The OP's idea will result in a very solid (and very inflexible) reinforced box frame, losing the ability to incorporate curves in the fascia. If that's what is wanted, it will work - and doesn't rely on driving screws into end grain.
My own shelf girders are actually C girders (steel studs, open sides facing the aisle) and have joists both over and under. There are hidden thoroughfare tracks between the C girders, and two layers of track (plus scenery) above them. All fasteners are driven from below, so later construction won't bury them. The upper joists overhang the front girder, allowing for the curvaceous fascia needed to clear my extremely non-curvaceous (more like spherical) bod.
Chuck (Modeling Central Japan in September, 1964)
mlehmanthe plywood of the subroadbed does double duty as the structural "girder" in front.
I bet the fascia contributes substantially to the "girdering" also by forming an "L" with the plywood. It is amazing how stiff thin material like that can be when you stand it up on it's edge.
I've been considering options like yours for my upper shelf where I want it to be as thin as possible - only I'm leaning to putting the shelf bracket upside down. The track is running along the side of a mountain so the scenery that slops up away from the track will hide the diagonal part of the brace.
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Nice work there, Carl.
I did something similar to what the OP suggested in the last extension I added to my Cascade Branch, although the components are somewhat differently arranged.
The rear rail is essentially the equivalent of the OP's idea, although not actually an L-girder. The crossmember simply rests on it. But since there is no front L-girder, there is nothing getting in the way of the x-members varying and flowing freely as with traditional L-girder construction.
Yes, it does require a metal shelf brakect of some kind. But the plywood of the subroadbed does double duty as the structural "girder" in front. The arrangement also allows a very shallow benchwork depth, which can be very important with multi-deck layouts. It's not quite as flexible as traditional L-girder, because it depends on the plywood.
In my case, because of aisle width limits at this location, the x-members were cutoff right at the edge of the roadbed. However, if need be they could extend outward past the plywood to allow for a more varied are between it and the fascia.
It also depends on the stiffness and strength of 3/4" plywood. It should work with 1/2" plywood, but you may need to add a 1x2 stifferner or limit the length of the span between wall brackets when using thinner plywood.
Thus, a slightly different approach than the OP's suggestion, but accomplishes similar goals with a but more flexibility.
Here's another shot without the fascia blocks attached.
Mike Lehman
Urbana, IL
carl425 I did it like this:
I did it like this:
Excellent benchwork, and if the trains don't work out you got such a strong base, you can have a machinist's "workbench". This is how the majority of my club's layout is built. Does allow a considerable amount of variation in isle/ facia and radius .
Modeling B&O- Chessie Bob K. www.ssmrc.org
Part of the benefit of L girder construction is the ability to vary the depth of the scene and provide a free flowing edge to the aisle. By putting the joists inside the L, you lose that advantage. I would say that if you are going to invert the L's you could just as well use open grid benchwork and not worry about the L at all. About the only thing the inverted L gives you is the ability to move joists (very few peopl I know have actually done that) and the ability to angle or put joists at odd spacing.
Dave H. Painted side goes up. My website : wnbranch.com
Has anyone tried 'inverting' the L-girders as used on the frame for a wall-mounted layout? By that, I mean that the L-girders rest on the wall brackets, the one nearest the wall having the 1x2 on the bottom with the lower leg of the 'L' pointing away from the wall and the nearest the edge having the 1x2 on the bottom with the 'L' pointing toward the wall.
The joists would sit within the 2 facing L's. This would be sort of a combination of the butt-joint framework and L-girder approaches. Advantage would be rigidity; disadvantage would be that the girder joint would be in tension rather than compression.