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06-21-2013, 11:46 AM

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Originally Posted by dr_dave View Post
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Originally Posted by SpiderWebComm View Post
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
That's a good idea. Maybe I'll add that to the document.
Done. Check out the latest Table Difficulty Factor (TDF) document. Here's the addition:

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


Thanks again,
Dave

Last edited by dr_dave; 06-22-2013 at 11:07 AM.
  
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06-21-2013, 11:48 AM

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Originally Posted by Mr. Bond View Post
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?
The vertical angle is not measured or included in the calculation. If you wanted to include this, it would need to be added as an additional factor. I personally have no feel, data, or analysis that assesses the relative importance of this variable. Do you?

Regards,
Dave
  
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06-21-2013, 11:51 AM

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Originally Posted by Fatboy View Post
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
Thanks for the input. This is exactly the sort of data and feedback I was hoping to get from people. I hope others will do the same.

Thanks again,
Dave
  
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06-21-2013, 11:54 AM

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Originally Posted by Mr. Bond View Post
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?

thats down angle, RKC can explane that real good, we changed that lots (i think 13 degrees is normal) on the "Fatboy" rails TAR used.


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As fatboy had pointed out...
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As fatboy had pointed out... - 06-21-2013, 11:57 AM

Quote:
Originally Posted by dr_dave View Post
The vertical angle is not measured or included in the calculation. If you wanted to include this, it would need to be added as an additional factor. I personally have no feel, data, or analysis that assesses the relative importance of this variable. Do you?

Regards,
Dave
As Eric pointed out, you need to weigh each factor differently.

the distance between the tits is going to play a much greater factor in overall difficulty than the difference between pocket entry width and pocket drop width. The depth of the shelf will have a greater impact on overall difficulty than down face angle.


I think with some testing and tweaking this could be great for analysis of table difficulty and playability.

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06-21-2013, 12:14 PM

Quote:
Originally Posted by dr_dave View Post
Done. Check out the latest Table Difficulty Factor (TDF) document. Here's the addition:

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


Thanks again,
Dave
You have my permission to post that on your website as long as I'm given proper credit. LOL


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06-21-2013, 12:16 PM

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Originally Posted by Fatboy View Post
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.
I am playing with new sets of balls and clean and polish them daily with a Diamond ball polisher.

They still gear, kick and skid all the time compared to the old Centennials.

Perhaps the cloth is a factor?

Bill S.
  
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06-21-2013, 12:24 PM

Quote:
Originally Posted by Fatboy View Post
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.
Maybe I'm missing something but how did you come up with 1.10?

9' Table = 1
3.99" Pocket Mouth = 1.15
3.75" Pocket Throat equals .24" difference = .95
1" Shelf = .90

1 x 1.15 x .95 x .90 = .98

Am I off on how I am calculating this?

Here's what I came up with on my home table.

9' Table = 1
4" Pocket Mouth = 1.15
3 5/8" Pocket Throat equals 3/8" difference = 1.0
1" Shelf = .90

1 x 1.15 x 1.0 x .90 = 1.04


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06-21-2013, 12:56 PM

For giggles, I went down and measured my oversize 8' A.E. Schmidt:

8' home table = 0.90
PSF = 0.95
PAF = 1.15
PLF = 1.05

Table Difficulty Factor = 1.03

I have a few observations to add.

1. My large 8' plays and feels pretty much like a 9' table to me. I don't think it's quite correct to neglect the difference between a standard 8' and a large 8'. I know they are not common these days, but they really feel like a bigger table for a lot of reasons. Maybe bump it up to a 0.95 instead of a 0.90? That would boost my table's difficulty factor to a 1.09.

2. All of your pocket angle factors move up by 0.05 for each 1/8" increment in difference, but you limit this at > 3/4". The back of my pocket openings are 4" while the front is 5". That is a full 1'' difference, creating a facing angle of 144º compared to a standard Diamond with 141º pocket facing angles. My corner pockets spit balls out so bad it's alarming. They play very tough compared to the Diamonds at my local pool room. My side pockets, however, play a lot softer than a Diamond. I can easily squeak narrow-angle shots into them that pros would play safe on a Diamond. So it's a trade off at times IMO.
  
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06-21-2013, 01:15 PM

Quote:
Originally Posted by bstroud View Post
I am playing with new sets of balls and clean and polish them daily with a Diamond ball polisher.

They still gear, kick and skid all the time compared to the old Centennials.

Perhaps the cloth is a factor?

Bill S.
Could just be bad karma.
  
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06-21-2013, 01:20 PM

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Originally Posted by berko View Post
Could just be bad karma.
I've had my home table for about 9 months now, with a used set of Aramith Super Pros. I never cleaned the cloth or balls once in that time, except for occasionally wipiong the CB on my shirt. I only had one skid in the almost entiere year. I guess my karma is good
  
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06-21-2013, 01:20 PM

FYI to everybody, I've tweaked some of the numbers and will probably do so again in the future. The recent tweaks are based on info I received both inside and outside of the thread and based on some more analysis I've done.

Hopefully, in the next hour, I will go through the thread and recalculate the TDF for all tables reported to date. I'll add this list to the first post of the thread so it will be easy to find, and so I can more easily update it in the future.

Thank you for helping me in this process. Hopefully, more people can take measurements on their favorite tables and comment on how well the TDF matches the perceived difficulty level, relative to the 9' spec standard (1.00 on the TDF scale).

Sorry for any confusion caused by my changes, but I think it will take a while before the system stabilizes.

Thanks for the help,
Dave

Quote:
Originally Posted by dr_dave View Post
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 1.20 x 1.03 x 1.05 = 1.30

Therefore, table “B” is about 27% more difficult than average, and the effective BU score on this table would be 130 x 1.30 = 169 (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

Last edited by dr_dave; 06-22-2013 at 11:06 AM.
  
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06-21-2013, 01:25 PM

Quote:
Originally Posted by bstroud View Post
I am playing with new sets of balls and clean and polish them daily with a Diamond ball polisher.

They still gear, kick and skid all the time compared to the old Centennials.

Perhaps the cloth is a factor?
The cloth has no direct affect on cling/skid/kick (unless the cloth is so slick that chalk smudges don't rub off the balls as easily, or unless the cloth is so full of chalk dust that it gets on the balls as they roll).

Regards,
Dave
  
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06-21-2013, 01:40 PM

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Originally Posted by dr_dave View Post
The cloth has no direct affect on cling/skid/kick (unless the cloth is so slick that chalk don't rub off the balls as easily, or unless the cloth is so full of chalk dust that it gets on the balls as they roll).

Regards,
Dave
You lot use different terminology but a new cloth certainly skids more than older, slower cloths eg backspin doesn't take hold as quickly. The CB aquaplanes a little, then grips.
  
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06-21-2013, 01:43 PM

Based on the new numbers, here's the data on my table:

TSF: 9' = 1
PSF: 4" = 1.20
PAF: 3/8" = 1.0
PLF: 1" = .9

1 x 1.2 x 1 x .90 = 1.08


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