Bridge at South Wayside

[doctorwayne]

On the casting, is it possible to cast two-sided objects? This would mean a two-part mold? The thinnest portion of the railings is .040 and overall the thickness is .100. Could a mold and resin be used for such a thin two-sided casting?

I'm sure that careful work could yield a two-sided part, but, yes, it would likely be a two-part mould. However, in the article which I cited, the author used Tichy multi-pane windows as part of his "masters" for the wall castings, and they reproduced very well with a cross-section of only .015" or .020". You could make the two sides as separate castings .040" or .050" thick, then cement them together back-to-back.

Wayne

[P5se Camelback]

"Double-sided" parts are doable if you build a two or three-piece mold, paying attention to draft angle, part depth, parting lines and then give the mold plenty of "air runners," small diameter runners that terminate at the "top" of the mold ("top" being where the "pour" opening is) to allow "trapped" air to escape from those bottom corners. Those runners are to help eliminate voids caused by trapped air in your cast part.

It is doable, and not all that difficult if you take your time and think out where the best places for parting lines will be, and then ... you spend the time to build the mold sections, put them together and secure them with tied up string, large rubberbands, clamps, or whatever (so they won't come apart or move. (There are a couple of tricks to use to get the multiple mold parts to key together with the right orientation. And there is an incredibly good feeling at the other end when you pull your first beautifully cast part from the mold!

[Gary S]

It will. The others have been FANTASTIC. For a modeler that professes to be new to scenery, you have a lot of us that have been doing this for 30+ years like myself beat by a long shot.

Tom, I built many models as a youngster growing up in the 60s and 70s, and have always been proficient at building stuff. I don't so much consider the bridges I have been doing as "scenery" but more just building models. To me, "scenery" means groundcover and trees and bushes, Now, I did do that little bit of static grass on the Mason Park bridge, and I am very pleased with how that turned out. Seriously, that was my first real attempt at permanent layout greenery.

On that note, I am feeling hugely confident that the homemade grassblaster is gonna be my ticket to some realistic scenery. I've put some thought into why alot of static grass on layouts doesn't look that great, and feel I know what to do to make it look good.

As for "beating" many of the 30+ year modelers, I don't know about that!!

But, as I say at work, there is ALWAYS something to be learned from EVERYONE, and I can't thank you enough for sharing your layout with us here virtually.

Thank you Sir! I enjoy "showing off" what I am doing, and sometimes feel I post too many "in progress" photos. Knowing that you enjoy the journey makes me feel good.

I can only hope to get the priveledge of seeing it in person next time I am in the Houston area. I'll bring beer.

Tom, I would be honored to have you visit the layout if you get to Houston sometime. Make sure you let me know when you'll be here, and we'll get together.

[Gary S]

DocWayne and biL, I don't know if I would have been able to accomplish a multi-part mold in the thin dimensions I needed. Wayne's suggestion of two thin pieces glued together may have been the ticket. Still, I am past that now! One of these days I will definitely try some plaster casting like Kurt did on the one building from his Miami layout (building which is now in my possession!).

With as many detail parts as I will need for this layout, I really do need to learn the casting techniques.

[Gary S]

Oh... meant to post a progress shot... here is a sample of the concrete segments put together:

   

Supposed to look like the upper rail of this photo. Looks like I need some more gray.

   

[Gary S]

Working on the girder. This is from a Central Valley 72 foot thru-girder bridge. Had to modify the ends and cut the length down just a bit. Instead of using the kit cross bracing, I am using square styrene to mimic the I-beams which are on the prototype.

   

[ocalicreek]

Working on the girder. This is from a Central Valley 72 foot thru-girder bridge. Had to modify the ends and cut the length down just a bit. Instead of using the kit cross bracing, I am using square styrene to mimic the I-beams which are on the prototype.

Now that's the best kind of cheating. Don't model what folks won't see...unless you just can't live with yourself.

Lookin' good!

Galen

[Gary S]

You're right Galen. The square styrene is cheaper and easier to work with than plastic I-beam. And it is mostly hidden in shadow, so the discrepancy won't show.

Been working on the base this morning, doing the cutting outside and then rushing back into the workroom to watch the Texans.

The base is 3/4" plywood that I've had in my attic for awhile. Cut the base to fit in the cut-out on the layout. Then laid out where the bridge and sidewalls would be. The sidewalls are made from two layers of 3/4" plywood glued and screwed together, then glued and screwed to the base. This thing will be quite sturdy! Building it seperately from the layout will allow all the intricate work to be done here at the workbench instead of in the train room.

   

[Gary S]

Some styrene put on for the walls. The styrene on top of walls will be covered in dirt, grass, or parking lots. I figured I should put the plastic on to help keep the water-based scenery from getting into the wood and causing it to come apart or warp.

The plastic was glued to the wood with 3M #77 spray-on glue. That stuff works well and dries fast. Much better for stuff like this than white glue.

   

[Gary S]

Got the abutments built using the prototype photos as a guide.

   

Then put in the supports for the road slope:

   

And the underlayer for the road. It is cut from 1/8" masonite:

   

[P5se Camelback]

Oooooooooo! Lookie, lookie! Things are rapidly taking shape! I'll bet this'll be another hum-dinger of a bridge.

I'm just sitting back and watching ... the build is fascinating and the progress frightens me ... it makes my build speed seem like it screams along at a common garden slug's pace!

[cnw1961]

Oooooooooo! Lookie, lookie! Things are rapidly taking shape! I'll bet this'll be another hum-dinger of a bridge.

I'm just sitting back and watching ... the build is fascinating and the progress frightens me ... it makes my build speed seem like it screams along at a common garden slug's pace!

Yeah, but an old and weary garden slug! When I see the incredible speed Gary’s projects are moving along at, it feels like I am making no progress at all. But that’s okay, because my layout is so small. If I’d build it at Gary’s speed, it would be finished within a week or two .

Keep up the fantastic work, Gary. I am still sitting here watching and enjoying the show.

[nachoman]

Gary, I know you have covered this before in one of your previous bridge threads, but remind me again how you created that concrete texture on styrene. I have a bridge pier to make, and I am leaning towards making a styrene box rather than cast plaster or a steel pier.

[Gary S]

biL, Kurt, this project is moving along rapidly only because I spent the major portion of the holidays working on it. Many hours in this one so far.

Kevin, the concrete look is not difficult. First, the plastic is sanded with just a few strokes of 150 or 220 grit sandpaper in the horizontal direction, then it is sanded more in the vertical direction. The vertical sanding will help later when the dark washes go on, the washes will give the appearance of rain streaking.

Paint is next, and can be a mixture of white, light gray, and antique white. As you know, concrete can be in many shades, sometimes very white, sometimes gray, and sometimes even with a tannish tent. Gray concrete can be done with just white and gray mixed, while the tan coloration can be gotten by using antique white in the mix. You want this first coat of paint to be lighter in color rather than darker (the dark washes will make it darker, so better to start with the initial coat being lighter). If a second coat is necessary, put it on. I've found that on white styrene, the second coat is not necessarily needed, but certainly doesn't hurt. I use craft paint for this, and make all the brush strokes going up and down for the rain streaking purposes. Don't worry about making the paint smooth and perfect. Some brush marks actually help, and if a little dust gets in the paint, all the better!

For large expanses of concrete, I'll add a bit of variation by adding a little gray into the original paint mix to come up with a slightly different shade, and then paint various segments with that, you can cover random sections completely or drybrush it in random areas, just to create some variations as occur in the real world.

After the paint is thoroughly dry, a couple (or several) thin washes of either medium gray, brown, or black will do the trick (craft paint). If working from prottype photos, that'll help determine the color of the wash. Heavily weathered concrete would use mostly black washes, less weathered would use medium gray or brown. Starting with thin washes allows you to judge what is happening and make changes to the color as desired. After a couple washes, doesn't hurt to throw a spray of dullcote on before doing further washes.

Powders can be used as an alternative or in combination with the washes, really dirty mildewy stained concrete can be done with black and brown powder, mostly black. Several thin layers is easier to control than one heavy layer.

If the expansion joints or form segments aren't showing up enough, a very fine brush can be used to put a dark wash exactly in the cracks. Best to hold the piece horizontally so the wash will fill the entire groove.

Finally, if there are corners and edges, a dry-brushing with white will bring those features out.

That's about it. A final coat of dullcote will seal everything. Actually, I have been using Krylon Matte finish in the big can - about one fifth the cost of dullcote in the little can. Of course, if you have an air brush, it may change the entire process....

[Gary S]

Progress photos:

Building up the concrete railings -

   

Although the parts are being glued together, small diameter wire is being inserted into all the joints for strength:

   

Here's one of the sidewalks and rail put together:

   

Some pieces made and some painted:

   

And a test fit of the painted sidewalk section: