sub rail angle
- Thread starter johnqbs
- Start date
No, not all all...they're not interchangeable.
It depends on the thickness of the rail.
THAT is what's wrong with the manufacturing end of this industry today. Anyone can figure out what bevel is needed to set the cushion height to 1 7/16" for any kind of cushion made on the market today, problem is, knowing what the bevel angle is...don't mean the cushions are going to play right. JUST as important as it is to have the correct nose height of the cushions, there's a lot more to it than that, you ALSO must take in consideration how thick the sub-rail is, as that height determines the backend height of the cushions and how that effects the action of the cushions overall. If you use for example K66 cushions and mount them on GC rails and you recut the bevel to set the nose height to be at 1 7/16"...but then you turn around and install the exact same cushions on a Gandy Big G set of rails with a sub-rail height of 1 5/8"ths...and use the same 1 7/16"ths nose height....the two sets of rails will play completly different...yet they have the SAME cushions, and the SAME nose height at the nose of the cushions....THAT is why your question can't just be simply answered.
Im new to all of this and trying to understand everything Im not a mechanic nor want to be one Im just learning more about tables for my own enjoyment. I assume the cushions sits on a specific angle so the cushion sits " level " and the sub rail should be of a height to let the nose height be 1 7/16" on a perfect table so what are those angles? I would like to check mine when I rip the cushions off and I would like to know if the cushion is tipped up or down from a perfect angle
What kind of table do you have?
This may shed a bit of info for you -
http://pooltablefeltcloth.com/Cushions-Supplies/Championship/Cushions-Mounting-Guide/index.shtm
JC
Coos Cues
Glen is this the dimension you changed on the diamonds to fix the playability? Rotating the rubber on it's center axis while maintaining the correct nose height until you liked the deflection characteristics and went with it? If this is the case can't you quantify the back end height for various rubber profiles for best play in order to give a person a modification goal to achieve this dimension no matter what the table starts out like or how they modify it to achieve the result? Understood different rails will require different modification strategy but shouldn't there be just one correct back end height for each rubber profile? This is the spec a person would need to work backward from. Can you share this calculation as you must have it, probably memorized in your head by now.
Edit: I hadn't looked at dartman's link when I posted. Do you agree with the dimensions there or is there different spec for different rubber manufacturers of the same profile?
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Yes, I lowered the backend height of the Diamond rails by 1/16"th of an inch, which in turn changed the way the balls react off the cushions, changing the banks and speed reactions off the cushions. That is just a part of the calibration of the sub-rails. Their is more to it than that though, knowing what kind of cushions are being installed, helps to determine what the sub-rail thickness needs to be, as well as the nose height of the cushions in order to get the maximum playability from the rails. Cloth and balls also play a role, along with how clean the table is kept, as well as humidity. It's just not a simple cut and dried solution, wish it were....but it's just not. It's kind of like math...first you have to add up all the numbers before you can get the correct answer you're looking for
JC
Coos Cues
It has to do with the angle the ball is compressing the rubber at. Imagine holding the cushion at 1 7/16 at the ball contact point and raising and lowering the back end of it to compensate for different sub rail height. As you change this dimension the rubber compresses in a slightly different direction which changes the rebound subtly. The necessary mounting angle of the wood also changes as the height of the subrail changes. So it seems to me the conclusion would be to design the sub rail height to the optimum for the rubber. Unfortunately different manufacturers don't seem to agree on what this height is making all the variations of play using the exact same rubber. In comes trial and error and redesigning.
now we're getting some where
This is a great discussion... very interesting!
Dartman, thanks for the Championship cushion documentation. It's very helpful.
Are other companies providing this level of documentation?
You may notice that the nose heights change with the set angle of the cushions... the 1 7/16" is not sacred for them. They seem to use that as the final tweak. Since the set angle on the cushion varies with different subrail thinknesses, the nose height seems to allow for adjustment in rebound, to keep the different setups consistent. Does that seem reasonable?
Whew.... in need more coffee.
This is a great discussion... very interesting!
Dartman, thanks for the Championship cushion documentation. It's very helpful.
Are other companies providing this level of documentation?
You may notice that the nose heights change with the set angle of the cushions... the 1 7/16" is not sacred for them. They seem to use that as the final tweak. Since the set angle on the cushion varies with different subrail thinknesses, the nose height seems to allow for adjustment in rebound, to keep the different setups consistent. Does that seem reasonable?
Whew.... in need more coffee.
Now you're catching on
At the time the BCA standards were wrote about the nose height being 63.5% of the ball thickness, +/- 1%....sub-rails were at 1 11/16"ths thick. With todays sub-rails being anywhere from 1 1/2" to 1 3/4"....you can throw that BCA rule out the door. On a sub-rail that is 1 1/2" thick, using K66 cushions, the needed nose height for the cushions to play right...it needs to be at 1 5/16" high, providing there's a cloth relief on the bottom of the rails, if not...then the nose height needs to be set at 1 1/4" first, then the thickness of the cloth on the bottom side of the rails will finish lifting the nose height up to play correctly. Now, where does the BCA spec's say ANYTHING about this
JC
Coos Cues
Now you're catching on
And this is where the years of experience come in folks. Because in order to figure this out you no doubt had to install some rubber based on the "accepted standards" only to learn that something wasn't quite right. And you probably had to wait for the cloth to break in to even know that for sure. Then figure out what to change to make it better, try that out and gauge the results, again after the cloth wears in. Just the tidbit of wisdom in the above paragraph about k66 rubber took many attempts over time to arrive at no doubt. Thank you for sharing it here.