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

rexus31 · Jul 19, 2013

Sloppy Pockets said:
Here's a writeup by Joe W. about making and using a stimpmeter for measuring table speed.

http://billiards.colostate.edu/PBReview/Stimpmeter1.htm

I'm going to make one (ain't spending $20 for a triangle of wood unless it racks the balls), but in order to have consistency among the data, I'll make it with dimensions I got from the photo you provided. Looks like the ramp is pretty close to 1 5/8" tall x 7 7/8" long (~12º ramp angle), with a 1/2" backer board glued to it. If anybody wants one, just send me a PM and I'll try to make a few extras with some shop scrap, which will be available for the cost of shipping (probably about $5).

I'll have to wait until next week at the earliest to do this, so put your "order" in now if you want one. Just don't "Bill Stroud" me if life gets in the way and I don't get around to it for a while.

Interesting. I'll post the measurements of the tool I purchased for accuracy in testing.

TATE · Jul 19, 2013

rexus31 said:
Attached is a photo to poolhuster's GC. Old School: Can you please give it the treatment?

Yes - and according to the formula this is 5% easier than a Diamond with relative buckets. That means the formula is wrong.

As I stated previously, pocket size needs to be given a lot more weight than shelf depth and cut angle. Also, pocket size difficulty can easily be measured by margin of error. Margin of error = pocket size - ball size. A 5" pocket with 2 1/4" balls has a total margin of error of 2.75". A 4.5" pocket has a margin of error of 2.25. A 4.5" pocket has an 18% smaller margin of error than a 5" pocket.

In my opinion, this table is about 15% more difficult than a Diamond. looking at the pocket size and cut angle, I think most would agree that this is a tight, tough table. My table has 4" pockets with less cut angle and a shallow shelf, and plays just a little more difficult then this one.

rexus31 · Jul 19, 2013

TATE said:
Yes - and according to the formula this is 5% easier than a Diamond with relative buckets. That means the formula is wrong.

As I stated previously, pocket size needs to be given a lot more weight than shelf depth and cut angle.

Old school informed me I will have to submit a better pic that is directly above the pocket and parallel to the slate surface. I may be over there this weekend but I'm not sure.

rexus31 · Jul 19, 2013

I'm also going to see if I can get a good pic of Corey's "Ernesto-ized" GC.

Sloppy Pockets · Jul 19, 2013

rexus31 said:
Old school informed me I will have to submit a better pic that is directly above the pocket and parallel to the slate surface. I may be over there this weekend but I'm not sure.

You want to get straight down, but you also want to get as high up as possible. Best bet would be to use a short telephoto lens (85mm - 135mm with a 35mm format) and get about 10' above it to optically flatten out the field. But, who uses those long lenses anymore? Portrait photogs is about it.

Ideally, I'd guess you'd use a lens of about 135mm in focal length. In contrast, the typical cell phone lens has an actual focal length of only about 4mm. No matter how much digital lens correction is added in-camera after the fact, they still distort like a MF'er. Point-and-shoots and now (much worse) cell phones have all but destroyed quality photography IMO (says a man with several thousand dollars invested in "antiquated" SLRs, lenses, and large-format equipment that you can't even give away on eBay these days).:frown:

Stand on a chair if you can, and try to get a shot angle where the thickness of the slate just barely disappears in the photo. Seeing the slate edge means you are shooting at an angle facing away from the pocket back. This will make the pocket shelf look deeper in the photo than it really is due to parallax effect. Don't worry about the small size of the pocket in the photo, it's easy to enlarge it (without distortion) using any photo editing software.

FWIW...

Using the photo you posted I get 4 1/4" at the mouth, 142º facing angles and 7/8" shelf depth. That comes out to a TDF of 1.04 by my calculations.

SloMoHolic · Jul 19, 2013

Here is another table specimen.

Stardust Club (Manchaca, TX) - Brunswick Medalist

Size: 8+ (Pro 8 ft)
Mouth: 4.85"
Throat: 4"
Shelf: 1.25"

0.95 x 0.95 x 1.04 x 0.95

TDF = 0.89

In my opinion, that TDF is RIGHT ON!

I'm fairly sure of the measurements, but here's a cell phone pic just in case oldschool has some time to kill.

ImageUploadedByTapatalk1374285569.609209.jpg

Thanks again, Dave!

-Blake

44Runner · Jul 19, 2013

TATE said:
Yes - and according to the formula this is 5% easier than a Diamond with relative buckets. That means the formula is wrong.

As I stated previously, pocket size needs to be given a lot more weight than shelf depth and cut angle. Also, pocket size difficulty can easily be measured by margin of error. Margin of error = pocket size - ball size. A 5" pocket with 2 1/4" balls has a total margin of error of 2.75". A 4.5" pocket has a margin of error of 2.25. A 4.5" pocket has an 18% smaller margin of error than a 5" pocket.

In my opinion, this table is about 15% more difficult than a Diamond. looking at the pocket size and cut angle, I think most would agree that this is a tight, tough table. My table has 4" pockets with less cut angle and a shallow shelf, and plays just a little more difficult then this one.

I 100% agree that pocket size should be the heaviest weighted factor by far.

There are tables in the chart with 5" pockets getting a huge boost from a large difference in throat size yet I guarantee it is still harder to play a 4.5" pocket table with next to no difference from mouth to throat.

I know my table is one stingy bastard and comparing my pockets to others on the list I think I know why.

Neil · Jul 19, 2013

TATE said:
Yes - and according to the formula this is 5% easier than a Diamond with relative buckets. That means the formula is wrong.

As I stated previously, pocket size needs to be given a lot more weight than shelf depth and cut angle. Also, pocket size difficulty can easily be measured by margin of error. Margin of error = pocket size - ball size. A 5" pocket with 2 1/4" balls has a total margin of error of 2.75". A 4.5" pocket has a margin of error of 2.25. A 4.5" pocket has an 18% smaller margin of error than a 5" pocket.

In my opinion, this table is about 15% more difficult than a Diamond. looking at the pocket size and cut angle, I think most would agree that this is a tight, tough table. My table has 4" pockets with less cut angle and a shallow shelf, and plays just a little more difficult then this one.

I've got to disagree with you here Tate. Those pockets look like anything that gets between the points goes down. That would make it easier than a Diamond. Granted, the opening is smaller, but that's not that big a deal IMO. To me, what makes them tough is getting the ball between the points and still not making it.

TATE · Jul 19, 2013

Neil said:
I've got to disagree with you here Tate. Those pockets look like anything that gets between the points goes down. That would make it easier than a Diamond. Granted, the opening is smaller, but that's not that big a deal IMO. To me, what makes them tough is getting the ball between the points and still not making it.

But I've played on this table quite a bit it's quite a bit more difficult than a Diamond.

oldschool1478 · Jul 20, 2013

Stardust Club (Manchaca, TX) - Brunswick Medalist

Good position over shelf. May be slightly off parallel with slate, but measurements should be within 1/16". The shelf radius is hard to see in this one.
I am not sure, but I think this method can be done with Google Sketchup, (which is a free download) in case some want to try it for themselves.
Again, I do agree with Dr Dave that quality measurements with a ruler may be more accurate, due to camera placement, focal length, and lighting. For this reason, and because I don't want to dirty the data, this will be my last one.

Dan

44Runner · Jul 20, 2013

Pic of pocket

sorry for the terrible contrast...

ENGLISH! · Jul 20, 2013

oldschool1478 said:
Stardust Club (Manchaca, TX) - Brunswick Medalist

Good position over shelf. May be slightly off parallel with slate, but measurements should be within 1/16". The shelf radius is hard to see in this one.
I am not sure, but I think this method can be done with Google Sketchup, (which is a free download) in case some want to try it for themselves.
Again, I do agree with Dr Dave that quality measurements with a ruler may be more accurate, due to camera placement, focal length, and lighting. For this reason, and because I don't want to dirty the data, this will be my last one.

Dan

I have not read the whole thread so please excuse me if this has already been pointed out in general. Look at the pic in Dan's post & please note that a line that would be the radius line of the pocket arc in the center of the arc cut would not go to the the back center of the pocket. This can be noted by the different lengths on the pocket facings from the arc of the shelf to the center line of the pocket. I have seen quite a few poorly cut pockets in my 47 years. In this instance it appears that a ball coming from the one (1) balls direction would have a better chance to fall than one coming from the 5 balls direction.

My point is that it is not so very rare that a pocket or several pockets on a table are cut improperly. There is a 9' Centenial table at what is now my home hall that has a pocket that kicks everyone's butt when coming from up table. I know why & will shoot into the other corner or the side given the opportunity for just that reason.

The point is that it is not just the angle of the facings & the depth of the pocket but also where the center line of pocket arc is aligned. I am quite sure that every technician that cuts the slate does not use the same system or method, While I am probably sure that there is a 'standard method, we know that human beings do make errors even when setting up for a machine cut or even a computer aided operation. Plus we need to keep in mind how old some of these tables are. My Sport King that I bought with my Dad is about 50 years old.

I just wanted to point out this other parameter. Why I certainly appreciate Dr. Dave's attempt at rating tables, it is certainly not a simple task.

Regards to ALL,
Rick

dr_dave · Jul 20, 2013

TATE said:
Yes - and according to the formula this is 5% easier than a Diamond with relative buckets. That means the formula is wrong.

As I stated previously, pocket size needs to be given a lot more weight than shelf depth and cut angle. Also, pocket size difficulty can easily be measured by margin of error. Margin of error = pocket size - ball size. A 5" pocket with 2 1/4" balls has a total margin of error of 2.75". A 4.5" pocket has a margin of error of 2.25. A 4.5" pocket has an 18% smaller margin of error than a 5" pocket.

In my opinion, this table is about 15% more difficult than a Diamond. looking at the pocket size and cut angle, I think most would agree that this is a tight, tough table. My table has 4" pockets with less cut angle and a shallow shelf, and plays just a little more difficult then this one.

TATE,

Here is a previous exchange we had on this topic:

dr_dave said:
TATE said:

As far as pocket opening goes, a simple comparison of a 4" pocket to a 4.5" pocket would show the 4" pocket as 11% smaller. Reality is a 4" pocket is considerably more difficult than 4.5". If you deduct for the diameter of the ball, the margin of error on a 4.5" pocket is 2.25". On a 4" pocket the margin is 1.75". The difference between them is close to 21%. That I think is pretty accurate.

Click to expand...

Good analysis! I had done something similar also (for all of the factors) before I posted the original version of the document. However, this analysis doesn't translate directly to a useful factor for the effect pocket size has on outcome of play (e.g., a BU score). For example, for many shots, especially for a better player, a significant portion of the pocket margin is available for pocket cheating. In other words, many balls can be easily pocketed, and making the pocket smaller does more to limit pocket cheating than cause misses. In other words, the 21% number you cite doesn't mean 21% more shots will be missed with a 4" pocket compared to a 4.5" pocket (although, this might be true for some types of shots and some players). I hope that makes at least a little sense.

I've tried to vary the numbers and ranges to best characterize a large range of shots and players, and have the results be inline with people's experiences, but this is a tough thing to do without lots of meaningful and accurate data. Regardless, the TDF is still useful as a relative measure, even if the number doesn't have an exact and literal interpretation.

Thank you for your input,
Dave

Again, the real question is: how more often will you miss a typical shot on a 5" pocket vs. a 4.5" pocket. It is not as simple as you suggest and it depends a lot on the type of shot (distance, angle, speed, amount of pocket cheat required, etc.).

Another subtle point is that the effective size of the pocket is a little larger than you suggest (and this depends on the facing angle and shelf depth). For more info, see the pocket size resource page. Therefore, the percentage differences aren't quite as large as you suggest.

I agree with you completely that pocket size should be weighted much more than facing angle and shelf depth ... and it is. Regardless, you've convinced me to look at my analysis closer and maybe increase the pocket size effect even more. When I do this, I'll post the new numbers and edit all of the previously reported TDF values soon.

Regards,
Dave

dr_dave · Jul 20, 2013

SloMoHolic said:
Here is another table specimen.

Stardust Club (Manchaca, TX) - Brunswick Medalist

Size: 8+ (Pro 8 ft)
Mouth: 4.85"
Throat: 4"
Shelf: 1.25"

0.95 x 0.95 x 1.04 x 0.95

TDF = 0.89

In my opinion, that TDF is RIGHT ON!

I'm fairly sure of the measurements, but here's a cell phone pic just in case oldschool has some time to kill.

View attachment 285508

Thanks again, Dave!

-Blake

Thank you for posting another table (and for being accurate with the numbers and math). Here's the latest:

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

name -- table_size:TSF -- pocket_mouth_size

SF -- mouth-throat_difference

AF -- shelf_depth

LF -- TDF (table description)
dr_dave -- 10':1.10 -- 4":1.15 -- 3/4":1.02 -- 1 7/8":1.03 -- 1.33 (fictitious tough 10' table example)
MahnaMahna -- 10':1.10 -- 5 1/2":0.85 -- 2":1.15 -- 2 1/2": 1.15 -- 1.24 (snooker table poorly converted into a pool table)
dr_dave -- 9':1.00 -- 3 7/8":1.20 -- 5/8":1.00 -- 1 7/8":1.03 -- 1.24 (fictitious example "B")
Bonus Ball -- 9':1.00 -- 3 7/8":1.20 -- 1/8":0.97 -- 3/4":0.98 -- 1.14 (Bonus Ball table)
Bob Dixon -- 9':1.00 -- 4":1.15 -- 1/2":0.98 -- 1 3/8":0.99 -- 1.12 (Pool Sharks, Las Vegas, money table, Diamond Pro-Am, red logo, Ernesto Dominguez-modified)
Qaddiction -- 9':1.00 -- 4 1/8":1.10 -- 3/4":1.02 -- 1 3/8":0.99 -- 1.11 (Diamond)
rexus31 -- 9':1.00 -- 4":1.15 -- 3/8":0.98 -- 1":0.98 -- 1.10 (mid to late 50's AMF Commercial Model similar to a Brunswick Anniversary/Sport King)
FatBoy -- 9':1.00 -- 4":1.15 -- 1/4":0.97 -- 1":0.98 -- 1.09 (Ernesto-Dominguez-modified Brunswick Gold Crown)
TATE -- 9':1.00 -- 4":1.15 -- 1/4":0.97 -- 7/8":0.98 -- 1.09 (Ernesto-Dominguez-modified Brunswick Gibson)
cigardave -- 9':1.00 -- 4 1/2":1.00 -- 1":1.08 -- 1 3/4":1.00 -- 1.08 (typical Pro-Cut Diamond)
Neil -- 7':0.85 -- 4 1/8":1.10 -- 1 1/4":1.17 -- 1 3/8":0.99 -- 1.08 (modified Valley "bar box")
JC -- 9':1.00 -- 4 7/16":1.00 -- 143 deg:1.08 -- 1 3/8":0.98 -- 1.06 ("Cobrasized" Brunswick Gold Crown III)
dr_dave -- 9':1.00 -- 5": 0.95 -- 1 1/8":1.14 -- 1 3/8":0.98 -- 1.06 (old Brunswick Gold Crown II at MatchUps, Fort Collins)
Sloppy Pockets -- 8'+:0.95 -- 5":0.95 -- 1 1/8":1.14 -- 1 3/4":1.00 -- 1.03 (A.E. Schmidt)
SloMoHolic -- 9':1.00 -- 4 1/2":1.00 -- 7/8":1.04 -- 1 3/8":0.98 -- 1.02 (2005 Diamond Pro with ProCut pockets and Red-label rails)
oldschool1478 -- 9':1.00 -- 4 1/2":1.00 -- 141 deg:1.02 -- 1 3/4:1.00 -- 1.02 (updated Red Badge Diamond Pro)
dzcues -- 9':1.00 -- 5":0.95 -- 15/16":1.08 -- 1 1/2":0.98 -- 1.01 (Gandy Big G)
dzcues -- 9':1.00 -- 4 7/8":0.95 -- 11/16":1.02 -- 1 15/16":1.03 -- 1.00 (typical League-Cut Diamond)
"standard" table -- 9':1.00 -- 4 7/16":1.00 -- 9/16":1.00 -- 1 5/8":1.00 -- 1.00 (WPA spec "standard")
Kelly_Guy -- 9':1.00 -- 4 1/2":1.00 -- 1/2":0.98 -- 1 5/8":1.00 -- 0.98 (Antique Brunswick Jefferson, circa 1900)
BryanB -- 9':1.00 -- 4 1/2":1.00 -- 3/4":1.02 -- 1 1/4":0.95 -- 0.97 (1931 Brunswick with double shimmed pockets)
mamics -- 9':1.00 -- 4 11/16":0.98 -- 7/8":1.04 -- 1 3/16":0.95 -- 0.97 (no-name "Chinese Cheapie" with Uylin cushions)
Pool Hustler -- 9':1.00 -- 4 1/4":1.05 -- 1/4":0.95 -- 15/16":0.95 -- 0.95 (modified Brunswick Gold Crown, measured by rexus31)
12squared -- 9':1.00 -- 4 7/8":0.95 -- 3/4":1.02 -- 1 1/2":0.98 -- 0.95 (Brunswick Gold Crown home table)
iusedtoberich -- 9':1.00 -- 5 1/8":0.90 -- 1":1.06 -- 1 1/2":0.98 -- 0.93 ("loose" Brunswick Gold Crown)
MSchaffer -- 9':1.00 -- 5 1/10":0.90 -- 3/4":1.02 -- 1 3/4":1.00 -- 0.92 (Brunswick Gold Crown II)
44Runner -- 8'+/-:0.925 -- 4 3/8":1.02 -- 3/4":1.02 -- 1":0.95 -- 0.91 (8' Diamond Pro-Am - blue label)
mfinkelstein3 -- 9':1.00 -- 5 1/8":0.90 -- 7/8":1.03 -- 1 1/2": 0.97 -- 0.90 ("loose" Brunswick Gold Crown III)
Vahmurka -- 9':1.00 -- 5 1/8":0.90 -- 7/8":1.03 -- 1 1/2": 0.97 -- 0.90 (Brunswick Centurion)
SloMoHolic -- 8':0.90 -- 4 3/4":0.98 -- 3/4":1.02 -- 1 5/8":1.00 -- 0.90 (old 8' Brunswick Medalist league table)
SloMoHolic -- 8'+:0.95 -- 4 7/8":0.95 -- 7/8":1.04 -- 1 1/4":0.95 -- 0.89 (Brunswick Medalist at Stardust Club in Manchaca, TX)
BRussell -- 8':0.90 -- 5":0.95 -- 13/16":1.04 -- 1 1/2":0.98 -- 0.87 (8' Olhausen)
Dopc -- 8':0.90 -- 4 1/2":1.00 -- 3/4":1.02 -- 1 1/4":0.95 -- 0.87 (8' Connelly Kayenta)
dr_dave -- 8':0.90 -- 4 3/4":0.98 -- 5/8":1.00 -- 1 3/8":0.98 -- 0.86 (8' Connelly home table)
dr_dave -- 8':0.90 -- 5":0.95 -- 1/2":0.98 -- 1 3/8":0.98 -- 0.82 (fictitious 8' example "A")
Mooneye -- 7':0.85 -- 4 7/8":0.95 -- 3/4":1.02 -- 1 5/8":1.00 -- 0.82 (7' Brunswick "Ranchero")
SloMoHolic -- 6':0.85 -- 4.5":1.00 -- 0":0.95 -- 5/8":0.95 -- 0.77 (old 6' Valley "bar box")
dzcues -- 7':0.85 -- 4 1/2":1.00 -- 0":0.94 -- 1/2":0.95 -- 0.76 (7' Valley "bar box")
dr_dave -- 7':0.85 -- 4 1/2":1.00 -- 0":0.94 -- 3/4":0.95 -- 0.76 (7' Valley/Dynamo "bar box" at West End, Fort Collins)

dr_dave · Jul 20, 2013

oldschool1478 said:
Stardust Club (Manchaca, TX) - Brunswick Medalist

Good position over shelf. May be slightly off parallel with slate, but measurements should be within 1/16". The shelf radius is hard to see in this one.
I am not sure, but I think this method can be done with Google Sketchup, (which is a free download) in case some want to try it for themselves.
Again, I do agree with Dr Dave that quality measurements with a ruler may be more accurate, due to camera placement, focal length, and lighting. For this reason, and because I don't want to dirty the data, this will be my last one.

Dan

Dan,

Thanks again for doing these. I'm glad you agree with me that careful measurements at the table are much better than the photo and software-measurement approach.

Here's SloMo's originial data:
SloMoHolic -- 8'+:0.95 -- 4 7/8":0.95 -- 7/8":1.04 -- 1 1/4":0.95 -- 0.89 (Brunswick Medalist at Stardust Club in Manchaca, TX)

and here's what you got from the photo:
SloMoHolic -- 8'+:0.95 -- 5":0.93 -- 1"(144 deg):1.08 -- 1 3/8":0.98 -- 0.94 (Brunswick Medalist at Stardust Club in Manchaca, TX)

I won't change the data unless SloMoHolic confirms that the photo measurements are better than his hand measurements.

Thanks again for your time and effort,
Dave

dr_dave · Jul 20, 2013

ENGLISH! said:
... I certainly appreciate Dr. Dave's attempt at rating tables, it is certainly not a simple task.

Thanks Rick. I certainly agree with the "not a simple task" part.

Catch you later,
Dave

Sloppy Pockets · Jul 20, 2013

dr_dave said:
I certainly agree with the "not a simple task" part.

Exceedingly difficult IMO.

The medical community uses similar risk factors (always less than 1) to assess a patient's likelihood of survival during major surgeries. They use the entire AMA, NIH, and CDC databases to establish these factors based upon surgical records for many decades. Needless to say, the "n" is very large in these studies. Still, they miss a hell of a lot.

For example, a patient may be assigned a risk factor of 0.70 for being diabetic, a 0.65 for being over 70 years old, a 0.83 for being overweight, a 0.75 for having high blood pressure, and so on. Having all of these health issues, then multiplying all of the applicable risk factors, a given patient would be assigned a mere 28% (0.28) chance of survival.

What is not assessed in the degree of morbidity that each factor is causing in the particular patient's health profile. How bad is the diabetes? For how long has the patients suffered with it? How much organ damage has accrued since the onset of the disease? Same with overweight, HBP, age, etc. It's just like all of the table variables, where with things like cloth speed, cushion rebound, cloth age, etc., it is almost impossible to determine the degree that these are present on any given table.

I went through all this when my mother needed heart valve replacement, quadruple bypass surgery, and carotid artery surgery all at the same time. I remember her combined risk factors put her at about a 20% chance of survival. Of course, they operated anyway (have to bring that much-needed money into the cardiac care unit, ya know?) And, of course, they killed her in there, but not before torturing her for three months (but that's a whole other story).

Dave isn't claiming that this formula is the be all and end all of table difficulty assessment. And besides, it's not complete yet, it is still very much a work in progress. When it is finished, there will still be a lot of tables that just don't fall where a given player personally thinks they should, but the tables and formulas are still valid for rough estimates of table difficulty. I actually was pretty skeptical of how this would play out, but at this point, I'm very impressed with the way things have evolved. Seems that most tables posted here actually fit pretty close to the opinions of the folks who posted their measurements. I know mine does.

dr_dave · Jul 20, 2013

FYI to all, I've made some changes to the PSF and PAF based on recent discussions and additional analysis. The latest procedure is below. If you have a printed or electronic copy of the Table Difficulty Factor (TDF) document, you should replace it with the new version (dated 7/20/2013).

I've also edited the numbers and calculations for all of the pool tables submitted to date. The updated list is in the first post of the thread and I'll quote it in my next post.

Regards,
Dave

The Table Difficulty Factor (TDF) is a percentage measure of how difficult or easy a particular table plays. It is based on table size and the three corner-pocket measurements illustrated below. If the cushion is not 2” (5.1cm) thick, measure the throat size 2” (5.1 cm) back from the cushion noses. You can lay down Post-It Notes or masking tape to better define the lines and intersection points to help with the mouth and throat measurements. If you have an angle-measurement device, you can measure the facing angle directly instead of measuring the throat size. The pocket shelf depth should be measured from the pocket mouth line to the slate top lip edge (where the pocket opening first starts).

Four factors are used to account for table size, pocket size, pocket facing angle, and pocket shelf depth. Each factor is a number less than, equal to, or greater than 1, where 1 indicates average or standard. By multiplying the four factors, you get the TDF which is a good measure of table “toughness.” If TDF=1, the table has an average level of difficulty; if TDF>1, the table plays more difficult than average; and if TDF<1, the table plays easier than average.

The four factors are defined as follows:

The total Table Difficulty Factor (TDF) is then calculated by multiplying the four factors:

TDF = TSF x PSF x PAF x PLF

The TDF can be used to adjust numbers from any scoring or rating system like the Billiard University Exams, “playing the ghost” drills, the Hopkins Q Skills drill, or the Fargo rating drill. An effective score, taking table difficulty into consideration, can be calculated with:

(effective score) = (raw score) x TDF

NOTE – The TDF and effective-score numbers should not be interpreted too literally since there are so many other factors that contribute to how difficult a table actually plays (cloth type and condition, ball conditions, pocket facing and shim properties, rail and cushion conditions, table levelness, humidity, etc.). Here’s a rough scale one can use to put the TDF factor in better perspective:

dr_dave · Jul 20, 2013

Below is the latest updated list after the recent changes to the PSF and PAF. Things didn't change very much overall, but the tables that people claimed were rated too low or high before, based on pocket size alone, now have more-appropriate ratings.

Please let me know what your think about the recent changes and new ratings.

Regards,
Dave

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

name -- table_size:TSF -- pocket_mouth_size

SF -- mouth-throat_difference

AF -- shelf_depth

LF -- TDF (table description)
dr_dave -- 10':1.10 -- 4":1.20 -- 3/4":1.02 -- 1 7/8":1.03 -- 1.39 (fictitious tough 10' table example)
dr_dave -- 9':1.00 -- 3 7/8":1.25 -- 5/8":1.00 -- 2 1/8":1.07 -- 1.34 (fictitious example "B")
Bonus Ball -- 9':1.00 -- 3 7/8":1.25 -- 1/8":0.97 -- 3/4":0.98 -- 1.19 (Bonus Ball table)
Bob Dixon -- 9':1.00 -- 4":1.20 -- 1/2":0.99 -- 1 3/8":0.99 -- 1.18 (Pool Sharks, Las Vegas, money table, Diamond Pro-Am, red logo, Ernesto Dominguez-modified)
MahnaMahna -- 10':1.10 -- 5 1/2":0.85 -- 2":1.09 -- 2 1/2": 1.15 -- 1.17 (snooker table poorly converted into a pool table)
Qaddiction -- 9':1.00 -- 4 1/8":1.15 -- 3/4":1.02 -- 1 3/8":0.99 -- 1.16 (Diamond)
rexus31 -- 9':1.00 -- 4":1.20 -- 3/8":0.98 -- 1":0.98 -- 1.15 (mid to late 50's AMF Commercial Model similar to a Brunswick Anniversary/Sport King)
FatBoy -- 9':1.00 -- 4":1.20 -- 1/4":0.97 -- 1":0.98 -- 1.14 (Ernesto-Dominguez-modified Brunswick Gold Crown)
TATE -- 9':1.00 -- 4":1.20 -- 1/4":0.97 -- 7/8":0.98 -- 1.14 (Ernesto-Dominguez-modified Brunswick Gibson)
Neil -- 7':0.85 -- 4 1/8":1.15 -- 1 1/4":1.14 -- 1 3/8":0.99 -- 1.10 (modified Valley "bar box")
cigardave -- 9':1.00 -- 4 1/2":1.00 -- 1":1.07 -- 1 3/4":1.00 -- 1.07 (typical Pro-Cut Diamond)
Pool Hustler -- 9':1.00 -- 4 1/4":1.10 -- 1/4":0.97 -- 15/16":0.98 -- 1.05 (modified Brunswick Gold Crown, measured by rexus31)
JC -- 9':1.00 -- 4 7/16":1.00 -- 143 deg:1.07 -- 1 3/8":0.98 -- 1.05 ("Cobrasized" Brunswick Gold Crown III)
SloMoHolic -- 9':1.00 -- 4 1/2":1.00 -- 7/8":1.04 -- 1 3/8":0.98 -- 1.02 (2005 Diamond Pro with ProCut pockets and Red-label rails)
oldschool1478 -- 9':1.00 -- 4 1/2":1.00 -- 141 deg:1.02 -- 1 3/4:1.00 -- 1.02 (updated Red Badge Diamond Pro)
"standard" table -- 9':1.00 -- 4 7/16":1.00 -- 9/16":1.00 -- 1 5/8":1.00 -- 1.00 (WPA spec "standard")
Kelly_Guy -- 9':1.00 -- 4 1/2":1.00 -- 1/2":0.98 -- 1 5/8":1.00 -- 0.98 (Antique Brunswick Jefferson, circa 1900)
dr_dave -- 9':1.00 -- 5": 0.91 -- 1 1/8":1.10 -- 1 3/8":0.98 -- 0.98 (old Brunswick Gold Crown II at MatchUps, Fort Collins)
BryanB -- 9':1.00 -- 4 1/2":1.00 -- 3/4":1.02 -- 1 1/4":0.95 -- 0.97 (1931 Brunswick with double shimmed pockets)
dzcues -- 9':1.00 -- 4 7/8":0.91 -- 11/16":1.02 -- 1 15/16":1.03 -- 0.96 (typical League-Cut Diamond)
dzcues -- 9':1.00 -- 5":0.91 -- 15/16":1.07 -- 1 1/2":0.98 -- 0.95 (Gandy Big G)
Sloppy Pockets -- 8'+:0.95 -- 5":0.91 -- 1 1/8":1.10 -- 1 3/4":1.00 -- 0.95 (A.E. Schmidt)
44Runner -- 8'+/-:0.925 -- 4 3/8":1.05 -- 3/4":1.02 -- 1":0.95 -- 0.94 (8' Diamond Pro-Am - blue label)
mamics -- 9':1.00 -- 4 11/16":0.95 -- 7/8":1.04 -- 1 3/16":0.95 -- 0.94 (no-name "Chinese Cheapie" with Uylin cushions)
12squared -- 9':1.00 -- 4 7/8":0.91 -- 3/4":1.02 -- 1 1/2":0.98 -- 0.91 (Brunswick Gold Crown home table)
iusedtoberich -- 9':1.00 -- 5 1/8":0.88 -- 1":1.05 -- 1 1/2":0.97 -- 0.90 ("loose" Brunswick Gold Crown)
MSchaffer -- 9':1.00 -- 5 1/8":0.88 -- 3/4":1.01 -- 1 3/4":1.00 -- 0.89 (Brunswick Gold Crown II)
mfinkelstein3 -- 9':1.00 -- 5 1/8":0.88 -- 7/8":1.03 -- 1 1/2": 0.97 -- 0.88 ("loose" Brunswick Gold Crown III)
Vahmurka -- 9':1.00 -- 5 1/8":0.88 -- 7/8":1.03 -- 1 1/2": 0.97 -- 0.88 (Brunswick Centurion)
Dopc -- 8':0.90 -- 4 1/2":1.00 -- 3/4":1.02 -- 1 1/4":0.95 -- 0.87 (8' Connelly Kayenta)
SloMoHolic -- 8':0.90 -- 4 3/4":0.95 -- 3/4":1.02 -- 1 5/8":1.00 -- 0.87 (old 8' Brunswick Medalist league table)
SloMoHolic -- 8'+:0.95 -- 4 7/8":0.91 -- 7/8":1.04 -- 1 1/4":0.95 -- 0.85 (Brunswick Medalist at Stardust Club in Manchaca, TX)
dr_dave -- 8':0.90 -- 4 3/4":0.95 -- 5/8":1.00 -- 1 3/8":0.98 -- 0.84 (8' Connelly home table)
BRussell -- 8':0.90 -- 5":0.91 -- 13/16":1.04 -- 1 1/2":0.98 -- 0.83 (8' Olhausen)
dr_dave -- 8':0.90 -- 5":0.91 -- 1/2":0.98 -- 1 3/8":0.98 -- 0.79 (fictitious 8' example "A")
Mooneye -- 7':0.85 -- 4 7/8":0.91 -- 3/4":1.02 -- 1 5/8":1.00 -- 0.79 (7' Brunswick "Ranchero")
SloMoHolic -- 6':0.85 -- 4 1/2":1.00 -- 0":0.95 -- 5/8":0.95 -- 0.77 (old 6' Valley "bar box")
dzcues -- 7':0.85 -- 4 1/2":1.00 -- 0":0.95 -- 1/2":0.95 -- 0.77 (7' Valley "bar box")
dr_dave -- 7':0.85 -- 4 1/2":1.00 -- 0":0.95 -- 3/4":0.95 -- 0.77 (7' Valley/Dynamo "bar box" at West End, Fort Collins)

ENGLISH! · Jul 20, 2013

dr_dave said:
Thanks Rick. I certainly agree with the "not a simple task" part.

Catch you later,
Dave

Hi Dave,

Let me just say that you will get no 'arguments' from me.

But just for a quick discussion clarification, does that mean that you disagree with the center angle radius line direction of the slate cut being a factor or is that just a factor that can not be calculated do to the inconsistency & difficulty in it's determination & therefore must be thrown out of the equation?

Best Regards,
Rick

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

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