We are in the process of planning a 2112 foot trestle, built full H.O. scale, that will be built out of five six foot long modules. The bridge was 110 feet high and is the second longest steel viaduct in Alberta. The module will be built so that it is free-mo compatable and we plan to show it in some western canadian locations. The project will be the first of a number of modules that will eventually be incorporated into a much larger project. If you would like to see what else is involved in the project, you can see it at www.forthjunction.com
My question is simply this. has anyone ever built a module of this complexitiy with this number of joints and have you learned some hard lessons from your experiances? The current plan it build the bridge so that on one end is a standard four legged module, with a shelf that the next module will sit on. the nextmodule will sit on the shelf and have two legs on the far end, with another shelf. these would have a locking pin to ensure that the bridges will line up properly, and should ensure that the module will be easy to set up.
We have seen this done with regular multi part modules andit works well. Any help or insight will be appreciatled.
There’s a couple of approaches to take with this. The first question to be answered is would the trestle structure be permanently affixed to the modules, or would it be something that would be set in place as part of the set up.
If the former, my suggestion would be to space the supports so there is a removable section at the joint that can be snapped into place, both electrically and mechanically, without having to manipulate track joiners or otherwise risk damaging the track or structure.
Given the length of the bridge, you’ll need to provide for electrical drops, which can be effected with wire running up the support bents.
If the bridge structure is to be removable, you could create a strong mechanical and electrical connection by installing headphone jacks at the base, to in effect, “plug” the bridge into the module.
To make sure everything lines up every time, you would need to include alignment pegs in the frames, and I would strongly suggest constructing the bridge piers out of brass stock so it is more sturdy.
In either case, you’ll need to construct a “coffin” to transport the set with a reasonable degree of confidence that it will arrive safely and assemble without incident.
I agree with you lee on many of the items that you mentioned. The river on the module is part of the problems that we will have. It is five feet from the edges of the long span in of the river. I think we will be trying to make the river out one way glass that has christmas tinsel under it. this will be lit with a couple of flourescent tubes that will double as a explaination about the bridge. I am leaning toward a removable set of bridge supports to compress the amount of space and weight that will have to be transported. if we leave the bridges in place, each section will be 18 inches high, from the bottom of the benchwork to the top of the rails. I will likely leave the two end sections intact as the bench work there is 18 inches anyway. On the three remaining sections, they can be reduced to about 8 inches, which will allow the bridge to fit a coffin about 66" high and two feet wide by 6 feet long.
The headohone jacks are what we plan to use, either for the legs at the footings, or for the removable sections of the track. all breaks have been designed to fit the 75 foot long sections that are in between the peirs.
All in all, the project seems to be in line with your advice. we will keep you up to date on the progress of the bridge. right now we are doing cost analysis and fundraising. thanks for your help.
The idea seems unworkable, particularly for the alignment/connection of the bridge sections and their ability to withstand repeated connection and disconnection without damage. If you find a practical solution, I’m sure the MR community would want to see how it is done. Good luck.
First I beleive you need a very rigid frame construction of the modules because you need a perfect alignement of all of them in the two dimension; square and height.
If I have to do that , I would built all the modules on a aluminium frame with some alignement device which oblige the module to be at the same height and the same square line.
By my job, I am a crafstman in wrought iron, I am sure you could realize this with a aluminium or such a metalic frame with a high precision fitings
This could be achevied easily with a very large rectangular tube such a 160x40x3mm.
A another smallest tube could be inserted in the big one to make the transition and the connection between the next modules; if you made it such a 60 cm lenght inserted 30 cm on each side of the big tube , you have a perfect square connection without any play.
You could fix all the traditionnal benchwork construction on this tube with screw and a construction adhesive.
Any aluminium sale factory could cut for you the tube at the lenght you want with precise and square cut.
The aluminium is light and don’t let is precise fit with all the move.
Don’t use wood for the frame of the module for a such long set which need such a quality of alignement.
By this system alignement will stay very precise for years even with many moves.
First build the modules, second lay the span; because the perfect alignement of the modules you can lay the bridge on a very precise line; why not to use a laser to align it?
My own Maclau River in Nscale is buit on a steel frame made of tube of 40x40mm and bolted togheter like a dominoes system.
I have move it twice whitout any distorsion in the wood
I would tend to agree that it seems like it’s not physically possible to build a bridge that would actually hold any weight and function as it should in sections. unless you actually intend to construct the bridge out of metal not styrene and use some sort of mechanical fastener to attach each section to the next. They don’t call bridges engineering marvels for nothing, most actually get their strength from the construction method and not the actual material.weight loading etc. forces pushing against each other working together to form a solid working structure. Think about the Keystone in an arched stone viaduct bridge. It in it self is insignificant until it’s put in place and then it’s the force that holds the entire bridge together, remove it and the bridge comes tumbling down. But I will say I would love to be proven wrong a bridge that size would be a marvel in it self.
It is interesting to read the posts that have been made on this subject. I am currently thinking that a set of three bridge sections could be built out of aluminum tubing. the bridge decks could be made as cosmetic peices and the strength of the bridge could be from the aluminum tubing. This way we could connect the bridges into one solid peice and aviod the problems of each individual span not being lined up correctly. The only other problem with this idea is that the river spans are 150 feet long and would be difficult to hide the tubing as there is no deep girders at this point of the span.
One of our members is a welder so welding a set of frames would not be difficult. When one looks at the bridge, that was built almost a hundred years ago with simple tools, it should not be too difficult to make a model of it today. Everything that has been built is impossible until it is done, then it is accepted. One thing is in our favour is that the bridge itself is only 110 feet time. This will limit the amount of misalignment that we might run into.
So if the frame is welded for strength, and the bridge is made solid so that it is in reality only supported at the ends by ends of the module, the bridge itself is mostly cosmetic, the only thing left is the 306 foot section over the river.
If the bridge is constructed as an aluminum tube, you could rig a spring loaded smaller tube that can be pushed back to allow the removable middle section to be inserted securely. Flush cut rail joints and the headphone connections at the base would give you the initial alignment, then snapping the spring tabs would lock it all together.
Perhaps a U-channel would be better for the main superstructure…
Each foot of the bridge which is a stone one could enclose a small aluminium tube where the phone jack could be fixed.
For the large span over the river, I come back to the first post I write in this topic and us the same method.
The 306 foot lenght could be divided in small part.
An aluminium tube form the deck of the bridge cut in a few segment to easier transport.
To connect the segments insert in the deck tube a smallest tube which had the same mensurations of the inside of the deck tube. Push it halway of it’s lenght so you have the "connector to the next bridge segment
By the way you have a perfect and strong alignement which could’nt move anyway.
The track could be glued on the tube or on a small roabed fixed on the tube. The side of the tube could be “clothed” by all the the bridge details deck.
To connect electricity between the segment use small connectors and run a double wire throught the tube.
A mechanical connection for electricity could be done but it would be difficult to do because of the connection system.
The plan now calls for the bridge to be made of the aluminum tube, and it will have a three removable, aproximatley 8 foot sections. the center spans on the river will be made of 1/4 steel rod, built like a warrren truss and then be covered with cosmetic bridge pieces. the aluminum tube will have a wiring bus runnine through it or on top of it, as each section needs electrical continuity. these wiring peices will be conected by anderson power poles hidden inside the frame. The frame will be welded tubing, with masonite decorative panels. This will be heavier than originally hoped for, but better in the long run. it will have two cases that will be used to protect it during transit, and these will stack for a better fit in the truck.
So far that is the plan. It should be a workable idea, and we are sure going to give it a try. And we just got a new hobby shop in town which means no more 2 hour drives to get a peice of track.
Any other suggestions as to what we should be doing in the design phase of this monster. We hope to be able to unveil it in time for Alberta freemo in Big valley, next August. We will be running a construction blog on www.forthjunction.com It will be a few weeks before we get all the plans drawn and the fundraising started. Thanks for the help so far, it has already resulted in a better bridge design.
Marc, your suggestions have been really helpful. most of what you have said has made it into the design
