I need a structural engineer!
Let's say that I want to build a 4'x8' module, 3' high.
To prevent lateral sway, I will add diagonal braces from the legs to the underside of the 8' horizontal members at the top of the module.
My question is, where should I position the diagonal braces?
For example, should the brace be placed 12" from the top of the leg and connect 12" into the horizontal member?
Or, maybe, 24" from the top of the leg and connect 24" into the horizontal member?
Or, maybe, 36" from the top of the leg (i.e., at the bottom of the leg) and connect 36" into the horizontal member?
Or, some other variation like 12" from the top of the leg and connect 36" into the horizontal member?
What would be the optimal position of the diagonal brace to minimize lateral sway?
Rich
Alton Junction
Rich,
Our engineers are apt to ask at least a couple questions before they offer up a design:
1) they will expect you're planning for more than just legs in the four corners. Two more, half way along the length ? Or more?
2) Width (top to bottom) of the edge framing, thickness of the outer framing, and material, dimensions and configuration of the legs?
Oh, one final item. Screws or bolts? That is, how easy to you want the tear-down to be for potential moves.
These are just the starters. I'm still just waking up!
BTW: "Dearborn Station" - is that Michigan? Go Blue! Beat that other team.
John
I'm not a structural engineer, but I play one around here.
Of your options, the 36"/36" is the theoretical best. It will load the diagonal member least, and have the greatest effect on the leg movement.
As those numbers decrease, the utility lessens. Happily, not by much until you get way up close to the "joint". I would say 12" is "way up close", and 24" is not.
Ed
Great question. We overbuild everything so the "best" to minimize sway, may be more than you need unless you are dancing on top the layout. It's a layout not a truss bridge.
I got my popcorn and I'm watching this thread.
Henry
COB Potomac & Northern
Shenandoah Valley
7j43k I'm not a structural engineer, but I play one around here. Of your options, the 36"/36" is the theoretical best. It will load the diagonal member least, and have the greatest effect on the leg movement. As those numbers decrease, the utility lessens. Happily, not by much until you get way up close to the "joint". I would say 12" is "way up close", and 24" is not. Ed
richhotrainWhat would be the optimal position of the diagonal brace to minimize lateral sway?
how much side load are you anticipating?
what size are the legs? how much might they bend
what is good enough (the motto at GE).
greg - Philadelphia & Reading / Reading
Go to the top of page where the black bar is and click on ''Get Started'' once the topic's show up....scroll down to the second one, which will be..''Build a table for a small model railroad''. They will show You how to build a 4x8 that You can either build it that way or gleam some ideas for Your own version.....
''Happy Thanksgiving''
Take Care!
Frank
gregc richhotrain What would be the optimal position of the diagonal brace to minimize lateral sway? how much side load are you anticipating? what size are the legs? how much might they bend what is good enough (the motto at GE).
richhotrain What would be the optimal position of the diagonal brace to minimize lateral sway?
All of the above is important.
Is the horizontal member sufficient to span the 8ft? Like a 6” deep board?
How stout are the legs?
As stated we usually over design benchwork.
So I’m assuming the above members are ok so you just need something at a 45 deg angle fastened to leg and horizontal. A 12” x 12” triangle would do.
danno54 So I’m assuming the above members are ok so you just need something at a 45 deg angle fastened to leg and horizontal. A 12” x 12” triangle would do.
A 12" x 12" triangle would do a nice job of anchoring rotation at the joint. But the legs below that 12" can still bend.
Consider that you can probably adequately lock up the joint (where the leg attaches to the layout frame) with TWO bolts/screws through the leg. Without the 12" x 12" triangle. This will, of course, do nothing about stopping leg bending and consequent sway.
BigDaddy I got my popcorn and I'm watching this thread.
I think in addition to lateral sway, which is prevented by any type of gusset really, you also want to minimize bending of the leg.
I'm going to struggle to explain this: Putting the support at the distance that will make the leg have the "shortest" unsupported distance will keep the leg from bending. That would be the middle.
So, for a 36 inch leg, my answer to your question is "none of the above".
I would say 18 inches. The point at which the leg is bisected.
The stoutness of your diagonal support matters too. A thin furring strip could itself bend if it was too long, like it would be if you attached it to the bottom of the leg. If the supporting diagonal piece is thin, I would think attaching higher up the leg would be better since it would be less apt itself to bend.
- Douglas
We don't have any popcorn either, but I can see the entertainment value potential of this thread. So, I'm sitting out and getting another slice of banana nut bread and cuppa coffee. And as for the walnut foo-foo business . . . around here nut bread is made with pecans. Thanksgiving is about the only time I get to have dessert after breakfast.
Robert
LINK to SNSR Blog
Doughless I'm going to struggle to explain this: Putting the support at the distance that will make the leg have the "shortest" unsupported distance will keep the leg from bending. That would be the middle.
The leg below that middle anchor point will be free to bend.
7j43k Doughless I'm going to struggle to explain this: Putting the support at the distance that will make the leg have the "shortest" unsupported distance will keep the leg from bending. That would be the middle. The leg below that middle anchor point will be free to bend. Ed
Ah, but if he anchors the bottom of the leg, the leg could bend in the middle, or at least vibrate more, which I suspect is part of Rich's question.
I think of it like plucking a guitar string. It takes less force to pluck a long string than a short one. But I'm not a guitar player.
Doughless Ah, but if he anchors the bottom of the leg, the leg could bend in the middle, or at least vibrate more, which I suspect is part of Rich's question. I think of it like plucking a guitar string. It takes less force to pluck a long string than a short one. But I'm not a guitar player.
Yes, it could and would vibrate. If plucked. How often does that happen? That event will be much rarer than people leaning on or touching the layout edge.
But, even if it vibrates, I doubt that will be much of a problem. I just struck the middle of a leg (2x2 wood) on my layout. It made a thunky noise and not much else.
Wood legs are going to also be very self-damping in vibration.
Just mount a diagonal board where it is needed. If that is not secure enough, just add another one.
ROAR
The Route of the Broadway Lion The Largest Subway Layout in North Dakota.
Here there be cats. LIONS with CAMERAS
I recall following many of the techniques in the Virginian project article (MR articles early 2012) for my 5'x10' layout. Mine is similar in having overhanging ends. You might check out the related article for the layout framing, but the technique is also described in this one (Part 3) of the many Virginian project videos:
http://mrr.trains.com/videos/project-layouts/2011/12/building-model-railroaders-ho-scale-virginian-ry-part-3
Good grief, why is the link click-able??
ANyway, it includes legs made of two 1x lumber pieces (1x4 and 1x3, I think) at 90-degree angles. It was easy to do that with some glue and a finish nailer. A 2x2 block near the bottom provides a place to mount rollers. I made my top frame, including joists, with 1x4 lumber. For my lower 1x4 horizontal stabilizer pieces I placed the back and side ones pretty low, maybe 12" above the floor, and the front one fairlly high (maybe 15" below the top) as a compromise, for easier access from underneath.
To your point, I added 1x3(?) diagonals, two at each spot where the inset legs join the top frame. I'd say about 18" down, which does not much restrict access. Those really stiffened things up. The following photo shows a diagonal, behind a 1x4 joist in the way of your view.
BTW, I assembled the 1x4 top frame on the floor, oriented so I was looking down on it so it resembled my diagram. I determined that it is a good idea to flip it over before adding the legs, unless you want the legs pointing up. I'm just concerned that someone might make that stupid mistake! And, I can also advise how not to trim your door length to allow for carpet clearance!
I'm a chemical engineer, so my advice here is questionable. If you want to distill your own ethanol or build a refinery or an ethylene plant, I'm your guy.
Happy Thanksgiving!
Paul
Modeling HO with a transition era UP bent
If you're building a 4 x 8 layout, and you just don't want ANY angle braces on the legs, I suggest using 2" x 1/8" steel angle iron. The weakest point will be where you attach the top of the leg to the layout. I would recommend, for each connection, four bolts in the 3/8" diameter range arrayed in the obvious way.
Cost will likely be $50 or so, including the hardware.
peahrens ANyway, it includes legs made of two 1x lumber pieces (1x4 and 1x3, I think) at 90-degree angles. It was easy to do that with some glue and a finish nailer.
ANyway, it includes legs made of two 1x lumber pieces (1x4 and 1x3, I think) at 90-degree angles. It was easy to do that with some glue and a finish nailer.
I've used that technique before, and will use it a lot on my next layout. Its easier to take the twist or warp out of a 1x by mating it with another at 90 degrees. One board provides rigidity to the other. The result will tend to be straighter than a stock 2x board, IMO. It's nearly impossible to take a warp or twist out of 2x with conventional hand/power tools.
I'll work with 8 ft length boards and cut them to whatever shorter length I need. Just need to remember to mark where the finish nails are located before sawing.
I think it would provide a sturdier, straighter leg than 2x2s and even 2x4s, and provide a wider surface with which to screw angle boards or gussets into.
Oh boy, I gotta lotta catching up to do with all these replies. That's what I get for starting this thread this morning, and then taking off for Thanksgiving dinner with my daughter and her family.
I appreciate all of the replies, so let me read through them and respond where appropriate.
John, that's Dearborn Station in Chicago.
Because I have a large number of 2x4s available, the bench work will be all 2x4 construction. I will only be using four legs on each "module", one in each corner. As with my current layout, I will be using coarse thread drywall screws.
My objective is to keep the benchwork as open and accessible as possible for ease in getting under the layout for Tortoise installation and for connecting feeders to the bus wires. On my current layout, I solved the diagonal sway problem by adding horizontal members along the bottom of the bench work, but that made access under the layout a bit difficult.
zstripe Rich, Go to the top of page where the black bar is and click on ''Get Started'' once the topic's show up....scroll down to the second one, which will be..''Build a table for a small model railroad''. They will show You how to build a 4x8 that You can either build it that way or gleam some ideas for Your own version..... ''Happy Thanksgiving'' Take Care! Frank
Also, I use the 4' x 8' table, or module, as an example, but this will be part of a much larger layout in a 42' x 25' space.
danno54 gregc richhotrain What would be the optimal position of the diagonal brace to minimize lateral sway? how much side load are you anticipating? what size are the legs? how much might they bend what is good enough (the motto at GE). All of the above is important. Is the horizontal member sufficient to span the 8ft? Like a 6” deep board? How stout are the legs? As stated we usually over design benchwork. So I’m assuming the above members are ok so you just need something at a 45 deg angle fastened to leg and horizontal. A 12” x 12” triangle would do.
Doughless I think in addition to lateral sway, which is prevented by any type of gusset really, you also want to minimize bending of the leg.
The legs will be constructed from 2x4's. How will they bend?
BroadwayLion Just mount a diagonal board where it is needed. If that is not secure enough, just add another one.
Tomorrow, I plan to build a 4' x 8' table, standing 36" high. I plan to install diagonal 2x4 bracing, so that is why I ask the question on positioning. This will be a test table to determine how best to eliminate sway. I can use that test table to store my existing structures as I build the new layout.
put the diagonals on with temporary clamps. You can try out different angles and distances and see what works.
If yer using 2 x 4's, you REALLY should be using angle iron legs. They go together, like bacon and eggs. Flux and solder. DCC and irritation.
Gussets are a good way to stabilize leg movement.
Bob
Don't Ever Give Up
richhotrain Doughless I think in addition to lateral sway, which is prevented by any type of gusset really, you also want to minimize bending of the leg. I'm confused by the references in a few replies to the leg "bending". The legs will be constructed from 2x4's. How will they bend? Rich
I'm confused by the references in a few replies to the leg "bending".
I probably didnt read your OP closely enough to notice you pla to use 2x for the legs.
Doughless I'm confused by the references in a few replies to the leg "bending".