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

#### dr_dave

##### Instructional Author
Gold Member
Silver Member
Why is pool's degree program figured on Dr. Dave's drills?
The drills in the BU Exams are not "Dr. Dave's." They came from a wide range of sources, but mostly from the Video Encyclopedia of Pool Practice (VEPP), for which Bob Jewett was co-author and a major influence. Also, the BU Exam drills and scoring system were developed with input from the founding professors of the BU:

Again the BU Exams are not just from me.

Why wouldn't it be based on one's average score while playing an equal-offense model?
That would be a good alternative system. Why don't you pursue this with your own set of founding professors and website development effort. I would be happy to take your exams if you did.

Regards,
Dave

#### ideologist

##### I don't never exaggerate
Silver Member
Do you have a way to account for cloth and rail types?

#### dr_dave

##### Instructional Author
Gold Member
Silver Member
The Pocket Angle Factor increases in a level progression from tier to tier of the "mouth-throat difference". I think they should increase geometrically. Not necessarily "much" higher, but higher. But, firguring out what is a correct geometric progression would have to be subjective, I think.

I think an average number for the PAF can be very inaccurate. On a soft table some shots off the point and rail will go that just won't go on a "hard" table. A geometric progression might capture a better approximation but still not tell the whole story.

I'm not a mathematician or engineer so I don't have any specific suggestions for improvement. That's your job. : )
I also had the sense that this factor might vary "geometrically." It also interacts in a fairly complicated way with shelf depth, but this "interaction" would be very difficult describe adequately without a lot of data.

A I get more data in the future, I can easily modify the numbers in the different ranges for the pocket angle factor (PAF). Until then, any changes would be total guesswork. BTW, the little analysis I did seemed to imply that the pocket angle effect was fairly linear (keeping everything else the same), but nothing beats hard data.

Thanks again for you input,
Dave

#### dr_dave

##### Instructional Author
Gold Member
Silver Member
Very good work, your not a Dr for no reason!!! NEver doubted ya for a minute. This IMO will give a balance to the equipment as good as can be done-for all potable balls. very impressive.

very best regards
eric:smile::smile:
Thank you for the positive feedback. I appreciate it.

BTW, I won't feel totally comfortable with my "Dr." title until I earn a Billiard University (BU) "Doctorate." I think it is a realistic goal (in the next year or two), but I still have more work to do. In the meantime, you should probably just refer to me as "Dave" (or "Dean Dave" if you prefer). :grin:

Thanks again,
Dave

#### BRussell

##### AzB Silver Member
Silver Member
You might be right --- but that lends to the question -- why create a test that replicates the approximated outcome of playing when you can just play? Sent you a PM, btw.

I see the BU drills as a way to break pool down into basic skills and practice them. I agree with you and I think it is a mistake to try to translate the scores on his drills to actual competitive playing ability. That's like translating grades in Business school to how successful you are in business. Dave does present some info on translating BU scores to other ratings, but in fairness, I never saw that as the primary purpose of the drills, and I don't think he focuses on that in his presentation.

Maybe I'm wrong and he does see it primarily as a system for rating competitive playing rather than skill development. Dave?

Last edited:

#### dr_dave

##### Instructional Author
Gold Member
Silver Member
Dave,

I like your formula for determining pocket toughness. It's very similar to the one I offered in an article I wrote, and was published here on AZ Billiards, a couple of years ago. Our two formulas are very similar in that they both consider pocket opening, throat opening, and shelf depth. Of the two, I think I like your formula best. Good job.

Roger
Thanks Roger. I remember your article. That's too bad that it's no longer online. I hope that gets fixed soon.

Regards,
Dave

#### SpiderWebComm

##### HelpImBeingOppressed
Silver Member
The drills in the BU Exams are not "Dr. Dave's." They came from a wide range of sources, but mostly from the Video Encyclopedia of Pool Practice (VEPP), for which Bob Jewett was co-author and a major influence. Also, the BU Exam drills and scoring system were developed with input from the founding professors of the BU:

Again the BU Exams are not just from me.

That would be a good alternative system. Why don't you pursue this with your own set of founding professors and website development effort. I would be happy to take your exams if you did.

Regards,
Dave
I have a really hard time believing that this collection of top instructors came up with that criteria to determine playing ability and not one person suggested an average on equal offense - which is basically the foundation of every single-player sport in the world? Why would pool be different than other sports?

If Butch Harmon, Sean Foley, David Leadbetter, Jim McLean and Hank Haney all came up with a new way to handicap golfers that didn't include playing a round, they'd all be laughed at. I'm still struggling to see why pool needs to be different -- why not copy the successful sports instead of having the sport that's doing the worst make-up its own methods? I'm not knocking - just trying to understand as I respect you and every person on that panel.

I don't want to hijack this thread more than I have on this particular topic. Back to the unified M-theory for factoring table difficulty.

P.S.
Dr. Dave - clearly, I'm a fan of outcome-based education Regardless of what your test scores are on any topic --- either you can execute or you can't.

Last edited:

#### dr_dave

##### Instructional Author
Gold Member
Silver Member
Do you have a way to account for cloth and rail types?
No. But they could easily be additional factors to add to the formula. The difficult part is deciding what to measure and how, and deciding how to set appropriate factor values for different ranges. I'm open to ideas on this.

Regards,
Dave

#### Magog30

##### AzB Silver Member
Silver Member
I like the idea, but I would prefer to leave table size out of the equation and focus on how easy the pockets play.

#### Fatboy

##### AzB Silver Member
Silver Member
Thank you for the positive feedback. I appreciate it.

BTW, I won't feel totally comfortable with my "Dr." title until I earn a Billiard University (BU) "Doctorate." I think it is a realistic goal (in the next year or two), but I still have more work to do. In the meantime, you should probably just refer to me as "Dave" (or "Dean Dave" if you prefer). :grin:

Thanks again,
Dave

i like calling you "Doc" with all due respect. and i'm not being sarcastic. I have watched you for years(and your videos) and chatted a little with you, and your doing great work. I asked about accounting for different pockets profiles to make the BU system a bit more accurate and poof!!! a solution. I'm sure others asked and you thought of it-i'm not taking credit for anything.

I'm going to get the calipers out and measure my pockets now. they are tough, which what prompted me to ask the question in the first place. I'm sure my score would be 35% lower on my table for most players. I is my postulate(I went to school to:wink that the more difficult the pockets the more adverse effect it will have on weaker players, so we then need to develop a curve for that after the pocket size coefficient as it relates to players respective strength in pocketing balls has been perfected<----it never ends,:wink::wink::grin:

Silver Member

#### dr_dave

##### Instructional Author
Gold Member
Silver Member
I see the BU drills as a way to break pool down into basic skills and practice them. I agree with you and I think it is a mistake to try to translate the scores on his drills to actual competitive playing ability. That's like translating grades in Business school to how successful you are in business. Dave does present some info on translating BU scores to other ratings, but in fairness, I never saw that as the primary purpose of the drills, and I don't think he focuses on that in his presentation.
Well stated. That is the primary purpose for the BU Exam and diploma process.

For those interested, here's the chart that shows how the BU score roughly correlates to playing ability. So far, the BU score and rating data in the BU thread seem to correlate fairly well with playing ability (both perceived and as roughly measured by the 10-ball "playing the ghost" drill).

Maybe I'm wrong and he does see it primarily as a system for rating competitive playing rather than skill development. Dave?
You are not wrong.

BTW, here's the Vision/Mission statement from the BU website:

to provide online assessment tools, a rating system, and learning resources to help pool players strive for and achieve excellence, and to officially acknowledge excellence through the awarding of diplomas.

The "rating system" is part of it, but not the main or only part.

Catch you later,
Dave

#### dr_dave

##### Instructional Author
Gold Member
Silver Member
I have a really hard time believing that this collection of top instructors came up with that criteria to determine playing ability

Catch you later,
Dave

#### SpiderWebComm

##### HelpImBeingOppressed
Silver Member

Catch you later,
Dave

I was just hung up on the "rating system" part--- based on your mission statement, you guys prob hit a home-run on the other 2.

#### dr_dave

##### Instructional Author
Gold Member
Silver Member
I like the idea, but I would prefer to leave table size out of the equation and focus on how easy the pockets play.
... but shot difficulty depends as much on shot distance (and hence table size) as it does on how "tight" the pocket is. If you prefer, you can leave out the table size factor. The result will be the "pocket only" difficulty factor.

Regards,
Dave

#### dr_dave

##### Instructional Author
Gold Member
Silver Member
i like calling you "Doc" with all due respect. and i'm not being sarcastic. I have watched you for years(and your videos) and chatted a little with you, and your doing great work.
Thank you!

I asked about accounting for different pockets profiles to make the BU system a bit more accurate and poof!!! a solution. I'm sure others asked and you thought of it-i'm not taking credit for anything.
I aim to squerve. :wink:

You certainly weren't the first to suggest that equipment should somehow be factored in, but the discussion in the BU thread certainly helped push me to do this. Thank you for helping with the push.

I'm going to get the calipers out and measure my pockets now. they are tough, which what prompted me to ask the question in the first place. I'm sure my score would be 35% lower on my table for most players.
Please report back with the TDF for your table to see how close it comes to 1.35 (your perceived value).

I is my postulate(I went to school to:wink that the more difficult the pockets the more adverse effect it will have on weaker players
I agree with that 100%.

Best regards,
Dave

#### dr_dave

##### Instructional Author
Gold Member
Silver Member
We could add a separate factor for those, but I wanted to keep the number of measurement and calculations as few as possible. Also, with most equipment (and in the WPA specs), the side pocket geometry is usually related to the corner pocket geometry (although, I know this isn't always the case).

Thanks for the input,
Dave

#### dr_dave

##### Instructional Author
Gold Member
Silver Member
I really can't grasp how the pocket angle effect could be linear except up to a certain point as it gets greater. At that certain point it seems to me it would have to begin increasing geometrically.
I would agree with this.

The only way I can think of to test this is to shoot balls at the pocket facing mechanically from different angles and do the same thing on another table with a different pocket profile.
Bob Jewett and I have done tests like this for a small number of tables, and it takes a very long time to do it well, but that is a good idea. BTW, Bob's recent articles in Billiards Digest are on this topic. Maybe Bob can post the articles online soon. Bob, if and when you do this, please try to remember to post the links here for people (me and others) who are interested.

Regards,
Dave

#### Mr. Bond

##### Orbis Non Sufficit
Gold Member
Silver Member
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).

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

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

Regards,
Dave

I was referring to the vertical angle, or pitch of the cushion facings, not the angle of the pocket 'cut'. Is the vertical angle included in the PAF?

#### Fatboy

##### AzB Silver Member
Silver Member
my pockets are 3.99" at the points, 3.75" at the back and the shelf is about 1"(Standard GC shelf) in the middle-had to eyeball that. 9' table.

so that comes to about 110% with the math you suggested.

Therefore(if i'm understanding this right) my table would get a 10% increase in scoring due to the tight pockets. If thats the premise here, its flawed. My table is much tougher than a 10% adjustment would account for.

this might be too complex to really get a accurate number on, the down angle of the pocket facing has lots to do with how a pocket takes balls.

The opening at the points IMO needs to be weighted more than the ratio of the back of the pocket and the points. Because more shots are missed by hitting the points than a pocket rejecting a ball. Therefore the distance between the points MUST be given more weight., shelf depth is also a bigger factor for balls to stand up than the angle of the opening(ratio of points and throat) of the pocket facings.

I believe this is a good start, however when i measured my pockets, 1.0925 exactly is not a accurate representation of how difficult my table is. So I think the numbers need to be re-worked. however its still a great starting point.

best
eric