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

dr_dave

Instructional Author
Gold Member
Silver Member
You must have a masters degree in line-item quotations and response "break-downs."

You have a ways to go yet, however, until you have a doctoral-level like your boy Patrick Johnson. He's definitely the 7-ball above you at that!
Thanks. That's funny. :thumbup:

Catch you later,
Dave

PS: Have you tried the BU Exams yet. If so, please consider posting your score (and videos if available) on the BU thread. Thanks!

Neil

AzB Silver Member
Silver Member
Mine was done on a modified 7' table. Score of 141, effective score of 130.3. All things exactly the same on pockets, only on a 9' table, effective score of 162.8. No way just a 7' to a 9' is worth 31.5 points! Especially when on a lot of shots, the pocket size either isn't much of a factor, or is essentially no factor at all.

Sorry Dave, but I don't think the system makes a fair correlation between table sizes. However, it does between tables of the same size to a certain degree. Just how much that degree is, is questionable.

You also have to take into account the margin of error for different angle shots, and different distance of shots. A whole lot to really take into consideration. So much, that I'm not sure it would even be worth it to really get an accurate comparison.

For example- I have a 30 degree shot to the corner. If it is near the pocket, I have a much larger margin of error than if it is far from the pocket. So, on a 7' table, I have a larger margin of error than on a 9' table with both ob,s at center table, and both cb's two diamonds away with pockets of the same size. But, how does the margin of error really equate with pocket size? It will vary according to the distance, and the angle to the pocket.

If the ball is near the rail, say a ball width off the rail, now you have to consider the springiness of the rail. Soft rails will allow you to have a much larger margin of error on the shot than bouncy rails will.

So, pocket size is not the only consideration. In your drill test, take the stop shots. I can hit every one absolutely perfect, stopping stone cold dead on contact, and still get a lower score than someone on a 9' table that actually miss-hits every single shot so that the cb hits the rail and rebounds to the acceptable target zone. With that shot, pocket size is going to have very, very, little effect on making or missing the shot until you get down to a pocket size very close to the ob size.

SpiderWebComm

HelpImBeingOppressed
Silver Member
Thanks. That's funny. :thumbup:

Catch you later,
Dave

PS: Have you tried the BU Exams yet. If so, please consider posting your score (and videos if available) on the BU thread. Thanks!

I've worked up the following equation to figure out the relationship between the scoring data and my interest:

I'm still trying to figure out why it always returns 0. I'll keep working on it

iusedtoberich

AzB Silver Member
Silver Member
Dr Dave, I like very much what you are attempting to do. I have a few comments, but I will have to read through what you did thus far first, so that I can make an informed comment.

One quick comment I'd like to make, is of course there are other things missing that determine how tough a table plays. But, one common factor in almost any comparison, is to be able to measure and put a number to it. Even if that is a simple as asking a person on a scale of 1-5 how hard this table plays, all things considered. Without having a number, it is very difficult if not impossible to measure improvement, or variations.

The formulas to get the numbers can be refined over time. But with no numbers to start with, its just more black magic type stuff.

This is one thing that bugs me so much about tables. A mechanic or player will say "this table plays the way its supposed to", but there is none or little numbers behind that, which leads to the understanding of WHY the table might play that way, and why another one does not. IMO, the biggest recent debate on this is diamond rails vs GC rails and how the balls react off of them.

BRussell

AzB Silver Member
Silver Member
Nice job Dave!

It would be nice to have some empirical validation that this translates into actual difficulty. It would be possible to see how people's BU scores change, or "ghost to 100," but because this TDF focuses so much on pocketing difficulty, I don't think that would be necessary. Instead, to speed things up, you could use the pocketing portion of the BU test, which only takes a few minutes. It would be cool to see how well your TDF predicts changes in the number of balls made. My guess is that it would do pretty well.

dr_dave

Instructional Author
Gold Member
Silver Member
Mine was done on a modified 7' table. Score of 141, effective score of 130.3. All things exactly the same on pockets, only on a 9' table, effective score of 162.8. No way just a 7' to a 9' is worth 31.5 points!
It's not that simple. On a 9' table, you would have been able to take the Doctorate Exam instead, which has more points available (albeit with greater difficulty level also). On the other hand, with those tight pockets on a 9' table, some shots (even the stop/follow-draw shots) might rattle due to the larger distances and additional precision required. But again, it's not that simple.

Especially when on a lot of shots, the pocket size either isn't much of a factor, or is essentially no factor at all.
I disagree. For people who aren't as accurate as you, both table size and pocket size make a huge difference, especially on bigger tables with tighter pockets.

Sorry Dave, but I don't think the system makes a fair correlation between table sizes. However, it does between tables of the same size to a certain degree. Just how much that degree is, is questionable.
I agree about the "questionable" part, but I had to start somewhere.

You also have to take into account the margin of error for different angle shots, and different distance of shots. A whole lot to really take into consideration. So much, that I'm not sure it would even be worth it to really get an accurate comparison.

For example- I have a 30 degree shot to the corner. If it is near the pocket, I have a much larger margin of error than if it is far from the pocket. So, on a 7' table, I have a larger margin of error than on a 9' table with both ob,s at center table, and both cb's two diamonds away with pockets of the same size. But, how does the margin of error really equate with pocket size? It will vary according to the distance, and the angle to the pocket.

If the ball is near the rail, say a ball width off the rail, now you have to consider the springiness of the rail. Soft rails will allow you to have a much larger margin of error on the shot than bouncy rails will.
Neil, good points; but the point of the TDF system isn't to describe difficulty level of individual shots. The purpose is to describe the average over a wide range of shots, and do so with as few measurements and calculations as possible to get a rough estimate for table difficulty. I think the current TDF system does a decent job at that; although, there is certainly room for improvement. It also needs to be tested thoroughly to be able to make meaningful improvements.

Thanks for you input,
Dave

dr_dave

Instructional Author
Gold Member
Silver Member
Have you tried the BU Exams yet. If so, please consider posting your score (and videos if available) on the BU thread. Thanks!
I've worked up the following equation to figure out the relationship between the scoring data and my interest:

I'm still trying to figure out why it always returns 0. I'll keep working on it
I think your formula has an attitude problem. Maybe you should try something simpler and more mature. :grin-square:

I hope you reconsider. I thought you were into this sort of thing (playing ability tests and rating systems ... not formulas). You certainly have been in the past with other playing-ability drills posted. I guess it must be me you don't like. :sorry:

Catch you later,
Dave

dr_dave

Instructional Author
Gold Member
Silver Member
Dr Dave, I like very much what you are attempting to do. I have a few comments, but I will have to read through what you did thus far first, so that I can make an informed comment.

One quick comment I'd like to make, is of course there are other things missing that determine how tough a table plays. But, one common factor in almost any comparison, is to be able to measure and put a number to it. Even if that is a simple as asking a person on a scale of 1-5 how hard this table plays, all things considered. Without having a number, it is very difficult if not impossible to measure improvement, or variations.

The formulas to get the numbers can be refined over time. But with no numbers to start with, its just more black magic type stuff.

This is one thing that bugs me so much about tables. A mechanic or player will say "this table plays the way its supposed to", but there is none or little numbers behind that, which leads to the understanding of WHY the table might play that way, and why another one does not. IMO, the biggest recent debate on this is diamond rails vs GC rails and how the balls react off of them.
Thanks for your input. I look forward to any additional feedback you might have after you look at the details and try it out.

Catch you later,
Dave

dr_dave

Instructional Author
Gold Member
Silver Member
Nice job Dave!
Thanks!

It would be nice to have some empirical validation that this translates into actual difficulty. It would be possible to see how people's BU scores change, or "ghost to 100," but because this TDF focuses so much on pocketing difficulty, I don't think that would be necessary. Instead, to speed things up, you could use the pocketing portion of the BU test, which only takes a few minutes. It would be cool to see how well your TDF predicts changes in the number of balls made. My guess is that it would do pretty well.
Good idea. I would love to see some data like this. I plan to generate some on my own, but I hope others will also. That would be great if people would post well-practiced BU scores (or partial scores) on different equipment. Please post results if you try some experiments.

Thank you for the feedback and input,
Dave

bstroud

Deceased
Dr. Dave,

Something you seem to be missing are the balls.

Perhaps it's just me (I quit playing for 30 so years) but the Aramith balls play completely different than the original Centennials.

They kick or skid ALL the time. They turn over much more and the cut angle needs to be much thinner.

If there is a trick to playing with them I would sure like to know.

Bill S.

SpiderWebComm

HelpImBeingOppressed
Silver Member
I think your formula has an attitude problem. Maybe you should try something simpler and more mature. :grin-square:

I hope you reconsider. I thought you were into this sort of thing (playing ability tests and rating systems ... not formulas). You certainly have been in the past with other playing-ability drills posted. I guess it must be me you don't like. :sorry:

Catch you later,
Dave

Relax - I was just yanking your chain.

I would be inclined to do the test if I really felt it served the purpose you're trying to have it serve.

I think to grade playing ability, you have to grade people "playing" --- something like:
Ghost scores race to 50 (then x2 for effective score)
Cue Skills - set of 10 games (out of 200 possible points)

^ Something like that. Drills cannot accurately determine one's exact playing level, at least not with the same accuracy as one of the above methods. Therefore, when you say you're awarding masters / doctorate degrees based on drills, it's misleading.

Nobody should have a doctorate unless they're a pro-level player. No one should have a masters unless they're a "competitive" open-level player. Bachelors should be a B+ to A level... you get the idea.

I told you in the post from the other thread, I kind of like your concept as it can hold a lot of promise and application within the sport. However, basing such achievements on your set of drills doesn't make any sense. You should base it on "playing."

I was just picking on ya w/ the equation comment because you have a total inability to "K.I.S.S." Coming up with equations for this stuff is really pointless.

It's WAY easier to just have 10 people play the 9ball ghost on a barbox (ANY barbox), the same 10 people play it on a 8'er (ANY), the same 10 people play it on a 9'er (ANY), the same 10'er (good luck finding one) and a finally 12'er (good luck finding one). Average their scores on each table type and you have your basic table factor. Will some tables of a class be easier than others - yeah, sure -- but it's way simpler than figuring a million factors and coming up with equations to describe stuff that's subjective.

K.I.S.S.,
Dave

SpiderWebComm

HelpImBeingOppressed
Silver Member
Just to expand:

In golf, one's playing ability is determined by their handicap -- which is figured from their average SCORE for PLAYING a full round as well as the slope rating (course difficulty).

In bowling, one's playing ability is determined by their average.

In darts, one's playing ability is determined by their average.

Tennis, one's playing ability is determined by w/l average and stats.

In race car driving, one's ability is determined by average lap time.

Why is pool's degree program figured on Dr. Dave's drills? Why wouldn't it be based on one's average score while playing an equal-offense model?

dr_dave

Instructional Author
Gold Member
Silver Member
Dr. Dave,

Something you seem to be missing are the balls.

Perhaps it's just me (I quit playing for 30 so years) but the Aramith balls play completely different than the original Centennials.

They kick or skid ALL the time. They turn over much more and the cut angle needs to be much thinner.
Agreed. The condition of the balls (among many other things) have an effect, but I had to draw the line somewhere and stick to the factors easily measurable that relate specifically to the table and pocket geometry.

If there is a trick to playing with them I would sure like to know.
One of the bars I used to play at in a league had terribly "clingy" balls (because they were very old, beat up, and filthy). Whenever I played there, I used "gearing outside english" whenever possible and avoided slow and stunny shots as much as possible.

Catch you later,
Dave

SpiderWebComm

HelpImBeingOppressed
Silver Member
Dr. Dave,

Something you seem to be missing are the balls.

Perhaps it's just me (I quit playing for 30 so years) but the Aramith balls play completely different than the original Centennials.

They kick or skid ALL the time. They turn over much more and the cut angle needs to be much thinner.

If there is a trick to playing with them I would sure like to know.

Bill S.
I'll tell you the trick to playing with them if you tell mhaimi what the trick is to getting the cue he won.

Last edited:

dr_dave

Instructional Author
Gold Member
Silver Member
Have you tried the BU Exams yet. If so, please consider posting your score (and videos if available) on the BU thread. Thanks!
I would be inclined to do the test if I really felt it served the purpose you're trying to have it serve.
What purpose do you think the BU Exams are trying to serve?

I think to grade playing ability, you have to grade people "playing" --- something like:
Ghost scores race to 50 (then x2 for effective score)
Cue Skills - set of 10 games (out of 200 possible points)
Sounds good to me, for the people who have that sort of time and dedication.

Drills cannot accurately determine one's exact playing level, at least not with the same accuracy as one of the above methods. Therefore, when you say you're awarding masters / doctorate degrees based on drills, it's misleading.

Nobody should have a doctorate unless they're a pro-level player. No one should have a masters unless they're a "competitive" open-level player. Bachelors should be a B+ to A level... you get the idea.

I told you in the post from the other thread, I kind of like your concept as it can hold a lot of promise and application within the sport. However, basing such achievements on your set of drills doesn't make any sense. You should base it on "playing."
Thank you for the input. After you try both BU Exams and see how you do, I'll be curious to see what your think then. Only a top-level player can do really well in the exams; and it is impossible for a low-level player to get a high score. The system might not be perfect, but I think it does a decent job in a short amount of time (while being fun and challenging at the same time). Again, I look forward to getting more feedback from you after you spend time with the exams.

It's WAY easier to just have 10 people play the 9ball ghost on a barbox (ANY barbox), the same 10 people play it on a 8'er (ANY), the same 10 people play it on a 9'er (ANY), the same 10'er (good luck finding one) and a finally 12'er (good luck finding one). Average their scores on each table type and you have your basic table factor. Will some tables of a class be easier than others - yeah, sure -- but it's way simpler than figuring a million factors and coming up with equations to describe stuff that's subjective.
If I had 10 people willing to do this test for different tables as your have suggested, I agree that this would be the best way to rate a wide variety of tables. But that isn't very practical. However, by knowing only the table size, and 3 simple pocket measurements, you can get a rough and fairly reliable estimate for table difficulty with a very simple and fast calculation (using the TDF system). To me, that's much simpler (but not better) than your approach.

Dave

"no buds chill"
Silver Member
Hahahaha

I'll tell you the trick to playing with them if you tell mhaimi what the trick is to getting the cue he won.

You beat me to it Spider.....

Fatboy

AzB Silver Member
Silver Member
Based on ideas from previous threads on this topic (tight pockets thread and pocket answers thread), and based discussion in the Billiard University (BU) thread concerning how to account for table difficulty in scoring and rating drills like the BU Exams, I decided to create a system for determining how difficult a table plays. It is described in detail in the Table Difficulty Factor (TDF) document, which is convenient if you want a printed copy.

Here's how it works:

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. Four factors are used to account for table size, pocket size, pocket wall 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, Hopkins Q Skills drill, or the Fargo rating drill or handicapping system. An effective score, taking table difficulty into consideration, can be calculated with:

(effective score) = (raw score) x TDF

Here's an example of how the TDF system is used. Let’s say two players (“A” and “B”) got an identical Billiard University (BU) score of 130. Player “A” took the exams on a fairly “easy” table with the following measurements:
Table “A”
table size = 8’, mouth = 5”, throat = 4 1/2”, (mouth-throat) = 1/2”, shelf = 1 3/8”
TDF = TSF x PSF x PAF x PLF = 0.90 x 0.95 x 1.00 x 0.95 = 0.81​

Therefore, table “A” is about 19% easier than average, and the effective BU score on this table would be 130 x 0.81 = 105 (much lower than 130).

Player “B” took the exams on a fairly “tough” table with the following measurements:
Table “B”
table size = 9’, mouth = 3 7/8”, throat = 3 1/4”, (mouth-throat) = 5/8”, shelf = 1 7/8”
TDF = TSF x PSF x PAF x PLF = 1.00 x 1.15 x 1.05 x 1.05 = 1.27​

Therefore, table “B” is about 27% more difficult than average, and the effective BU score on this table would be 130 x 1.27 = 165 (much higher than 130). This helps put the BU scores in better perspective based on table difficulty.

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

Thank you,
Dave

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:

SpiderWebComm

HelpImBeingOppressed
Silver Member
What purpose do you think the BU Exams are trying to serve?

Sounds good to me, for the people who have that sort of time and dedication.

Thank you for the input. After you try both BU Exams and see how you do, I'll be curious to see what your think then. Only a top-level player can do really well in the exams; and it is impossible for a low-level player to get a high score. The system might not be perfect, but I think it does a decent job in a short amount of time (while being fun and challenging at the same time). Again, I look forward to getting more feedback from you after you spend time with the exams.

If I had 10 people willing to do this test for different tables as your have suggested, I agree that this would be the best way to rate a wide variety of tables. But that isn't very practical. However, by knowing only the table size, and 3 simple pocket measurements, you can get a rough and fairly reliable estimate for table difficulty with a very simple and fast calculation (using the TDF system). To me, that's much simpler (but not better) than your approach.

Dave

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.

Roger Long

Sonoran Cue Creations
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

Fatboy

AzB Silver Member
Silver Member
Dr. Dave,

Something you seem to be missing are the balls.

Perhaps it's just me (I quit playing for 30 so years) but the Aramith balls play completely different than the original Centennials.

They kick or skid ALL the time. They turn over much more and the cut angle needs to be much thinner.

If there is a trick to playing with them I would sure like to know.

Bill S.

buy a new set, your a better player than me, however i played long enough to know what your talking about and i have played with worn out balls. horrible experience-especially when the one is the smallest ball.