Question about cushion down angles

D

darmoose

Shutin@urhole is OVERATED
Silver Member
This is no doubt a dumb question, but I have to ask it. The OB makes contact with the cushion at approx 1 7/16" above the playing surface. The same is true when the OB hits the cushion end (inside the pocket). How does the down angle of the pocket cuts have any effect on the CB and how it enters or is accepted by the pocket? It is said and seems to be universally accepted that greater down angles like 15 degrees accept the balls better than lesser down angles like 12 degrees. Why does anything but the nose (point) of the cushion matter?

I do understand how the depth of the shelf matters, but again I don't see how the down angle has any effect on the depth of the shelf.
 
I'm no mechanic in any way, but I took on the project to design and built my own table.
I love these Tech Talks
So I'll give it a try

here's my 2 cents:
Point 1
The rubber on the cushion has a slight downwards angle to the point where the OB makes contact
Point 2
When an OB hits the cushion of a rail, there is compression of the rubber.
The harder it hits, the more compression, the more reaction of the rubber flexing back.
Point 3
When the OB hits the inside end of the rail, there is a changing difference of height of the rail, the point of contact for the OB changes
Point 4
If the down angle should be 0°, the point of contact would be at ½ of the ball size = 1¼"

So to have consistent reaction of any part of the rail, the down angle must be so that the height of contact point is the same at every point.

Is this something in the right direction.
 
Also not a mechanic, but I enjoy learning how tables work and I’ll take a stab. I was wondering about this also and couldn’t find any answers online, but when carefully looking at actual balls in pockets, the answer seems pretty simple.

Balls will normally intercept the cushion nose and the angle under the rail doesn’t really matter. But this is only true if there is slate under the ball.

If you look at the inner rail corners, they terminate well past the edge of the slate. A corner from my GC6 is shown below. Balls hit into this corner area where the face extends past the shelf ledge, laws of gravity cause them to contact a much larger & lower portion of the facing than when its on a normal part of the table/rail. As such, a greater down angle (say 15 deg) will have a downward funnel effect on the ball at contact, causing more potted balls. Vs a steeper down angle (eg 12 deg) which causes the ball to deflect more horizontally & possibly rattle out.

Seems like there is a relationship between the shelf depth and down angle. As in - steeper down angles have more impact (play tougher) on pockets with shallower shelves…

Is that in the ballpark?

✌️

F6C0AE51-9CBF-4AE4-9D15-DA1955B63387.jpeg
 
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Glen,

st the risk of another wrong answer.....i suspected that the reason for having an inward down angle at the pockets was to provide room for compression that would not be there if the face was at zero degrees. That seems to make some sense to me, and the only reason for more angle like 15 as opposed to 12 is to provide for more compression on harder hit shots.....more puzzling to me tho is how any of this can make a shelf deeper...

P,S....maybe you should jelly me a little for providing opportunities to expose your intelligence.....😁
 
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The downward angle in the pocket directs the ball toward the pocket (down). It's like a funnel. The steeper the angle, the more downward force applied to the ball. It's kind of like a backboard behind a basketball hoop.

The downward angle is required, in order to keep the balls from flying upward upon impact with the facing.. Suppose there were no downward angle at all. When a ball impacts the facing, the facing will compress. When this happens, since the contact point is 1 1/8" from the surface of the slate, it's as if the angle is actually upward, which will serve as a springboard for the ball. Therefore, a downward angle should be steep enough to compensate for the facing/cushion compression from a firmly struck ball.

For a shallower shelf table, I like using a 12 degree downward angle, particularly when tightening the pockets (which reduces the shelf depth).
For a deeper shelf table (such as Diamond), the typical downward angle is 15 degrees (if I recall correctly).
Valleys, which practically have no shelf, use 10 degrees.
 
darmoose said:
Glen,

st the risk of another wrong answer.....i suspected that the reason for having an inward down angle at the pockets was to provide room for compression that would not be there if the face was at zero degrees. That seems to make some sense to me, and the only reason for more angle like 15 as opposed to 12 is to provide more compression on harder hit shots.....more puzzling to me tho is how any of this can make a shelf deeper...
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The downward angle has Zero effect on shelf depth....

Downward angle is dependent on shelf depth. Not the other way around.
 
bradsh98 said:
The downward angle has Zero effect on shelf depth....

Downward angle is dependent on shelf depth. Not the other way around.
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Very good answers Jeff, I figured you'd jump in sooner or later. The big mouth so called top tier table mechanics never do get involved in conversations like these! They like the idea of being thought of as a top level mechanic, rather than exposing themselves as just regular old hacks because when it comes right down to it, they don't really know shit about top tier level work!
 
Okay, let's elaborate on what Bradshaw posted.

First off, when dealing with balls being pocketed you're dealing with the forces of forward momentum. When pocketing balls, you're requiring the pocket to change the angle of a moving object, that requires a greater force needed to overcome the momentum of the moving object, being the object balls.

If you had zero down angle, or a 90 degree down angle, depending on how you want to look at it, with the forward momentum force of the object ball hitting the inside pocket angle, with no down angle at all, the forward momentum force of the object ball would in fact cause the object ball to jump straight up out of the pocket and off the table, because all that energy is going somewhere if its not contained inside the pocket.

Now, downangle is actually another word for deflection in the case of the pockets. When you add a negative down angle, meaning a tilting back angle to the pocket facing, what you're essentially doing is creating a wall that when the object ball runs into it, the ball is deflected, or driven down towards the slate. When this action occurs, the speed of the ball is greatly reduced, and that reduction translates into the balls sitting on the pocket shelf. The greater the down angle, the higher the deflection result. Diamonds use a deeper shelf on their 9fts than most other 9fts, so they use a 15 degree down angle. Brunswick uses a 12 degree down angle. The difference between the two is the Diamond down angle helps assist the object balls to deflect deeper towards the throat of the pocket, trying to help pocket the ball, but at the same time, the deeper down angle also exposes a little more slate shelf for the balls to sit on when they come to a rest.

So, if you used the Diamond 15 degree down angle on the typical GC pocket down angles, they would cause the pockets to play bigger by deflecting the balls deeper towards the throat of the pocket, but with the shorter shelfs, balls fall in much easier!

Nose heights can vary anywhere from 1 5/16" to 1 3/4" so thats why the nose height has nothing to do with how the actual pockets play, and requardless of how thick or thin the rails are, the down angle in the pockets serve to do the same thing requardless of who made the pool table.

Then the other factor that can screw up any down angles from working correctly, and that is the use of soft facings and soft cushions. The combination of those two together can make pockets play so badly you end up with the Olhausen pocket rattle!
 
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Not a mechanic here either but the down angle refers to the surface where the facings get glued on inside of the pocket. the part of the cushion that the ball hits when you shoot straight down the rail. I believe. It helps drive the ball into the pocket once the ball gets inside the jaws.
 
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A real good clue of what area of the table down angles refer to are pocket specs. Whenever mechanics talk about pocket specs your hear things like pocket opening size, pocket angles, and down angles all mentioned together.
 
realkingcobra said:
They also determine how a pocket is going to react to balls being shot into them, as to whether the balls will go in, or not go in!
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As a seasoned pool character, you’re supposed to have a good sense of humor! Whats the point of AZB, if we can’t cuss & poke fun at each other & ourselves? ✌️😘
 
realkingcobra said:
So when it comes to people skills, you need to check your own out, because you have no where near the skills needed to critique my skills at working on pool tables, or criticism of those that do work on them!!!
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There's another thing about this statement I'd like to point out.. I never even hinted that I knew as much about pool tables as you do.

You are very good at what you do, and I will never achieve that level. At the same time you will never be on my level when it comes to applying fertilizers and pesticides on a commercial level. That's what I do everyday. And I do it correctly and with pride.

We each have our own thing. I do my homework , and I've used a lot of tips that you've provided to all of us . When I work on a pool table I always try to do my best work, because I want the table to play well.
 
buckshotshoey said:
There's another thing about this statement I'd like to point out.. I never even hinted that I knew as much about pool tables as you do.

You are very good at what you do, and I will never achieve that level. At the same time you will never be on my level when it comes to applying fertilizers and pesticides on a commercial level. That's what I do everyday. And I do it correctly and with pride.

We each have our own thing. I do my homework , and I've used a lot of tips that you've provided to all of us . When I work on a pool table I always try to do my best work, because I want the table to play well.
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And for that statement you just made, you have my ultimate respect 100%. I couldn't possibly know what you do in your world for income, but in here, this is my world, and any conversation I have, its in my world. But as I said, I respect you for learning the RIGHT ways of doing this work!!
 
buckshotshoey said:
There's another thing about this statement I'd like to point out.. I never even hinted that I knew as much about pool tables as you do.

You are very good at what you do, and I will never achieve that level. At the same time you will never be on my level when it comes to applying fertilizers and pesticides on a commercial level. That's what I do everyday. And I do it correctly and with pride.

We each have our own thing. I do my homework , and I've used a lot of tips that you've provided to all of us . When I work on a pool table I always try to do my best work, because I want the table to play well.
Click to expand...
And for that statement you just made, you have my ultimate respect 100%. I couldn't possibly know what you do in your world for income, but in here, this is my world, and any conversation I have, its in my world. But as I said, I respect you for learning the RIGHT ways of doing this work!!
 
realkingcobra said:
If you want NICE, don't contribute to a thread im posting in, chances are I might me pissed off at the OP already and you're NOT helping matters any!!!
Click to expand...

So, correct me off I’m wrong, what it sounds like you are saying is that when you reply in any thread, that is now your thread and everyone who wants to read that thread has to put up with your condescending attitude.

Is that about right?
 
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