Learn something new every day. :yes:
Do pool tables frame need cross beams AND center beams.
- Thread starter preacherman
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Learn something new every day. :yes:
Think about it for a second, it wouldn't make any difference if the crossmembers were built out of 2"×12"s if they're attached to 2"×4"s as the main perimeter support, the frame is still going to sag in the middle.
Yes.
I understand they want beams to support slate from bending?
I am little confused.
That's what people don't understand. The minute there is frame sag from end to end on a table, say a 1/4" or 5mm sag in the middle. So, at the seams of the slate, you shim up both sides of the seam, at both seams, on both sides until the slate is now level end to end. Guess what, once doing that the slates are no longer touching ANY of the crossmembers....because they too saged with the outside frame of the table...why?....because the crossmembers are attached to the outside frame of the table. So now, what support are those crossmembers providing?
The outside frame support is the most important part of the frame when it comes to being able to level the slates. If its weak, then you have to shim the slates up in the middle to compensate for the weak frame. Once doing so, NOW if the slates are a little swayback side to side, THEN the crossmembers play a roll in leveling the slates....they provide a place to place a shim between the crossmembers and the bottom of the slate so that as you tap the shim in with a hammer, that raises the center of the slate to level side to side....but be careful not to tap the wedge in to far, as it takes almost NO effort with the shim to raise the center of the slate!!!
The GC4, 5, & 6 all have flawed frames, because someone, .maybe even someone here on AZB....thought it was a great idea to build the crossmembers as big as the main frame supports without realizing they play a very small roll in leaving the slates, but what they failed in class....was the effects humidity has on wood!!! When the air is very dry, it evaporates the moisture content out of those timbers used as crossmembers, causing the wood to shrink, not to bad of effect, BUT...when the air is wet, HIGH humidity, those very same crossmembers suck up the moisture like a sponge, and be cause of how they're built, they can only expand in ONE direction....UP!! The result of that....is a crowned slate....which may have been flat in the winter...but NOT in the summer depending on where you live and how much swing there is in the humidity
GC 1,2,&3's used 2"×4"s and 2"×6"'s for crossmembers, the 4, 5, & 6's use massive timbers for crossmembers....figure that one out!!
So now, does ANYONE else want to talk about THEIR ideas on MUST have crossmembers???
I don't have any ideas, but a question. Why does slate warp/bow at the center? If the slate doesn't need much support in the center, then what gives?
It's called gravity, and it'll cause solid steel I beams to sag as well. That's why bridges are built with an arch, tractor trailers are built with an arch as well.
But very little support is needed to compensate the gravity's effect on the center of the slate from side to side, and I mean very little, which means you'd have the same level of support on a GC5 to support the slate side to side with a 2"×6" but without the same problems the massive crossmembers they decided to use when they switched away from the GC1 center support design.
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That makes a lot of sense and great examples. Thanks
I have no pre-conceived ideas, but I do have a table I would like to understand better. It's that photo on the first few pages.
Are you saying that generally speaking slate is supported around the perimeter? So slate at the end would be supported on the sides and end of the table?
My table appears different. The four steel beams appear to carry most of the weight of the slate from the center, and the sides of the slate are mostly hanging in space. Where each piece joins the other there is a cross beam and the slate is attached to it near the edge, though if I recall they shimmed it first to be flat then screwed it down.
Here you can see it being screwed down to the cross member.
The slate is mounted on a perimeter of wood, and the other holes you see in the slate attach it to that wood. It's just those eight screws, as best I can tell, holding it down, with the weight on the steel. The edges of the slate are hanging in space, e.g. between where the guy is working and the corner pocket.
The cross members, except near the edges, appear shaped so there's a 1/16 or so gap between the slate and the member, as though its intent is to be used for shims (and there are several in there).
I am not arguing whether this is good or bad, but I am curious if it is different from how most are done. I had another more conventional table for about 15 years but paid zero attention to how it was constructed (it was 9' and 3 pieces of slate, but that's all I recall).
Here's another view of how it sits:
I have no pre-conceived ideas, but I do have a table I would like to understand better. It's that photo on the first few pages.
Are you saying that generally speaking slate is supported around the perimeter? So slate at the end would be supported on the sides and end of the table?
My table appears different. The four steel beams appear to carry most of the weight of the slate from the center, and the sides of the slate are mostly hanging in space. Where each piece joins the other there is a cross beam and the slate is attached to it near the edge, though if I recall they shimmed it first to be flat then screwed it down.
Here you can see it being screwed down to the cross member.
The slate is mounted on a perimeter of wood, and the other holes you see in the slate attach it to that wood. It's just those eight screws, as best I can tell, holding it down, with the weight on the steel. The edges of the slate are hanging in space, e.g. between where the guy is working and the corner pocket.
The cross members, except near the edges, appear shaped so there's a 1/16 or so gap between the slate and the member, as though its intent is to be used for shims (and there are several in there).
I am not arguing whether this is good or bad, but I am curious if it is different from how most are done. I had another more conventional table for about 15 years but paid zero attention to how it was constructed (it was 9' and 3 pieces of slate, but that's all I recall).
Here's another view of how it sits:
Where do the crossmembers and 4 long center supports connect???
Sorry, of course these all connect to the sides and ends.
I guess I was interpreting your comments that there was some more continuous support along the edges of slate and they mostly hung loose in the center. This just seemed different.
Not suggesting how things ought to be, just trying to understand how they are.
The entire ability to maintain a level slate on that table is relying on the strength of those 4 outer main support rail sills. Everything support wise in the middle connects to them, if they can't handle the 618lbs of the slate as well as the weight of the center supports too, they're going to sag end to end and side to side. Look were the legs are positioned, at each corner of the frame, so they do nothing to cut down the span of the bridge so to speak end to end, and that's a lonnnnng' bridge for such small main supports.
If the side and end main support panels were deeper the closer you get to the middle of the frame, they'd be much stronger and offer more support.
Still not sure center beam necessary or not?
Still not sure center beam necessary or not? Some of the advice has been helpful and is appreciated. I just don't know how both no center beam and no center beam are among answer. I would think it would be one way or the other. Some good views on both sides of this.
Still not sure center beam necessary or not? Some of the advice has been helpful and is appreciated. I just don't know how both no center beam and no center beam are among answer. I would think it would be one way or the other. Some good views on both sides of this.
All 3 piece slate tables in some how, some way, have a support system that provides the ability to shim the seams to flat. So, yes, some kind of crossmembers are needed, either down the middle, or across side to side under each slate seam. They only serve the purpose of matching the seams and providing a place to provide lift, or pull down in the center of the slate.
If you mean in mine, the table is a conversion. So the whole design is aimed at keeping out of the way of people who may sit -- the legs go way out to the corner and straight down, the sides have minimal vertical dimension. The side rails LOOK really strong, about 1 5/8" solid wood with a thick stainless wrap (not sure if the wrap makes a difference, depends if it's glued to the face as a stiffener or not).
As best I can tell the vast majority of the weight is on the ends, not the side pieces. The cross beams do not appear to hold any weight of substance, just provide a surface to mate them up and level. The ends though do have to resist all that weight, about 1000#, plus reserve for any fool that climbs up on it.
I can do the steel calculation, and the deflection in the center of those beans would not be measurable with any reasonable tool, but I have no idea how to calculate the deflection on the end piece. Wood to me is magic, not engineering. Art more than science.
But my reason for interest is I have wondered since getting it whether they made compromises in the quality of the table as a pool table to make it a dining conversion. So far it has held up well, but 2 years is not out of infancy yet.
Thanks for the interesting conversation. Not sure if any of this is helping the OP.
Thanks appreciate your explanation. Very helpful.