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cushioncrawler
12-04-2006, 03:01 PM
With 2 balls touching, ie a set (which some call a plant) -- u want to pot the "2nd" ball, by hitting the 1st ball -- but u can see that the "line of centers" is pointing a long way off the pocket. Ok, how would u maximize the throw, to get the pot -- i think that there are 4 things u shood do.

Q1... Where would u place the qball (in hand) to throw the 2nd ball to the max??
Q2... What contact would u make on the 1st ball??
Q3... What spin or screw would u put on the qball??
Q4... How hard would u hit (ie to get max throw)??
madMac.

Bob_Jewett
12-04-2006, 03:41 PM
<blockquote><font class="small">Quote cushioncrawler:</font><hr> With 2 balls touching, ie a set (which some call a plant) -- u want to pot the "2nd" ball, by hitting the 1st ball -- but u can see that the "line of centers" is pointing a long way off the pocket. Ok, how would u maximize the throw, to get the pot -- i think that there are 4 things u shood do.

Q1... Where would u place the qball (in hand) to throw the 2nd ball to the max??
Q2... What contact would u make on the 1st ball??
Q3... What spin or screw would u put on the qball??
Q4... How hard would u hit (ie to get max throw)??
madMac.
<hr /></blockquote>
There is a theoretical result, but I'll take a guess while Dr. Dave is doing the calculation: Place the cue ball in inline with the two balls. Play a half-ball stun shot on the appropriate side of the nearer ball. (Actually, I want the cue ball to travel more or less parallel to the line of centers of the object balls, but in-line is close enough.) Play the shot just hard enough to get the object ball to the pocket. Do not use side.

I think that the equations governing throw are complicated enough that the result will be most easily determined by calculation for various cases rather than by just solving an equation.

dr_dave
12-04-2006, 04:11 PM
<blockquote><font class="small">Quote Bob_Jewett:</font><hr> <blockquote><font class="small">Quote cushioncrawler:</font><hr> With 2 balls touching, ie a set (which some call a plant) -- u want to pot the "2nd" ball, by hitting the 1st ball -- but u can see that the "line of centers" is pointing a long way off the pocket. Ok, how would u maximize the throw, to get the pot -- i think that there are 4 things u shood do.

Q1... Where would u place the qball (in hand) to throw the 2nd ball to the max??
Q2... What contact would u make on the 1st ball??
Q3... What spin or screw would u put on the qball??
Q4... How hard would u hit (ie to get max throw)??
madMac.
<hr /></blockquote>
There is a theoretical result, but I'll take a guess while Dr. Dave is doing the calculation: Place the cue ball in inline with the two balls. Play a half-ball stun shot on the appropriate side of the nearer ball. (Actually, I want the cue ball to travel more or less parallel to the line of centers of the object balls, but in-line is close enough.) Play the shot just hard enough to get the object ball to the pocket. Do not use side.

I think that the equations governing throw are complicated enough that the result will be most easily determined by calculation for various cases rather than by just solving an equation. <hr /></blockquote>

I'll add this to my future studies list. I've avoided multiple ball collisions up till now, because the physics modeling is as much an art as it is a science. One of these days, I'll need to bite the bullet and research this. Have you seen any good and useful theoretical work on multiple pool ball collisions?

Regards,
Dave

Bob_Jewett
12-04-2006, 04:17 PM
<blockquote><font class="small">Quote dr_dave:</font><hr>... Have you seen any good and useful theoretical work on multiple pool ball collisions?... <hr /></blockquote>
Nope. I think even something as simple as the double-ball spot shot is only do-able by numerical methods.

cushioncrawler
12-04-2006, 05:10 PM
<blockquote><font class="small">Quote Bob_Jewett:</font><hr> ....There is a theoretical result, but I'll take a guess while Dr. Dave is doing the calculation: Place the cue ball in inline with the two balls. Play a half-ball stun shot on the appropriate side of the nearer ball. (Actually, I want the cue ball to travel more or less parallel to the line of centers of the object balls, but in-line is close enough.) Play the shot just hard enough to get the object ball to the pocket. Do not use side..... <hr /></blockquote>
Hi Bob...
Q1 -- Yes -- in line is good, in fact 4 balls clear (and in line) seemed to be best in my tests.
Q2 -- No -- a 1/2ball contact on 1st ball waznt az good az a ?/? contact in my tests.
Q3 -- Yes -- stun was best. In fact, the biggest surprize that i got doing the tests was just how weak the throw was if u tryd to use much side.
Q4 -- Yes -- softish was best. But, u havta hit the qball pretty hard even tho the 2nd ball might only just make it to the pocket (but here i have probably given the answer to Q2 away).

One little problem -- when u play this sort of combination, the qball takes a much wider angle than u might think (albeit a stun angle), and it is very eezy to scratch (what happened??!!) -- koz the wt of both (object) balls gets into the equation.

So, Q2 is still out there. But, perhaps 2-1/4" ballz etc iz different to 2-1/16", and perhaps someone might kum up with a different alternative mix. madMac.

Jal
12-04-2006, 05:11 PM
<blockquote><font class="small">Quote Bob_Jewett:</font><hr>...I think that the equations governing throw are complicated enough that the result will be most easily determined by calculation for various cases rather than by just solving an equation.<hr /></blockquote>Unless you have a computer that will do it for you. I have a program that finds it using Newton's method, but of course it's only applicable to the two ball case.

Mac's question points out a potential problem with the established dependence of the coefficient of friction on surface speed. In the tests I've seen, two balls are frozen together and the cueball collides with one of them, the latter acting as a proxy cueball. But this affects, to some extent or another, the ability of the proxy cueball to shed surface speed by slowing down and acquiring spin. At severe cut angles this shouldn't make much difference, but it could skew the results at fuller hits. Maybe Marlow did his tests without frozen balls?

Jim

Jal
12-04-2006, 07:18 PM
<blockquote><font class="small">Quote cushioncrawler:</font><hr>...Q2 -- No -- a 1/2ball contact on 1st ball waznt az good az a ?/? contact in my tests......But, u havta hit the qball pretty hard even tho the 2nd ball might only just make it to the pocket (but here i have probably given the answer to Q2 away).<hr /></blockquote>In order to get maximum throw you want the least amount of tangential surface speed between the first and second object ball consistent with them sliding across each other during the entire contact period. And let's assune that you get maximum throw on a normal non-combination shot for these balls at a 30 degree cut. And let's further assume that in the combination shot, the first object ball cannot contribute to reducing surface speed by slowing down and picking up spin as readily as with a normal shot.

All of this suggests that maximum throw should occur when you have half the normal tangential surface speed compared to the 30 degree cut for the non-combination shot. SOoo, I'm guessing about a 3/4 ball hit (~ 15 degree cut). But this is in the opposite direction of your hint, which is indicating that it's larger than 30 degrees. So apparently all of this impeccable reasoning is for naught.

Ah, physics, you can't live with it, and you can't live without it.

Jim

cushioncrawler
12-04-2006, 09:03 PM
<blockquote><font class="small">Quote Jal:</font><hr> ....In order to get maximum throw you want the least amount of tangential surface speed between the first and second object ball consistent with them sliding across each other during the entire contact period. And let's assune that you get maximum throw on a normal non-combination shot for these balls at a 30 degree cut. And let's further assume that in the combination shot, the first object ball cannot contribute to reducing surface speed by slowing down and picking up spin as readily as with a normal shot. All of this suggests that maximum throw should occur when you have half the normal tangential surface speed compared to the 30 degree cut for the non-combination shot. SOoo, I'm guessing about a 3/4 ball hit (~ 15 degree cut). But this is in the opposite direction of your hint, which is indicating that it's larger than 30 degrees. So apparently all of this impeccable reasoning is for naught. Ah, physics, you can't live with it, and you can't live without it ..... <hr /></blockquote>

Hi Jim.
I think i follow -- but i think that the ball-to-ball sliding must be a bit different when the 1st OB is sqeeezed between 2 balls during the whole process (or allmost -- the 2 collisions overlapping i guess) -- so i wont try to imagine this stuff, i will go straight to the next para.

I agree that a 3/4ball contact between qball and an OB in an ordinary (stunned) collision should give most throw -- and, that a 1/2ball contact on the 1st ball of the above "set" would in theory tend to give the 1st ball that line approx -- but, here again, what with the 1st ball being sqeezed from 2 sides, i reckon that in our "set" the 1st ball duz most of its "work" on the second ball while heading much thicker than simple collision-theory might say.

In other words, the time for collision-1, between the qball and the 1st ball, is much longer than for a simple 2-ball collision -- in other words, the 1st ball is dragged with the qball much more than u think -- in other words, the 1st ball has to be contacted much finer than u might think, ie to contact the 2nd ball 3/4 ball.

At first "glance", this sqeez effect appears wrong, koz the 1st ball ends up going allmost square to the center-to-center line -- but this "ultimate" trajectory is due more to the second collision.

Q2 -- so, anyhow, ?/? is finer than 1/2 ball. Tests will show. madMac.

cushioncrawler
12-05-2006, 02:46 PM
Q2.... My tests showed that the best contact on the 1st OB was 1/4 ball. No other attempts varying Q1, Q2, Q3, and Q4 got a better rezult -- varyations usually got much less throw. The next question is...

Q5.... What is the biggest throw angle that u can hope to get (ie for 2 balls touching). Here, for one particular set of balls, my max throw angle was 1 in 7. This is huge -- and raises another question....

Q6.... How come u can get a throw of say 1 in 7 for a touching 2ball combination shot, when u karnt get much better than say 1 in 14 for the throw for a simple ball to ball collision.

The answer is in the ball to ball friction. One little clue is that when doing the tests, when polishing the balls between shots, u will find that the polishing takes more time and effort than the polishing that is needed for similar tests where the 2 objectballs are not touching.

Koz, the sqeez-effect (when the balls are touching) increases the contact time -- it allso increases the roughness of the "impact mark". I should say "impact marks", koz there are 3 marks (koz there are 3 balls).

Hitting harder is counterproductive, koz an impact mark is a complicated thing. An impact mark allways includes an amount of powder, ie burnt and abraded plastic -- this residue acts as an oil, or as ball-bearings even. Hitting very hard increases the amount of abrasion, but allso increases the amount of residue (lots) -- hence, something in between very soft and very hard duz the trick. madMac.

cushioncrawler
12-05-2006, 03:04 PM
<blockquote><font class="small">Quote cushioncrawler:</font><hr> .... I should say "impact marks", koz there are 3 marks (koz there are 3 balls).. <hr /></blockquote>
Karnt agree -- the way i see it, there haztabe 4 impacts marks (koz there are 3 balls).

cushioncrawler
12-05-2006, 03:17 PM
<blockquote><font class="small">Quote cushioncrawler:</font><hr> .... Hitting harder is counterproductive, koz an impact mark is a complicated thing. An impact mark allways includes an amount of powder, ie burnt and abraded plastic -- this residue acts as an oil, or as ball-bearings even. Hitting very hard increases the amount of abrasion, but allso increases the amount of residue (lots) -- hence, something in between very soft and very hard duz the trick.... <hr /></blockquote>
I can add one more effect. When u hit real hard, the temporary flatspot(s) on the ball(s) is bigger, and u will looz up to say 1dg of throw, ie if the balls had zero friction, the OB would have a trajectory say 1dg off the center-to-center line. This "flatspot-sqeez" trys to take up to say 1dg off the throw -- but for soft shots the loss might be only say 1/4dg. A minor point, but us theoreticians looz sleep over this sort of thing.

colincolenso
12-06-2006, 09:23 AM
<blockquote><font class="small">Quote cushioncrawler:</font><hr>
Hi Jim.
I think i follow -- but i think that the ball-to-ball sliding must be a bit different when the 1st OB is sqeeezed between 2 balls during the whole process (or allmost -- the 2 collisions overlapping i guess) -- so i wont try to imagine this stuff, i will go straight to the next para.

I agree that a 3/4ball contact between qball and an OB in an ordinary (stunned) collision should give most throw -- and, that a 1/2ball contact on the 1st ball of the above "set" would in theory tend to give the 1st ball that line approx -- but, here again, what with the 1st ball being sqeezed from 2 sides, i reckon that in our "set" the 1st ball duz most of its "work" on the second ball while heading much thicker than simple collision-theory might say.

In other words, the time for collision-1, between the qball and the 1st ball, is much longer than for a simple 2-ball collision -- in other words, the 1st ball is dragged with the qball much more than u think -- in other words, the 1st ball has to be contacted much finer than u might think, ie to contact the 2nd ball 3/4 ball.

At first "glance", this sqeez effect appears wrong, koz the 1st ball ends up going allmost square to the center-to-center line -- but this "ultimate" trajectory is due more to the second collision.

Q2 -- so, anyhow, ?/? is finer than 1/2 ball. Tests will show. madMac. <hr /></blockquote>
Hi madMac,
Just thought I'd add my 2c on this one as I've messed around quite a bit with seeing how much I could turn plants off their lines.

I also found a 3/4 ball hit at slowish speed the most effective, and it seems to work better if the CB hits that point from a full ball angle (if you know what I mean, rather than cutting across the face of the front ball.

btw: I'll be back in Australia in 10 days so might get a chance to play some english billiards with you.

Cheers,
Colin

cushioncrawler
12-06-2006, 02:13 PM
<blockquote><font class="small">Quote colincolenso:</font><hr> ... Hi madMac, Just thought I'd add my 2c on this one as I've messed around quite a bit with seeing how much I could turn plants off their lines.

I also found a 3/4 ball hit at slowish speed the most effective, and it seems to work better if the CB hits that point from a full ball angle (if you know what I mean, rather than cutting across the face of the front ball.

btw: I'll be back in Australia in 10 days so might get a chance to play some english billiards with you... Cheers,
Colin <hr /></blockquote>
Hi Colin -- I saw your dad playing in a billiards final at the Geelong VRI, and had a long yarn with him. Yes, for sure, we will have to have a few 100up, at say the Geelong RSL (we won the premiership this year). I will get to tott, play a nice gather, then run a nursery to the pocket, and jam'em, and make u sit &amp; watch for a while -- Yeesssss!!! It takes me 60minutes to get to geelong throo the bush and wheatfields -- my house (&amp; table) at garibaldi wont be ready till July 07.

Hitting the 1st ball more or less directly, from a pozzy to the side, is allmost as good -- in my tests, doing it my way (ie 1/4ball contact on 1st ball) there was a very small gain over doing it your way -- but your way is simpler. I guess that in a game, exactly what sort of pozzy etc u chose to hit from would depend on whether u needed to leave good pozzy for the next shot (in which case my way might be better), or simply wanted to avoid a scratch (in which case your way would be better).

Catchyasoon madMac.

PS (whatever that meenz). In a few minutes time i am putting the trailer on the old ford, and driving throo geelong and melbourne to mt eliza, where we are selling our house (at 21 eumeralla grove, u can see the photos if u google "Redfirst"). On the way throo melbourne I will be selling a copy of The Cushion Crawler'z Bible to a guy from New Zealand who is viziting (it saves him $21 postage). Chapter 77 of the Bible haz about 10 pages about this 2ball-set stuff -- i will send u a pdf of the whole chapter, either now or when i get back in a couple of days.

slim
12-06-2006, 03:39 PM
<blockquote><font class="small">Quote cushioncrawler:</font><hr> With 2 balls touching, ie a set (which some call a plant) -- u want to pot the "2nd" ball, by hitting the 1st ball -- but u can see that the "line of centers" is pointing a long way off the pocket. Ok, how would u maximize the throw, to get the pot -- i think that there are 4 things u shood do.

"SEE INSERTS IN CAPS BELOW"

Q1... Where would u place the qball (in hand) to throw the 2nd ball to the max??
45 DEGREES OFF CENTER HIT ON FIRST BALL

Q2... What contact would u make on the 1st ball??
FROM THE SIDE THE CUE BALL IS "PUSHING" THE SECOND BALL AWAY FROM THE SIDE YOU CONTACT THE FIRST BALL.
Q3... What spin or screw would u put on the qball??
INSIDE
Q4... How hard would u hit (ie to get max throw)??
madMac.
DEPENDS ON HOW DIRTY THE BALLS ARE, THE DIRTIER THE MORE CUE BALL SPEED, CLEANER LESS SPEED, BUT IN GENERAL A MEDIUM TO SLIGHTLY LESS.
<hr /></blockquote>

HOPE THIS HELPS

cushioncrawler
12-06-2006, 04:42 PM
Hi Slim -- placing the qball at about 45dg and hitting the 1st ball full (using stun) is about what Colin said -- and it sure gives plenty of throw. But in my tests i got a tad more throw doing it my way.

Re "inside spin" -- yes, i reread my notes, and in fact, contrary to what i said earlier, "inside spin" is ok (possibly gives a tad less throw than pure stun) -- i shood have said that "outside-english" is poison.

Re "dirty balls" giving more throw at higher-speed -- i remember that i used the 2-ball set to experiment with the effect of old and new "impact marks" (ball-to-ball impact marks) on the object-balls. This is how i found that an impact mark with much of its "powder" still in place gave a little extra friction (compared to a polished surface), and that an impact mark with the powder lightly brushed away (but not enuff to polish the ball) gave a very very hi friction (ie throw).

I dont think that dirty balls are the problem -- the problem is the old and new impact marks -- i reckon that these (impact marks) would affect say 1 shot in 100 -- hence the skid that one gets at times. And u can add the effect of new and old qtip chalk marks -- these might add a 1 in 100 skid allso -- i think that Dr Onada looked into this sort of thing back in about 1989. madMac.

slim
12-06-2006, 05:18 PM
Older balls are more porus and cause and effect are impacted by this aspect.

cushioncrawler
12-08-2006, 03:35 AM
<blockquote><font class="small">Quote slim:</font><hr> Older balls are more porus and cause and effect are impacted by this aspect. <hr /></blockquote>
Yes -- i love the old balls -- they were heavier, harder, and they werent hi-gloss -- much better than the krapamiths that we have had foisted on us nowadays. The kraps would have been illegal in the old days -- hi-gloss balls not allowed.

The new kraps have killed the poor old English Billiards players -- the krap "natural angle" is all over the place -- too varyable -- but its not such a big worry for the play of pool etc -- and its only a small problem for the play of snooker.

When u contact the manufacturers, they feed u bullshit -- "We dont use any fillers for our phenolic resin balls" -- 2 lies in one sentance -- they should say "our bakelite balls" -- but, of course, they still use clay for filler, just like in the oldendays, but less i guess, and its covered by that beewdifulllll vitreous layer -- look lovely in the box -- and they last and last and last and last. U dont see tiger woods using a golf ball koz it lasts and lasts and lasts and lasts -- he wouldnt stand for krap. madMac.