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jviss
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Resurrecting an old thread... - 02-01-2019, 08:24 AM

It's a shame the videos and pics are no longer available!

I'm interested in this topic for my scale pool table project.
  
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Bob Jewett
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02-01-2019, 08:46 AM

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Originally Posted by jviss View Post
It's a shame the videos and pics are no longer available!

I'm interested in this topic for my scale pool table project.
I think no picture for the timed method of measuring pool table speed is needed. Were the instructions not clear?

Cushion rebound is harder to measure in part because it depends on how new the cloth is, as mentioned above.


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02-02-2019, 07:25 AM

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Originally Posted by Bob Jewett View Post
I think no picture for the timed method of measuring pool table speed is needed. Were the instructions not clear?

Cushion rebound is harder to measure in part because it depends on how new the cloth is, as mentioned above.
Thanks, Bob. Yea, I guess your method doesn't require pics, but it's generally disappointing when threads age and pics and videos evaporate.

I'm interested in various methods. Have you ever run statistics on your method to determine the repeatability, the 'resolution,' so to speak?

I must say that I'm reading and re-reading your article from April 1995 on this topic, and I haven't completely wrapped my head around it yet. I though it produced an absolute speed number, but then I saw that there's a correction factor for 10' tables, which hints that the method is actually calibrated to 9' tables, which I didn't think was the case. For example, for a ball to make it the length of a 10' table the initial "launch velocity" from the foot rail would have to be higher than on a 9' table. Similarly, it would be slower still for an 8' table. One would expect that if we measure the 10', 9', and 8' total distances for the same ball on the same table, that the times should be the same, leading to the same cloth speed.

A nice aspect of your method is that it doesn't require any special tool, and every smartphone has an excellent stop watch!

Very interested in this topic, thanks.
  
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Bottom Line - 02-02-2019, 09:32 AM

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Originally Posted by neonlight View Post
I'm really surprised the BCA does not maintain speed standards. A measurement system would be easy. It is done all the time on golf greens. A similar sloped apparatus would offer consistent measurements.
Mfg, could care less, that has been the norm for decades....the home market is their target.


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02-02-2019, 01:09 PM

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Originally Posted by jviss View Post
... but then I saw that there's a correction factor for 10' tables, which hints that the method is actually calibrated to 9' tables, which I didn't think was the case. ...
The number that is multiplied by the square of the rolling time in seconds is related to the rolling distance from the last cushion until the ball stops. For a table 100 feet long but with normal cloth, you would expect about a 25 second lag time if the ball stops just before the cushion and the multiplying factor would be something like 1/6 instead of 2 since the lag is 12 times longer than a "normal" lag.

On the other hand, if your lag only comes back 60 inches (on any table) and it does it in 6.0 seconds, the multiplying factor is about 3.333 (due to the short length) and the nominal speed of the table would be 6*6*3.333 = 120.

The speed of the cloth has nothing to do with the length of the table. It is only related to how fast the rolling ball slows down. The different factors quoted for different lengths of table just save you from having to do the math like in the 60-inch lag -- the lag length is built in to the factor.


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02-03-2019, 05:06 AM

Quote:
Originally Posted by jviss View Post
It's a shame the videos and pics are no longer available!

I'm interested in this topic for my scale pool table project.
Here it is, good luck with your project.

https://photos.app.goo.gl/cF23ZZpkqUSQWbKp6


Edit:
In the past I would only leave a video up as long as there was interest.
Nothing lasts forever.
In this case, I expected only one comment, but that never happened.
steven

Last edited by driven; 02-09-2019 at 03:22 AM. Reason: .
  
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02-04-2019, 06:16 AM

Quote:
Originally Posted by Bob Jewett View Post
The number that is multiplied by the square of the rolling time in seconds is related to the rolling distance from the last cushion until the ball stops. For a table 100 feet long but with normal cloth, you would expect about a 25 second lag time if the ball stops just before the cushion and the multiplying factor would be something like 1/6 instead of 2 since the lag is 12 times longer than a "normal" lag.

On the other hand, if your lag only comes back 60 inches (on any table) and it does it in 6.0 seconds, the multiplying factor is about 3.333 (due to the short length) and the nominal speed of the table would be 6*6*3.333 = 120.

The speed of the cloth has nothing to do with the length of the table. It is only related to how fast the rolling ball slows down. The different factors quoted for different lengths of table just save you from having to do the math like in the 60-inch lag -- the lag length is built in to the factor.
Thanks Bob. Still working on this, trying to thoroughly understand it.
  
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