New videos from Dr. Dave and Bob Jewett

dr_dave · **New videos from Dr. Dave and Bob Jewett -** 04-05-2009, 07:18 PM

FYI, Bob Jewett and I filmed a bunch on stuff together a couple of weeks ago, and I finally got everything edited and posted. The first stuff we shot dealt with some pool physics topics:

HSV B.43 - break squat
HSV B.44 - cloth compression and cue ball trajectory for draw shots of various elevations
HSV B.45 - effective mass of various ball racks and clusters
HSV B.46 - CB and OB hop and spin transfer during follow shots
HSV B.47 - effect of shaft endmass and squirt on miscue limit

Most people will probably be more interested in the rules quiz we put together. We have 100 shots for you to call "fair" or "foul," in quiz format. Here's the scoring sheet. Here's the quiz video:

NV B.61 - Referee quiz, with Bob Jewett

Here's the quiz answer summary sheet with all of the correct rulings (we think). Don't cheat ... take the quiz before looking at the answers. Here is a video that also contains all of the answers:

NV B.62 - Referee quiz answers

Again, don't cheat!

Please let us know how you did, and let us know if you have and comments, suggestions, or questions. Also, please let me know if you spot any errors. I put many, many hours into the quiz stuff, and there are bound to be errors.

Enjoy,
Dave

Klopek · 04-05-2009, 07:32 PM

Dr. Dave,

In "HSV B.47 - effect of shaft endmass and squirt on miscue limit", (in the final test), couldn't the increased squirt be directly related to the greater english applied?.

Jal · 04-05-2009, 08:14 PM

I haven't had a chance to view anything, but a special thanks for the effective mass of the rack video, and a general thanks for all. They promise to be very interesting.

Jim

John Biddle · 04-05-2009, 09:51 PM

Bob & Dr Dave,

I only got an 81, and feel fairly ashamed of my score. I thought I would do much better.

I want to thank you both for your excellent work putting this fine quiz together. It is obvious that it took a great deal of effort and the results are outstanding. I have no idea how many pool players will watch this, but I believe virtually all of them would learn quite a bit if they did so.

What I liked the most about your quiz was that it teaches how to call the shot correctly even though the shot itself takes place so fast you can't possibly see it in detail. This kind of thing is known by such a small percentage of players. They could be purposely hiding their knowledge because the call goes against them, but I prefer to give them the benefit of the doubt and say they are just lacking in the appropriate knowledge.

I've seen many people play at being a ref who have no idea how to call a shot properly. Maybe this will set them right. With my low score I guess 20% of the time I was one of those people and I know it has helped me to make far fewer errors going forward.

Thanks again to both of you for this wonderful quiz.

For those of you who like quizzes, I've got two on my blog, one on the 8 Ball rules and one on the General rules. They not video, though, just text questions. Just click on the quizzes link on the upper right hand corner of my home page.

djpstacked03 · 04-05-2009, 10:47 PM

Good quiz. I got 70 :l
The push shots are the most difficult shots to call. I would like to take a ref course eventually just to expand on my own knowledge of those shots. Thanks for posting.

madfox · 04-06-2009, 04:28 AM

I generally agree with your quiz, but no. 1, 15,22 where CB and OB are frozen I don't agree. The tip stays too much on the cue ball, due to the opposition of the OB so it is a push shot,there for a foul.
6.8 Push Shot
It is a foul to prolong tip-to-cue-ball contact beyond that seen in normal shots.

Patrick Johnson · 04-06-2009, 06:45 AM

Quote:

I generally agree with your quiz, but no. 1, 15,22 where CB and OB are frozen I don't agree. The tip stays too much on the cue ball, due to the opposition of the OB so it is a push shot,there for a foul.

This has been examined on high speed videos, and it's clear that the tip does not stay on the cue ball more than a normal amount of time.

No foul.

pj
chgo

Tennesseejoe · 09:52 AM

I have downloaded the Media Player but cannot get the topics to open. Any help would be appreciated from this friendly and knowledgeable group.

EDITED: Sorry about this post--My computer is just a little slow in loading. All is OK.

dr_dave · 12:01 PM

Quote:

Originally Posted by Klopek

Dr. Dave,

In "HSV B.47 - effect of shaft endmass and squirt on miscue limit", (in the final test), couldn't the increased squirt be directly related to the greater english applied?.

That's a good point. With more tip offset, you get more squirt. However, if you watch all of the shots in the video, you will see that the cue with the added endmass had much more squirt than the cue without the added endmass, much more than can be explained by a small difference in tip offset. Also, with more squirt comes less English (for a given tip offset) because the effective offset is less. If you look at the stripe on the ball in the super-slow-motion clips, you will see that the CB actually has slightly more English with the low-squirt cue (due to a larger "effective tip offset"), even though the "actual tip offset" is slightly greater with the added-endmass cue!

Regards,
Dave

dr_dave · 04-06-2009, 08:42 AM

Quote:

Originally Posted by Jal

I haven't had a chance to view anything, but a special thanks for the effective mass of the rack video, and a general thanks for all. They promise to be very interesting.

Jim,

I look forward to your comments and questions. I'm also curious to see how you and others do on the quiz.

Regards,
Dave

dr_dave · 04-06-2009, 08:51 AM

Quote:

Originally Posted by Grampa000

I only got an 81, and feel fairly ashamed of my score. I thought I would do much better.

81 is probably pretty good for a typical player, but I'm not sure. That's why we are hoping lots of people can take the quiz (and help spread the word), so we can see what scores are typical. I would hope a typical referee could do a lot better than 81, but I'm not sure if that is the case or not.

Quote:

Originally Posted by Grampa000

I want to thank you both for your excellent work putting this fine quiz together. It is obvious that it took a great deal of effort and the results are outstanding. I have no idea how many pool players will watch this, but I believe virtually all of them would learn quite a bit if they did so.

What I liked the most about your quiz was that it teaches how to call the shot correctly even though the shot itself takes place so fast you can't possibly see it in detail. This kind of thing is known by such a small percentage of players. They could be purposely hiding their knowledge because the call goes against them, but I prefer to give them the benefit of the doubt and say they are just lacking in the appropriate knowledge.

I've seen many people play at being a ref who have no idea how to call a shot properly. Maybe this will set them right. With my low score I guess 20% of the time I was one of those people and I know it has helped me to make far fewer errors going forward.

Thanks again to both of you for this wonderful quiz.

You're welcome. Please help spread the word about the videos so more people can improve their knowledge. I plan to put out a set of detailed instructional videos (with added super-slow-motion video) to help people better understand exactly what to look for with different types of shots. I'll announce when the new videos are posted.

Quote:

Originally Posted by Grampa000

For those of you who like quizzes, I've got two on my blog, one on the 8 Ball rules and one on the General rules. They not video, though, just text questions. Just click on the quizzes link on the upper right hand corner of my home page.

Thanks for the info. I'll check them out.

Regards,
Dave

Mantool · 04-06-2009, 09:00 AM

Dr. Dave,
You are the best!
Thanks for your efforts and contributing your information to others.

Neil · 04-06-2009, 09:33 AM

You got me with the two unintentional miscues. I looked at them as scoop shots. Hard to differentiate without being there I think. You also got me on 4 of the frozen to the rail shots. The WPA rules don't seem to be very clear on the issue. At least, I couldn't find it. I remember that the cb had to hit the rail, or the ob be driven to a different rail. The same long rail, even across the side pocket, did not count for a different rail. Seems that in the WPA that is allowed, although it is not clear in the wording. Anyway, I scored a 91. (Would have been a 97 without those mentioned.

)

Neil · 04-06-2009, 09:38 AM

On shot #37, I have to disagree with you. You called it a foul because the cb went too far forward. (jump-draw shot). I had called it good, then when I saw your ruling, I watched it about ten times hitting the pause button and play button as fast as I could. I agree it went a little forward on the shot. But that could also be due to the speed of the shot. I could not see a double hit. When in doubt, it goes to the shooter, correct?

dr_dave · 04-06-2009, 10:11 AM

Quote:

Originally Posted by djpstacked03

Good quiz. I got 70 :l

Thank you for sharing your score. I hope others do also.

Quote:

Originally Posted by djpstacked03

The push shots are the most difficult shots to call. I would like to take a ref course eventually just to expand on my own knowledge of those shots. Thanks for posting.

Bob plans to use the videos when he teaches ref courses. I think the videos are also useful for players to improve their ability to make the right calls when a ref isn't around.

Regards,
Dave