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dr_dave
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01-09-2018, 09:32 AM

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Originally Posted by Black-Balled View Post
In addition to being side pocket dumb, I am also combo handicapped as well...too.
I am often shocked by how poorly people (even pros at times) aim small-gap-combos due to an insufficient understanding of basic throw concepts. I hope this new video helps you and others do better in this regard.

Catch you later,
Dave
  
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01-09-2018, 10:00 AM

isn't this related to the fact that you don't see much throw until ~25 degree cut angles?

btw your past stuff on throw really helped my game. i try to explain it to people and even really good players don't really believe/understand it. but i still think they eventually learn how to visualize it
  
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01-09-2018, 12:32 PM

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Originally Posted by longhorns2 View Post
isn't this related to the fact that you don't see much throw until ~25 degree cut angles?
Cut-induced throw (CIT) increases fairly linearly between 0 and about 30 degrees (see the plots in "Throw - Part II: results" - BD, September, 2006). It is maximum close to 30 degrees, but it is about half maximum at 15 degrees.

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Originally Posted by longhorns2 View Post
btw your past stuff on throw really helped my game. i try to explain it to people and even really good players don't really believe/understand it. but i still think they eventually learn how to visualize it
I'm glad to hear it. FYI, if you want to suggest a good learning resource for throw, here's a good place to start:

throw tutorial

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Dave
  
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Dan White
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01-09-2018, 02:06 PM

Great stuff, Dave! It is one thing to "kinda sorta" know how to hit a close combination, but I had no idea there was a sweet spot where you could hit the shot almost anywhere (up to half ball or so) and still have the combo go straight.

Along the lines of your last graph in the second link, have you considered what the upper and lower bounds are for the 3/8" gap shot where you can still expect to pocket the ball straight in? I know it depends on shot length and pocket opening, but let's say I estimate a 1/4 inch gap. Can I figure it will still be straight with maybe a little throw, and vice versa for a shot that is closer to 1/2 inch?


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01-10-2018, 12:37 AM

Really helpful. I've always known about the frozen ball thing but you do a great job at breaking down the small gap scenario. Playing a lot of straight pool lately, looking forward to using this knowledge.

Hey Dr.Dave, how do you find the Revo shaft? Also what is your preference or favorite shaft and why? If ya don't mind me asking.
  
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01-10-2018, 08:30 AM

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Originally Posted by Dan White View Post
Great stuff, Dave! It is one thing to "kinda sorta" know how to hit a close combination, but I had no idea there was a sweet spot where you could hit the shot almost anywhere (up to half ball or so) and still have the combo go straight.
I was also shocked by the precision over such a large angle range, both with the analysis plot and the results at the table (in the video).

Quote:
Originally Posted by Dan White View Post
Along the lines of your last graph in the second link, have you considered what the upper and lower bounds are for the 3/8" gap shot where you can still expect to pocket the ball straight in? I know it depends on shot length and pocket opening, but let's say I estimate a 1/4 inch gap. Can I figure it will still be straight with maybe a little throw, and vice versa for a shot that is closer to 1/2 inch?
Thank you for asking this. It encouraged me to add a new page to the analysis file. Gaps between 1/4" and 1/2" give good results over 15-20 degrees. 3/8" has superior accuracy, but 1/4" offers a wider range of angles with decent accuracy with faster-speed shots. Check out the plots on the new last page.

Regards,
Dave
  
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01-10-2018, 08:42 AM

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Originally Posted by Shotcy View Post
Really helpful. I've always known about the frozen ball thing but you do a great job at breaking down the small gap scenario. Playing a lot of straight pool lately, looking forward to using this knowledge.
I'm glad to hear people like the new video. Straight pool players definitely have the most to benefit from this info; although, small-gap combos also come up fairly often in bar-box 8-ball.

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Originally Posted by Shotcy View Post
Hey Dr.Dave, how do you find the Revo shaft?
I like it. It is smooth (and should stay that way for a long time), it stays clean (and is very easy to clean with a damp towel when it does get dirty), it should be warp free, it is difficult to ding or scratch, and it looks cool. Its CB deflection is also similar to the Z2 (which I used for many years), so I didn't have to adjust how I aim sidespin shots.

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Also what is your preference or favorite shaft and why? If ya don't mind me asking.
I like small diameter and low deflection. Nothing else really matters to me. The reasons I like LD are here:

advantages of LD shafts

I also prefer a harder tip, per the info here:

tip hardness effects

I don't care about the "feel" of the hit or "feedback," per the info here:

cue "feel," "hit," "feedback," and "playability"

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Dave
  
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01-10-2018, 08:58 AM

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Originally Posted by dr_dave View Post
I was also shocked by the precision over such a large angle range, both with the analysis plot and the results at the table (in the video).

Thank you for asking this. It encouraged me to add a new page to the analysis file. Gaps between 1/4" and 1/2" give good results over 15-20 degrees. 3/8" has superior accuracy, but 1/4" offers a wider range of angles with decent accuracy with faster-speed shots. Check out the plots on the new last page.
It is important to point out that all of the results will vary slightly based on ball conditions. I used what are considered typical values for friction in my analysis, but the amount of throw with vary from one ball set to the next (see the ball cleaning and surface condition effects resource page).

Regards,
Dave
  
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01-10-2018, 03:30 PM

Quote:
Originally Posted by dr_dave View Post
Quote:
Originally Posted by Dan White View Post
have you considered what the upper and lower bounds are for the 3/8" gap shot where you can still expect to pocket the ball straight in? I know it depends on shot length and pocket opening, but let's say I estimate a 1/4 inch gap. Can I figure it will still be straight with maybe a little throw, and vice versa for a shot that is closer to 1/2 inch?
Thank you for asking this. It encouraged me to add a new page to the analysis file. Gaps between 1/4" and 1/2" give good results over 15-20 degrees. 3/8" has superior accuracy, but 1/4" offers a wider range of angles with decent accuracy with faster-speed shots. Check out the plots on the new last page.
FYI, to those interested, I just posted another new version of TP B.21, so now there is an additional "last page" showing how things change (or don't change) with ball conditions.

Also, with encouragement and help from Bob Jewett, I added an analytical derivation for the optimal gap size. It is in fact 3/8" (9.5 mm). That's on the bottom of the 2nd page of the new version of the document.

I hope the math and physics nerds out there like it (I do),
Dave
  
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Dan White
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01-10-2018, 05:01 PM

Quote:
Originally Posted by dr_dave View Post
I was also shocked by the precision over such a large angle range, both with the analysis plot and the results at the table (in the video).

Thank you for asking this. It encouraged me to add a new page to the analysis file. Gaps between 1/4" and 1/2" give good results over 15-20 degrees. 3/8" has superior accuracy, but 1/4" offers a wider range of angles with decent accuracy with faster-speed shots. Check out the plots on the new last page.

Regards,
Dave
Those last few additions are very helpful. Here's what I think I can remember long term from all of this. Correct me if I'm wrong.

For cases where the combination balls are lined up to center pocket:

If the gap is about the diameter of my cue tip (1/2 inch) then I can slop it in up to about a 3/4 ball hit whether I hit it soft or hard. This means I can cut to the left or right depending on where I need the cue ball to go and still pocket the ob!

If the gap is about half the diamater of my cue tip (1/4 inch) then I can shoot up to a half ball hit at pocket speed, or 3/4 ball hit if I shoot hard.

If the gap is about 3/4 the diameter of my cue tip (3/8 inch), the ob will go straight up to a half ball hit at pocket speed. At fast speed, I can only go up to about a 3/4 ball hit and expect the ob to still go straight.

Hit a few practice shots to test table conditions.

So the common thing about all gaps from half the tip diameter up to the tip diameter (easy to compare) is that as long as you shoot less than a 3/4 ball hit at any speed, the ball should go in.


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01-11-2018, 08:52 AM

Quote:
Originally Posted by Dan White View Post
Those last few additions are very helpful. Here's what I think I can remember long term from all of this. Correct me if I'm wrong.

For cases where the combination balls are lined up to center pocket:

If the gap is about the diameter of my cue tip (1/2 inch) then I can slop it in up to about a 3/4 ball hit whether I hit it soft or hard. This means I can cut to the left or right depending on where I need the cue ball to go and still pocket the ob!

If the gap is about half the diamater of my cue tip (1/4 inch) then I can shoot up to a half ball hit at pocket speed, or 3/4 ball hit if I shoot hard.

If the gap is about 3/4 the diameter of my cue tip (3/8 inch), the ob will go straight up to a half ball hit at pocket speed. At fast speed, I can only go up to about a 3/4 ball hit and expect the ob to still go straight.

Hit a few practice shots to test table conditions.

So the common thing about all gaps from half the tip diameter up to the tip diameter (easy to compare) is that as long as you shoot less than a 3/4 ball hit at any speed, the ball should go in.
Those are good approximate rules of thumb. Also, instead of "shoot less than a 3/4 ball hit," I would say "hit fuller than a 3/4 ball hit."

Good job,
Dave
  
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01-11-2018, 09:22 AM

Quote:
Originally Posted by Dan White View Post
Those last few additions are very helpful. Here's what I think I can remember long term from all of this. Correct me if I'm wrong.

For cases where the combination balls are lined up to center pocket:

If the gap is about the diameter of my cue tip (1/2 inch) then I can slop it in up to about a 3/4 ball hit whether I hit it soft or hard. This means I can cut to the left or right depending on where I need the cue ball to go and still pocket the ob!

If the gap is about half the diamater of my cue tip (1/4 inch) then I can shoot up to a half ball hit at pocket speed, or 3/4 ball hit if I shoot hard.

If the gap is about 3/4 the diameter of my cue tip (3/8 inch), the ob will go straight up to a half ball hit at pocket speed. At fast speed, I can only go up to about a 3/4 ball hit and expect the ob to still go straight.

Hit a few practice shots to test table conditions.

So the common thing about all gaps from half the tip diameter up to the tip diameter (easy to compare) is that as long as you shoot less than a 3/4 ball hit at any speed, the ball should go in.
FYI, I just added the following to TP B.21:

Here's a good overall simplified "rule of thumb:" If a small-gap combo is wired to the center of a pocket, with a gap size between 1/4" (6 mm, about 1/2 the width of a typical shaft) and 1/2" (13 mm, about the width of a typical shaft), anything fuller than a 3/4-ball hit (14.5 degrees) between the 1st and 2nd ball will result in pocketing the 2nd ball (at any speed).

Thank you again,
Dave

Last edited by dr_dave; 01-11-2018 at 09:27 AM.
  
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01-11-2018, 09:43 AM

Quote:
Originally Posted by dr_dave View Post
FYI, I just added the following to TP B.21:

Here's a good overall simplified "rule of thumb:" If a small-gap combo is wired to the center of a pocket, with a gap size between 1/4" (6 mm, about 1/2 the width of a typical shaft) and 1/2" (13 mm, about the width of a typical shaft), anything fuller than a 3/4-ball hit (14.5 degrees) between the 1st and 2nd ball will result in pocketing the 2nd ball (at any speed).

Thank you again,
Dave
Nice! I couldn't have said it better myself.


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01-13-2018, 09:44 AM

Has anybody tried out the magical 3/8" (1/3 ball radius) combo gap size at a table yet? If so, did you get results similar to that demonstrated in the video?

I also posted this on Facebook, and I have been shocked by how little response it got. I personally think this is one of the most dramatic physics-related effects I've ever seen on a pool table.

Regards,
Dave


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Originally Posted by dr_dave View Post
Check out the following new video dealing with small-gap combos, where cut-induced throw is very important. Physics effects are covered first, and then practical game-situation examples are demonstrated.

NV J.1 - Small-Gap-Combination Throw Effects and Game-Situation Examples

And for the math/physics nerds out there, check out the following analysis proving a gap of 3/8" (9.5 mm) produces interesting results (as shown in the video). I know some of you might know about this effect already; but for those who don't, it might be quite interesting and surprising.

TP B.21 - Small-gap-combination throw effects

Even if you aren't a math/physics nerd, you still might be interested in looking as some of the plots and bold-text conclusions in the analysis document.

Enjoy,
Dave
  
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01-13-2018, 09:48 AM

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Originally Posted by dr_dave View Post
Has anybody tried out the magical 3/8" (1/3 ball radius) combo gap size at a table yet? If so, did you get results similar to that demonstrated in the video?

I also posted this on Facebook, and I have been shocked by how little response it got. I personally think this is one of the most dramatic physics-related effects I've ever seen on a pool table.
FYI to those interested, I just created a resource page summarizing all of the interesting and useful conclusions from the physics analysis. Here it is:

small-gap combo resource page

Enjoy,
Dave
  
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