Double the rail maximum

E

eze123

AzB Silver Member
Silver Member
Question: on the table you generally play, what is the farthest you can double the rail? Long and short?
Starting basically right straight off the rail, I can hit just past 3, maybe 3.2, shooting towards the short rail, so I'm thinking I should be able to make about half that shooting towards the long rail, maybe 1.5, or so. I always come in short, maybe 1.4 at best. Seems a little short to me, my table, my stroke? what's the problem? I should be able to get a little farther, no?
 
I'm unfortunately *nowhere* near a table to be able to try and tell you my experience with that, but I seem to recall that either the first or the Advanced Byrne book had a diagram of what he considered the 'maximum' to be. Worth checking it out.
 
eze123 said:
Question: on the table you generally play, what is the farthest you can double the rail? Long and short?
Starting basically right straight off the rail, I can hit just past 3, maybe 3.2, shooting towards the short rail, so I'm thinking I should be able to make about half that shooting towards the long rail, maybe 1.5, or so. I always come in short, maybe 1.4 at best. Seems a little short to me, my table, my stroke? what's the problem? I should be able to get a little farther, no?
Click to expand...

This is extremely equipment dependent, and is directly related to coefficients of friction. On brand new cloth with very clean balls, it is hard to get beyond 2 diamonds the long way. On the Verhoeven I play on, with nine month old cloth and my own freshly cleaned balls, I get just over 3. On a table with sticky rails and using dirty balls it is possible to hit the opposite long cushion.

The key is how much the english grabs the second cushion and, hence, how much english is left to act on the third. Since the hit on the first cushion is almost parallel to the rail it has very little effect on the path and uses up very little angular momentum. High friction makes the ball bite more on the second and uses up more spin so there is less spin on the third.

I can't answer why your results are different going the short way.

Mark
 
Ah, ok, that makes sense, you're saying on a decently maintained table, not brand new cloth and such, you hit past 3 going the long way. I get that, too, about 3.1, 3.2. So the short way should be about half, 1.5-1.6 or so, I get about 1.4, small difference, maybe my corner's are a little crappy. What do you get the short way, though, about 1.5?
I just thought it odd that Byrne was saying you can get 2 the short way. I don't remember ever seeing that far of a spread. Makes sense again, though, probably on old unheated tables with gummy rails and old cloth.
 
For me it seems my maximum is about 3 and 1.5. I seem to do better going the long way for some reason, but I'm just a novice.
 
mbvl said:
This is extremely equipment dependent, and is directly related to coefficients of friction. ..
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I used to play on a table in the Student Union on which you could play the long way and just get to the opposite long cushion and almost reverse that corner too. I think the first corner was a little funny.
 
Bob Jewett said:
I used to play on a table in the Student Union on which you could play the long way and just get to the opposite long cushion and almost reverse that corner too. I think the first corner was a little funny.
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Bob,

Now that you've checked in...

In the portion of my post that you quoted I say that the return "is directly related to the coefficients of friction". I meant that figuratively, but is it true literally? Is the relation direct or more complicated?

Mark
 
I play for 3 and 1-1/2 as my standard. Then check the table.

There's a table I played on in Missouri that I can hit the second diamond from the corner on the opposite long rail. The table is close to the hamburger grill. Funny thing is, the locals think that's how a table should play and complain when new cloth is put on. Boy is that table hard to play on with old cloth!!
 
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eze123 said:
I always come in short, maybe 1.4 at best. Seems a little short to me, my table, my stroke? what's the problem? I should be able to get a little farther, no?
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Assuming friction coefficients and rail efficiencies at different corners isn't the reason, it could be the differences in the mechanics of your stroke between the two tests.

If your cue is more elevated when shooting the short way vs the long way, then there will be more curving into the 1st rail the short way. That increases the input angle and reduces the output angle. Shooting from too close to a rail (natural for the short way) can cause your cue to be more elevated than shooting from closer to the middle of the table (natural for the long way).

If you want to make a better comparison, make sure you are starting the same distance, speed and cue elevation when testing.

Also, how are you measuring your distances up the rails? You are distorting the results if you compare the actual contact points of the balls with the rails and will always measure less the short way for otherwise equal shots. It's geometrically more precise to extend the final path of the ball centers through to where they touch the noses of the cushions, which is always farther than where their contact points are. Otherwise, your long way shot path is roughly 1/2-ball longer than double the distance of where you're measuring the short way.

Robert
 
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mbvl said:
Bob,

Now that you've checked in...

In the portion of my post that you quoted I say that the return "is directly related to the coefficients of friction". I meant that figuratively, but is it true literally? Is the relation direct or more complicated?

Mark
Click to expand...
I think it's more complicated. An example is an extreme side-spin shot in which the object ball will be slipping on the cushion at the end of contact. In that situation, the contact becomes "nonlinear" and simple proportional rules don't apply.

If the ball has so little side spin on it that it is not slipping at the end of contact, which I think is often the case unless the cue ball has struck an object ball and had its spin "multiplied," then I think the coefficient of friction is not a major factor in the angle change. I think that the required side spin for shooting up the center of the table and coming back to either corner does not depend much on the rail friction.
 
Bob Jewett said:
If the ball has so little side spin on it that it is not slipping at the end of contact,
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For you physics geeks, this is what French physicists like Coriolis and Petit call adherence. (Bob knows this already :)) American physics writers seem to avoid analyzing ball-cushion interactions, but talk about the same concept as it relates to throw in ball-ball interactions. Unfortunately, they haven't settled on a nice single term like adherence , so the literature remains fragmented.

which I think is often the case unless the cue ball has struck an object ball and had its spin "multiplied,"
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This is exactly the source of the error that both Coriolis and Petit make in their test shots for measuring the rail friction coefficient. (Their test is stunning perpendicularly into a rail with max sidespin and calculating the coefficient from the resulting angle). They both assume that you can bypass the adherence regime and achieve sliding directly with a cue without using spin multiplication off a ball, which is impossible without extremely low-friction cloth. That's why they significantly underestimate the rail coefficient in their books.

Better is to stun off a ball close to the rail onto the perpendicular incidence line with max sidespin to ensure sliding from spin multiplication (being sure to use left and right spin to balance errors). Either that, or else shoot directly as in the original test shot, but with a specific tip offset to use in the calculation and just assume adherence. Unfortunately, neither is especially easy to do with great precision without access to Iron Willie :)

Robert
 
Older Cloth will Produce Better Results.

If you have a cloth on the table that is worn down, say maybe, 3 to 6 months old, you'll get more consistent results, but only if you REALLY know the proper place to aim on the first cushion, this is the key to double the rail shots, and of course a consistent stroke would help too.
Mr3cushion (Bill Smith)
 
Robert Raiford said:
This is exactly the source of the error that both Coriolis and Petit make in their test shots for measuring the rail friction coefficient. (Their test is stunning perpendicularly into a rail with max sidespin and calculating the coefficient from the resulting angle). They both assume that you can bypass the adherence regime and achieve sliding directly with a cue without using spin multiplication off a ball, which is impossible without extremely low-friction cloth. That's why they significantly underestimate the rail coefficient in their books. Robert
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Oh man, oh man, and some people thought the "long vs. short" argument was going to scare off new players. I had to go look up terms I haven't seen since college.

"If your cue is more elevated when shooting the short way vs the long way, then there will be more curving into the 1st rail the short way. That increases the input angle and reduces the output angle. Shooting from too close to a rail (natural for the short way) can cause your cue to be more elevated than shooting from closer to the middle of the table (natural for the long way)."
I think this is correct, jacking up because of the rail costs me about a .1 loss. Straight on I get almost exactly half going the long way. The thing that started it for me was reading the Byrne book where it talked about maybe getting 2 or 4 on a double the rail shot. I've never seen that, good stories, but I guess I've had the misfortune of playing on decent tables.
 
eze123 said:
Oh man, oh man, and some people thought the "long vs. short" argument was going to scare off new players. I had to go look up terms I haven't seen since college.

"If your cue is more elevated when shooting the short way vs the long way, then there will be more curving into the 1st rail the short way. That increases the input angle and reduces the output angle. Shooting from too close to a rail (natural for the short way) can cause your cue to be more elevated than shooting from closer to the middle of the table (natural for the long way)."
I think this is correct, jacking up because of the rail costs me about a .1 loss. Straight on I get almost exactly half going the long way. The thing that started it for me was reading the Byrne book where it talked about maybe getting 2 or 4 on a double the rail shot. I've never seen that, good stories, but I guess I've had the misfortune of playing on decent tables.
Click to expand...
Just a reminder eze123, An elevated butt changes the center ball contact point ie a masse the center is at the North Pole.
 
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