Cushion Profile Dynamics

G

Greenthumb

Registered
I’m looking for info on cushion profile dynamics to understand the broad cushion profile used with snooker tables. I play on a new Riley Aristocrat table which has a broad cushion profile similar to the L77 type. It appears from youtube videos, that a similar broad cushion profile is used by other snooker table manufacturers as well. I've read that pool tables typically use the K-66 profile, and carom tables use the K-55 cushion profile. In contrast to these narrow nose profiles, the Riley table cushions I’m familiar with have a nearly 1/2 inch width ball contact dimension, rather than the narrow nose common to pool and carom tables, and as I’ve experienced on a Brunswick snooker table.

I’ve made some approximate measurements on the Riley Aristocrat table which point to the lower part of the nose being near 0.5D, and the upper part being at 0.7D, where D is the snooker ball diameter, 2 1/16 in. It seems that most or all of this broad nose is in contact with the ball when it strikes the cushion. I would appreciate thoughts on why snooker tables benefit from use of such cushions, or where I might get information on the physics behind this design.
 
Greenthumb said:
I’m looking for info on cushion profile dynamics to understand the broad cushion profile used with snooker tables. I play on a new Riley Aristocrat table which has a broad cushion profile similar to the L77 type. It appears from youtube videos, that a similar broad cushion profile is used by other snooker table manufacturers as well. I've read that pool tables typically use the K-66 profile, and carom tables use the K-55 cushion profile. In contrast to these narrow nose profiles, the Riley table cushions I’m familiar with have a nearly 1/2 inch width ball contact dimension, rather than the narrow nose common to pool and carom tables, and as I’ve experienced on a Brunswick snooker table.

I’ve made some approximate measurements on the Riley Aristocrat table which point to the lower part of the nose being near 0.5D, and the upper part being at 0.7D, where D is the snooker ball diameter, 2 1/16 in. It seems that most or all of this broad nose is in contact with the ball when it strikes the cushion. I would appreciate thoughts on why snooker tables benefit from use of such cushions, or where I might get information on the physics behind this design.
Click to expand...
Are you a fitter?
 
I've wondered that as well. Wouldn't a flat cushion like a snooker table eliminate all the hoopla around nose height?
 
realkingcobra said:
Are you a fitter?
Click to expand...
No, I'm not a fitter. I'm a retired chemist, with access to a senior center facility with 3 pool tables, and 1 snooker table. We mostly play Golf on the snooker table. The new snooker table with the broad profile cushions is interesting, and puzzling to consider why the cushions are designed this way for snooker.
 
xianmacx said:
I've wondered that as well. Wouldn't a flat cushion like a snooker table eliminate all the hoopla around nose height?
Click to expand...
Yes, it does seem that the broad cushion design may integrate the properties of narrow nose cushion designs. The Brunswick snooker table I played on previously had the narrow nose cushion design, which seemed to perform okay within consideration of its old age, probably 50 yr.. Some sections of the cushions were rather non-responsive, and the cushion response generally was sluggish. It's of interest to me to understand how the broad cushion profile came into being, and what the purported advantages are. I've talked with more experienced players who didn't know either, and recommended that I try this forum.
 
Greenthumb said:
Yes, it does seem that the broad cushion design may integrate the properties of narrow nose cushion designs. The Brunswick snooker table I played on previously had the narrow nose cushion design, which seemed to perform okay within consideration of its old age, probably 50 yr.. Some sections of the cushions were rather non-responsive, and the cushion response generally was sluggish. It's of interest to me to understand how the broad cushion profile came into being, and what the purported advantages are. I've talked with more experienced players who didn't know either, and recommended that I try this forum.
Click to expand...
I think the "why" is historical, not physical. I don't know a lot of the history, but I believe that Phelan developed the triangular pointy-nose profile around 1850. It seems not to have migrated back to the old country, which appears to have had a separate rubber-cushion evolution. You may want to ask Mike Shamos or maybe one of his articles covers that part of the development of the game.

As for the "what".... You have already noticed the serious difference in geometry. Have you noticed any difference in how the ball reacts off the cushion? Of course that reaction is what's important to the player. The main difference I've noted is that the ball tends to go longer in general so that you have to aim a lot shorter for multi-rail kicks. A complete answer would require noting the differences over a wide range of conditions of wear and weather -- the same variations that you will encounter in play.

One difference I've experienced myself was with slightly sticky snooker cushions. This was on a British table (Riley or BCE) with the standard fuzzy cloth. If the weather was right you could get six lengths shooting over the spots (brown to black and back and back and back...) so that you could hit the cushion you were shooting from (the baulk cushion) three times. There was a post some time ago of someone's experience in a club with very worn cloth and the ability to get nine lengths. I'd pay to see that.
 
Bob Jewett said:
I think the "why" is historical, not physical. I don't know a lot of the history, but I believe that Phelan developed the triangular pointy-nose profile around 1850. It seems not to have migrated back to the old country, which appears to have had a separate rubber-cushion evolution. You may want to ask Mike Shamos or maybe one of his articles covers that part of the development of the game.

As for the "what".... You have already noticed the serious difference in geometry. Have you noticed any difference in how the ball reacts off the cushion? Of course that reaction is what's important to the player. The main difference I've noted is that the ball tends to go longer in general so that you have to aim a lot shorter for multi-rail kicks. A complete answer would require noting the differences over a wide range of conditions of wear and weather -- the same variations that you will encounter in play.

One difference I've experienced myself was with slightly sticky snooker cushions. This was on a British table (Riley or BCE) with the standard fuzzy cloth. If the weather was right you could get six lengths shooting over the spots (brown to black and back and back and back...) so that you could hit the cushion you were shooting from (the baulk cushion) three times. There was a post some time ago of someone's experience in a club with very worn cloth and the ability to get nine lengths. I'd pay to see that.
Click to expand...

The flat edge cushions are bouncier...I feel it was developed for 6x12s...
...I'm sure the snooker world was aware of the carom rubber profile.
Short angles tend to be even shorter on snooker rubber, and less sensitive to spin,
which is why I prefer pool rubber, even on a snooker table.

Nine lengths on snooker rubber? I seriously doubt that...he may have been confused
with nine RAILS which any reasonable snooker table can handle....
...nine LENGTHS could be potentially lethal.

We had a BCE Westbury in Toronto that a guy got ten rails on, and half way to the 11th.
...those tables are too fast and no fun to play on.
 
pt109 said:
...
Nine lengths on snooker rubber? I seriously doubt that...he may have been confused with nine RAILS which any reasonable snooker table can handle.... ...nine LENGTHS could be potentially lethal.
...
Click to expand...
I'm pretty sure he meant nine lengths. I can imagine it happening if the nose of the cushion is sticky and the rubber is lively. On a typical pool table, a ball going straight into a cushion typically loses 75% of its energy. Yes, the loss is that high. If you could somehow reduce that to a loss of only 50% you could get to nine rails with the same starting speed. It would probably require that the ball come off the cushion with the top/bottom spin reversed. Usually the ball comes off the cushion with nearly no spin.
 
Bob Jewett said:
I'm pretty sure he meant nine lengths. I can imagine it happening if the nose of the cushion is sticky and the rubber is lively. On a typical pool table, a ball going straight into a cushion typically loses 75% of its energy. Yes, the loss is that high. If you could somehow reduce that to a loss of only 50% you could get to nine rails with the same starting speed. It would probably require that the ball come off the cushion with the top/bottom spin reversed. Usually the ball comes off the cushion with nearly no spin.
Click to expand...

You would have to use extreme draw to keep whitey on the table....
...but the backspin harms the forward motion speed.
Our table where the guy hit 10 rails?....he could hit almost seven lengths.
His fighting weight was 250....and he had an excellent stroke....but if he hit hard enough
to go nine lengths, no way was whitey staying on the table.

Now you got me thinking about it, Bob...I’m going to a room with steelblock Westburys...
....gonna get some guys trying it.
 
pt109 said:
You would have to use extreme draw to keep whitey on the table....
...but the backspin harms the forward motion speed.
Our table where the guy hit 10 rails?....he could hit almost seven lengths.
His fighting weight was 250....and he had an excellent stroke....but if he hit hard enough
to go nine lengths, no way was whitey staying on the table.

Now you got me thinking about it, Bob...I’m going to a room with steelblock Westburys...
....gonna get some guys trying it.
Click to expand...
The next time they are refitting the cloth, try playing the shot with the bed cloth on and the rail cloth off. The easiest way to do this is get to the table just before they start and cut the cloth off the end cushions. Yes, I'm serious.
 
Bob Jewett said:
I'm pretty sure he meant nine lengths. I can imagine it happening if the nose of the cushion is sticky and the rubber is lively. On a typical pool table, a ball going straight into a cushion typically loses 75% of its energy. Yes, the loss is that high. If you could somehow reduce that to a loss of only 50% you could get to nine rails with the same starting speed. It would probably require that the ball come off the cushion with the top/bottom spin reversed. Usually the ball comes off the cushion with nearly no spin.
Click to expand...
Is this only true when the ball rolls into the rail? In other words, does a ball sliding straight into the rail (no top/bottom rotation) have rail-induced follow on the rebound (from the rail's perspective)?

pj
chgo
 
Bob Jewett said:
The next time they are refitting the cloth, try playing the shot with the bed cloth on and the rail cloth off. The easiest way to do this is get to the table just before they start and cut the cloth off the end cushions. Yes, I'm serious.
Click to expand...
The idea here is that the exposed rubber won't allow the ball to slide against it, so it will induce "rebound follow" rather than "rebound stun"?

pj
chgo
 
Bob Jewett said:
The next time they are refitting the cloth, try playing the shot with the bed cloth on and the rail cloth off. The easiest way to do this is get to the table just before they start and cut the cloth off the end cushions. Yes, I'm serious.
Click to expand...

You got me thinking about it, Bob.
I remember the Anniversary 6x12s I played on years ago....
...when the cloth got a year old...the tables would be at least a half length faster....
...it was a busy room so the rubber was getting ready to show through the cloth.

I’ve never hit into bare rubber...I’ll get it on the IPad and post it.
 
I think the "why" is historical, not physical. I don't know a lot of the history, but I believe that Phelan developed the triangular pointy-nose profile around 1850. It seems not to have migrated back to the old country, which appears to have had a separate rubber-cushion evolution. You may want to ask Mike Shamos or maybe one of his articles covers that part of the development of the game.

As for the "what".... You have already noticed the serious difference in geometry. Have you noticed any difference in how the ball reacts off the cushion? Of course that reaction is what's important to the player. The main difference I've noted is that the ball tends to go longer in general so that you have to aim a lot shorter for multi-rail kicks. A complete answer would require noting the differences over a wide range of conditions of wear and weather -- the same variations that you will encounter in play.

One difference I've experienced myself was with slightly sticky snooker cushions. This was on a British table (Riley or BCE) with the standard fuzzy cloth. If the weather was right you could get six lengths shooting over the spots (brown to black and back and back and back...) so that you could hit the cushion you were shooting from (the baulk cushion) three times. There was a post some time ago of someone's experience in a club with very worn cloth and the ability to get nine lengths. I'd pay to see that.

Bob Jewett
SF Billiard Academy

*********************************
Bob, Thanks very much for your reply. I'm new with AZ so am responding by copying your response here so I can view your post as I type. I would think there are academics who have or would be able to analyze the effects of the broad cushion profile. Maybe Dr. Alciatore or a student in his group would be interested. I assume Riley and other manufacturers who use the broad profile have some rationale for using it, but it may be considered proprietary. The reaction I've noticed off the broad cushion profile seems more responsive to English and from several Corner 5 shots I've repeated there is consistency, and the cushion reaction appears normal with running English. There is more hop than I expected, even at low to medium speed, with near normal incidence angles. Verne
 
Greenthumb said:
Maybe Dr. Alciatore or a student in his group would be interested.
Click to expand...
I don't have much experience with Snooker equipment, and I don't have convenient access; but like you, I am curious to know all of the differences. Thank you for posting so we can hear from the people with experience and understanding of the differences.

Regards,
Dave
 
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