Interesting, new super-slow-motion videos

Thanks for the vids Dr. Dave.

Question on the draw video: Can I look at the amount of rotation induced as the ball leaves the frame and conclude that the near level cue imparts greater draw? From the physics I want to say yes, but there have been many on this forum that promote elevating the cue to get better draw. It looked like the contact point for all strokes was just about a half tip below the stripe.

Personally, I don't elevate for power draw.

Thanks,
Steve
 
Runnin8 said:
Question on the draw video: Can I look at the amount of rotation induced as the ball leaves the frame and conclude that the near level cue imparts greater draw? From the physics I want to say yes, but there have been many on this forum that promote elevating the cue to get better draw. It looked like the contact point for all strokes was just about a half tip below the stripe.
Click to expand...

IAMDD (I Am Not Dr. Dave), but...

I would say the more level the shaft is with the table surface, the better the draw you can get. Reason is - I believe more level = longer tip contact with the cue ball as the stroke goes through = more rotation imparted upon the cue ball. Note how little the cue ball hopped off the table with a level stroke.

With an elevated stroke, the cue ball is getting pushed into the table more, making it hop more - and that hop takes the cue ball away from the tip sooner, as best I can tell.

But then the opposite of that thought may hold true as well - that the more the cue ball hops off the table, the longer it gets to spin backwards freely without friction from the table surface starting to bleed off the spin.
 
ScottW said:
That's some neat stuff. :D

Dave, re: reputation - see the green blocks below your name over on the left? That's your reputation indicator.

People can give good/bad rep to other people's posts - see the "rep" and "bad" buttons at the bottom left of every post. These actions increase/decrease the poster's total reputation value.

The forum code is set so that people cannot just dogpile good/bad rep onto another individual - one has to "spread it around". This is to prevent abuse.

Some people consider their forum rep to be gospel, others could care less, and most are somewhere in between. :P
Click to expand...
Thanks. Now I understand.

Regards,
Dave
 
Jerry Yost said:
The double hits were often difficult to detect even with the high speed video slow motion. I think anyone making that call with the naked eye at full speed at worst is just guessing and at best is making an educated guess based on their understanding of the physics.
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Agreed. For close calls, we need to trust the ref or our opponent (provided he or she has decent physical understanding), and give the benefit of doubt to the shooter when the naked-eye visual evidence is inconclusive.

Regards,
Dave
 
elevated cue for more draw?

Runnin8 said:
Question on the draw video: Can I look at the amount of rotation induced as the ball leaves the frame and conclude that the near level cue imparts greater draw? From the physics I want to say yes, but there have been many on this forum that promote elevating the cue to get better draw. It looked like the contact point for all strokes was just about a half tip below the stripe.

Personally, I don't elevate for power draw.
Click to expand...
I have some good general advice about draw and cue elevation here:
http://billiards.colostate.edu/threads/draw.html

I also have some experiments and analyses planned on this topic. I hope to complete it and write an article soon (within the next 2-3 months).

I think cue elevation might provide more draw on some shots because the CB spends more time in the air during hops with cue elevation. When the CB is in the air, there is no drag action (i.e., the bottom-spin doesn't wear off). But the amount of draw also depends on how much is lost when the CB is driven down into the table and on when the CB bounces before hitting the OB. I need to think about this more, do experiments, and do some analysis before I can be confident with any conclusions.

Regards,
Dave

PS: I don't elevate for power draw either.
 
dr_dave said:
Agreed. For close calls, we need to trust the ref or our opponent (provided he or she has decent physical understanding), and give the benefit of doubt to the shooter when the naked-eye visual evidence is inconclusive.

Regards,
Dave
Click to expand...

I also find that with regard to the double hits on close but unfrozen balls, you could often call them blindfolded since while you have little chance of seeing them, you can HEAR them quite clearly.

Joe
 
ScottW said:
...I believe more level = longer tip contact with the cue ball as the stroke goes through = more rotation imparted upon the cue ball.
Click to expand...

I believe:

1. contact time is about the same (or possibly a little longer with an elevated cue), and

2. longer contact would not = more rotation anyway.

The video shows no appreciable difference in the amount of backspin on the cue ball for the different stick elevations. If you look carefully at how far the cue ball rotates before leaving the frame, you'll see it's just about 1/2 ball of rotation in every case.

pj
chgo
 
dr_dave said:
A lot of people seem to have trouble judging double hits. With a little basic understanding, many arguments and bad calls can be avoided. Although, even with high-speed video, it is sometimes difficult to tell if a shot is strictly a double hit or not. In the cases which are borderline, it seems the benefit of doubt should go to the shooter. If a double hit is suspected but not obvious in real-time, the shot should not be ruled a foul, even if a high-speed-camera might show otherwise (if one were available). What do people think about this?
Click to expand...

I agree the benefit of the doubt should be given to the shooter.

1. If there's nobody watching who knows what to look for, then this rule makes sense just to avoid unresolvable arguments.

2. If there is somebody watching who knows what to look for, but no suspicious cue ball action can be seen, then it doesn't really matter whether there was technically a double hit or not - if no detectable "harm" occurred, then the outcome is the same as if there was no foul (a "victimless crime"), so no foul should be called.

Without high speed video replay of every shot this is the best we can do, and I think it's plenty good enough.

pj
chgo

P.S. "What to look for" = cue ball (or object ball) action that would not be possible without a foul.
 
double-hit sound

junksecret said:
I also find that with regard to the double hits on close but unfrozen balls, you could often call them blindfolded since while you have little chance of seeing them, you can HEAR them quite clearly.
Click to expand...
The visual evidence is also is also usually very clear in these cases (e.g., see HSV A.12).

Regards,
Dave
 
no obvious detection = no foul

Patrick Johnson said:
I agree the benefit of the doubt should be given to the shooter.

1. If there's nobody watching who knows what to look for, then this rule makes sense just to avoid unresolvable arguments.

2. If there is somebody watching who knows what to look for, but no suspicious cue ball action can be seen, then it doesn't really matter whether there was technically a double hit or not - if no detectable "harm" occurred, then the outcome is the same as if there was no foul (a "victimless crime"), so no foul should be called.

Without high speed video replay of every shot this is the best we can do, and I think it's plenty good enough.
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Agreed. Good summary.

Dave
 
dr_dave said:
Joe,

I didn't see your earlier message. If you let me know exactly what you want to see, I can let you know if I have it already. If not, I will add it to the list for my next video shoot, which is planned for the end of the month.

Regards,
Dave
Click to expand...

Hi Dave,
I was talking about this guess I made in post #39 http://forums.azbilliards.com/showthread.php?t=94747&page=3
about the possiblity of the cb jumping more with an elevated draw stroke as opposed to a more level follow stroke being a cause for different amounts of squirt & swerve. Guessing the hop makes it tougher for the swerve to grab?
 
swerve and drag hop effects

Joe T said:
Hi Dave,
I was talking about this guess I made in post #39 http://forums.azbilliards.com/showthread.php?t=94747&page=3
about the possiblity of the cb jumping more with an elevated draw stroke as opposed to a more level follow stroke being a cause for different amounts of squirt & swerve. Guessing the hop makes it tougher for the swerve to grab?
Click to expand...
Thanks for the link. I'm glad the draw shot clip (HSV B.1) shows what you wanted to see. I plan to shoot more closeups of draw and follow reaction and ball hop during my next video session.

The swerve (and drag loss) occurs only during the bounces (in bigger chunks) and obviously doesn't occur at all while the ball is in the air. FYI, Bob has a good summary of the hop effects at the bottom of the page here:

http://billiards.colostate.edu/threads/draw.html

Regards,
Dave
 
dr_dave said:
Thanks for the link. I'm glad the draw shot clip (HSV B.1) shows what you wanted to see. I plan to shoot more closeups of draw and follow reaction and ball hop during my next video session.

The swerve (and drag loss) occurs only during the bounces (in bigger chunks) and obviously doesn't occur at all while the ball is in the air. FYI, Bob has a good summary of the hop effects at the bottom of the page here:

http://billiards.colostate.edu/threads/draw.html

Regards,
Dave
Click to expand...

Thanks, I'm going to mess around with some long draw shot based on what Bob says there, let you know how I make out.

I started messin with the firm draw with pennies out in front of my cb problem is I can hear it hit or clear with a sofT & medium stroke but am not sure at the firm speed.
 
Master Dr. Dave- whats up doc

View Your (shot-photo Online) 1. go to www.drdave.com/shotshow 2. Enter the following Photo Id. Thanks for proving many good points and for teaching how to shoot shots correctly- many will still view the video's and still eat the pages, Welcome. mark
 
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