Yeah. I was planning on going back to the book and using the recommended overhang. I can pretty much put the supports where ever I want.
I have another question. How important is lateral stability? I will have roughly 50' of suspended track in 8' sections. The corners will be anchored shelves. Can I use wires to support the track, or do I need something more rigid so the track won't swing.
If it would work, having wires at an angle to the span that were connected to hooks would be very convenient. My concern would be swinging even to the point of causing problems in the corner. However, the spans would be secured together well and would be well-secured to the corners.
RetGMNothing to add Re: the Beam, but IIRC, Lynn Wescott recommended legs or vertical supports be placed @ 1/5 and 4/5 distance for minimum sag...The 1/3, 1/3 will have a little sag on the ends, if any,,,,RetGM.
Nothing to add Re: the Beam, but IIRC, Lynn Wescott recommended legs or vertical supports be placed @ 1/5 and 4/5 distance for minimum sag...The 1/3, 1/3 will have a little sag on the ends, if any,,,,RetGM.
Correct. And when you have to support a beam at the ends instead of at the ideal points, the unsupported beam length is longer, requiring greater beam rigidity for the same allowable deflection under load. In my case, it is not practical to support a removable section anywhere except the ends. So I must use the entire 66" beam length in my rigidity calculations. OTOH, if I were able to move the supports in 12" at each end, I would only have 42" unsupported. I could then use lighter construction to achieve the same rigidity and deflection.
yours in engineering
Fred W
JHarveytomikawaTTprefer to lay the track on thin extruded foam. Where does this foam come from?
tomikawaTTprefer to lay the track on thin extruded foam.
Where does this foam come from?
..... Bob
Beam me up, Scotty, there's no intelligent life down here. (Captain Kirk)
I reject your reality and substitute my own. (Adam Savage)
Resistance is not futile--it is voltage divided by current.
JHarvey tomikawaTTprefer to lay the track on thin extruded foam. Where does this foam come from?
Mine is fan-fold underlayment, leftovers from when I had vinyl siding installed on my former home. It's about 9mm thick, and comes in linked 2' by 4' sheets that can be stretched out to 4' by 50' with crushed spots every 2 feet. If you know somebody who installs vinyl siding, you might be able to get a few scraps - buying the whole bundle (200 square feet) is gross overkill!
Actually, any kind of roadbed can be used - even cork, which I don't use because of its limited lifespan under high temperature/low humidity conditions. (It's about 100 degees and 9% humidity in my layout space right now.) The foam layer quiets things down, which is why I use it on permanent construction.
Chuck (Modeling Central Japan in September, 1964)
I went for known overkill because I wanted very low risk. I didn't want to experiment with failure to see what I could away with. I'm familiar with foam sandwich construction and its strength from boatbuilding. In this instance, all the parts of the box beam - 3.5" deep sides, foam sandwiched between plywood top and bottom - all add to the rigidity.
In my case, I needed a light weight removable section of minimum depth that would span a 60" wide window well (with a few inches added on either end to sit on supports). Section had to be manageable by myself, and storeable on a high bookshelf when layout is not in use. Section had to be wide enough (8") to hold 3 HO tracks. Support is at the ends only. The usual way to gain sufficient rigidity for this situation is to make the vertical elements deeper - a method which conflicted with my minimum depth requirement. Using 1/4" or even 1/8" ply on the verticals would have made my design significantly lighter without removing much strength. Construction would have been more difficult though without the rabbets which make gluing the plywood top and bottom extremely easy.
Westcott's book on benchwork construction mandates 1x4 vertical elements on L-girders spanning 8ft. He assumes 1/500" maximum deflection with a 250 lb point load in the center - a reasonable design scenario when you consider stumbles or leans. The box beam essentially gives me double L-girders with 1x3 verticals, and a top surface to lay track on. If I'm having a clumsy day, I know that thanks to the overkill, falling into the removable section isn't going to break it.
A U trough would be nearly as strong - it loses the foam sandwich - but would weigh almost as much and is actually harder to build. The sides now have to maintain their plumbness without support. Having the track exposed on top of the box beam allows me to easily use the section as a fiddle yard when it is in place - something a U trough would not be as convenient for. This is especially true for my case where the track is at 60" above the floor.
Your circumstances may favor a different solution, I present mine as an alternative that works for me.
JHarvey Chuck, I like the guard rail aspect of that. It has potential. How would you anchor pieces together at the ends?
Chuck, I like the guard rail aspect of that. It has potential. How would you anchor pieces together at the ends?
The ends of the steel stud need to be supported from below, preferably on something of about two inches along-the-track dimension and the full width of the stud.
Anchoring the ends depends on how permanent you want the connection to be. For a removable bridge, a couple of vertical bolts with their heads up and one nut under the beam provide either a semi-permanent anchorage (hex nuts or wing nuts on the bolt-ends that project downward through the supporting structure) or a quick pickup (no nuts, or ogive nuts dropping into holes of appropriate size. I would personally go for wing nuts - slight loss of convenience, massive increase in safety.
Mounting a miniature stereo plug and its matching jack vertically at one or both ends could power the rails without any additional fuss. An interlocking circuit to protect the approach tracks when the bridge is absent would be a good idea, and can be had by powering one approach rail from the left end with a gap at the far right, with the other rail connected in the reverse manner. The potentially dead rail should be long enough to hold a standard-length train - to prevent repeats of the notorious Canandaigua Southern disaster. (Before the CS main line was completed across the 'Bentless Trestle,' John Armstrong would back a train to the end of track and start it from there. Having a short passenger train back into the abyss convinced him to finish the track and thereby close the mainline route.)
Fred, why use the box instead of a single beam?
If in doubt, use steel! Specifically, a heavywall steel stud, with the track laid in in rain gutter fashion.
I have used steel stud 'rain gutters' to support tangent tracks in the netherworld of hidden staging and thoroughfares on my layout, and use lengths up to 56 inches as cassettes, to remove excess rolling stock from the layout and hold it in 'extended storage' on shelf brackets. Since they are already the right shape (including built-in safety railings) fabrication is minimal, and they can be had in lengths up to 10 feet at most big box home improvement emporia. For longer (or wider) you can search out a builder's supply yard.
I have used latex caulk to fasten Atlas flex directly to the steel, but actually prefer to lay the track on thin extruded foam.
I have used a glued composite box beam. Verticals are 1x3, rabbeted 1/4" for 1/4" plywood top and bottom of the box. Glue 2" foam inside the box. This type of box can be up to a foot wide, and won't need intermediate supports for an 8ft span. It is pretty light for its size. Roadbed and track go on top of the top piece of 1/4" ply.
To hide the wiring, use 1x4 for the verticals, notched 1" up from bottom for the 1/4" plywood. This gives a 1" deep inverted U channel under the box beam. I made the notches in the side pieces 1/4" deep by 1/4" wide to make a much stronger glued joint between plywood and side piece.
If you need really light weight, you can use 1/4" ply for the sides instead of 1x, but will probably need internal corner braces of perhaps 3/4" x 3/4" to glue and fasten the plywood strips. This will make gluing the foam more difficult. And the foam does add a lot of rigidity if properly glued to the top and bottom pieces of the box.
just my ideas and experiences
I would use plywood. But otherwise I agree.
Dave
Lackawanna Route of the Phoebe Snow
Those are both excellent ideas that I haven't even considered. Thanks!
Try a small wooden I-beam.
Or perhaps a steel stud under your plywood for stifness would save weight.
I want to run a single track around the perimeter of my basement. I want to make the section where the stairs enter the basement removable. I have been thinking of making that section suspended so that it can be removed as a single piece that is 8' long. I would prefer the majority of the track to be suspended and removable like this with the section in my layout room being a more typical shelf.
I would like to have as few supports as possible to make it easier to take down. So, my biggest concern is bowing. A friend of mine has been suggesting MDF as the base, but I don't know if an 8' x 3" strip would support itself. Another option I am considering is 3/4" plywood. If the wood can support itself, then I would have hangers at 1/3 and 2/3 its length that merely hold it up. The hangers would either clip or screw into the joists above (unfinished basement).
The plan then is to put cork on top of the wood and run electrical underneath.
So, any suggestions? I don't have a lot of layout experience, so any advice is welcome.