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

dr_dave

Instructional Author
Gold Member
Silver Member
Dave,

I measured the angle directly in a few places on the table, to make sure things were consistent. I was going to double check with the throat measurements, but I didn't get a measurement 2" back from the front (that's not the back of these pockets due to the shallow angle)
lmb4tKa.jpg


It turns out I read the angle wrong, as the numbers were obscured. It's really showing 146 degrees, not 134. The PAF now goes from .94 to 1.09.

This is showing me that the PAF is accounting for the difficulty with bobbles. No problem there, now.

The measurements I got:
7' home table (legacy)
Points: 5.125"
Throat (at back of facing, very close to 2" back): 4"
Shelf: just over 1.5"
Facing angle: 146 degrees (direct measurement)
Facing down angle: 14 degrees

So this gives it:
TSF: 0.85
PSF: 0.88
PAF: 1.09
PLF: 1.00
TDF: 0.82

0.82 is way more in line with my expectations than the 0.72 that I came up with earlier.
Thanks for the info. I'll add your table to the list.

I think what is not shown in these factors is how they affect the play of the game. With these angles, anything harder than a slow roll will bobble if you're not playing them like 4" pockets. This limits what you can do with english and position play somewhat. It's not that certain things are harder, certain things are just not going to happen on this table because of the pockets.
Good points. There are certainly many factors that affect how difficult a table plays for different players, games, and shot types. The TDF is meant just to provide an average measure of fundamental toughness for comparison purposes.

Thanks again for posting,
Dave
 

dr_dave

Instructional Author
Gold Member
Silver Member
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: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)
dr_dave -- 10':1.10 -- 4":1.20 -- 3/4":1.02 -- 1 7/8":1.03 -- 1.39 (fictitious tough 10' table example)
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)
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)
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 -- 143deg: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 -- 141deg: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)
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)
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)
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 (Brunswick Gold Crown home table)
iusedtoberich -- 9':1.00 -- 5 1/8":0.88 -- 1":1.05 -- 1 1/2":0.97 -- 0.90 (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 (Brunswick Gold Crown III)
StraightPoolIU -- 9':1.00 -- 4 7/8":0.91 -- 3/4":1.02 -- 1 1/4":0.95 -- 0.88 (Brunswick Gold Crown I)
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)
RobMan -- 9':1.0 -- 5": 0.88 -- 3/4":1.01 -- 1.5":0.97 -- 0.86 (Brunswick Gold Crown)
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)
jtaylor996 -- 7':0.85 -- 5 1/8":0.88 -- 146deg:1.09 -- 1.51":1.00 -- 0.82 (7' Legacy home table)
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)
 

Sloppy Pockets

AzB Silver Member
Silver Member
Dave, I have an interesting subjective evaluation to bring up regarding my table.

Last fall, after having my slates separate twice on me, A.E. Schmidt (maker of the table) offered to send me new replacement slates free of charge. The dealer I bought the table from agreed to exchange them and reinstall the cloth for the same low price. Yeah, amazing, but that's not why I'm bringing it up here.

The company is now getting slates out of Brazil instead of Italy. The new slates come in with the pocket cutouts already done and the shelf edges radiused. The edge radius on the Brazilian slates is quite a bit larger, making the effective pocket shelf about 1/4" shallower as can be seen in the before and after photos.

The effect of this slight change is enormous. Balls that rattled violently and then got spit out drop in just like they are supposed to. I would never have thought such a small change could effect the way a table plays, but the change was noticeable immediately. The table went from frustrating and somewhat difficult to stupid easy just like that. I can fire balls in pretty hard now when I need to instead of having to baby them.

The interesting part is that when I went to post this info I noticed that according to your PLF table there is no change in difficulty. Both shelf depths are within the range you specify for a difficulty factor of 1.00, and yet, anybody beyond a rank beginner could tell that the table plays easier now, and yet the "total difficulty factor" remains unchanged.

I'm curious to hear what you think about this?
 

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dr_dave

Instructional Author
Gold Member
Silver Member
Dave, I have an interesting subjective evaluation to bring up regarding my table.

Last fall, after having my slates separate twice on me, A.E. Schmidt (maker of the table) offered to send me new replacement slates free of charge. The dealer I bought the table from agreed to exchange them and reinstall the cloth for the same low price. Yeah, amazing, but that's not why I'm bringing it up here.

The company is now getting slates out of Brazil instead of Italy. The new slates come in with the pocket cutouts already done and the shelf edges radiused. The edge radius on the Brazilian slates is quite a bit larger, making the effective pocket shelf about 1/4" shallower as can be seen in the before and after photos.

The effect of this slight change is enormous. Balls that rattled violently and then got spit out drop in just like they are supposed to. I would never have thought such a small change could effect the way a table plays, but the change was noticeable immediately. The table went from frustrating and somewhat difficult to stupid easy just like that. I can fire balls in pretty hard now when I need to instead of having to baby them.

The interesting part is that when I went to post this info I noticed that according to your PLF table there is no change in difficulty. Both shelf depths are within the range you specify for a difficulty factor of 1.00, and yet, anybody beyond a rank beginner could tell that the table plays easier now, and yet the "total difficulty factor" remains unchanged.

I'm curious to hear what you think about this?
Thank you for sharing this. Did anything else change (e.g., with the cushion cloth, humidity, or cleanliness)? It seems odd that the table plays so differently with such a small change in shelf (with nothing else changing).

BTW, with your table (with a PAF of 1.10), you should be using the 3rd row in the PLF factor table below:

table_difficulty_PLF.jpg

Your shelf numbers happen to be right at the cutoffs between the ranges. With the original shelf depth of 1 3/4", the PLF is 1.00. If the depth were a hair larger than this (> 1 3/4"), the PLF would be 1.03. With the new shelf depth of 1 1/2", the PLF is 0.99. So changing from slightly more than 1 3/4" to 1 1/2" corresponds to a change in difficulty (according to the PLF table) of about 4% (from 1.03 to 0.99). Maybe this difference should be greater based on your experience, but it is tough to say without more examples and further study.

Catch you later,
Dave
 

hustlefinger

Registered User
Silver Member
Looks like you've done a lot of work, great job Dave. You might want to consider a factor for the side pockets in your overall "Table Difficulty Factor." We've got tables with 4.5 inch side pockets and they play much more difficult than a table with 5 inch side pockets.
 

Sloppy Pockets

AzB Silver Member
Silver Member
Thank you for sharing this. Did anything else change (e.g., with the cushion cloth, humidity, or cleanliness)? It seems odd that the table plays so differently with such a small change in shelf (with nothing else changing).

BTW, with your table (with a PAF of 1.10), you should be using the 3rd row in the PLF factor table below:

Your shelf numbers happen to be right at the cutoffs between the ranges. With the original shelf depth of 1 3/4", the PLF is 1.00. If the depth were a hair larger than this (> 1 3/4"), the PLF would be 1.03. With the new shelf depth of 1 1/2", the PLF is 0.99. So changing from slightly more than 1 3/4" to 1 1/2" corresponds to a change in difficulty (according to the PLF table) of about 4% (from 1.03 to 0.99). Maybe this difference should be greater based on your experience, but it is tough to say without more examples and further study.

Yeah, I just noticed that about the PAF requiring the use of the figures in the third row (which is definitely the right way to go IMHO). Plus, I really could have "nudged" the shelf depth in either direction in both cases and it would fall into the next brackets. Just a 1/32" either way puts you clearly in another bracket. Hard to measure exactly where the beginning of the edge radius really is, or to tell which way to go when you are right on the cusp like that. I still think the table plays lot easier now than a 1/4" difference in shelf depth would have predicted.

BTW notice I said it plays easier, not differently. Nothing else about the table was changed. Same cushions, same cloth (maybe stretched a wee bit tighter this time), same pockets angles. The only thing that is really different is that the table plays more fair now. I think that the combination of open pocket facing angles and deep shelves create an exercise in frustration, but if you reduce the shelf depth to just the right amount to allow the balls to pass over open space and let gravity take over, the whole character of the table feels different.

Balls that hit inside the points go down like they should. This relieves some of the anxiety you have when putting a good stroke on the ball to move it around the table, so you can open your stroke up without anticipating that nerve-racking rattle. You shoot straighter, with more confidence, and it is just way more enjoyable. Nobody likes being cheated out of a nice shot by a gaff pocket.

I think the game you enjoy has a lot to do with it. The way my table is right now, I think it might be perfect to break Mosconi's 14.1 record on (by somebody besides me Lol). The way it was before, you'd be playing real timid because there was always a good chance that a ball hit much harder than pocket speed might come flying back out of the pocket, ending your run.
 

book collector

AzB Silver Member
Silver Member
I find it much harder to play well with loose, faulty equipment, than extremely tight equipment that is consistent.
Bad sets of balls , loose rails , not a level surface.
I used to play in a room where the main table was set up to be a real home town advantage.
I actually learned to play really well on it , I also saw a lot of champions play on it.
Some of them played great within 15 minutes, some played pretty bad because they were used to playing on only the best equipment.
 

dr_dave

Instructional Author
Gold Member
Silver Member
Looks like you've done a lot of work, great job Dave.
It was a lot of work, and I incorporated input from many people. Thank you for the supportive comment.

You might want to consider a factor for the side pockets in your overall "Table Difficulty Factor." We've got tables with 4.5 inch side pockets and they play much more difficult than a table with 5 inch side pockets.
I agree with you that this can be an important factor on some tables (e.g., on a Valley bar box where the corners play like giant buckets and the sides are very stingy). There are also many other things that would be nice to consider (e.g., vertical facing angle, ball and cloth conditions, table levelness, etc.), but I wanted to keep things as simple as possible while still capturing the most important and easily-measured parameters.

Thanks for your input,
Dave
 

dr_dave

Instructional Author
Gold Member
Silver Member
The way my table is right now, I think it might be perfect to break Mosconi's 14.1 record on (by somebody besides me Lol). The way it was before, you'd be playing real timid because there was always a good chance that a ball hit much harder than pocket speed might come flying back out of the pocket, ending your run.
Now that your table is playing so much easier, are you ready to give the BU Exams a go? If so, please post your scores (and videos is possible) on the AZB BU thread. If you tried the exams before your changed the slate, it would be interesting to know how much your score and rating improves with the easier shelf.

Catch you later,
Dave
 

Sloppy Pockets

AzB Silver Member
Silver Member
Now that your table is playing so much easier, are you ready to give the BU Exams a go? If so, please post your scores (and videos is possible) on the AZB BU thread. If you tried the exams before your changed the slate, it would be interesting to know how much your score and rating improves with the easier shelf.

Catch you later,
Dave

C'mon, Dave, it's still pool. It may be easier, but it's never easy. Lol

I didn't take the exam before I had the slates changed, but I wouldn't expect the score to change all that much compared to how much nicer the table is to play on now. Like I said, it's more of a subjective thing. All I know is there's a lot more balls going past the pockets points and staying there than there was before. Hard to put a number on that, though.
 

dr_dave

Instructional Author
Gold Member
Silver Member
C'mon, Dave, it's still pool. It may be easier, but it's never easy. Lol

I didn't take the exam before I had the slates changed, but I wouldn't expect the score to change all that much compared to how much nicer the table is to play on now. Like I said, it's more of a subjective thing. All I know is there's a lot more balls going past the pockets points and staying there than there was before. Hard to put a number on that, though.
Regards, please consider trying the BU Exams and posting scores.

BTW, I think the BU Exams are a good way (in addition to the TDF) to "put a number" on how difficult a table plays.

Thanks,
Dave
 

jburkm002

AzB Silver Member
Silver Member
I have had this discussion many times. I play on barboxes. Rarely is there a diamond. There are fast, slow, tight and buckets. The first diamond I played on had tight pockets and I saw many bobbles. The last diamond I played on had much more forgiving pockets. I like diamonds to a degree. My only gripe is they roll to darn easy. I watch pros and amateurs tapping balls that would roll 20 feet if there were no pockets. Seems the game has become easier on diamonds. No need to stroke balls like on an old valley. I think the cloth has a lot to do with table difficulty.

Sent from my SCH-I545 using Tapatalk
 

dr_dave

Instructional Author
Gold Member
Silver Member
I have had this discussion many times. I play on barboxes. Rarely is there a diamond. There are fast, slow, tight and buckets. The first diamond I played on had tight pockets and I saw many bobbles. The last diamond I played on had much more forgiving pockets. I like diamonds to a degree. My only gripe is they roll to darn easy. I watch pros and amateurs tapping balls that would roll 20 feet if there were no pockets. Seems the game has become easier on diamonds. No need to stroke balls like on an old valley. I think the cloth has a lot to do with table difficulty.
Agreed. Cloth speed can make a big difference, depending on the player and the game being played.

Regards,
Dave
 

jtaylor996

AzB Silver Member
Silver Member
Speaking of... built a bucket ball polisher and shined up my 8 year old super aramith pros, and used a little meguire's gold class wax. My already fast table got a lot faster. English is vastly more effective... and I've entered scratch city.

Having to think about scratches three rails ahead will really stretch your position play!
 

Ralph Kramden

BOOM!.. ZOOM!.. MOON!
Silver Member
Agreed. Cloth speed can make a big difference, depending on the player and the game being played.

Regards,
Dave

I agree that pocket size, facing angles, shelf depth and cloth speed effect how the table plays.

A table toughness factor, that should also be taken into consideration, are the pocket facings.

Facing materials, facing thickness and facing hardness can make tables play harder or easier.
 

dr_dave

Instructional Author
Gold Member
Silver Member
I agree that pocket size, facing angles, shelf depth and cloth speed effect how the table plays.

A table toughness factor, that should also be taken into consideration, are the pocket facings.

Facing materials, facing thickness and facing hardness can make tables play harder or easier.
Agreed. Facing properties can make a big difference, as can humidity, cleanliness, table levelness, rail and cushion type and condition, cloth type and condition, etc!

However, I wanted to keep things as simple as possible while still capturing the most important and easily-measured parameters.

Thanks for the input,
Dave
 

dr_dave

Instructional Author
Gold Member
Silver Member
Anybody have any tables to add to the list, maybe some tough gambling tables out there?

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: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)
dr_dave -- 10':1.10 -- 4":1.20 -- 3/4":1.02 -- 1 7/8":1.03 -- 1.39 (fictitious tough 10' table example)
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)
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)
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 -- 143deg: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 -- 141deg: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 (average-difficulty table)
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)
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)
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)
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 (Brunswick Gold Crown home table)
iusedtoberich -- 9':1.00 -- 5 1/8":0.88 -- 1":1.05 -- 1 1/2":0.97 -- 0.90 (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 (Brunswick Gold Crown III)
StraightPoolIU -- 9':1.00 -- 4 7/8":0.91 -- 3/4":1.02 -- 1 1/4":0.95 -- 0.88 (Brunswick Gold Crown I)
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)
RobMan -- 9':1.0 -- 5": 0.88 -- 3/4":1.01 -- 1.5":0.97 -- 0.86 (Brunswick Gold Crown)
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)
jtaylor996 -- 7':0.85 -- 5 1/8":0.88 -- 146deg:1.09 -- 1.51":1.00 -- 0.82 (7' Legacy home table)
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)
 

derangedhermit

AzB Gold Member
Gold Member
Silver Member
What is the rationale for not taking into consideration (or not stating how they are taken into consideration) the two side pockets? I would say one substantial difference in playing on a Valley 7' and a Diamond 7' is the side pocket play.

PAF (facing angle factor) and PLF (shelf depth) are each dependent on the other. The PLF table attempts to capture the dependence on the PAF. There is one error or at least extraneous qualification in that table: "PSF≤0.90 or PAF≤0.90". There are no values below 0.94 in the PAF table.

The PAF table does not attempt to capture the PLF dependence. If the shelf is shallow, the facing angle becomes less important. That "less important" brings up that I think perhaps weighting factors are needed.

The approach you have taken is to normalize (probably the wrong term) each of the four parameters around 1.0 and then multiply them together to get your adjustment factor for table difficulty. I think this is fine for showing the approach and allowing discussion of each component. My preference for usage would be to have an equation to plug in the physically measured values and produce the TDF directly, without the intermediate rounding or grouping.

Last, I think aiming offset (as defined in http://billiards.colostate.edu/technical_proofs/TP_3-5.pdf) may be a significant factor in TDF, if it varies significantly based on combinations of the pocket parameters PSF, PAF, and PLF. I see what I believe is +/- 0.5" in aiming offset in http://billiards.colostate.edu/technical_proofs/TP_3-6.pdf. According to the TP 3.6 offset chart, I would say offfset is to some degree understood as players advance, but that graph for offset shows that the needed offset is anything but intuitive.

If a study manipulating PSF, PAF, and PLF shows little impact on that graph, then there is no need to incorporate aiming offset into TDF.

However, I would say that a fundamental goal of pocket design should be that aiming offset be a "smooth" function of shot angle. One could set further goals for specific cases, such as minimizing aiming offset, to make the table easier to play. But I think the baseline goal should be that an intuitive understanding of the needed offset can be developed over time. A simpler shot-angle / aiming offset relationship than the ones in TP 3.5-3.7 is needed (the offset graph in TP 3.8 appears to be missing).

I think the same applies to effective pocket size. I find the graph of effective pocket size in TP 3.6 (corner pocket, slow shot) to be contrary to my experience and feeble calculations. It seems to show that there is a range of angles close to the rail, of about 5 degrees (say 38-43 degrees), where the effective pocket size is about 0.25" larger than a straight-in shot (e.g. object ball on spot). I need to dig into the math, since I am sure the error is mine.

In any case, if TP 3.6 reflects actual playing conditions, then I submit varying pocket parameters so that slow corner pocket shots' effective pocket size graph more like fast pocket shots (TP 3.8), or, to a lesser extent, side pocket effective size (TP 3.5 and 3.7) - not necessarily in difficulty, but in predictability and intuitiveness, would be a substantial improvement. If there is a combination of pocket parameters that makes effective pocket size more predictable and consistent across the range of pocketable shot angles, that table will be better to play on - not necessarily easier, since the pockets could still be made arbitrarily difficult, but less bewildering.
 
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dr_dave

Instructional Author
Gold Member
Silver Member
What is the rationale for not taking into consideration (or not stating how they are taken into consideration) the two side pockets?
The side pockets are not taken into consideration separately; although, they easily could be with an additional factor. The main reasons for excluding them here include:

1.) The corner pocket difficulty is a much bigger concern with most games and most tables, and for most people.

2.) I wanted to limit the number of measurements and calculations to as few as possible to keep things as simple as possible while still capturing the most important factors that contribute to table difficulty (for most people and most games).

PAF (facing angle factor) and PLF (shelf depth) are each dependent on the other. The PLF table attempts to capture the dependence on the PAF. There is one error or at least extraneous qualification in that table: "PSF≤0.90 or PAF≤0.90". There are no values below 0.94 in the PAF table.
Thank you for pointing this out. I've eliminated the unused range.

The PAF table does not attempt to capture the PLF dependence. If the shelf is shallow, the facing angle becomes less important. That "less important" brings up that I think perhaps weighting factors are needed.
Agreed, but that's what the dependence of PLF on PAF attempts to quantify.

The approach you have taken is to normalize (probably the wrong term) each of the four parameters around 1.0 and then multiply them together to get your adjustment factor for table difficulty. I think this is fine for showing the approach and allowing discussion of each component. My preference for usage would be to have an equation to plug in the physically measured values and produce the TDF directly, without the intermediate rounding or grouping.
I agree, an equation would be nice, except:

1.) The Equation would be extremely complicated.

2.) Pool players don't like equations and complicated calculations.


Last, I think aiming offset (as defined in http://billiards.colostate.edu/technical_proofs/TP_3-5.pdf) may be a significant factor in TDF, if it varies significantly based on combinations of the pocket parameters PSF, PAF, and PLF. I see what I believe is +/- 0.5" in aiming offset in http://billiards.colostate.edu/technical_proofs/TP_3-6.pdf. According to the TP 3.6 offset chart, I would say offfset is to some degree understood as players advance, but that graph for offset shows that the needed offset is anything but intuitive.

If a study manipulating PSF, PAF, and PLF shows little impact on that graph, then there is no need to incorporate aiming offset into TDF.
The TDF is an average number that applies to a wide range of shots, over a wide range of people, over various types of games. It doesn't take individual shots at different angles, distances, and pocket-center offsets into consideration (not directly anyway).


However, I would say that a fundamental goal of pocket design should be that aiming offset be a "smooth" function of shot angle. One could set further goals for specific cases, such as minimizing aiming offset, to make the table easier to play. But I think the baseline goal should be that an intuitive understanding of the needed offset can be developed over time. A simpler shot-angle / aiming offset relationship than the ones in TP 3.5-3.7 is needed (the offset graph in TP 3.8 appears to be missing).
Good luck with that ... changing the design of the pockets. I'm not saying it won't happen, but it certainly wouldn't be easy.


I think the same applies to effective pocket size. I find the graph of effective pocket size in TP 3.6 (corner pocket, slow shot) to be contrary to my experience and feeble calculations. It seems to show that there is a range of angles close to the rail, of about 5 degrees (say 38-43 degrees), where the effective pocket size is about 0.25" larger than a straight-in shot (e.g. object ball on spot). I need to dig into the math, since I am sure the error is mine.

In any case, if TP 3.6 reflects actual playing conditions, then I submit varying pocket parameters so that slow corner pocket shots' effective pocket size graph more like fast pocket shots (TP 3.8), or, to a lesser extent, side pocket effective size (TP 3.5 and 3.7) - not necessarily in difficulty, but in predictability and intuitiveness, would be a substantial improvement. If there is a combination of pocket parameters that makes effective pocket size more predictable and consistent across the range of pocketable shot angles, that table will be better to play on - not necessarily easier, since the pockets could still be made arbitrarily difficult, but less bewildering.
Again, it would be extremely difficult to convince the industry to fundamentally change the design of the pockets. The current design does result in some complex and interesting effects concerning effective size and effective center of the pocket at different angles and speeds (and conditions), but that's part of what makes the game so challenging and interesting (e.g., when adjusting to different tables and conditions).

BTW, the fact that the effective size of a corner pocket at slow speeds is larger at shallow angles into the rail (on most tables) has been verified experimentally (in addition to theoretically). Bob Jewett and I did a set of experiments that showed a big different in effective pocket size and center at different angles into the pocket, along with a peak at shallower angles. He wrote this up in BD a couple of years ago, but I don't think he has the articles online. Bob, are you out there listening. If so, could you post those articles? I'll send him a PM also.

Thanks,
Dave
 
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derangedhermit

AzB Gold Member
Gold Member
Silver Member
Thank you for pointing this out. I've eliminated the unused range.
Thank you. I hope the inclusion of the offset chart in TP 3.8 makes it onto your to-do list. These are very helpul documents.

I agree, an equation would be nice, except:

1.) The Equation would be extremely complicated.

2.) Pool players don't like equations and complicated calculations.

Well, you could have some code at the top of a BU web page on TDF that lets players put in the four measurements from their table and gives them the TDF number. They need not even consult any tables or read any text from the .pdf, or do any multiplication, if the TDF number is all they want.

Good luck with that ... changing the design of the pockets. I'm not saying it won't happen, but it certainly wouldn't be easy...

Again, it would be extremely difficult to convince the industry to fundamentally change the design of the pockets. The current design does result in some complex and interesting effects concerning effective size and effective center of the pocket at different angles and speeds (and conditions), but that's part of what makes the game so challenging and interesting (e.g., when adjusting to different tables and conditions).

Diamond has changed their rail/cushion design at least 3 times, I think, in 20 years, so change is going on. Valley changed their rails not that long ago. And custom rails and cushions can be (and are being) built, both by table mechanics and by folks like Ridgeback Rails. And then there are English cushions...

I have to confess that I'd like to convince you (or someone, but you're the natural candidate) to compare English rounded pocket corners (used for both snooker and pool) with US angled ones, at US (say 4.5") and snooker (say 3.5") pocket sizes. I suspect the English pockets would remove some of the steep slopes and inflection points for both effective pocket size and aiming offset. I've been looking into small British pub tables and moving onto the largest pool and snooker audience market in the world, China, and how China has decided on a combination of snooker size and shape pockets on a 9-foot table using US size balls for Chinese 8-ball. I find that choice interesting, and personal interest aside, it is a large part of the future of 8-ball.

You can buy a British bar table and have it delivered to the US from the UK for not too much money (e.g. a Supreme Winner), and I'm sure you can soon have a Chinese-spec 8-ball table delivered to the US as well from China.

Here's a link to the WPBSA 2005-2006 corner and side pocket diagrams in the happy case intellectual curiosity gets the better of you.

BTW, the fact that the effective size of a corner pocket at slow speeds is larger at shallow angles into the rail (on most tables) has been verified experimentally (in addition to theoretically). Bob Jewett and I did a set of experiments that showed a big different in effective pocket size and center at different angles into the pocket, along with a peak at shallower angles. He wrote this up in BD a couple of years ago, but I don't think he has the articles online. Bob, are you out there listening. If so, could you post those articles? I'll send him a PM also.

Thank you very much for doing that. I look forward to reading about it, and figuring out where I went wrong.

Thanks,
Lee

PS I have a 8' Diamond Pro 2014 ("blue badge"). I'll soon send you the numbers for your collection.
 
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