Close to building needed, 3' long entry spanner, for my small HO, a-t-r, p-to-p switching layout-in-progress. Will use bi-level twin trackage, as trackplan has twice-around main [ at 3 1/2" difference in elevation ]. Since 2 rail lines cross space, prefer single swing-down [ or up ] unit, instead of two separate bridge sections [ that would be a BIG PAIN ! ]. It could swing up or down on right side, as there's room there. Really LIKE this kind of engineering challenge! Read about several types of : span, hinge, lock mechanism, track power cut-off [ to stop 'deep-six' ] designs, so am not starting blind. If anyone has actually done this, am open to and would appreciate good suggestions. My biggest concerns: weight/ rigidity of unit. TTFN.....Old Tom aka papasmurf in NH
I've never built one of these, but there may be one in my future. So, I've given it some thought and I've payed special attention to such bridges on other layouts that I've seen.
Being a scenery guy, I think I would build it as a bridge. For the single-level application that would fit my layout, I'd probably use a section of steel stud or channel for stiffness and light weight, and put causeway and bridge sections on top of that. If I were building a double-deck bridge, I think I'd make the upper level out of brass, for stiffness and strength. Remember, sooner or later you'll have to "recover" a train that's stuck in the lower section, so make allowances for that.
One trick that I saw employed on a club layout was to offset the rail gap where the ballasted fixed track meets the bridge rails by about an inch from the hinge point. This allows the joint to be made more smoothly, as you have a bit of track you can bend to compensate for slight mis-alignment of the hinge.
I don't know how hard it would be to do detail work on steel stud, but one option for you would be to run one track on top of the stud and the other inside of it. If it can be cut relatively easily, think of cutting out the bridge girder pattern from the sides of the stud, rather than building up the sides from brass or plastic strips. If nothing else, you could use a section of stud in this one-over, one-through mode teporarily to get your bridge up and running, while you work on a nicer version to replace it later.
Keep us posted. This has the potential to be an interesting project.
It takes an iron man to play with a toy iron horse.
MANY THANKS for your kind reply! To-date, must move pc desk first, before any work on this can continue and we have a very small home! Steel stud and birch plywood were two material choices on my short list. Stud will wrack, so must devise way to stabilize same. 3/4" birch plywood is Great Stuff: lightweight, cuts easily; is very stable and will use in this project. Will keep you posted if yours truly has a 'breakthrough', LOL! TTFN.....Old Tom aka papamurf in NH
You're probably looking for guidance from someone who's actually built one. My design is pretty simple, I have a hinge at one end, and a barrel bolt on the other. Electrical connections are by modular phone jacks.
Hinge end.
Barrel bolt end. The little junction box connects the track power.
At the barrel bolt end, I used Atlas re-railers to ensure a good transition, and the tunnel portal provides the sabilizers to keep the bridge from rolling left or right.
With some ballast and paint, the bridge blends in nicely, keeping this area useful for photography.
Hope this helps.
Lee
Route of the Alpha Jets www.wmrywesternlines.net
WOW; A GREAT SETUP & PHOTOS! Really appreciate your post, as the more info/ideas I gather, the better. Very Nice Layout! TTFN.....papasmurf