I am considering an alternative that my engineering mind has been thinking about for awhile. The laminated floor beam has replaced 2 x 10s for floor joists and are far superior. Why not make a modeling version? I could cut a 2 x4 down the middle, dado a groove in each piece and use a 3" strip of OSB for the web. But that is only 8' you say. Not if i stagger the joints. I could make it 100' long if I wanted to and cut off the lengths I need on each wall. Two rock solid support beams with only four legs probably up to in excess of 20'. Thoughts?
Sure, why not? If you have the equipment and materials, and enjoy crafting things for novel applications, fill yer boots. I can get 10' clear spruce up here, so I can make L-girders up to that long. I haven't felt a need to go beyond that span, but who knows, it may happen in a future build. (I refuse to settle on this being my last layout)
Part of the appeal of L girder is the ease of attaching cross pieces from below, and moving them if desired. Is your first cut to produce two 2x2 or two 1x4 pieces? Why not buy which ever you want?
Dave
So, your beams would run the length of the layout, what about "joist" ? still use the 1x4's or 3's ? or place sheating right over the beams?
It could get a little "bouncy" in the center if it's a long span. Maybe add a 3rd beam?
I dunno... just thinking your idea over.
I haven't done any math as far as whats cheaper, your beams, or regular dimensional lumber.
Considering a house, using 2x8's as floor joist (not that I would) you can span almost 12', with joist on 16" centers.
Mike.
My You Tube
You might be building the analogue to the Tacoma Narrows Bridge on those longer spans if you don't put in some cross webs to accommodate the torsion. This need not be either particular heavy or particularly strong, though: I'm thinking composite of a couple of comparatively thin compression members (at the 'flanges') with a tension member (cable or even fishing line) to a grommet in the web between them. A similar approach anywhere you're 'moving' a crossmember gives you the flexibility mentioned above for L girder at the cost of a couple of holes and grommets...
Carrying the idea a little further, why not make the flanges as if 'glulam lite' by using staggered glued 1x2 (or rabbet the joints in each flange rather than just staggering butt or biscuit joins).
The only concern I have (and it's not that much of one) is that any flaws in the composite or bonding of the OSB might introduce a critical weakness at points in the web integrity, and the joints between web pieces might need to be carefully strapped and cross-bolted or screwed.
I say build some experimental runs, put them on 'abutments' and test them with weights at various positions to see how they behave, including acoustically when loaded. This could be interesting.
Well part 2 is to use 30" and 36" hollow core doors held with a screwed s clamp to the flanges. That will give a second beam construction in both length and width. I have about 20 doors that were free on craigs list. Can't beat the cost. I also want to experiment with underlayment flooring foam between the doors and track to isolate sound. Bottom line is no further support of any kind. A completely open underneath with a pocket behind the facia for dcc wiring
These days they are called I joists. I'm not sure I see the torsion as a problem in a layout vs a suspension bridge. Sheldon ought to know something about the distance you can span without extra legs, but I suspect it's going to be a lot less than you propose.
I like Doc Wayne's underlayout storage with sliding doors, but that is beyond my carpentry skills.
Henry
COB Potomac & Northern
Shenandoah Valley
My experimental layout section has a 6 1/2 foot span of L grider that has been together for a year, most of that loaded with 400 pounds of extra weight, and it has not sagged a bit.
.
I think the contructed beam will be plenty strong, but I do not see it having construction advantages over L-Girder or Open Grid.
-Kevin
Living the dream.
In Linn Westcott's original benchwork book, there is a chart of spans for various size L girders. 20 feet is easily doable. I'd take those tables and reduce them by maybe 85% to compensate for the reduced quality of today's lumber, unless you cut your own 1x's from 3/4" 13 ply plywood.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
I was originally thinking of using engineered joists for supporting the partial upper level of my layout, hence the construction shown here...
However, with the layout room finished, there was no way to bring a 20' and 24' engineered joist into the basement, let alone into the layout room. They likely would have been too deep, anyway.I ended-up using open grid constructed of 1"x2"s and 1"x4"s, supported by welded angle-iron brackets, which left lots of clearance between levels and allowed fluorescent fixtures to be hung from the underside, in order to illuminate the lower level.
BigDaddyI like Doc Wayne's underlayout storage with sliding doors, but that is beyond my carpentry skills.
There was very little in the way of carpentry skills needed to build those storage areas, as it's all framed using mostly 2"x4"s, nailed together. Some of it has a plywood floor/shelf, about about 7" above the basement's concrete floor...
...and when I ran out of plywood, used some decking planks which I had on-hand.....
Some of the storage space has no such base, but is useful for storing long items or stuff that is okay to be sitting on the concrete. Only a few areas have the sliding doors - they're cut from either 1/8" or 1/4" Masonite, and slide in plastic track, made specifically for this use, by Stanley Tools, I think,...
The rest of the panels are lift-offs, made from 1/8" Masonite...
...and they're hung from 1/2" dowels. pegged into the upper 2"x4"s which support the open grid layout. All of the construction is very basic carpentry - no cabinet-making skills required, and fairly reasonably-priced materials, too.
Wayne
A good rule of thumb is that the span of a beam shouldn't be more than 20 times its depth. With a 1/4" groove the depth with a 3" web would be 5". Therefore the recommended maximum span would be 100" or 8'4". You should make the web deeper for longer spans. Still very doable.
The nice thing about "I" joists compared to "L" girders is that you can attach risers to either side using the top and bottom flanges. With "L" girders the risers have to be attached to one side only or on cross members.
Ray
If you attach the benchwork to the wall there isn't any need for the "L", just use brackets as joists.
Dave H. Painted side goes up. My website : wnbranch.com
ndbprrBut that is only 8' you say. Not if i stagger the joints. I could make it 100' long if I wanted to and cut off the lengths I need on each wall.
assume you're thinking of an engineered I-joist
the top and bottom plates of an I-beam are in compression and tension. The webbing prevents buckling. a solid piece is needed if in tension. so piecing a bottom plate together w/ shorter lengths isn't the same.
not sure how many layouts would need such a long beam requiring no support
greg - Philadelphia & Reading / Reading
Colorado RayWith "L" girders the risers have to be attached to one side only or on cross members.
Most folks build L-girder with joists resting on top of the flanges. Risers attach to the joists, not the L-Girders
Layout Design GalleryLayout Design Special Interest Group
gregcnot sure how many layouts would need such a long beam requiring no support
Lee Nicholas' Utah Colorado Western (and a few others) use pre-fab glue-laminated floor beams for very long runs (e.g., 26 feet) without legs. Lee's are 9 inches deep. Joists sit atop, just as in L-Girder construction.
http://www.ucwrr.com/construction.htm
Just in the way to build extension of my layout.
Rigidity is an important factor and to acheive it in wood you need to construct heavy structure like L girder.
I make an other approach by building the wood structure of the layout on a steel frame.
Course these frames are steel tubes soldered together and you need the skill to solder steel
Anyway the advantages are great, an extremly rigid construction with less foot under the layout and a wood structures simplified with better rigidity.
here are some schematic of the future steel structures which will support my N scale layout.
An existing part of the layout is already build this way and had no suffers from severals moves including accross the atlantic to live with me in Québec