Carom cushion P37 profile question

HaiNhi

AzB Silver Member
Silver Member
Hello pros.

I was wondering what’s the half-circle recess in the back of the cushion meant for? Is it meant to be open or filled with mating “tongue”?

I saw that Gabriel’s subrail profile has the tongue.

But other subrails for K66 or k55 profiles are just flat.

I’m making a router bit with the P37 profile to cut my subrail to have the positive tongue just like the one from Gabriel’s.

Thanks
 

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Ssonerai

AzB Silver Member
Silver Member
Ever since i saw the other post a while back (that you refer to) I've wondered the same thing. Which way is correct - fill it with wood tongue to locate it? or leave the air bubble, possibly for better bounce????

I’m making a router bit with the P37 profile to cut my subrail

But where i would go if the answer is "tongue it" :wink: would be shaper knives. Easier to make and tool up, and you can feed the rails with power feeder.

smt
 

bradsh98

Bradshaw Billiard Service
Silver Member
Tongue it. The open cavity does not create a better rebound.. The open air space causes a bit of energy loss... Since most tables have a flat sub-rail face, we have grown to accept this to be the norm.

Think about it like this: ever play 'egg toss'? If you try to catch the egg with your hand held out firmly, the egg will break on impact. However, if you pull your hand back as the egg makes contact, the blow is softened, and the egg does not break.

I believe you will get a better rebound with the tongue. I have only played on one Gold Crown pool table with a tongued sub-rail face. The cushion response was incredible. However, those rails had a few other variables to consider.. The tongue wasn't the only thing that affected the play.
 

Texas Carom Club

9ball did to billiards what hiphop did to america
Silver Member
Very good explanation, makes sense to me
They sell the sub rail wood with this bump in europe but if you can make it yourself, much better
 

realkingcobra

Well-known member
Silver Member
The cavity on the back side of the cushions are there as an alignment guide when extruding the cushions through an extrusion moulded press, no other reason.
 

HaiNhi

AzB Silver Member
Silver Member
Great!

Thanks for all the responds.

My router bit is on its way here. I don't have a shaper yet but unless I turn full time mechanic or table builder, I won't be buying one any time soon. :)
 

Ssonerai

AzB Silver Member
Silver Member
Thanks for the tech info, guys!
Now if i could only clear the shop and LR from other projects.....

Hai - router sounds like torture to me, but also sounds like you know what you are doing, so should be a success. I'm glad to follow in your footsteps as far as learning the specs.

smt
 

tjohnson

AzB Silver Member
Silver Member
The cavity on the back side of the cushions are there as an alignment guide when extruding the cushions through an extrusion moulded press, no other reason.

RKC and Geoff, are there any disadvantages to having a subrail (on a GC like Geoff described, for instance) that has a tongue along its face that would fit into the cavity?
 

realkingcobra

Well-known member
Silver Member
RKC and Geoff, are there any disadvantages to having a subrail (on a GC like Geoff described, for instance) that has a tongue along its face that would fit into the cavity?

Yes, first of all you have to have a cutter head custom made in the exact profile of the cushions you're intending to mount, and the sub rails would need to be replaced with new liners....all that time and money spent to do what??? If it makes the cushions play better, why hasn't Brunswick ever adopted the design???
 

bradsh98

Bradshaw Billiard Service
Silver Member
Cost...

It would be difficult to measure any quantifiable benefit. I have zero interest in creating a DOE for it, and I would guess the same for Brunswick.

Also, all cushion manufacturers use different dimensions. So, the sub-rail would then become exclusive to one particular cushion.
 
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tjohnson

AzB Silver Member
Silver Member
Yes, first of all you have to have a cutter head custom made in the exact profile of the cushions you're intending to mount, and the sub rails would need to be replaced with new liners....all that time and money spent to do what??? If it makes the cushions play better, why hasn't Brunswick ever adopted the design???

Thanks Geoff and RKC, makes perfect sense.
 
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