I have a need for an elevated roadway on my layout that I envisioned looking like this:
I plan on using wooden dowels for the vertical supports (7/16ths") which scale out to approximately 38" diameter. I plan on using 9/16"square stock for the horizontal support and then using Evergreen Styrene I beams for the actual roadway support.
I originally planned on an 80 scale foot spacing for my vertical supports, but the styrene I beams come 14" long. Should I cut the beams down to match my spacing or increase the spacing to match the length of the beams? Do the ends of the I beams need to sit on the horizontal supports or can I add a splice plate where the beams meet? This will be my first attempt at scratch building and I’d like for it to turn out decent looking…thanks for any advice you can toss my way.
I’d use square styrene tubing for the vertical supports, as you can then use solvent cement for the entire assembly procedure. Also, make sure to include the bracing between the “I” beams, and, regardless of how you finish the upper surface, use .060" styrene sheet as a sub-base over top of the “I” beam assembly. As for the spacing, I’d leave it at the 80’ that you first decided upon, and cut the “I” beams to suit. However, unless the load on the structure is going to be excessive, you could probably get away with splicing, although it might be a good idea to alternate the joints on every other length of “I” beams: that way, only half of the “I” beam joints would fall between any set of two supports. The weakest part of the whole assembly will be the joint between the vertical posts and the horizontal supports for the “I” beams.
Thanks for the reply. My reasoning for using wood dowels for the vertical supports is I can drill down into my plywood deck with a Forstner bit and recess the posts into the plywood. Same idea for the top of the dowel where it joins the horizontal support. The dowel would be recessed into and glued to the horizontal members. I could use some flat styrene on top of the horizontal supports to act as a spacer for the I beams as well as helping to keep the I beams from walking sideways off of the horizontal support. The roadway won’t be supporting anything other than some vehicles at various locations on the road. I think I agree with your idea of cutting down the I beams to the same length of my support spacing rather than trying to splice them.
I’m sorry, I thought that maybe you weren’t aware of the availability of the square styrene tubing. Your idea to drill the plywood is a good one, but then why not use round tubing instead of wood dowels: the solvent cement will give you a better bond, and mortising into the horizontal supports should make it practically indestructible. You should be fine with the bottom of the legs simply nested into the blind holes in the plywood, with no need for glue there. You never know when you might want to remove the bridge for cleaning or adding scenery.
Gaging from the hood of the car in the pic, the I beams appear to be more like 7-8ft centers. An approximation for a reference, use the front tire diameter. The average diameter for that vehicle would be 26-27".
They make both a short one, which is just the horizontal part, and a longer kit with supports. I used a short one myself, and it came out pretty well. The bridge is 3 inches wide, which is appropriate for a 2-lane roadway.
I’ve used a number of the Evergreen H-column pieces in my subways. They look fine, but they are very thin and light, and won’t provide much structural strength.
I was originally going to say 4’ or 5’, based on the light fixture, but those things come in a wide range of sizes. Looking at the parking space lines, though, I’d say that 6’ would be a good guess. If you know how many lanes of traffic are on the roadway above, it should be pretty easy to calculate more accurately, although 6’ or 8’; who’s going to quibble?
I know about the Rix overpass and I’m planning on using one on another part of my layout. The reason for wanting to scratch-build this roadway is twofold: the cost of using premade kits and the length of the roadway. It will be against the back of my layout, running parallel to my yard. It will be about 12’ long. That’s also why I planned on using wood dowels and wood for the horizontal supports. I can buy wooden dowels for much less than styrene tubing. The only styrene I’ll need to buy is the I beams and some C channel for spacing and joining the I beams to each other as in the photo.
Wayne,
I guess the spacing isn’t terribly critical. If I build the supports on 8’ centers, they will be under the roadway and out of sight for the most part. I doubt someone will try to stick a scale under there to measure the spacing…however, I’ll know what the spacing is and if it isn’t correct, it will tend to drive me nuts as I’m just a little bit anal that way…[:-^]
If you notice there are parking stall lines painted on the ground in front of the car. Parking stalls are 7-8 ft wide and the beams are closer than that.
I wouldn’t really sweat the exact distance. Depending on the materials, the load the span the girder size, etc different bridges will have different spacings. It will be especially non-apparent if the finished bridge is against the backdrop and running parallel to to the backdrop. Reasonable will be good.
Yes you can splice the girders, they do on the real ones. If you want cut the ones facing the outdise over the girders and then splice the rest. Nobody will see the joints anyway.
If you use rectangular or square tube for the vertical supports you could fit a dowel inside them.
I would suggest going to a plastics supplier in your area to see if they have any plastic shapes that might be usable. For example a lot of railroad bridges have hexagonal or octagonal concrete piles. You can model them with miniblind wands (the plastic pieces you use to open/close the blinds). They may have premade rectangular pieces in loooong pieces. that’s also a good place to get the .060 styrene for the deck. You should be able to pick up a 4x6 sheet of .060 for about the same cost as 4 or 5 packs of Evergreen.
Thanks for the input. There is a plastics supplier here in town that stocks .060 styrene in 4’x8’ sheets for about $22.00.
Am I missing something here? Everybody keeps suggesting the use of styrene for the vertical supports…I was planning on painting the wood components with Pollyscale Concrete color…as an avid woodworker, building those components will not be difficult and less costly than styrene. Unless, as I said earlier, I’m missing something that should be painfully obvious…
From my perspective, the styrene would be a lot easier to work with, but that is because I am not so skilled with ‘fancy’ wood joints like you are talking about. Many regularly use styrene and just keep working with it even if there is an alternative material available.
Also, how are you planning to model the deck and the railings if you plan to model it like it is in the picture? Styrene? That could get tedious for a 12’ long bridge…
You could also go wood all the way! Home Depot and others stock basswood strips in 3’ & 4’ lengths. Thin balsa glues top & bottom would make an I beam. This should also be less expensive than the styrene, and painting the dowels & I beams with the Poly S will come out looking the same. Just my[2c][:D]
I’m not sure what type of ‘fancy’ joints you’re referring to…a wooden dowel set down into a flat bottomed hole in my plywood deck, with the top of the dowel set into a matching hole on the bottom side of my horizontal support. That’s all it would be…
As far as the deck, that’s why I referred to the sheet of styrene I could purchase. The railings…hmmm, what I really want is to find a pre-made railing similar to the railing supplied with the Rix highway overpass kit…but if I can’t find anything similar, I may have to improvise and design something else that can be easily built.
