- 15/16":0.95 -- 0.94
Neil -- 7':0.85 -- 4 1/8":1.10 -- 5/8":1.00 -- 1 3/8":0.99 -- 0.93
iusedtoberich -- 9':1.00 -- 5 1/8":0.90 -- 1":1.05 -- 1 1/2":0.98 -- 0.93 ("loose" GC)
MSchaffer -- 9":1.00 -- 5 1/10":0.90 -- 3/4":1.02 -- 1 3/4":1.00 -- 0.92
BRussell -- 8':0.90 -- 5":0.95 -- 13/16":1.05 -- 1 1/2":0.98 -- 0.88
Dopc -- 8':0.90 -- 4 1/2":1.00 -- 3/4":1.02 -- 1 1/4":0.95 -- 0.87
dr_dave -- 8':0.90 -- 4 3/4":0.98 -- 5/8":1.00 -- 1 3/8":0.98 -- 0.86
example "A" -- 8':0.90 -- 5":0.95 -- 1/2":0.98 -- 1 3/8":0.98 -- 0.82
Valley "bar box" -- 7':0.85 -- 4 1/2":1.00 -- 0":0.94 -- 3/4":0.95 -- 0.76 (typical Valley/Dynamo "bar box")

SloMoHolic said:

Dave,

I measured one of my league tables.

Mouth = 4.75"
Throat = 4"
Shelf depth = 1 5/8"
This is an 8' table.

It plays very easy, so I would subjectively guess the TDF to be around .80 or so.

(I'm in league at the moment, so I'll have to do the calculation later.)

Thanks again,

-Blake

Click to expand...

Thank you for posting. Are you sure it is an 8' and not a 7'? Please check the playing area dimensions (cushion nose to cushion nose) if you are not sure.

Here's the latest updated list, with your info added:

Data reported by AZB users in table difficulty factor (TDF) order, based on the table size factor (TSF), pocket size factor (PSF), pocket angle factor (PAF), and pocket shelf factor (PLF):

name -- TSF -- PSF -- PAF -- PLF -- TDF
tough 10' -- 10':1.10 -- 4":1.15 -- 3/4":1.02 -- 1 7/8":1.03 -- 1.33
example "B" -- 9':1.00 -- 3 7/8":1.20 -- 5/8":1.00 -- 1 7/8":1.03 -- 1.24
Bonus Ball -- 9':1.00 -- 3 7/8":1.20 -- 1/8":0.97 -- 3/4":0.98 -- 1.14 (Bonus Ball table)
Qaddiction -- 9':1.00 -- 4 1/8":1.10 -- 3/4":1.02 -- 1 3/8":0.99 -- 1.11
rexus31 -- 9':1.00 -- 4":1.15 -- 3/8":0.98 -- 1":0.98 -- 1.10
cigardave -- 9':1.00 -- 4 1/2":1.00 -- 1":1.10 -- 1 3/4":1.00 -- 1.10 (typical Pro-Cut Diamond)
FatBoy -- 9':1.00 -- 4":1.15 -- 1/4":0.97 -- 1":0.98 -- 1.09
TATE -- 9':1.00 -- 4":1.15 -- 1/4":0.97 -- 7/8":0.98 -- 1.09
dzcues -- 9':1.00 -- 4 3/4":0.98 -- 5/8":1.00 -- 1 7/8":1.03 -- 1.01 (typical League-Cut Diamond)
SloMoHolic -- 9':1.00 -- 4 3/8":1.02 -- 5/8":1.00 -- 1 3/8":0.98 -- 1.00
"standard" table -- 9':1.00 -- 4 7/16":1.00 -- 9/16":1.00 -- 1 5/8":1.00 -- 1.00 ("standard")
Sloppy Pockets -- 8'+:0.95 -- 5":0.95 -- 1":1.10 -- 1 3/4":1.00 -- 0.99
JC -- 9':1.00 -- 4 7/16":0.98 -- 9/16":1.00 -- 1 3/8":0.98 -- 0.96
12squared -- 9':1.00 -- 4 7/8":0.95 -- 3/4":1.02 -- 1 1/2":0.98 -- 0.95 (typical Gold Crown)
mamics -- 9':1.00 -- 4 5/8":0.98 -- 13/16":1.05 -- 1 1/4":0.95 -- 0.98
rexus31 friend GC -- 9':1.00 -- 4 1/4":1.05 -- 1/4":0.94 -- 15/16":0.95 -- 0.94
Neil -- 7':0.85 -- 4 1/8":1.10 -- 5/8":1.00 -- 1 3/8":0.99 -- 0.93
iusedtoberich -- 9':1.00 -- 5 1/8":0.90 -- 1":1.05 -- 1 1/2":0.98 -- 0.93 ("loose" GC)
MSchaffer -- 9":1.00 -- 5 1/10":0.90 -- 3/4":1.02 -- 1 3/4":1.00 -- 0.92
SloMoHolic league table -- 8':0.90 -- 4 3/4":0.98 -- 3/4":1.02 -- 1 5/8":1.00 -- 0.90
BRussell -- 8':0.90 -- 5":0.95 -- 13/16":1.05 -- 1 1/2":0.98 -- 0.88
Dopc -- 8':0.90 -- 4 1/2":1.00 -- 3/4":1.02 -- 1 1/4":0.95 -- 0.87
dr_dave -- 8':0.90 -- 4 3/4":0.98 -- 5/8":1.00 -- 1 3/8":0.98 -- 0.86
example "A" -- 8':0.90 -- 5":0.95 -- 1/2":0.98 -- 1 3/8":0.98 -- 0.82
Valley "bar box" -- 7':0.85 -- 4 1/2":1.00 -- 0":0.94 -- 3/4":0.95 -- 0.76 (typical Valley/Dynamo "bar box")