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

dr_dave · 05:31 AM

Calculate your Table Difficulty Factor (TDF) to determine how tough it plays in comparison to other tables. Only three pocket measurements are required, and you can use the online mobile-friendly TDF calculator (created by "Isaac") or the TDF Excel spreadsheet calculator to get your results.

Measurements and Data Reported by AZB Users:

username - table size:TSF, pocket mouth size:PSF, mouth-throat difference:PAF, shelf depth:PLF - TDF (table description)
Vahmurka - 12':1.25, 7.2cm:1.55, 125deg:0.97, 25mm:0.98 - 1.84 (12ft Russian pyramid table)
Side Pocket - 10':1.10, 4 1/4":1.10, 1 1/4":1.14, 2 1/4":1.07 - 1.48 (10' 1920-1925 Brunswick, modified 9/2016)
CaptiveBred - 10':1.10, 4 1/8":1.15, >143.5deg:1.14, 1 1/2":0.99 - 1.43 (10' Brunswick Anniversary re-machined to Diamond specs)
Bob Dixon - 9':1.00, 4":1.20, 145deg:1.14, 1 5/8":1.00 - 1.37 (Pool Sharks, Las Vegas, money table, Diamond Pro-Am, red logo, Ernesto Dominguez-modified)
gregcantrall - 10':1.10, 4":1.20, 5/8":1.00, 1 1/2":0.99 - 1.31 (10 foot Diamond in the Sun City West, AZ Rec Center)
Ricky Sy - 9':1.00, 3 3/4":1.31, 1/4":0.97, 5/8":0.98 - 1.25 (money table at Hard Times in Bellflower, CA)
acedonkeyace - 9":1.00, 4":1.20, 1/2":0.99, 2":1.03 - 1.22 (gamble table at sidePocket in Largo, Florida)
ChrisinNC - 10':1.1, 4 1/4":1.1, 11/16":1.02, 1 5/16":0.99 - 1.22 (shimmed 10' Gabriel Sentinel, Ernesto Dominguez modified, at Family Billiards in Boone, NC)
Bonus Ball - 9':1.00, 3 7/8":1.25, 1/8":0.97, 3/4":0.98 - 1.19 (Bonus Ball table)
Marc Vidal - 9':1.00, 4 1/8":1.15, 7/16":1.05, 1":0.98 - 1.18 (shimmed Brunswick Tournament Edition)
chevybob20 - 9':1.00, 4 1/8":1.15, 7/8":1.05, 1":0.98 - 1.18 (Mark-Gregory-modified Centennial)
Baxter - 9':1.00, 4 1/4":1.10, 143deg:1.09, 1 1/8":0.98 - 1.18 (Donny-Wessels-modified AMF Grand Prix)
Qaddiction - 9':1.00, 4 1/8":1.15, 3/4":1.02, 1 3/8":0.99 - 1.16 (Diamond)
angluse - 8'+: 0.95, 3 13/16":1.25, 9/16":1.00, 7/8":0.98 - 1.16 (modified 1935 Brunswick Challenger)
Tom Cruise - 9':1.00, 4":1.20, 1/8":0.97, 1 3/8":0.99 - 1.15 (Golden West)
ChrisinNC - 10':1.1, 4 3/8":1.05, 11/16":1.02, 1 5/16":0.98 - 1.15 (original 10' Gabriel Sentinel, Ernesto Dominguez modified, at Family Billiards in Boone, NC)
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 GC)
TATE - 9':1.00, 4":1.20, 1/4":0.97, 7/8":0.98 - 1.14 (Ernesto-Dominguez-modified GC)
Mikjary - 9'-1.00, 4":1.15, 9/16":1.00, 1 5/16":0.98 - 1.13 (Brunswick Centurion)
ChrisinNC - 9':1.0, 4 1/8":1.15, 5/8":1.0, 1 1/4":0.98 - 1.13 (tightest Gabriel's Signature Pro, Ernesto Dominguez modified, at Family Billiards in Boone, NC - Table 7)
Cardigan Kid - 10'-1.10, 4.5":1.00, 0.88":1.04, 1.5":0.98 - 1.12 (Gold Crown from Steinway Billiards - Earl Strickland's former practice/match-up table)
Ralph Kramden - 9':1.0, 4 5/16":1.05, 1":1.07, 1 3/4":1.00 - 1.12 (1962 Nine foot Gold Crown 1)
pocket - 9':1.00 - 4 3/16":1.10, 7/16":0.99, 1 7/8":1.03 - 1.12 (unknown)
Justaneng - 8':0.90 - 4":1.20, 7/8":1.05, 1 1/2":0.99 - 1.12 (Olhausen)
kanzzo - 9':1.00, 10.7 cm:1.10, 1.7 cm:1.02, 2.7 cm:0.98 - 1.10 (Gold Crown V tournament edition)
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")
MahnaMahna - 10':1.10, 5 1/2":0.85, 2":1.09, 2 1/2": 1.07 - 1.09 (snooker table poorly converted into a pool table)
tjlmbklr - 8'+:0.95, 4":1.15, 141deg:1.02, 1 1/4":0.98 - 1.09 (unknown, maybe homemade or a kit table)
Cardigan Kid - 9':1.00, 4 1/4":1.10, 0.45":0.99, 1 5/16":0.99 - 1.08 (GC II)
MSchaffer - 9':1.00, 4 7/16:1.00, 15/16":1.07, 1 5/8":1.00 - 1.07 (GCII, RKC mod)
cigardave - 9':1.00, 4 1/2":1.00, 1":1.07, 1 3/4":1.00 - 1.07 (typical Pro-Cut Diamond)
peppersauce - 9':1.00, 4 1/4":1.10, 3/8":0.98, 1 1/4":0.98 - 1.06 (GC 3)
Side Pocket - 10':1.10, 4 7/8":0.91, 1":1.07, 1 1/2":0.98 - 1.05 (10' 1920-1925 Brunswick)
Pool Hustler - 9':1.00, 4 1/4":1.10, 1/4":0.97, 15/16":0.98 - 1.05 (modified GC, measured by rexus31)
JC - 9':1.00 - 4 7/16":1.00, 143deg:1.07, 1 3/8":0.98 - 1.05 ("Cobrasized" GC III)
Banger - 9':1.00, 4 1/2":1.00, 7/8":1.04, 1 3/4":1.00 - 1.04 (RKC-modified GC III)
Jimmorrison - 7':0.85, 3 7/8":1.25, 7/16":0.99, 3/4":0.98 - 1.03 (modified Ruxton)
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)
CoreyClark - 9':1.00, 5":0.91, 1":1.07, 2 1//8":1.05 - 1.02 (GC I)
"standard" table - 9':1.00, 4 7/16":1.00, 9/16":1.00, 1 5/8":1.00 - 1.00 (average-difficulty table)
kanzzo - 9':1.00, 11.4 cm:1.00, 1.7 cm:1.02, 3.3 cm:0.98 - 1.00 (Gold Crown V tournament edition)
coxcol15 - 7':0.85, 4.25":1.10, 1":1.09, 1.25":0.98 - 1.00 (Valley barbox w/ Ridgeback pro cuts)
Goldball - 8':0.90, 12.2cm:0.91, 4cm:1.14, 5.4cm:1.07 - 1.00 (Heiron & Smith)
dr_dave - 9':1.00, 5": 0.91, 1 1/8":1.10, 1 3/8":0.99 - 0.99 (old GC II at MatchUps, Fort Collins)
Call_me_Tom - 7':0.85, 4":1.20, 1/2":0.99, 1":0.98 - 0.99 (Valley bar box with Penguin Pro rails)
MVPCues - 9':1.00, 4 1/2":1.00, 1/2":0.98, 1 5/8":1.00 - 0.98 (Antique Brunswick Jefferson, circa 1900)
oldschool1478 - 9':1.00, 4 1/2":1.00, 0.625":1.00, 1.5":0.98 - 0.98 (updated Red Badge Diamond Pro)
freds - 8'+: 0.95, 4.9":0.91, 1.1":1.1, 1.8" 1.03 - 0.98 (Gandy Big G, oversized 8)
Cardigan Kid - 9':1.00, 4 1/2":1.00, 3/4":1.02, 1 1/16":0.95 - 0.97 (GC III Table 7 at Premium Billiards, Syracuse, Mark Gregory-modified w/ Artemis cushions)
wigglybridge - 9':1.00, 4 1/2":1.00, 5/8":1.00, 1 1/2": 0.98 - 0.98 (GC 1.5, rails rebuilt & cushions replaced by Jay Spielberg)
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)
Poolmanis - 9':1.00, 10.9cm:1.05, 1cm:0.97, 3.1cm:0.95 - 0.97 (modified SAM)
Vahmurka - 9':1.0, 12.5cm:0.91, 20mm:1.04, 45mm:1.03 - 0.97 (Brunswick Metro)
mamics - 9':1.00, 4 11/16":0.95, 143deg:1.07, 1 3/16":0.95 - 0.97 (no-name "Chinese Cheapie" with Uylin cushions)
dzcues - 9':1.00, 4 7/8":0.91, 11/16":1.02, 1 15/16":1.03 - 0.96 (typical League-Cut Diamond)
jviss - 9’:1.00, 4.98”:0.91, 0.76”:1.04, 1.625”:1.00 - 0.95 (GC I)
logical - 9':1.00, 5": 0.91, 7/8":1.04, 1 3/4":1.00 - 0.95 (GC II)
dr_dave - 9':1.00, 5": 0.91, 1":1.07, 1 1/5":0.98 - 0.95 (Olhausen purchased from Robert Byrne)
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)
Corwyn_8 - 9':1.00, 4 3/4":0.95, 1 3/4":1.02, 1 1/4":0.95 - 0.92 (Gandy Winchester)
beetle - 9':1.00, 13.1cm:0.88, 2.2cm:1.03, 4.3cm:1.00 - 0.91 (Olhausen York)
frigopie - 9':1.00, 11.5cm:0.95, 138.7deg:0.98, 3.5cm:0.98 - 0.91 (Eurotour Dynamic III)
12squared - 9':1.00, 4 7/8":0.91, 3/4":1.02, 1 1/2":0.98 - 0.91 (GC home table)
iusedtoberich - 9':1.00, 5 1/8":0.88, 1":1.05, 1 1/2":0.97 - 0.90 (GC)
MSchaffer - 9':1.00, 5 1/8":0.88, 3/4":1.01, 1 3/4":1.00 - 0.89 (GC II)
mfinkelstein3 - 9':1.00, 5 1/8":0.88, 7/8":1.03, 1 1/2": 0.97 - 0.88 (GC III)
StraightPoolIU - 9':1.00, 4 7/8":0.91, 3/4":1.02, 1 1/4":0.95 - 0.88 (GC I)
Vahmurka - 9':1.00, 5 1/8":0.88, 7/8":1.03, 1 1/2": 0.97 - 0.88 (GC)
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)
RobMan - 9':1.0, 5": 0.88, 3/4":1.01, 1.5":0.97 - 0.86 (GC)
sniggihs - 7':0.85, 4 1/2":1.00, 5/8":1.00, 1 3/4":1.00 - 0.85 (7’ Diamond - Blue Label)
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)
buckshotshoey - 8':0.90, 4 3/4":0.95, 3/4":1.02, 1 1/2":0.98 - 0.85 (American Heritage "Independence")
nateobot - 7':0.85, 4 3/8":1.05, 1/2":0.95, 1 3/4":1.00 - 0.85 (custom-made)
angluse - 8'+: 0.95, 4 5/8":0.95, 7/16":0.98, 1 3/16":0.95 - 0.84 (1935 Brunswick Challenger)
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)
Lovepool - 9':1.00, 13cm:0.88, 1cm:0.96, 3.5cm:0.97 - 0.82 (home table)
jtaylor996 - 7':0.85, 5 1/8":0.88, 146deg:1.09, 1.51":1.00 - 0.82 (7' Legacy home table)
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 "bar box" at West End, Fort Collins)

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).

For more information, see the TDF document. And to do the calculations automatically, use the online mobile-friendly TDF calculator (created by "Isaac") or the TDF Excel spreadsheet calculator.

The TDF system is based on ideas from previous threads: tight pockets, pocket answers, and Billiard University (BU)).

GeoEnvi · 08:35 AM

My MS in Civil Engineering loves what you are doing, Dr. Dave!

I'd love to see how the local league tables stack up around here. I'm going to add a 6 inch engineering ruler to my cue case for measuring on the fly!

In my vocation, we use a similar method of combining partial factors of safety to get an overall factor of safety. Partial factors are usually empirically derived or manually set to get the 'spread' in the data that seems appropriate. I'm curious as to how you decided on the various Factor values...

bdorman · 06-21-2013, 08:39 AM

Very interesting. I can't wait to measure the table at our community center. I'm sure it's well under 1.0

The only limitation I see is using the table score to adjust the shooter's score. There is a very good chance that the shooter would have scored nearly as well on a more difficult table since most(?) of the drills are more about CB positioning than OB pocketing. Likewise, a shooter wouldn't necessarily score 20% higher on an easy table than he did on his tough table. You could probably apply another factor to account for pocketing vs. positioning, but I can feel Occam's Razor beginning to cut.

Jaden · **I think this would only be the case... -** 06-21-2013, 08:43 AM

Quote:

Originally Posted by bdorman

Very interesting. I can't wait to measure the table at our community center. I'm sure it's well under 1.0

The only limitation I see is using the table score to adjust the shooter's score. There is a very good chance that the shooter would have scored nearly as well on a more difficult table since most(?) of the drills are more about CB positioning than OB pocketing. Likewise, a shooter wouldn't necessarily score 20% higher on an easy table than he did on his tough table. You could probably apply another factor to account for pocketing vs. positioning, but I can feel Occam's Razor beginning to cut.

I think that what you're describing would only be the case if you were attempting to discern the level of the player with this. It is more about the difficulty of the table.

There is room for improvement, but then you're getting too deep into the weeds. and it's time to take a drop.

I think what Dave has done here is great without getting too deep in the weeds.

Hell, I could see writing an app with this formula for checking a table on the fly.

Jaden

Mr. Bond · 06-21-2013, 08:47 AM

Dave, what is the presumed angle of the cushion facings?

And, do we not suppose that this angle is inconsistent from table to table?

And if so, does this angle not make a difference when it comes down to what stays in the pocket and what doesn't?

SpiderWebComm · 08:50 AM

There's so much that goes into how a table plays:

type of cloth, tightness of cloth, wear of cloth, type of rails, tightness of rails, type of balls, condition/cleanliness of balls, type of light, position of light, brightness/quality of light, cue ball type/size/condition, type of pocket facing/shim (material) and then, of course, the factors you pointed out with table size and pocket cut.

I see where you're going with the playability factor and it's not a bad idea --- I just think the conclusion can never be as specific as your example. Meaning, you can never say based on the 3 factors, table A plays 27% harder than table B.

The specificity of your result is just too great for something that is clearly subjective. You can never accurately ascertain exact factors since you're not dealing with tables made of the same material and manufactured the same way. For example, the pocket facings/shims can be made of different material and installed WAY differently from table to table and that plays a huge role is whether or not the pocket takes a shot.

Therefore, you can never have a result down to a single percentage and have it mean anything other than conjecture.

I don't think there's any way to scientifically determine table difficulty without having a player play the ghost 100 racks on table A and compare to table B. You might have a bar box that plays tough as hell (generally speaking) and a 5x10 that just accepts everything and has perfect speed.

The rating system would be more meaningful if you changed your calculations in order to reduce your resultants down to 5: super easy, easy, par, hard, very tough

How much harder (%-wise) is an easy table compared to a hard table? You'd never know without collecting data. Even then, you'd never have a margin of error within 1%. You'd have to round to the nearest 10 just to account for variation in a player's ability from day to day.

dr_dave · 04:28 PM

Quote:

Originally Posted by GeoEnvi

My MS in Civil Engineering loves what you are doing, Dr. Dave!

Thanks.

Quote:

Originally Posted by GeoEnvi

In my vocation, we use a similar method of combining partial factors of safety to get an overall factor of safety.

I'm curious as to how you decided on the various Factor values...

The table size factor (TSF) was easy. Shot difficulty is directly related to shot distance which is directly related to table size on average, so I just had to look at percentage changes in table size and round off. The pocket size factor (PSF) was also easy. If you look at the effective size of the pocket (i.e., how much you can be off in either direction and still pocket the ball), I just calculated the percentage change associated with each pocket size, and rounded off.

The pocket angle factor (PAF) and Pocket Shelf Factor (PSF) were a little trickier. Luckily, I've done an extensive analysis on these effects in the past. For more info, see the pocket "size" and "center" resource page. I used my TP 3.6 document to analyze changes in each pocket spec. I also interviewed several experienced players asking for their gut feel on each factor. And then I rounded off some.

I also did some calculations on a few tables to see if they came out about where I thought they should. For example, this is what I got for my home table:
size: 8', mouth: 4 3/4", throat: 4 1/8", (mouth-throat): 5/8", shelf: 1 3/8"
TSF=0.90, PSF=1.00, PAF=1.00, PLF=0.95
TDF = TSF x PSF x PAF x PLF = 0.90 x 1.00 x 1.00 x 0.95 = 0.81

and this is what I got for my VNEA league's Valley/Dynamo "bar boxes:"
size: 7', mouth: 4 1/2", throat: 4 1/2", (mouth-throat): 0", shelf: 3/4"
TSF=0.80, PSF=1.05, PAF=0.94, PLF=0.90
TDF = TSF x PSF x PAF x PLF = 0.80 x 1.05 x 0.94 x 0.90 = 0.71

Both of these numbers seemed appropriate to me. My home table seems about 20% easier than standard, and the bar box seems about 30% easier than standard, in general (although the numbers might be a little high). The best test would be to have a bunch of people do the BU Exams on various tables and correlate the factors with the scores. I plan to do this for myself and my students in the future. I also hope some AZBers do the same and share their results.

I look forward to getting feedback from AZB'ers after they take measurements on their favorite tables and comment on how well the TDF matches what they perceive.

Catch you later,
Dave

GeoEnvi · 06-21-2013, 08:55 AM

Not likely applicable for adjusting the scores from the BU tests, as they tend to require hitting to the same pocket, but perhaps there's another factor?

Pocket Variability Factor (PVF) - Adjusts for the variability in the other factors as you move around the table from one pocket to another.

On a poorly set-up bar table, you might have mis-matched rails or uneven pocket cuts that result in each of the pocket's measurements not being alike. If I was trying to quantify the TDF for all the tables in my league, this might be an important extra factor for fitting them all into a model.

Jaden

Quote:

Originally Posted by SpiderWebComm

There's so much that goes into how a table plays:

type of cloth, tightness of cloth, wear of cloth, type of rails, tightness of rails, type of balls, condition/cleanliness of balls, type of light, position of light, brightness/quality of light, cue ball type/size/condition, type of pocket facing/shim (material) and then, of course, the factors you pointed out with table size and pocket cut.

I see where you're going with the playability factor and it's not a bad idea --- I just think the conclusion can never be as specific as your example. Meaning, you can never say based on the 3 factors, table A plays 27% harder than table B.

The specificity of your result is just too great for something that is clearly subjective. You can never accurately ascertain exact factors since you're not dealing with tables made of the same material and manufactured the same way. For example, the pocket facings/shims can be made of different material and installed WAY differently from table to table and that plays a huge role is whether or not the pocket takes a shot.

Therefore, you can never have a result down to a single percentage and have it mean anything other than conjecture.

I don't think there's any way to scientifically determine table difficulty without having a player play the ghost 100 racks on table A and compare to table B. You might have a bar box that plays tough as hell (generally speaking) and a 5x10 that just accepts everything and has perfect speed.

The rating system would be more meaningful if you changed your calculations in order to reduce your resultants down to 5: super easy, easy, par, hard, very tough

How much harder (%-wise) is an easy table compared to a hard table? You'd never know without collecting data.

It's going to have a lot to do with the type of player, do they finesse the balls, do they slam everything, do they try to play pinpoint shape, do they shoot for general areas???

There is an nth degree of depth to the level of difficulty a certain table plays for different players.

For a while I couldn't play well on a diamond proam because I was used to shooting for center pocket, and I couldn't understand why I could consistently run out on a gold crown with 3 7/8" pockets but would hang balls on a 4.5" diamond.

I've adjusted because I realized that I have to shoot for a specific part of the pocket on a diamond and not just shoot center pocket on every shot.

I don't necessarily like it, it adds a different dimension to the game, but I can play well on a diamond now though.

That's why I preferred the tight pockets of the diamond that Glen did up at the golden fleece, I could aim for center pocket and fire away...

Of course, from what I understand, they only allow one hole on that table now...I got to play rotation games on it after it was first done though...

Jaden

dr_dave · 06-21-2013, 08:59 AM

Quote:

Originally Posted by bdorman

Very interesting. I can't wait to measure the table at our community center. I'm sure it's well under 1.0

Please post the info and your impressions after you do this.

Quote:

Originally Posted by bdorman

The only limitation I see is using the table score to adjust the shooter's score. There is a very good chance that the shooter would have scored nearly as well on a more difficult table since most(?) of the drills are more about CB positioning than OB pocketing. Likewise, a shooter wouldn't necessarily score 20% higher on an easy table than he did on his tough table. You could probably apply another factor to account for pocketing vs. positioning, but I can feel Occam's Razor beginning to cut.

Well stated. I agree completely ... especially concerning "Occam's Razor."

Regards,
Dave

Mr. Bond · 06-21-2013, 08:59 AM

Quote:

Originally Posted by SpiderWebComm

There's so much that goes into how a table plays:

type of cloth, tightness of cloth, wear of cloth, type of rails, tightness of rails, type of balls, condition/cleanliness of balls, type of light, position of light, brightness/quality of light, cue ball type/size/condition, type of pocket facing/shim (material) and then, of course, the factors you pointed out with table size and pocket cut.

I see where you're going with the playability factor and it's not a bad idea --- I just think the conclusion can never be as specific as your example. Meaning, you can never say based on the 3 factors, table A plays 27% harder than table B.

The specificity of your result is just too great for something that is clearly subjective. You can never accurately ascertain exact factors since you're not dealing with tables made of the same material and manufactured the same way. For example, the pocket facings/shims can be made of different material and installed WAY differently from table to table and that plays a huge role is whether or not the pocket takes a shot.

Therefore, you can never have a result down to a single percentage and have it mean anything other than conjecture.

I don't think there's any way to scientifically determine table difficulty without having a player play the ghost 100 racks on table A and compare to table B. You might have a bar box that plays tough as hell (generally speaking) and a 5x10 that just accepts everything and has perfect speed.

The rating system would be more meaningful if you changed your calculations in order to reduce your resultants down to 5: super easy, easy, par, hard, very tough

How much harder (%-wise) is an easy table compared to a hard table? You'd never know without collecting data. Even then, you'd never have a margin of error within 1%. You'd have to round to the nearest 10 just to account for variation in a player's ability from day to day.

I hear what you're saying and I agree. But, the pocket information is not without merit.
It is real and relevant, and without a doubt, gives you very specific insight as to how a table will play, regardless of the various other factors involved. Is the pocket info all that matters ? Certainly not, but at the same time, having this information is certainly better than not having it.

GeoEnvi · 06-21-2013, 09:01 AM

Quote:

Originally Posted by Mr. Bond

Dave, what is the presumed angle of the cushion facings?

And, do we not suppose that this angle is inconsistent from table to table?

And if so, does this angle not make a difference when it comes down to what stays in the pocket and what doesn't?

I think the Table Angle Factor takes care of the presumed angle of cushion facings.

Clearly, the shallower angle facings have higher difficulty factor than the steeper facings. Makes sense to me, given that a shallower cut would likely deflect a ball more toward the other facing than the shelf. Unless I'm getting it backwards, a shallower cut would result in more 'rattles' than a steeper cut for the same shelf.

dr_dave · 06-21-2013, 09:01 AM

Quote:

Originally Posted by Jaden

I think that what you're describing would only be the case if you were attempting to discern the level of the player with this. It is more about the difficulty of the table.

There is room for improvement, but then you're getting too deep into the weeds. and it's time to take a drop.

I think what Dave has done here is great without getting too deep in the weeds.

Thanks for the input. I agree.

Quote:

Originally Posted by Jaden

Hell, I could see writing an app with this formula for checking a table on the fly.

That's a great idea. Do it.

Catch you later,
Dave

Bob Jewett · 06-21-2013, 09:03 AM

Quote:

Originally Posted by dr_dave

... I will be curious to see what you guys think, and I look forward to your suggestions and feedback. ...

I think that the ideal measure would be the size of the pocket as a function of speed, angle and spin on the shot but that is much, much harder to measure than the factors above. It also has a lot more dimensions. It would be nice to have a comparison of the two methods over a variety of tables, but that's probably a few-month project.

As pointed out above, lousy pocket facings can make a table play much more difficult on some shots but I see no easy way to quantify that other than by a lot of shots to determine the effective pocket size.

dr_dave · 06-21-2013, 09:04 AM

Quote:

Originally Posted by Mr. Bond

Dave, what is the presumed angle of the cushion facings?

The angle is not presumed ... it is determined from the (mouth - throat) difference. For the "standard" table (PAF = 1.00), the pocket angle is close to the WPA spec (142 degrees).

Quote:

Originally Posted by Mr. Bond

And, do we not suppose that this angle is inconsistent from table to table?

The pocket angle can vary significantly among different table brands, models, and builds.

Quote:

Originally Posted by Mr. Bond

And if so, does this angle not make a difference when it comes down to what stays in the pocket and what doesn't?

The pocket angle can make a big difference. That's what the "pocket angle factor (PAF)" is for.

Regards,
Dave