# Material used to make a viaduct



## avlisk (Apr 27, 2012)

What do you experts recommend for making a viaduct. The plan is to have it S curved, 10 foot long, 18" high. All I can think of is to put in some wooden forms and mix up a batch of concrete. Any other ideas?
Thanks. Ken Silva 
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## lownote (Jan 3, 2008)

you could make it from rigid insulation foam, and then paint the foam. The foam can be worked with a knife or carved with hot-wire foam cutter


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## spincaster (Mar 10, 2012)

Ken, 

Why a duck? Why not a duck? (Marx Bros) 

Building a curved via duct sounds tough! What do you want it to look like? Stone, concrete, etc. What climatic conditions does it have to survive? 

I am not keen on the idea of a true s curve in a railway. 

Formed concrete would require a lot of work in building the form but would go quickly once the form is done. Designing a curved form would be a major project. Building stone by stone on/in forms might be a lot easier and provide some fudge factor. 

If you want to go the insulation foam route you could build your support and then use the foam as a facade. 

Lot's of possibilities which is what makes "making things" fun!


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## Cougar Rock Rail (Jan 2, 2008)

I made my curved (and sloped) viaduct using wood forms and concrete. It takes more work but then you have something that is going to last. I more recently built an avalanche gallery and used a combination of wood forms for the vertical forming and foam shaped as required for the blockouts. I'm sure this has been covered quite a few times in the forums in the track section, so you might want to search and look there for ideas too. 

Keith


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## avlisk (Apr 27, 2012)

Foam doesn't sound very sturdy or rugged to me, especially with the monsoons and high winds that we get here several times a year. And then, there's the sun and heat, too. Building a wooden form and filling it with concrete sounds pretty simple, though. I've rethought the S curve, and will make it a simple bend to the right instead. Thanks for your ideas. 
Ken Silve 
Phoenix, AZ


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## moonspenders (May 7, 2012)

Monsoons?? High Winds?? Yes, I think something sturdier than foam or even wood would be in order. My vote is for Portland cement... something fine enough like that would let you have the option to add stone/brick details if you wished and bring out some details while still holding up to nature's fury. You can even add powder colors to it to make it stand out a bit. Given a sturdy foundation and not too much abuse, it could easily last 20 years.


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## avlisk (Apr 27, 2012)

Mr. Moon Suspenders, (I joke), I may not last another 20 years even with no abuse and a weakening foundation of my own. Could you tell me more about the portland cement option of construction. That is, adding stone/brick details. Are you saying I can scratch in the details after the stuff is dried and the forms removed? Or, are you suggesting another plan of attack? 
Thanks. 
Ken Silva in Phoenix


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## John J (Dec 29, 2007)

Posted By avlisk on 10 May 2012 08:35 PM 
Foam doesn't sound very sturdy or rugged to me, especially with the monsoons and high winds that we get here several times a year. And then, there's the sun and heat, too. Building a wooden form and filling it with concrete sounds pretty simple, though. I've rethought the S curve, and will make it a simple bend to the right instead. Thanks for your ideas. 
Ken Silve 
Phoenix, AZ 
If you build forms and use concrete to make arches and a curve in the bridge.

The inside arches of the curve will be closer together than the ones on the out side of the curve.

JJ


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## moonspenders (May 7, 2012)

Posted By avlisk on 11 May 2012 07:26 PM 
Mr. Moon Suspenders, (I joke), I may not last another 20 years even with no abuse and a weakening foundation of my own. Could you tell me more about the portland cement option of construction. That is, adding stone/brick details. Are you saying I can scratch in the details after the stuff is dried and the forms removed? Or, are you suggesting another plan of attack?

I've had this username for more than a decade, Ken... I've heard them all! (It actually comes from the book title "Moonspender" by Jonathan Gash, author of the Lovejoy mystery series.)

Portland cement is basically the same thing as your standard concrete, minus the coarser materials. Probably the best way of adding details is inside the mold you make for it (if you feel like all that painstaking effort). I'd say that etching in details while it's still wet is an option, or coating the finished viaduct with a thin layer of it and etching in details afterward is another possibility. If you wait until it's dry, you would have to use some heavy duty tools to etch in the details. Portland cement, when dry and cured, is about as tough as limestone. So unless you happen to be a stone mason with a few tiny chisels sitting around, I'd work with the still-wet version if I were you.

It comes in large bags, available at almost any building supply/hardware store. You can always mix up a tiny batch of it and experiment before attempting the full-sized project. A project your size would easily use 10 or so bags of it (somewhere in the neighborhood of $10 each). Even if it does outlast you, just think of the fun any future owners of the property will have attempting to remove it! They will probably have two choices: buy a jackhammer or build a garden railroad of their own.


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## avlisk (Apr 27, 2012)

Good stuff moonspenders. I'll check for that book. I'm partial to Old Time Radio shows such as Broadway is My Beat, Box 13, Philo Vance, Richard Diamond, and such, and to British TV, Jeremy Brett's Sherlock among my favourites, so those books sound interesting to me. I didn't know about portland cement's characteristics, so thank you. The viaduct has undergone several changes of plans already, as the layout design changes in my mind, and the latest design it's finding a tough time fitting in, unless it's only 2 feet long and partially obscured by a post at that! And that doesn't seem worth it. Or, it could be 35 feet long, on a 10 foot radius curve, and a 4% grade. I've got more figuring to do. 
Thanks, all. 
Ken Silva 
Phoenix, AZ


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## avlisk (Apr 27, 2012)

Oops. That should read "diameter curve", not radius. 
Ken Silva


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## Jerry Barnes (Jan 2, 2008)

I made mine with the foam. Inner structure is treated wood, the foam is glued/screwed to that. I scored in block patterns and painted it with acrylics.


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## moonspenders (May 7, 2012)

Jeremy Brett was one of the best Sherlocks ever (though the new series Sherlock on BBC is actually quite good as well). 'Lovejoy' was airing on PBS around the same time, based on the books. (I might recommend starting with "The Judas Pair", published in 1977, even if it's not the first in the series.) 

Take your time and get the details worked out before beginning to the cement project. Once you have it poured and in place, it's as good as permanent! Of course, in the mean time, you could always just use some plywood and sawhorses for a temporary "bridge". Certainly not realistic, but it gets the track functioning.


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## SteveC (Jan 2, 2008)

Ken

While the following may not be exactly what you wish to do, maybe you can get some ides from what Tim did. Feel free to download a copy of the PDF file if you like.







Oh, the other thing pay attention to Tim's comments regarding weight, when considering how you're going to go about the forms/mold, because if it isn't in the correct position when you take the forms/mold off you could have a problem.









Tim Hytrek's - Stone Arch Bridge (PDF 3.37MB)[/b]


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## avlisk (Apr 27, 2012)

Moonspenders. Jeremy Brett is the best Sherlock ever, I agree. I haven't seen the new one with the guy from The Office, but I loved the UK Office, too, so I'll give it a look. Regarding the viaduct, I'm thinking of building it modularly, in concrete, a piece at a time. That will keep it small and moveable if necessary, and give me the 2' piece right away. If the rest of the line ends up also being viaduct, (which I'm not sure of at the moment), I can build additional pieces in 2' sections as I go. This is assuming a 2' section is light enough to move around. 
Ken S.


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## astrayelmgod (Jan 2, 2008)

I tried cutting detail into cement after it was set; it is astoudingly time consuming, even with power tools, and generates more dust than you ever imagined would be possible (dust that is very, very bad to inhale, by the way). I ended up putting another layer of cement over the whole thing, and starting over. All forming should be done while it is wet. Actually, that is where the rigid foam would work well: cut the detail into it, then use it as the inside face of the form. 

You might also look into plastic cement; it has added chemicals to inhibit cracking. It will still crack if it dries too quickly.


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