Now that I have a track plan “concept” roughed out, I now am ready to build the benchwork for my new layout. I plan on using L-girder construction for my benchwork. I have one room dimension that is 11 feet and I plan on putting legs about 1 foot in from each end, which would leave 9 feet of unsupported L-girder.
My question is: will I need another leg in the middle of that span to prevent sag, or are the legs at each end sufficient support for that span?
Tom:
A couple observations.
Scale matters, as O scale and N scale weight different amounts.
Depth of the girder matters, a 1x6 will take a lot more before saging than a 1x4.
Dave
That’s quite a span. What are you making your “L” girders out of? Maybe if you used 1x6 for the vertical leg, and depending on the depth of your layout, maybe on 12" centers? And, what is your scenery going to be made of? heavy hard shell? foam? Things to consider.
I think I’d just go with a support in the middle, and not have to wory about it.
But that’s just me.
Mike.
AN L-girder made with a 1x4 verticla will handle an 11 foot span, per the chart Linn Westcott compiled as part of his benchwork book.
So 9 feet - no problem. If you’re worried, move the legs in 6 inches, for a foot and a half overhang at each end and now only an 8 foot span in the middle.
–Randy
Cool, I didn’t realize there was such a chart! Does it mention on what centers to go with?
Mike.
I have ran a 1X4 on edge for just over 6ft,without issue.I feel sure a proper made ‘‘L’’ would work to hold a couple pounds of plastic and plaster.
But, if your concerned,as Randy said just move the legs in a little,or add one
I think so. I don;t have the original book, it’s long out of print. I have Jeff Wilson’s newer book (which may also be out of print now) and I think he replicated at least the one chart in the L-girder section. There may have been others. Basically it’s a list of the maximum span for various sizes of L girders.
I’ve always use regular grid construction, but this time I want to minimize legs, and also not have a mostly flat railroad, so I am going with L girder for the lower level on this one.
–Randy
The chart in question:
|
Span |
Overhang |
|
|
1 x 2 |
29 |
9 |
|
1 x 3 |
54 |
18 |
|
1 x 2 L |
72 |
24 |
|
1 x 4 |
90 |
30 |
|
1 x 3 L |
Thanks Carl!
Mike.
you could go the entire span if you made engineered floor trusse.
Oh yeah, forgot to mention: I’m modeling in HO and my L-girders are made of 1" x 3" for the web and 1" x 2" for the flange
Correction: the web will be of 1" x 4" instead of 1" x 3"
I also have Linn Wescott’s book (Kalmbach Handbook No. 14), but I would also like to know what any of you all’s experiences have been.
Also, my scenery will be quite minimal, as it will be an industrial switching layout, with some rural areas. no mountains, as I’m modeling northwest Ohio, which is flat as a billiard table. There may possibly be some rolling scenes on this layout, but mainly worked in as low profile view blocks. My benchwork top will be of 1/2" birch plywood.
Thanks for all the input so far.
[quote user=“carl425”]
mbinsewi
Cool, I didn’t realize there was such a chart!
The chart in question:
|
Span |
Overhang |
|
|
1 x 2 |
29 |
9 |
|
1 x 3 |
54 |
18 |
|
1 x 2 L |
72 |
24 |
|
1 x 4 |
90 |
The whole point of the girder construction is that it is meant to be very rigid if constructed properly and the right materials are used. You can even use unequally distributed loads on them…up to a point. We’re not talking about 70 lbs, but for what most of us use for risers, roadbed, ballast, and scenery construction, perhaps 15 pounds or so per yard, it is essentially immaterial.
From experience, I have always used only 1X4 clear spruce. I rip one of the lengths in half using a table saw, which leaves me with two flanges, and I use both glue and 1.5" wood screws. When it is all together and the glue is dried, that sucker will take my weight, all 160 pounds of me, supported on 8’ spreads. Not bouncing, but it will take my weight if I hang from it. Add one more on the other side of your frame section, top it with plywood or some other structure, and it will hold a lot of weight.
To me this L gider thing, I would probably just do with some 2"x4" on edge, instead of going through the work of turning a 1"x4" into a L girder.
By the time you buy your premium 1x4, I’m thinking construction grade 2x4 would be less money, time, and stronger.
But I’m used to useing 2x4’s, for walls, formwork, whatever I’m planning, so benchwork for a model railroad would be the same.
Mike.
Have any doubts, check this out.
Go buy yourself one LP i-joist. 9 1/2" witdh is the narrowest width sold in random lengths. It is too wide for our model railroad benchwork needs. It’s a construction member stronger than (all get-out), much lighter and stronger than a 2x10 floor joist. Also known as the silent floor system.
So you take one of these LP i-joists and rip it in half with your circle or table saw. Wood glue and sandwich two pieces of 1x2 construction grade board on both sides of the OSB on the ripped side. Fasten together with 1 1/2" drywall screws or a 2" finish nailer at an angle is faster and strong enough.
For our model railroad load bearing needs you can span darn near anything and park an elephant on it.
The finished result I-beam is only 4 3/4" wide. I have done this before in other applications. Believe me it is strong enough for anything we are doing here and doesn’t cost that much either.
TF
PS If you want to use these, put the factory side down.
Maybe less money, but if you go to Home Depot, you will have no trouble finding warped 2x4’s The L-girder resists warping because the 2 pieces want to warp in different directions, so they oppose each other’s tendency.
I pick through the stack and take what I want, same at Menards, or my local lumber yard, or what ever lumbar yard I’m at, and no matter what size lumber I’m buying, even if I were buying the 1x4’s. You don’t have to settle for whats at the top of the pile.
TF’s idea sounds interesting, starting with an engineered joist.
Yea, I’m quite familar with the purpose of “L” girder technique. I’ve done that with a 2x6 and a 2x4 for formwork stiff backs, among other applications.
I guess to each his own, just saying.
Of course mine is already built, to suit what I needed, and who knows when, and especially where, the next layout will be.
Mike.
That is, indeed an interesting idea, TF. I will look into that regarding cost and the tools that I have. I know those things are very strong. I didn’t think of ripping the thing in two though. So, for every 8’ length of the joist material there is actually 16’ of useable benchwork girder, if I’m reading you correctly.