Tidy Cat Mill

If I'm going to have any mining activity on the SR&G then I need to have a concentration mill. I had to do a lot of research on this because I don't know a whole lot about mining or the processing of ore. The Tidy Cat produces kitty litter, so the reduction process is fairly simple, but I thought researching precious metal processes would be more interesting. The milling process for gold ores can become complicated but the general steps are: sorting the ore and breaking the larger rocks to manageable size; crushing the ore in a stamp battery; capturing free gold on the amalgamation tables; saving the concentrate for further refining.
I got much of my information from The Metallurgy of Gold by T. Kirke Rose (Charles Griffin and Company: London 1898) which I found on Google Books in PDF form. This is an exhaustive description of the methods for gold ore refining available around the turn of the last century. I am building my mill to the general design shown in the book as there is a very nice drawing of the structure with the various pieces of equipment involved.

This is where the concentrated ore is stored for shipment. I already have the Sawpit Ore Bin built from a kit, so I took the general construction of my three-bay bin from that. This type of construction is very common, at least in Colorado. The major frame members are 12 x 12 with the bin walls constructed of 4 x 12 planks. The walls of the house are board-and-batten.

I thought I would try to make a corrugated steel roof rather than the wooden roof of the Sawpit bin. I wasn't sure how I was going to do this other than buying the sheet from one of the scratch building material vendors. I saw some of this stuff at the store and it was ridiculously expensive (I thought). I figured I could do it myself with aluminum foil, but couldn't figure out how to do the grooving until I saw a guy at the Boulder Valley Model RR Club show doing it with a little jig he had made with grooves cut in it. When I saw it, I realized I had exactly what I needed with the die I had machined for the sides of the 30-foot box car. I use an aluminum foil tape that is 5mil thick; this is much heavier than regular aluminum foil and has the added advantage of an adhesive backing. I made some strips and attached them to a piece of card stock to flatten them out.

I weathered this model with all acrylics. I painted everything a lightly tan gray color, then applied a Raw Umber wash over the outside later on. I scuffed it up a little with sandpaper to get some of the gray to come out and give the beams a little texture. The roof was painted with a mix of Sky Blue and Heritage Brick with a little Raw Umber to try to simulate oxidized metal. I have a picture of the Comstock bin up on the Oh-My-Gawd road above Idaho Springs and the roof is a very bright purple. I didn't achieve this color and think I need a darker blue or just get some purple. Nevertheless, the roof turned out pretty well.

This bin is at the end of the milling process. I am building the mill backwards, so the next step will be the concentration house behind this.

The concentration tables are housed in this building. Concentration consists of separating the precious metal bearing ore of the pulp after it leaves the amalgamation tables above. The concentration tables use water flow and the difference in density of the metal-bearing and gangue rock to separate the two and 'concentrate' the metal bearing ores. These are shipped out and subjected to further refining processes.

I built my concentration house with a frame of 12x12 timbers. From the diagram it can be seen that the upper reaches might be built of lighter members, but it was easier to do it with 12x12s and nobody is going to see it anyway. I didn't brace the inside too well, and should probably do more of this on future buildings, just to keep things straight. I tried to assemble the frames as bents and then glue cross beams to them; I haven't found any good drawings or pictures of this type of framing to use as examples.
The Concentrator building has windows. The windows are Tichy which are half the price of the Grandt products. The walls are Black Bear 12in board-and-batten. I printed a cardstock template with the windows, then cut out the window holes and used this to cut the wood siding. Originally, I was going to glue the wood straight to the frame, but decided it was easier to glue it to the cardstock, then glue the assembly to the frame.
The roof is 4x8 perlins with 4x4 cross beams. I make the corrugated roofing with the 1x3 box car side die I made at Bob's. What I finally figured out was that I would print a cardstock template for the roof frame, then use that to attach the corrugated tin, then glue this to the roof frame as with the sides walls.