Slate mystery

7

7forlife

AzB Silver Member
Silver Member
So i'm position this here cause anyone may of ran across it, or at least so i hope.

A friend of my and room owner was in the process of redoing the tables a process he is accustomed too. He calls me yesterday to tell me about a situation that he ran across that has him lost, so i'm asking here to see what others say or who may of ran into this. Just keep in mind that the basic scenarios has been considered, we are no looking outside the box.

After taking the cloth off the table a noticeable "bow" can be observed with the naked eye he says, now this is a gold crown so that mean 3 pieces of slate but what could of cause these 3 pieces to "each" practically bend (based on his description) each a bit more than the other?
 
Gravity?


I would ask in the table mechanic forum, but I have heard that certain series of GC can suffer from slate sag.....and mechanics add bracing to prevent it.







.
 
Table

It's a common on these tables.....generally on the GC brunstone will be concave, slate will be convex.



Rob.M
 
if you're saying that it's common then wouldn't it happen to more of the tables since they are all GC?
 
When I got a Golden West 9 foot table, the slabs were warped. I added some support construction to the table & waited a year for the GRANITE slabs to go back flat. It was a nice table...
 
7forlife said:
... After taking the cloth off the table a noticeable "bow" can be observed with the naked eye he says, now this is a gold crown so that mean 3 pieces of slate but what could of cause these 3 pieces to "each" practically bend (based on his description) each a bit more than the other?
Click to expand...
The GC3 that I used to play on all the time ended up with a foot-section slate that bowed up in the middle. That vintage of GC3 did not have pins between the slates to keep them aligned, so there was a noticeable bump going across the slate break. The mechanic ended up drilling a hole in the center of the slate and running a screw through into the frame and pulling the slate down to flat.

It is strange that the slates would bow up. It seems more likely that they would sag.
 
Bob Jewett said:
The GC3 that I used to play on all the time ended up with a foot-section slate that bowed up in the middle. That vintage of GC3 did not have pins between the slates to keep them aligned, so there was a noticeable bump going across the slate break. The mechanic ended up drilling a hole in the center of the slate and running a screw through into the frame and pulling the slate down to flat.

It is strange that the slates would bow up. It seems more likely that they would sag.
Click to expand...

If it is true that everything is relative - you could say they just sagged in a different frame
of reference:)

On a more serious note, I have seen on a few VERY old antique tables a screw in the middle of the slate sections
at the seam.

Dale
 
Slares

Leave som slates outside - they will curl toward the sun.

Slate contains a lot of moisture.
They can 'dry' out and depending on the circumstances in the room (like sitting above a floor heat duct) slates can move.

Just another opinion.

Mark Griffin
 
Thanks a bunch guys. It was refreshing to hear suttle instances where people ran across it and found a fix or just plan know about it and Bob yes that is exactly what had us stomped "how could the slate (stone) curve?".
He was looking to taking a sander to it, now i have to run and stop him before it's too late.
 
The only Gold Crowns I know of that don't suffer from some kind of roll off are the ones done by Glen Hancock where he turns the 3 pieces of slate into a one piece slate and has a leveling system for leveling the slates.
 
The slate can indeed bow, warp, sag and even twist or shatter for no apparent reason.
But usually there is a reason.
Many times it's gravity ( lack of support) or moisture related, but many times it's the movement of the wood.

" when you're working with wood you are working with water"

Wood is constantly shrinking and swelling based on its water content, and when there is a slate bolted to it, the slate is also subjected to the stresses of that shrinking and swelling.

Generally speaking, since the slate is bound to the frame all the way around, when it's placed under stress, it can't really move anywhere but up or down. Warp and bow.
 
Mr. Bond said:
The slate can indeed bow, warp, sag and even twist or shatter for no apparent reason.
But usually there is a reason.
Many times it's gravity ( lack of support) or moisture related, but many times it's the movement of the wood.

" when you're working with wood you are working with water"

Wood is constantly shrinking and swelling based on its water content, and when there is a slate bolted to it, the slate is also subjected to the stresses of that shrinking and swelling.

Generally speaking, since the slate is bound to the frame all the way around, when it's placed under stress, it can't really move anywhere but up or down. Warp and bow.
Click to expand...

Good points - +1 to you.

Dale
 
I was told that they can sag if stored improperly.
Like putting shingles over the roof line to get them to bend in the middle.
Not as dramatic, but same effect.
I think the proper way is on their edges in a framework to keep it upright..
I'm really looking forward to RKC answering this , I have had lots of "geniuses" tell me rock can't bend, but I could never get any of them to bet.
I know for sure it can bend, all you have to do is look in a geology book and you can find examples.
That is with tremendous heat and or presssure though.
I am not positive about just sitting on a table and bending, or bowing.
He will certainly know.
 
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book collector said:
... , I have had lots of "geniuses" tell me rock can't bend, but I could never get any of them to bet.
I know for sure it can bend, all you have to do is look in a geology book and you can find examples.
That is with tremendous heat and or presssure though.
...
Click to expand...
All materials bend. The amount of bend is directly proportional to the load applied until the material fails. (This applies to solids under more or less normal conditions.) The simple theory says that there is no permanent deformation until elastic failure but lots of materials are not simple. https://en.wikipedia.org/wiki/Deformation_(engineering)

Pool tables are supposed to be designed to stay flat and level during play. Here is an excerpt from the WPA equipment specs:

The thickness must be at least 1 inch [2.54 cm], and the playing surface must be capable, either by its own strength or a combination of its strength and that of the table base frame, of maintaining an overall flatness within +-.020 inches [.508 mm] lengthwise and +-.010 inches [.254 mm] across the width. Further this surface should have an additional deflection not to exceed .030 inches [.762 mm] when loaded with a concentrated static force of 200 pounds [90.7 kg] at its center.​

Taking a permanent bow as some slates do puts them out of spec for the overall flatness mentioned above. I suspect that happens from adjusting to the moisture in the room. This seems to confirm that: http://www.mapei.com/public/US/linedocument/TB_Moisture_Sensitive_Stone_EN.pdf
 
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