Hi guys. A follow up with the main question to cut to the chase. I’ll have four 150’ city viaducts kits (20 1/2" long) running down an approx. 1% grade: from 5.5 inches down to 4" over 10-12 ft. (I’m thinking, probably 12’). In the “other” thread, someone mentioned having to change/adapt the under side’s center beam in order to angle the viaduct as opposed to simply raising the legs on one end, burying them/shortening on the other. Could I please get a specific recommended method (step by step) to accomplish the grade drop? Would simply angling the cookie cut roadbed or adding a wooden wedged shim at the correct grade be enough to accomplish the 1+/- % grade travel? Simple pedestal “cement” blocks of differing lengths? I’ve given up on the idea of running a track beneath the viaduct but have four kits on the way and need to prepare and no one in our immediate area has or has worked with these kits. Thank you Thank you Thank you! This is the next step in the layout’s progress and want to get it going as soon as the kits arrive.
If you angle the base you add to your problems because then all the towers will be leaning.
What I would do is to find the straightest 1x2 about 6-7 feet long I could find. I would make the base flat.
Then I would position a support as high as the bottom of the girders at the mid point. So if the top of rail is going to be 5.5 Inches high at one end and 4" high at the other, and the top of rail ro the bottom of the girder is 3/4" then at the center the bottom of the girder will be at 4.75" at the high end and 3.25" at the low end and 4" in the middle. I would put the 1x2 on the low end than then position the towers under the 1x2 so they just touch the bottom of the 1x2, shimming the high end to make the tower supports vertical> Once you figure out what combination of shims levels each tower you can add those shims to the TOP of each tower. Then position each tower under the 1x2 in position and cut the foundations to raise the whole tower up level (or extend the legs down to reach the base.)
The key is to keep the towers vertical, to raise them on foundations and then to shim one end of the tower where the girder rest to create the grade.
Thanks very much, Dave. I think I understand your directions. Once the kits arrive if I’m still needing a touch of clarification or reality checking, would you mind a PM? I’d like to see if I can come up with a way to mock these up before using styrene glue so i can pull them apart as I try the shimming. Maybe a dab of laytex caulk? Once I have the kits and get to try their placement on the bench top, I’ll know the definite hight of each end of the grade at the lst and last tower… I’m a visual learner and if anyone else has a “method” they’d use that differs, I’d appreciate hearing about other approaches to this (if there are any). Thanks again for the step by step specifics!
If this viaduct will be 12 ft long then a consideration will be it will actually have to support the weight of the train, which for a couple engines and a dozen or more cars, can run to several pounds.
Another consideration is that you will have to keep all those little bridge pieces in line. If I was building that bridge I might be tempted to use a QUALITY piece of board, or a piece of aluminum channel as a “core” between the bridge girders. I would put the bridge girders and core in place, the building shim the towers up to the girders/core. That would make sure there was a smooth run across the bridge.
I’ve never built one of these kits myself, but my concern would be the joint between the vertical towers and the horizontal girder pieces. If the kit is designed to be on a flat surface, then the towers should meet the girders at exactly a right angle. Your adaptation will not do this. So, you may need to do some shimming on one side of this connection so that the pieces come together with a solid joint. Play with this on your bench before you glue it together, and be sure you’ve got the angle right.
I probably would go with 3/4" plywood instead of a board; it would be less likely to warp.
Dave, there will be several towers between the ends of that 12 ft. grade. I think…there are two tower sets on ea. 20.5" viaduct section. I’ll see how strong things look with the under the deck horiztontal center beam that’s part of the kit. Aluminum sounds like a good back up base if needed. It sounds like I’ll need to do a bit of experimenting and shimming-things new to me. I think I’ve lined up a couple of club member friends who might advise or help me with the project. If not, I’ll be back with more questions, for sure! Keep the ideas and advice coming if there’s more… I’ll need as much info. as I can get to approach this job, before the kits arrive in order to get ready. The club guys suggested making blocks or dowel piece footings and angling those while simultaneously shimming the tops of the towers with styrene or wood wedges. This may become more obvious as I start getting the kits onto the workbench but I don’t want to saw into the kits until I know it’s the right thing to do and hopefully not have to shorten any legs at all… Can anyone recommend a book that shows how to “grade” bridges or viaducts on flat surfaces (without “stepped” scenery bases, etc.)? I have Jeff Wilson’s bridges book but it doesn’t cover this. Thanks!