Building the Roundhouse and Shops, Part 1

After completing the turntable and before getting too far ahead with laying track I decided to take on building the roundhouse.  Ten years ago I had bought a Thomas Yorke roundhouse kit on eBay and never got around to assembling it.  A few months after buying it my wife and I sold our home and belongings and moved onto our boat with the intention of spending the next 15 years sailing around the world.  I did put my train stuff in storage thinking I would want to get back to it in my old age.  As it turned out, medical issues prevented us from chasing that dream and six years later we were back on dry land planning my next layout.  I'm so glad I saved my train stuff.

I've gotta admit that the roundhouse kit intimidated me.  I had enough wall sections for five stalls, nine pieces altogether, plus several other wall sections the supplier had sold me to play with.  The walls are heavy cast plaster and carved to look like stone with large industrial windows in each section.  There are buttresses that extend out from the ends and midpoints and dressed stone framing around each window.  The instructions for painting were included but this was what held me back from starting the model.  I looked around the internet and saw what other folks had done and couldn't find a technique that really satisfied me.  I decided to shelve the project until I found something I really liked because with plaster you really only get one try.  Here's a shot of the original kit.

While researching the smelter I stumbled across a painting technique for plaster cast stone walls that was exactly what I had been looking for (click here).  Now I was finally ready to build the roundhouse.  The first thing I did was clean up the wall castings.  Most of the stone detail on the outside surface was of excellent quality but the inside surface was just flat plaster and not exactly flat either.  I used a course wood file and sanding block to smooth out the inside walls with the plan to have them look like the stone had been plastered over and then painted.  I carved in stone detail along the top edge and where the walls protruded beyond the doors in the front. The mating edges and bottoms of the walls also required squaring up to get a tight fit between wall sections and to get the walls to stand vertically without falling over.  The window openings are sized for Grandt Line parts and I spent time making sure everything would fit snugly.

While laying out where the walls and track would go I decided I needed a car shop and machine shop to complete the roundhouse.  I'm severely restricted on space though so I decided to build a combined car and machine shop with a small boiler room off the back.  This was plan A, later modified.  When I first laid this part out I simply ran a track to it from the turntable but then realized that prototype railroads wouldn't do this.  The track should come in directly from another part of the yard and this required me to re-position the shop.  I turned it 90 degrees and ran the track in from over by the ash pit.  Much better.

With the shop turned sideways to the turntable it just screamed out to be made of stone also, just like the roundhouse, as if they had been built at the same time.  I decided to make molds of some of the roundhouse wall sections and use them for the shop.  I would need four new full size wall castings and one additional one that I could cut up and use sections of.  The original side walls angle down towards the back and the roundhouse has a flat roof.  I wanted a pitched roof on the shop so I'll have to modify my new castings to straighten the top edge.

I sat down and made full size scale drawings (1/4" = 1') showing side, front and bird's eye views.  The interior footprint (7 3/4' x 10 1/4' or 31' x 41')) was chosen mostly because of available space on the layout but is still big enough for a respectable machine shop.  Originally I was going to have the car shop take up half the space but then decided to add a raised deck down the outer side and use that for an outdoor car shop.  Now I have some serious space to work with.  The shop will eventually have an overhead belt drive system run by a single cylinder steam engine and dedicated boiler.

Once I settled on a design I saw that things would look better if the roundhouse had the same skylights which would require modifying one wall section to match the shop's end wall.  This was the beginning of the snowball.  Things quickly got out of hand but I did learn a lot about working with plaster.  More on that later.

OK, so I got 8 molds made and I built some really excellent support frames for each one.  I felt confident that my castings would come out really well.  I hadn't poured plaster castings in something like 30 years but I didn't remember it being a major challenge.  Of course I was doing rock castings and retaining walls in HO scale and now I'm doing O scale, 1/4" = 1', so the castings are much larger.  For the shops side walls I used one section of wall from the roundhouse that had two windows.  The shop walls have three windows so I had to make a total of five castings and "cut and paste" to get what I wanted.  The plaster cuts like wood so I used a small handsaw for dissection and yellow wood glue to reassemble my parts.  In the picture below you can see the two new wall sections and one original as well as the Latex mold and support frame.

With the side walls completed I made another mold to pour the end walls and spent three days hand carving stone.  I painted the walls using watered down acrylics in five different earth tone colors.  Here's my technique:  First seal both sides of the plaster casting with flat or satin clear spray paint.  I use DecoArt acrylic paint in Grey, Mississippi Mud, Burnt Umber, and Burnt Sienna working from lightest to darkest.  Use a quarter size blob of paint with two siphon loads of water for each color.  Starting with Grey and a damp natural sponge lightly dab the color to the casting for a blotchy effect.  All the steps here use a damp sponge, never dry, and clean the sponge between each color.  Then add Mississippi Mud to whatever's left of the Grey and lightly dab on.  Mix in Burnt Umber and brush onto random stones before lightly dabbing on with sponge to blend.  Mix in Raw Sienna to the Grey/Mud/Umber mix and use a heavily loaded brush to run along the grout lines, then wipe the surface of the casting with a clean sponge.  Separately mix Raw Sienna (don't mix with other colors) with two siphons of water and dab on lightly and sparingly with a clean sponge.  Clean the mixing tray and add a quarter size puddle of India Ink and at least two siphons of water (make sure the ink is pure black.  I use "JapanBargain Japanese Caligraphy Ink - Black" from Amazon.  Some India Inks have purple mixed in and it will show).  Use one clean sponge to wipe ink across the casting surface and into the grout lines.  Then use a second clean sponge to wipe across the surface of the stones.  Work in 3" x  3" areas at a time.  Allow the casting to dry overnight.  Then fill the grout lines with wallboard mud, smeared on with a sponge, and clean off with a second clean sponge to expose the stones.  The mud works like a polishing paste and brings out the different colors to look like Pennsylvania field stone.  Cool!  Allow to dry.  I use a short-bristle wet brush to scrub excess wallboard mud from corners and other areas that are too heavily loaded with the white mud.  This can be done when the mud is wet or dry.  Once completely dry seal with a coat clear flat spray paint.