Good morning. I am building a trestle to cross a river on my HO layout, it is approx. 3’ ling and 8’’ tall. When placing the trestle, is it better to do the scenery befor or after the trestle is installed?Also, how is the best way to secure the trestle to the river bed? Has anyone ever built or seen a wooden trestle that supports 2 sets ov tracks? I like pics. Thanks Mike[:)]
I have seen them installed both ways. I put my current ones on foam so I chose to hang the trestle and build scenery up to it. I find it difficult to get messurements close enough building the scenery first, though I think many have done that very well. I have not built double track wooden trestles, though I have seen them. My steel arch bridge was designed for two tracks, but I use it as a single.
You can do what ever you want. Kalmbach’s bridge books do give good background info.
What I do is build the structure and fit the land form to the bridge. Then remove the bridge and continue the scenery, like plaster and paint. Then install the bridge and finsh detailing the scenery.
Will your bridge sit on piers in the river or are the pilings driven into the river bed?
[#ditto] to Gary, they’re the steps I am currently taking, once the trestle is finished I will place it and “rough-in” the scenery base, remove the trestle and continue scenicking low foliage and ground cover, then replace the trestle, weather it and blend it(hopefully seamlessly) into the terain and then add the trees and other details.
Have fun & be safe
Karl.
EDIT: My first trestle on the old layout supported two tracks, tho it wasnt based on any prototype.
I have seen a dual track wooden trestle. It was the east approach to the McKinley bridge in St Louis. That was truly impressive (seemed like miles of bridge), although I believe it has been completely torn down by now.
In my case, I did the scenery, in this case a gully/rock slide that would have been about 85’ across, but I left the footing area bare foam. Then, I laid flextrack in the curve needed over that gully, and let it sag as it wanted to. In the meantime, I constructed the trestle to fit the height, keeping the tie to footing distance in mind, and adding 10% to the bents. Once it was ready, I would attempt to slide the trestle under the sagging flextrack segment, and nipped off some of each bent with a sprue cutter until it slid into place nicely, and kept the flextrack on an even grade. At that point, I added hydrocal, but I hear that sculptamold would have been better. At any rate, that acts as “gravel” and I added small rocks at the bottom to act as rip-rap.
I forgot to mention that I also built lumber retaining abuttments at each end of the gap, and the stringers lay on those for about 8 scale feet.
Rough in the benchwork under the embankments, good and solid, because this is what will support the middle of your three foot bridge. Some prototypes cut the embankments in a series of stairsteps, others stuck bents into sloped ground.
Decide what your footing is going to be, earth, rock terraces, timber cassions, what have you. If timber, build those first and place them. Next place the deck, shimming as necessary to avoid vertical curves on the bridge approaches. Put temporary vertical wood blocks under the span to support the deck, make sure you don’t have a block where critical (load bearing) bents will go.
Now, and only now do you have a good idea of the bent heigth. Build them a little tall, ala Selector, cut them to get close, sand for final adjustments, run lots of trains a long time to check for problems.
Place your load bearing bents, shimmed to perfect heigth, yank the temp blocks. Run some more trains.
Fill in the “curtain” bents, those that are not needed to carry the deck and which can be a little short for ease of installation.
Now the major choice…either get a butter knife and small screwdriver to scenic between bents (and even more fun, between bent members if you don’t use a footing), or else pull the deck and scenic from above. Plusses and minuses to each approach.
Don’t forget your buttresses at either end, and ake sure all the engineers know the bridge is out.
I also use the approach that gsetter outlined.
Smitty, they may have paid to get bits of it torn down, but there are still sections of it sagging and letting nature and gravity have their way!