Tag Archives: scratchbuilt

Installing Plate Girder Bridges

Plate Girder Bridge Finished
The finished curved bridge over Straight Creek–still a long way to go on scenery, but it’s starting to take shape

I’ve got four bridges on the upper deck that need to go in before I can lay track, so here’s my walk-through on how I installed the two plate deck girder bridges. I started with two Micro Engineering deck girder bridges, a 30′ and a 50′. I built them according to instructions but omitted the ties (or concrete) that go on top of the bridge because I planned to build my own out of basswood to go well with the rest of the hand-laid track. I sprayed them flat black with an airbrush.

Plate Girder Bridge Abutments
Building the abutments from sheet styrene. I just used rough shapes and measurements taken from Google Earth

The most challenging part of these builds was the abutments. You have to build the abutment just the right height and size or your track won’t work well. I started by cutting out a section of the subroadbed where I wanted the bridge to go–I just set the bridge on top of the subroadbed, marked it with a pencil, added a scale 6″ or so to both sides to account for the abutment, and cut it with a circular saw. Next, I installed the basic creek bottom with plywood to get a firm foundation. Then I made tracings of the end of my subroadbed where I’d cut the section out and marked the height of each side to the top of the subroadbed on a piece of paper. Next I sketched the basic shapes of the abutments made from looking at images on Google Earth. I also used the ruler tool in Google Earth to get some basic dimensions for the width of the abutments and the length of the “wings.” In this case, each of the bridges has one “normal” abutment that is rectangular and a few feet deep and one “snaky” abutment with wings that extend at different angles rather than going straight back along the tracks. All of the abutments have a central section about 18-20 scale feet wide that goes between the bridge and the ground, and this section has is stepped to provide a base for the bridge feet. I made my central sections 18 scale feet with with an 1.5 scale foot wide step for the bridge feet. The elevation of the step depends on the bridge type, so I just marked the total height of the bridge and foot against the height markings on the paper to get my basic design.

Plate Girder Bridge Abutments
I ran the plastic over rough sandpaper using a block to guide the movement and give it a rough-lined texture

I cut the abutment pieces from .040″ black sheet styrene, and I angled the tops of some of the wings (eyeballed until they looked about right). I added pieces of .020″ styrene to the back side of the abutments to make them look thicker and glued and sanded the pieces to look like a single piece. Before gluing the main pieces together, I took a piece of course sandpaper, held it down with a wooden block, and rubbed the abutment pieces and back and forth using the wood block as a guide to get horizontal lines scratched into the face of the plastic. This gives the “concrete” a rougher look and simulates the grain from using wood forms to build the prototype. When this step was complete, I assembled the abutments using styrene cement and filled in any gaps with model putty which I shaped and sanded when dry. I was able to assemble some of them before the “scratch treatment,” but anywhere I had an interior joint (90 degrees or less), I scratched the pieces first because otherwise it’s nearly impossible to do once assembled.

Plate Girder Bridge Abutment Painting
I painted the abutments with an airbrush and thinned Tamiya “deck tan” color

Next I painted the abutments with an airbrush and thinned Tamiya “Deck Tan” paint. The deck tan is a nice gray-tan color and dries very flat. I made sure to spray at least the tops of the insides of the abutments too because they’ll be sticking out above the scenery. I also used some of the deck tan color to lighten the bridges and fade them a bit. I weathered the bridges and abutments using a combination of flat black and light rust colored washes. The entire bridge inside and out got a couple coats of the light rust wash–I left the wash on and set the bridge upright to get the rust to concentrate on the bottom of the panels. All of the abutments got 2-3 liberal washes of flat black. I targeted the rust washes to the areas behind and under the bridge, wiping the wash down to simulate rusty streaks from numerous rain storms over the years. I kept making the wash thicker and thicker and applied it to a smaller and smaller area to get thick streaks just under the bridge feet. I dry-brushed some black in these feet areas as well to darken the streaks and dry-brushed a few more streaks vertically down the walls. Finally, I used some Tamiya weathering powders to add a few more black streaks and white blotches.

Plate Girder Bridge Weathering
I weathered the bridges with rust-colored washes
Plate Girder Bridge Abutment Weathering
I weathered the abutments with black washes and rust washes, focusing the rust on the area under the bridge feet

Next I made the decks. The 30′ span was easy because it was straight. I simply drew a scale 30′ x 10′ rectangle as my template, cut a few dozen scale 10′ sections of scale 8×10″ basswood using a Northwest Shore Line “Chopper”, laid down two strips of scale 3×6″ basswood along the edges of the template (slightly in from the edges), and laid the ties onto these strips one-at-a-time using small drops of Elmers white glue. I use white glue because it’s easy to work with, does the job, and seems to take stain slightly better than wood glue. The track over the 50′ span is on a 24″ radius curve, so it took a bit more work. For the template, I traced the bridge, then used my 24″ radius template (a plywood cutout) to mark a track centerline on top of the bridge outline, making the line about equal distance from both bridge sides (as measured at the ends of one side and the middle of the other side). Standard bridge ties are about 10′, but with 24″ radius that wouldn’t quite cover the bridge, so I opted for scale 11′ ties and marked an outline on the template 5.5 scale feet from the center line on both sides. To make sure the ties held the right curvature, I laid these ties on top of two strips of scale 3×8″ basswood laid straight so they would fit inside the bridge panels. I pinned these down with tacks on top of the template, then laid the ties one-at-a-time using the curved lines I’d drawn. Once this dried, I flipped it over and laid the 3×6″ edge boards using tacks to curve the boards until they dried.

Plate Girder Bridge Drawing
This is my 1:1 drawing of the two bridge decks made from tracing the space available on the layout
Plate Girder Bridge Ties
The curved deck was easier to make when I built it on top of two straight pieces that would fit inside the bridge sides
Plate Girder Bridge Edges
I built the decks on top of a cardboard box so I could use tacks to hold the curved pieces in place
Plate Girder Bridge Straight Ties
The straight deck was very straightforward – just some ties on two parallel edge boards

I gave the decks a little more detail by adding some nail/bolt marks using a thumbtack. When stained, the tack mark shows up extra dark and gives the illusion of a nail/bolt without having to install hundreds of castings. I put a bolt hole in the edge board over each tie, and I put four offset bolts in each tie over where it would attach to the girder underneath. I use a ruler to make sure each line of bolts is straight. This adds some nice detail to the deck, and it’s quite striking to see a line of straight bolt heads against the curvature of the rail on a curved bridge. I finished the decks by staining them with Minwax “Ebony” stain, dabbing up the excess with a paper towel, and letting them dry.

Plate Girder Bridge Bolt Holes
I made some bolt detail on the edge boards and ties using a thumbtack

Now I had all the pieces to install my bridges! I waited until I’d finished the sanding and staining of the adjacent track ties as this would have ruined the abutments if I tried to do it with them installed. First, I test fit everything to make sure my bridge ties were at the same level as the adjacent ties. If not, I either sanded a bit off the bottom of the abutment (difficult) or added some thin pieces of styrene to the bottom to get them to the right height (easier). Lesson learned: when in doubt, make the abutments slightly short and shim them up–the base will be covered by scenery, and it’s a lot easier to add then remove at this point. With the heights correct, I then test fit the entire bridge structure and moved the pieces around until I was happy that 1) the bridge was in the right spot, and 2) the abutments were centered on the bridge. When happy, I used a pencil to mark the corner positions of the abutments onto the plywood beneath and removed everything.

Plate Girder Bridge Test Fit
Final test fit before gluing everything in place on the small bridge
Plate Girder Bridge Glued Down
Here’s the final bridge with everything glued down and ready for rails

I applied some Pliobond adhesive to the bottom of the abutments and the portions of the abutments that would touch the adjacent subroadbed and set them in their marks on the layout to dry. Next I used some Pliobond on the bridge feet and carefully set the bridge in place on the abutments. Once dry, I used a little Pliobond in lines on the bottom of the bridge tie section and set it in place on top of the bridge. Once happy with the alignment with the adjacent ties, I set a couple blocks of wood on top to help it all dry flat and level.

Plate Girder Bridge Rails
The final bridge showing the bolt detail alongside the rails

The final step was adding the rail. I just ran the long rails over the bridge just like the other ties and spiked the ties adjacent to the bridge. I used Micro Engineering “micro spikes” on the bridge (I use “small spikes” elsewhere). Since the spikes were slightly longer than the ties are deep, I used a No 79 drill bit to predrill the spike hole, especially where the spike would go into the plastic bridge. I spiked about every fifth tie. A look at prototype photos doesn’t reveal any guard rails, so I omitted them on my models as well.

That’s it–bridges installed and now handling trains!

Operating Dwarf Semaphore

Working Dwarf Semaphore HO scale model
The Black Mountain Local stops to reset the dwarf semaphore now that their work is complete

Semaphores were a common way of signaling trains on the Southern Railway. Semaphores were often used at stations to indicate whether or not the train was cleared to proceed or needed to stop (or at least slow down) to pick up orders. Semaphores were also used to protect branches when trains were working on them, and these semaphores were usually set by the crews themselves. The St Charles Branch employed three such semaphores to protect the lines RR west of St Charles. Here’s the exact verbiage from the Employee Timetable:

“At points shown below, semaphore signals will govern the movement of trains and engines. When track is not occupied, signal will indicate proceed. When in either position, stop or proceed, signal will be fastened and locked with a switch lock. When indicating stop, position will not be changed until train or engine occupying the track clears it and the crew of same restores signal to proceed indication. West of St. Charles—located at the junction between Bailey Trace and Fawns Branch lines.”

I definitely wanted to model this aspect of operations, and as a bonus, two of the locations of these semaphores correspond with long sections of hidden track on my layout, the hidden track between St Charles and Mayflower on the Bailey’s Trace Branch, and the helix between St Charles and Turner’s Siding on the Black Mountain Main. These would not only serve the purpose of adding more prototypical operations, but they would also serve a very practical function of protecting trains that can’t be seen without a dispatcher.

I learned from a former Southern employee who worked in this area that these were “dwarf semaphores.” I haven’t been able to find a picture of one of these exact devices near St Charles, so I Googled “dwarf semaphore” to see what they were all about. They operate just like the tall semaphores and come in both upper- and lower-quadrant designs, and most have lights. They only sit about 3-4 feet tall, though, and have a blade somewhere around 14″ long–that’s super tiny in HO scale! I picked a Union Switch and Signal upper-quadrant, two-light design. I didn’t see anything resembling this available in HO scale, so I set about building my own operating version from sheet brass and wire.

Working Dwarf Semaphore HO scale model
Faceplate and blade made from brass with the swivel wire soldered in place

I made a drawing of the blade and faceplate with the lights, sized it down to HO scale, and printed it on sticker paper. After sticking it to a sheet of .005″ brass, I was able to drill holes for the lights, swivel and actuating arm and then cut it out with scissors. After cleaning it up with a file, I bent a piece of .015″ brass wire, inserted it through the swivel hole, and soldered it to the faceplate. I drilled a hole for the wire through a piece of 1/16″ brass tubing for the base. I wanted to use fiber optics for the lights, so I soldered a 1/16″ long piece of tube to the tall tube angling up to where the light would be to hold the fiber optic strand. I painted the faceplate and tubing black, then made lenses by melting the end of a piece of fiber optic into a mushroom shape holding it near a soldering iron. A little red for the blade and a white sticker stripe and the faceplate was complete.

Working Dwarf Semaphore HO scale model
Completed dwarf semaphore model and lever mechanism

I mounted the base post in a piece of plywood and drilled a hole for a second piece of 1/16″ brass tube underneath the blade for the actuator arm. After inserting the faceplate and securing it with a bend on the back side of the tube, I had a faceplate that swiveled freely. A piece of .012″ steel music wire bent at a 90 degree angle at the end was inserted into the blade and the tube for the actuating arm. On the bottom, I made a lever for the actuator that raised the actuator just slightly while allowing for significant travel for the longer actuating rod connected to the fascia. I filed the end of a fiber optic strand so it would be parallel to the faceplate and inserted it into the little brass holder and through a hole in the base. A little silver paint for the post, and the tiny dwarf semaphore was complete!

One of the things I wanted to model was the use of switch locks. I found some Miniature Locks on Amazon that suit this purpose perfectly! I decided to use a slide-switch mechanism like I use for all my switch controls, but I needed a longer slide to enable the lock to go in front of and behind the control knob to “lock” it into either position. I found some old three-position slide switches on eBay that did the trick! The slide switch serves two purposes–it “snaps” into position to hold the control and semaphore securely in position, and it allows for the routing of power to LEDs, in this case some bi-color red and green LEDs that change color when the polarity is reversed, something easy to do with a slide switch. After mounting the switch to the layout using a piece of 1×4″ board, I drilled two holes in the slide handle and used .o62″ steel wire  to connect the slide to the lever under the semaphore and a separate rod through the fascia for the control knob, a 1/2 ball piece of wood.

Dwarf semaphore control mechanism with lock
Semaphore control in the “stop” position showing the red fascia indicator and lock

For the lock mechanism, I used a bar of 1/4″ x 1/2″ basswood with a hole drilled for the lock and inserted it through a hole in the fascia and benchwork adjacent to and just touching the control knob. The hole sits just ahead of the control knob when it’s pressed in and just behind it when pulled out. I also connected two LEDs to the slide switch and a 12V DC power supply. One LED is mounted behind and just through the fascia to serve as an easy indicator for the full-size operators. The second was inserted into a hole drilled in the semaphore base where it can shine into the fiber optic strand.

The result is a semaphore with working lights, blade and a switch lock. While the dwarf semaphore sits about 3′ from the aisle and is tough to see, it is pretty cool to have an operating model and a tiny little red or green glow that matches the indicator on the fascia. Now the operators on the St Charles Branch, just like their real-world counterparts, have to stop at the semaphore, unlock the lever, change the indication, and re-lock the lever before proceeding up the branch (and do the reverse on the way back). While I’m not sadistic enough to make operators lock and unlock every switch they need to throw, working with switch locks a couple times during a session is one more step toward replicating the actions required on the real thing, and it adds a little prototypical time to the work required. Oh, and it helps protect trains without a dispatcher which is pretty useful.

[Note: since I first published this post, I decided to reverse my control mechanism so “proceed” is pulled out and “stop” is pushed in. It just required me to reverse the lever used to lift the arm. I figured having the crew move the lock to the front of the pull knob where it’s more obvious makes more sense.]