John
Your table looks first class , but i have a question , can this type of bench work support you if you have to crawl on top to work on track or scenery , like 2X4 lumber or will i crash through it ?
thank you techman
Well, I'm #190, and I've been all over it, no problem so far. I don't think I'd have a dance up there, but one person's weight doesn't seem to be an issue.
John
You mean i cant let the cloggers on the car insurance commercial practice on it .Well i am 6"3 and #300 so i might be pushing it thanks
#300 might be over the limit, I think for your benchwork, 2x4's are the right choice! 
Weight capability can increase with closer cross member spacing. Talk to Tim about that. He can arrange any assembly configuration. I would think that 16" spacing of cross members no longer than 30" should prevail.
However, my primary concern would be to design a layout that would not require any need to get up on it.
If you need to get up on the layout, IMO, there was a design oversight. None of us gets any younger or more agile.
However, before you make any bench work commitments look at the web site of custom model railroad benchwork. An OGR advertiser. They make custom curved flowing framework to suit any available room.
I am considerable larger than GRJ and crawled all over his platform that has wider support spacing than I would design, but there was no discernible flexing with my weight over the 1/2" multiply Birch.
Tom, you were the layout "proof" test, just like we test gun barrels.
I’ve been able to reassess the size of my room and will be able to build a slightly larger layout.
I will now be able to have a 5x12 layout. This should make a difference in the number and size of the sheets of plywood. How should they be cut so I have a slight overhang.
Also John, I contacted the lumber yard you got your plywood from and they said they no longer stock the birch plywood at their Reading location they only have it at their Delaware location.
Wow, they had stacks of it in Reading when I picked it up! It's a longer drive for me to go to Delaware, so I'm glad I have all I need. 
One other question. I know that the standard height is 40 inches. Is this the overall height or is this the measurement from the floor to the bottom of the “I Beam”.
I’m planning on ordering the transformer cart and will need clearance for my Lionel ZW-L transformer.
The 40" is the length of the legs. The I-Beams hang down from that 3 5/8", and the leveling feet will increase that height. The top of the benchwork will be in addition to the length of the legs and the height of the leveling feet. Since my top is 1/2" multiply birch and 1/2" Homasote, it added one inch. Also for me, since the floor is anything but level, at places the leveling feet and/or spacing blocks I used added up to 2", depending on location. The top of the benchwork is level to within about 1/8", or at least it was when it was completed.
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Birch veneer plywood is nice, but for a train platform, I think there are plenty of options that you can get at your local big box. Seems like overkill to go all the way to Reading to get plywood. Just scanning through the selection at HD, I see 12mm sanded plywood, 18mm sanded plywood, ¾” maple veneer, ¾” MDF and ¾” oak veneer that I wouldn’t hesitate to use. I’ve built cabinets with oak veneer from HD. It’s not the best in the world, but if you screw it down to the benchwork, it should be fine.
The reason I went with the Birch multi-ply was the rigidity of even the 1/2" sheets, also the 5x5 size fits better with building with the Mianne benchwork. I agree, thousands of layouts have been built using any number of materials and they've turned out fine. Out local big box stores didn't have that form-factor, and also Russell Plywood had much better prices than either HD or Lowes on any size plywood.
I have Mianne Benchwork for 2 years now and I am up on it all the time with no problem. The product is great.
I went to the big box stores to buy plywood for the layout about 15 years ago and mostly all of it was warped to the extent that I considered it difficult to use. I ended up buying perfectly flat 1/4 inch peg board and covering it with indoor/outdoor carpet. It's not good if you weigh 250 lbs, but it's fine for me. And I can poke a wire through it within one inch anywhere on the layout. I would buy the birch if I had not thought of this. After all why skimp on the foundation?
Construction grade plywood might be a problem, but any of the grades I listed above should be OK.
@cjack posted:After all why skimp on the foundation?
I thought the same thing. The difference in the price of the wood using the "good one side" plywood from HD and using the 11-ply birch was less than $100. The difference in rigidity of the HD plywood and the multi-ply is considerable. I'm putting a few thousand into new track and Ross switches, it didn't seem like the place I should try to save a few bucks.
I'd like to point out that baltic birch plywood and birch veneer plywood are two different things. For our purposes, the veneer of the plywood is immaterial. Unless you are planning to clear coat it and see it, it will be covered by scenery of some kind- paint at the minimum. What is important for quality is the core, and Baltic Birch is generally manufactured to higher standards with more plies and fewer voids. But for train tables, almost anything will suffice, honestly.
If you plan on walking on it, you are making a deck. You need more cross members, more legs and thicker ply. If you are not planning on walking on it, you are making a table. My small layout is a table and it is 1x 4 framing with 1/4" ply. so I can put it away after Christmas. I have a 1" layer of foam on this, so it is as flat and rigid as it can be.
It's definitely possible to over-engineer a train table. The HO guys use L girder construction- very light and flexible for design, but that is a whole different discussion.
Gunrunnerjohn, I like the look of your leveling feet for your table. Would you share some details ?
Doug
Doug, from this thread: New Train Room Finally Getting A Layout!
@Apples55 posted:Tim also offers some additional fasteners which can be used in between the legs. I have 16 extras which I won’t be using (see pic below). The long end rests under the lip of an I-beam, the short end rests on the underside of the plywood. When you screw up through the hole, it snugs the plywood to the i-beam. If you can use them, shoot a note to my e-mail (in my profile).
I received these brackets from Paul and am in the process of assembling the bench work. How exactly do these brackets work. I can’t figure out how the the short end, with the hole, rests on the plywood.
Never saw those when I did mine, and I'm having a bit of trouble seeing how they work as well.
The only thing I can imagine is as follows.
Put the clip with edge A on the edge of the I-beam top section, seated against the Masonite center piece. Edge B sits on the plywood and forms a U against the plywood. The screw goes through hole C and holds this in place, clamping the I-Beam to the plywood.
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@gunrunnerjohn posted:Never saw those when I did mine, and I'm having a bit of trouble seeing how they work as well.
The only thing I can imagine is as follows.
Put the clip with edge A on the edge of the I-beam top section, seated against the Masonite center piece. Edge B sits on the plywood and forms a U against the plywood. The screw goes through hole C and holds this in place, clamping the I-Beam to the plywood.
Hi John,
Thanks, I’ll try that and if it does not work I’ll get new brackets at HD. Seems to me that in order for it to work there would need to be a a hole on both edges.
No, one screw would be plenty if it's long enough to "bite" the plywood.
These pictures show the brackets supplied by Mianne with my 12'-by-8' table around 1999 - used to fasten the plywood top to the legs and beams. They came with the countersunk holes and screws.
I used a different approach for my 10'-by-5' table in 2014. I cut wood blocks (3-inches square by 1/2-inch thick and glued them to the underside of the tabletop plywood in the corners of the Mianne framework. The blocks locate the plywood within the framework but allow the plywood to be lifted off the table. This facilitates disassembly if the layout ever has to be transported to a new site.
MELGAR
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a picture of them in place would be nice!
@MELGAR posted:These pictures show the brackets supplied by Mianne with my 12'-by-8' table around 1999 - used to fasten the plywood top to the legs and beams. They came with the countersunk holes and screws.
You should look at the thread, he's talking about clamps that are not attached to the legs. These clamps are to secure the plywood along the I-beam. Didn't you notice the clamps look nothing like you're showing? 
@CurtisH posted:a picture of them in place would be nice!
The picture of the clamps we're talking about is in this post.
@gunrunnerjohn posted:The picture of the clamps we're talking about is in this post.
I see that, but am referring to having THOSE clamps installed picture. That I have not seen. If an installed picture was posted it would eliminate a lot of questions.
Well, I didn't have them to illustrate, so I didn't post an "installed" picture. However, my description of how they would be used is the only thing that makes any sense for these. I never even heard of these before, so I suspect a lot of folks with Mianne don't know about them.
@WaynePa posted:I received these brackets from Paul and am in the process of assembling the bench work. How exactly do these brackets work. I can’t figure out how the the short end, with the hole, rests on the plywood.
Ed;
I must apologize... I swear I replied to your question this afternoon (I was away all morning). Here is a picture of one of the clips on my layout. One end of the L bracket goes under the wood at the top of the I-beam and the other goes against the plywood and the screw holds everything tight.
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Look at that, I guessed right. I couldn't see any other way it would work.
Thank You for the Picture as I was having a hard time trying to visualize it.
@Apples55 posted:Ed;
I must apologize... I swear I replied to your question this afternoon (I was away all morning). Here is a picture of one of the clips on my layout. One end of the L bracket goes under the wood at the top of the I-beam and the other goes against the plywood and the screw holds everything tight.
Thanks Paul,
A picture is certainly worth is a thousand words.
