I used vegetable oil as a mould release, wiping it on with a paper towel just before assembling the mould. I'm not sure where it goes during the casting process, but there seemed to be none left on the mould when it was opened and none on the castings either. I coloured the piers with a wash of water-based paint, and there was no beading-up of the paint, as you might expect if there were oil on the casting. By the way, the castings came out very cleanly, leaving nothing in the mould to be cleaned up - another wipe with oil and it was ready for another pour.
Wayne
Very cool
Hello Allegheney ...... The piers are about 11" tall. .. I referred to MR's book on Bridges and Trestles to determine the angels and the tapering. I used construction adhesive such as Liquid Nails. I filled the joints with spackling compound. I used a few layers of common household latex paint with sanding between each layer. The coloring is with acrylics, and I am still not completely pleased with the color. It is what it is now, though. ...... The entire multi-span bridge is four feet long.
GARRY
HEARTLAND DIVISION, CB&Q RR
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Gary, great looking piers what are the dimentions? how did you assemble the plywood with just carpenters glue?
Wayne did you find it necessary to use any sort of mold release with the stuff you used. I've dine some resin castings for making out of production tail light lenses and had to experiment with different mold release agents.
Garry, your bridge piers turned out great and way better than I could have accomplished in wood.
The moulds are made almost entirely from .060" sheet styrene, which I buy in 4'x8' sheets. I use a large carpenter's square and an 8' straightedge for doing the layout work on the sheet (on the floor of the layout room) then use the straightedge and a utility knife to cut the sheet - mostly a "score and snap" operation. For cement, I use ordinary lacquer thinner, applied with a brush to both surfaces. Use a brush sized to the job, a 1/2" is good for most, but a 1" is better for larger areas.
The hardest part was adding the detail to represent the form boards, and it really doesn't appear to have been worth the effort. With the flat fluorescent layout room lighting, the detail is barely visible, although it may show better when I finally get around to weathering the piers. I scored the joints between "boards" with a knife, then dragged a #17 X-Acto chisel blade across some of the boards, leading with the non-tapered edge.
When filling the moulds, I poured some plaster in, then rapped the mould lightly on the top of the workbench to help any trapped air bubbles to escape, repeating these steps until the mould was filled to the proper height. I also poked a piece of piano wire into the corners of the mould where the sides meet the bottom, again to prevent air pockets.
The Durabond has a catalyst in it, so the mould will warm as the setting process occurs - I used Durabond 90, which sets in about 90 minutes, but there are other setting times available - the number following the name is the setting time in minutes. The moulds came off very easily and there were almost no voids on the surface - any present were filled with more Durabond. It's available at most home improvement stores in, I believe, 2 and 5lb. boxes and 33lb. bags. Plaster of Paris and Hydrocal should also work, as will dental plaster, but I've found the Durabond to be cheapest, easiest to work with, and strongest. Don't use drywall mud.
When designing the mould, you need to picture not only how it will go together (you should include a mating surface where the mould sections meet - this will ensure that the mould assembles in exactly the same manner every time), but how it will come apart. That means that you can add low-relief items, such as the blocks which I added to create pockets in the finished casting, or create fairly shallow pockets in the mould, which will produce a raised area on the casting. All of these additional pieces should have either straight (perpendicular) edges, or edges which are widest where they attach to the main part of the mould. In other words, no undercut detail work which would make the mould difficult or impossible to remove. If you need such features, cast them as separate pieces, then cement them to the main casting using white glue or carpenters glue.
If you need several similar castings of varying heights, make one mould for the highest pier, then cast them all using that mould, filling it to the height required for each individual piece. That's why all of my moulds are upside down - they give the finished top for the pier and keep the width of the various piers constant - after all, all of the piers are of the same width at the top, with the taller ones being wider at their base. You could also make them straight-sided, or stepped, like a wedding cake.
Wayne's bridge piers are truely outstanding. It's good to see how he made them.
Here are photos of the double track bridge over the Mrs. Hippy River. I made the piers and abutments from 1/4" plywood.
Wayne,
I have to say that is pretty a work of genius the end result looks as good if not better then most of the commercial castings on the market. How did you create the top pice with the two pockets, is it several pieces glued together or did you mill out the perimeter so it would fit flush? I bet they come out of the mold needing very little work befroe you plant them as well. Also what did you use to cut the .060 styrene sheets a little think for an exacto blade?
Egad, more white paint...
If one ignores the white paint covering graffiti, here is a useful example for weathering concrete. While the cement abutment is wide enough to two tracks, only a single-track girder bridge is used. While half of the bridge is mostly grey/black tones with a bit of tan, that under the bridge is mostly tan. Perhaps this is due to decades of dust falling from the ballasted-deck bridge. ... Come to think about it, white cover-up paint is a detail that shouldn't be overlooked for contemporary, accessible bridge piers.
Thanks for the kind words, Will.
I didn't use any sealer, simply some PollyScale thinned (quite a bit, as I wanted a wash rather than paint) with water. I doubt that the colour was anything straight out of the bottle, though, as I mix almost all of my colours on an as-needed basis. I'd guess some type of grey with some buff added, or vice versa. Your question, though, reminds me that I really should weather all of the installed piers and abutments one of these days.
Excellent, excellent work there!! When you start painting the piers, do you seal them first with a basic primer like a lot of people do with plaster. Also, what color is your final coat?
Again, great work and tutorial!
You can also cast your own piers and abutments using simple styrene moulds and a strong patching plaster such as Durabond.
I make my moulds from .060" sheet styrene, usually in three separate sections: two "L"-shaped sides and a separate top to suit the particular bridge. Mine aren't especially tall, but I made most of the moulds taller than required - if I need a taller bridge, I'll already have a suitable mould, and, by partially filling it as it sits upside down, I have a pier that can be used for a lower bridge, too.
Here's a plain one, unassembled. I scraped some detail into the inner face of the sheets to represent the form boards which the prototype would have used. This was done before assembling the parts. The reinforcing strips along the edges help to keep the mould from bulging and also interlock with the other sections when assembled
Here's the same mould partially assembled. I use a paper towel to wipe a light coating of vegetable oil on the inside faces of the mould before assembly - this prevents the plaster from sticking to the mould. The elastic is around what will be the top of the pier, but the bottom of the mould. The styrene blocks about half way to the other end are simply to prevent the next elastic from slipping out of position as the mould is filled. Also seen is the bottom section of the mould - the two squares of styrene cemented to the inner face will form pockets in the finished casting, which will be on the top of the installed pier, providing locators for the bridge's steelwork:
Here's the same mould, fully assembled and standing next to a pier cast in it. For this pier, the mould was filled only to a point slightly higher than that required, then the bottom was filed to obtain the proper height. Two pads on the bottom of the steelwork supporting the spans fit into the two locator pockets on the pier's top surface, although here they're not seated.
Here's a mould for a shorter pier, one having a stepped top to accommodate bridge girders of different depths. Again, the bottom of the mould forms what will become the top of the pier, with the two sides interlocking, then the bottom inserted into the mated sides:
Here's the same mould, assembled and ready for pouring. It's standing alongside a pier made from it. Note how the corners of the mould overlap and how the bottom supports the sides and also projects up into the mould:
If you want stone detail, you can carve the Durabond after has set and been removed from the mould, but before it's completely cured, as it becomes extremely hard as it cures. It can be coloured like any plaster casting - I find that a wash of well-thinned PollyScale works well, applying successive coats until you get the depth of colour desired.
If you plan the construction of the moulds carefully, a handful of styles can serve for several different bridges, and the Durabond sets-up fast enough that you don't need more than one mould of any type.
You can also used extruded foam as well as wood, strong and easier to shape. Went to a clinic where the fellow cut pieces with a home-made hot wire cutter, then scribed in the seams between the stones with a pen tip. If you were modeling concrete, no scribing needed just paint and wash.
Good luck,
You can also make your own piers out of wood. A one-by would work. (1x4, 1x6 or whatever, and cut to the length youu need) Just cut a notch out of it. (You can use a table saw.) Paint it a concrete color and then apply a black wash. Simple, cheap, and creative modeling.
If you want stone, apply embossed stone sheeting to it.
Elmer.
The above is my opinion, from an active and experienced Model Railroader in N scale and HO since 1961.
(Modeling Freelance, Eastern US, HO scale, in 1962, with NCE DCC for locomotive control and a stand alone LocoNet for block detection and signals.) http://waynes-trains.com/ at home, and N scale at the Club.
How tall do you want?
One solution for now might be to stand the piers you have on top of a plinth at the top of a lower pier... this can be either stone or concrete... could be stone that has had a concrete shell added to strengthen it.
Don't forget that with very tall piers the lower stone blocks are often larger than higher ones. Also that civil engineers often raise very tall piers by levels rather than in one straight line. You can use this to figure out ways of combining smaller ready made models.
I am looking for some tall double track bridge piers anyone kow of any mom & pop outfit or anyone who makes some nice tall one? I have Chooch double track cut stone piers that just aren't tall enough for the look I am trying to get. Any help is appreciated.
Thanks