When installing a scratchbuilt trestle, which comes first: the streambed/ canyon or the trestle? Or do you sort of build in place?
First comes the framing supporting the bents and abutments. This dictates the heights of bents, all of which may be different. Natural canyons are seldom symmetrical.
Then the bents should be fabricated - in a jig, so they will have identical angles on the vertical timbers and identical depths (from the bottom of the stringers) at horizontal braces.
Finish the piers and abutments so the bents can be temporarily erected. With the bents in place and checked for vertical, install the stringers and the easy-to-reach inter-bent horizontal and cross-bracing.
Take the trestle back to the bench to install the rest of the timberwork.
Build the terrain (at least that below bridge level.) When reasonably complete, install the trestle and lay track.
Using this sequence will be the least likely to result in damage to the trestle or an impossible-to-scenic situation underneath it. I will be using the same sequence for my big bridge - a concrete spandrel arch on a curve.
Chuck (Modeling Central Japan in September, 1964 - with lots of bridges, no timber trestles)
Agreed. You should fix in your vision what the scene should look like when done, set up a platform or several as footings for the bridge or treste, and then build the trestle to those dimensions. Test fit it in place, and once you know you have it pretty darned close, set it aside and begin to layer scenic goop around the footings and the banks up to the abutments. You should probably have your abutments figured out first as well, and glue them into position. Scenic up to them as you do the footings and sills, and then finish to your taste with detailed flora and fauna.
I like to have the rails laid across the gap, too, supported by the real abutment, the one behind the fake scenery abutment. That way, you can trim your trestle’s supports so that it nicely nestles snuggly under the ties above and doesn’t cause a bump anywhere that ruins your grade.
This may sound fastidious, but it can be done with patience, and the results, both for the locomotives and any track-level photographs down the bridge deck, are going to be very natural and convincing.
Crandell
I build the trestle first. But, I draw the basic contour of what I want the land forms to be like directly under the trestle. I build my bents to fit this contour and then basically finish the trestle. Then I frame the area and build the land forms up so the footings of the trestle just meet the bottoms of the bents.
In Search our Community (to the right on this page) type in Building a Trestle for Deep Gulch This is an outline of how I just built and installed my trestle on my layout. It’s 5-6 pages long and covers how I do this very well.
I like to plan the scene first, then build the bridge following the basic scenic plan. I then construct the scene, and incorporate the necessary supports into the scenery. I finish by building up natural dirt and rocks around any piers, abutments, bents, etc.
Here’s a photo I’ve used in the forum previously, showing a finished steel trestle added to a scene that’s in the process of being finished around it. I still have to build up around the concrete piers.
Gidday, Just making NP2626 thread clickable, has one or two hiccups but my idea of a good how-to -do.
http://cs.trains.com/TRCCS/forums/p/202778/2216017.aspx#2216017
Have fun,
Cheers, the Bear.
OK. Thanks for the answers. Also, what kind of abutments would you recommend for a 1920-'30 logging RR? Thanks
From what I could see in photos, the big trestles on the West Side were supported by fairly small (in horizontal dimension) poured in place concrete footings. The abutments were likewise. Those trestles were built of squared timbers.
Some older photos show pile bents, with the ends of the pilings driven into the ground. If meant for temporary use (to be pulled for their timber after the camp was abandoned) the abutments might have been logs stacked against a pile-driven low bent.
It really depends on what your prototype did, or the engineering standards you want to freelance…
Chuck (Modeling Central Japan in September, 1964)
I was thinking either block or timber, and since i’m freelancing i’ll probably use block, especially if the West Side didn’t use timber. Thanks.
Gidday, I presume you have had a look here ?
Cheers,the Bear.