Last week I made some Thin brick slabs out of oven bake clay. This week I am trying to cut them and put them together forming abutments. I am having a hard time visualizing what I want to do here. All I have is two rectangles so far.
If you guys wouldn’t mind posting some pictures of your own abutments or other images you have, that would be great. Anything you wish to say about them that you think may help would also be very much appreciated. Thanks for your help in advance[;)]
Track Fiddler
I cast my “concrete” piers and abutments in Durabond 90 patching plaster. The wing walls on the abutment are separate, glued-on, castings…
…and a closer view, with the bridge removed (this area will eventually be covered in trees and undergrowth)…
…and same for the one on the higher, unoccupied bridge in the background…
…and a closer look…
This one was done with .060" sheet styrene…
…as was the one at the other end of the same bridge…
Everything in the way of abutments or retaining walls here is also .060" sheet styrene…
This barely-visible one (apparently shot during the dry season) is Durabond, but both it and the one at the other end of the bridge aren’t visible at all from normal viewing places…
For your situation, there doesn’t appear to be room for a wing-wall to the left, so a retaining wall of some sort will be necessary if that area will be visible from the other side - I’d suggest .060" sheet styrene, wit
Bridge abutments do two things: they hold up the bridge (much like the intermediate piers), and they hold back the soil.
The masonry in the above could arguably hold up the bridge, but it could not hold back the soil. The pressure of the dirt behind it would blow it out. However, it COULD be argued that it is a masonry-faced concrete form. But it would be a rare railroad that would go to the added expense.
The reason concrete is so common is partly because it would form a monolithic “wall” in the above picture. But even more important, a concrete structure can be built that ties that wall back into the “hillside”.
A typical design for an abutment (leaving out the wing walls for now) is a vertical load bearing wall, a horizontal “floor”, and one or more tie-back walls that physically connect the wall with the floor. The weight of the dirt holds down the floor. Because the wall is tied to the floor, the wall cannot be tipped by the force of the dirt behind it. Here’s an illustrative picture:
Note that the bridge goes to the left, and the dirt to the right. You can see the tie-backs in the plan view.
Sometimes the tie-backs are replaced by wing-walls. To be effective, they have to go “backwards” enough, though. In the photo, a retaining wall on the left side would do a good job of that. A CONCRETE retaining wall, because there will be a lot of force transmitted at the corner. And stacke
TF … In model railroading, we sometimes need to fit things together when we do not have a enough space. I think you ar doing a great job of fitting your bridge abutmnt where you have a tight location.
Wayne… Your bridges, abutments, and piers look great.
Below is an abutment and retaining wall made of casted plaster which I fit into a space too small for it.
Next is a “concrete” abutment and pier which I made of 1/4" plywood.
Fiddler,
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My only comment is that the bridge should sit on top of the pier. There should also be a “shoe” beneath the bridge and on top the pier.
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The shoes on oppsite ends of the bridge should be different designs, but since you can rarely photograph both ends of a bridge at the same time I don’t bother.
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-Kevin
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You could use RTV rubber to make a master of the clay bake you already have. That would give you multiple polyurethane resin castings to use as you wish. Resin castings are great for things like this.
Easier that clay baking many others.
Just a thought.
Patrick
Ed:
Thanks for the detailed information on abutments. Very interesting.
Dave
Track Fiddler, I think your abutmant’s look fine. Now all you need are Wing wall’s
Slightly off topic…
I will never laugh as hard as I did, when Christopher Walken said that on Saturday Night Live !
Yup, that was the inspiration for my remark, and it still makes me smile.
Wayne
Thanks for all the help guys. A lot of good information here that really did help. I don’t know why I could not visualize it but all the sudden I think I got it.
There is some nice custom looking work here. Your abutments look nice. I was working on it last night and this morning I think they look okay. I put the cowbell on the top of the side wings[(-D]
I thought of a question after another look at things. Should I have came out level a little bit on the side wings before I angled down or is it prototypical either way? Thanks
doctorwayne your molded piers and abutments look great. I would be very interested in seeing the molds you make.
Garry nice job. That was a good solution for a tight spot.
Ed you certainly handled the scientific end of things, interesting stuff, thanks.
Patrick that’s a great idea, this clay bake stuff takes too long. I have Woodland scenic’s rubber mold product. I am not familiar with this urethane product, can you tell me what I’m looking for and where I get it. Thanks all
Note that the weight of the bridge is supported by the “wall” of the abutment. But there’s a kupla feet of dirt and ballast above the top of that wall. To keep that off of the top of the wall (why?–just because?), they build a little mini-wall kind of behind the main wall.
I brought that up because the top of the wing walls are also there to retain the top of the dirt behind them. There’s no reason to go higher. And you can’t go lower.
So, to answer your question: The top of the wing walls should be at the height where the dirt behind them naturally falls–the “slope”.
Ed
I mentioned the short wall behind the main wall because sometimes people forget them because they’re kind of hard to see, what with a big old bridge obstructing the view.
There are reasonably priced bridge shoe castings in metal from Durango Press and Micro Engineering, and both are very nice; Walthers just released a set in plastic which I have yet to inspect. Greenway offers a gorgeous bag of bridge shoe castings in brass. By the way Greenway is about to do its annual winter shut down so visit the site pronto if you’ve been holding back on getting their unique stuff that nobody else seems to offer. Like a basic brass boiler for a 4-8-4 !
The idea with bridge shoes is that one end of a bridge is firmly attached to the abutment via bridge shoes; the other end can move with expansion and contraction and the bridge shoes either have two sliding plates of steel, or rollers.
Dave Nelson
A lot of the commercial abutments appear to be brick type but for western seems concrete is often more common. My plans are to go with concrete. If I can’t find any the right shape size I’ll form them out of Evergreen sheet plastic.
NOTE: Not all bridges use or used bridge shoes.
I’ll add my creation to the Pile. The pier on the right is made out of pink foam while watching hockey. I used a styrene I-Beam to cut the stone.[(-D] I then rubbed tile grout all over for the mortar look.
Thanks to all for your kind comments.
Fiddler, I had to look-up the thread in Big Blue, and discovered that it, like all of my threads there with attached photos, the recent site “update” had reversed the order of the pictures, so they didn’t match at all to the captions.
I’ve just now corrected that situation, and you can view the photos HERE.
Wayne
Wayne that is quite the ingenuity on your molds. Very cool[Y].
Brent looks great. I’ve made some things out of foam too
These tunnel portals were made out of half inch foam and separate foam rims put on after imprinting with a ballpoint pen. I never thought of your I beam styrene idea though, great idea. I will be using that one, thanks[:D]
Not bad…not bad at all! I would never have guessed them to be foam.
Wayne
TF, those portals look really good.