I haven’t even gotten my railroad together from the last time I tore it apart and I’m already thinking of the next time I tear it apart.
Anyway, I want to tear out my pylon bridge. lower the front about 6 " and put in a trestle. Here’s what it looks like now.
So it seems to me it would be a heck of a lot easier to make a jig and build the bridge all one height across the 4ft expanse–but then getting the mountain built around it might be pretty tricky.
Then again. If I built the terrain first, I’d have to custom cut every support, and if I have one every 1 1/2 to 2" that wold be a lot of custom work.
there have been several articles over the years on how to build and install a trestle. In the late 50’s there was even a series of articles on trestle construction designed to be cut out and placed in a three ring binder. Basically you have a chicken or egg situation that calls for a little of both at the same time. You need to be sure the substrate is rock solid and the place blocks of wood for you pier supports. Following that you can do the scenery before installing the trestle bents. The most important part is to not allow the scenerry to from a wedding cake look because it isn’t done that way in real life. If you have installed the blocks of wood correctly your vertical trestle bents should either step the way you want or be the same height.
Chip,
You could build the bridge as you want, with all the bents/ supports the same. The only trouble with this method, is the bridge needs to be installed first and all other work for scenery grades, plastering and painting have to be done around it. Also the footings for each bent will have to be faked or hidden by scenery. I find it difficult to work around such delicate models while forming the surrounding scenery.
You can set a flat base mark the bridge footprint, if the bridge is already built, do a rough install to get abutments and approximate bent/support lengths. Mark the footprint and install riser blocks that will hold the final pier/ footings for the supports.
I have used this method many times, it works very good especially for ME Steel viaduct, where tower heights really can only be cut/ kitbashed to certain heights. In this case, I have adjusted the scenery and concrete footing heights to match my towers.
In a deep ravine, the support frame was basically stepped w/ blocks and scrap plywood to fit the towers. One bridge was temp installed for a show, it can easilly be removed to complete the scenery. One note, I usually like to handlay the approaches to the abutments so the bridge track and guard rails can be spiked down to install the bridge. This allows a solid fit that can even take an occasional nudge or bump. The feeders can come up behind the abutment also.
Bob K.
The idea or putting the bridge in and out is a little scary to me, just because it is four feet long. Rignt now I’m toying with the idea of putting in the scenery and cutting groves in the plaster so the the bridge can slide into place and all I have to do is patch the holes. I figure I can disguise a lot with rocks and plants.
Chip,
I don’t usually install and remove the bridges, this was only done due to an upcoming show. When the ME bridge was actually being built, the curved treste was built to a template. This template was used for abutment shape/ placement, as well as scenery contours. While the bridge was being built, the spline stayed in place to keep the div in operation. Was cut and installed when needed.
I do have to remove it now to continue work on the backdrop and scenery.
There are many ways to build and, I guess it’s still a case of- “the chicken or the egg”
A wooded ravine w/ lots of rock can help in disguising any bents/ footings or lack of.
For safe handling or even tranportation of the bridges, I will generally secure them to a board even fabricating jigs if nec. The curved ME girder span was just rubber banded to the board w/ the template for safe keeping.
Bob K.
I would use a reasoned approach from a master plan that had me making a roughed in terrain, complete abuttments (cuz they anchor the whole thing and dictate where your track will meet the bridge deck…a primary reference point if there is to be one on a layout, IMO) a roughly tailored trestle with bents a bit too long, make the cribs and place them where they should be in the obstacle (gorge, valley), and then fit the trestle to the cribs and make the deck level with the tracks plus roadbed. The actual mountain can be scenicked therafter.
So, establi***he water course, establish footings/cribs, establish abuttments/ramps, then dimension out the trestle so that you only need to use nippers to trim the bents to get the whole lined up with your approaches at each end. This technique worked for me.
I’m planning a river course–granite boulders–but no actual water, unless it is just a hint to give the course a reason. I’m wondering what kind of abutments would have been used in this loose boulder type footing in the 1880’s.
When the creator started this layout it was just a piece of plywood, Tater Mountain, the flatlands and a tribe of Chumash Indians. Then came the surveyors and then the Chinese and they started blasting and cutting through and under Tater Mountain. With the railroad came the townsfolk and the silver mine.
But Dang it, the creator got things all wrong and put in a stretch of prairie where there should have been a gorge. And of course, the railroad had no way of knowing it wasn’t supposed to be a prairie and built the wrong type of bridge.
When Otto Mears initiated surveying for the Silverton Railroad, this put him in contact with the chief engineer for the Denver and Rio Grande who had done initial grade survey work for that railroad before management’s decision not to lay rail from Silverton on up to the Red Mountain divide.
The engineer, C.W. Gibbs, was then hired to serve as chief engineer for construction for the Silverton Railroad, and subsequently the Rio Grande Southern. For this reason, I consider engineering work along all three lines to be an accurate indicator of established D&RG(W) engineering practice, at least in the absence of location specific evidence to the contrary, as different problems often necessitate individual solutions.
This photograph of the still existing RGS trestle at Trout Lake demonstrates a possible answer for your questions, one that will simplify the construction process.
As you can see, they cut the original grade in stairsteps prior to stick building the bents to fit. The cuts were made to below proposed finish grade, and foundation stones were cut and laid, with the surrounding area then backfilled to nearly flat (probably 1 inch to the foot slope for drainage) with smaller stones unearthed during excavation.
For reconstruction on your model then, you could start with a series of wood platforms, each slightly more than one fill boulder’s radius below proposed finish grade. The bent sill support stones could be cut to resemble concrete blocks at first to ease bent measurment and placement before being placed directly on the stairstep benchwork.
At this point, I have decided to install the trestle deck and support it with temporary props deliberately placed to miss planned permanent bent placements, but you could leave the trestle deck for last just as easily.
In any event, the stairstep abutments appear to be simple
YW, Chip. Selector’s pictured tie stacks and cribs offer interesting support possibilities too, in many ways more interesting than selected or cut stonework. Either way, establishing finished supports down to “bedrock” finishing the terrain around them, and then adding bents and possibly bridge deck afterward seems to be the path of least resistance.
