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.
My You Tube
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
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
rrinker per the chart Linn Westcott compiled as part of his benchwork book.
Cool, I didn't realize there was such a chart! Does it mention on what centers to go with?
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
mbinsewi rrinker per the chart Linn Westcott compiled as part of his benchwork book. Cool, I didn't realize there was such a chart! Does it mention on what centers to go with? Mike.
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.
mbinsewiCool, I didn't realize there was such a chart!
The chart in question:
I have the right to remain silent. By posting here I have given up that right and accept that anything I say can and will be used as evidence to critique me.
Thanks Carl!
you could go the entire span if you made engineered floor trusse.
davidmurray 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
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.
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 30 1 x 3 L 114 38 1 x 4 L 156 52
mbinsewi Cool, I didn't realize there was such a chart!
The correct amount of overhang is important because it balances out the load. If you don't have enough overhang then it will sag in the middle. If you have too much overhang then it will bow up in the middle.
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.
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.
mbinsewiBy the time you buy your premium 1x4, I'm thinking construction grade 2x4 would be less money, time, and stronger.
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.
Henry
COB Potomac & Northern
Shenandoah Valley
BigDaddyMaybe 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.
Track fiddler 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.
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.
Mike
As construction progresses, the longest span of 1x3 L girder should be about 66 inches. One track spanning a river with a bridge. I expect it to work fine.
- Douglas
Doughless As construction progresses, the longest span of 1x3 L girder should be about 66 inches. One track spanning a river with a bridge. I expect it to work fine.
Why only 66", when every one here seem to think that a 3" web L-girder can have a span that easily exceeds 8ft.? I may, for safe keeping, still put a leg at the half-way point in the span anyway. I am, however trying to maximize the space for storage under the layout, as well as an area to put my work bench, which will also go under the layout.
On another note, I correct myself AGAIN; I do not have a 4", but a 3" web L-girder. I looked in my storage unit yesterday to inventory the salvagable benchwork I have and the existing L-girders have a 3" web
E-L man tom Doughless As construction progresses, the longest span of 1x3 L girder should be about 66 inches. One track spanning a river with a bridge. I expect it to work fine. Why only 66", when every one here seem to think that a 3" web L-girder can have a span that easily exceeds 8ft.? I may, for safe keeping, still put a leg at the half-way point in the span anyway. I am, however trying to maximize the space for storage under the layout, as well as an area to put my work bench, which will also go under the layout. On another note, I correct myself AGAIN; I do not have a 4", but a 3" web L-girder. I looked in my storage unit yesterday to inventory the salvagable benchwork I have and the existing L-girders have a 3" web
A good rule of thumb is a span of 20 times the beam depth. With a 1x2 on top of the 1x3 the depth is 3.25 inches. That's a span of 65 inches. You can stretch that a bit, but you'll get more deflection and potentially some lateral sway, particularly with the unbalanced "L" rather than a symetrical "T".
Ray
The L piece makes it no longer a simple beam and imparts much additional strength. The twisting - yes, when you just have the basic structure with the only joists being at the legs. Once you put joists on, every 16" or so, there will be very little ability for the L girder to twist. Linn Westcott tested this all out, he didn;t pull the numbers in that chart out of his hat. And we're talking about static loading, there is for all intents and purpsoes no liv eload in a model railroad - the weight of the locos and cars is insignificant compared to scenery back in the day which was almost exclusively plaster based. Modern lightweight methods reduce the load even more. And those spans are rated to carry human weight and higher, so if you want to climb all over your layout then yes, you want to use more supports.
rrinker The L piece makes it no longer a simple beam and imparts much additional strength. The twisting - yes, when you just have the basic structure with the only joists being at the legs. Once you put joists on, every 16" or so, there will be very little ability for the L girder to twist. Linn Westcott tested this all out, he didn;t pull the numbers in that chart out of his hat. And we're talking about static loading, there is for all intents and purpsoes no liv eload in a model railroad - the weight of the locos and cars is insignificant compared to scenery back in the day which was almost exclusively plaster based. Modern lightweight methods reduce the load even more. And those spans are rated to carry human weight and higher, so if you want to climb all over your layout then yes, you want to use more supports. --Randy
Good point Randy. As I recall, my old layout had an unsupported span of about 84". And, no, I don't intend to climb onto the layout at any time. The major concern here, of course, is regarding sag. I made the mistake on my old layout of using 3/8" CDX and I did have significant variations in height, but I think that it was probably due to warping of the CDX, rather than sag. That was the intent of my original question - - at what distance between legs can I expect sag? I do believe the question has been answered, but I wanted to make sure I was on the right track (no pun intended!). Thank you all.