|View single post by Keith Pashina|
|Posted: Sat Apr 1st, 2017 09:10 pm||
|Now, we'll conclude the overview of Black Hawk milling machinery, with a look at some more of the secondary concentration and cleanup equipment.
Concentrating tables and jigs were looked at in my previous posts. So, to better capture the slimes, the too-finely crushed ore particles, other processes included gravity separation in tanks or buddles, and the use of additional grinding equipment to rework the ores.
Buddles were commonly used in the Black Hawk mills, at least in the early years. Buddles were of two types – stationary and revolving. The stationary types basically ran the slime or slurry down a small trough, to the top of a cone-shaped table. The cone evenly distributed the slurry out into a shallow square or circular box (both were used). Some buddles were small, perhaps 8’ x 8’, but could get larger – some districts used buddles up to 16’ diameter, but I don’t know if this was used in Gilpin County. Gravity separated out the heavier metal particles from the lighter sand-like materials – the lighter sands spread out near the perimeter, and the heavier particles near the center. Once the shallow box was filled, the valuable concentrate was hand-shoveled out, and then the sands shoveled out and disposed of. Very labor intensive, but also very simple, too. This equipment hasn’t been offered as kits, but it wouldn’t be that hard to scratchbuild, either.
Slime tables differed from buddies - the separated sands and concentrating were washed off, whereas a buddle collected the material inside the box or tank. Every so often, the flow was stopped, and the waste and concentrates hand-shoveled out
The above view shows a Callow cone inside the Frontenac/Black Hawk mill. A simple piece of equipment, easy to model. Also, note the electric motor and belt drive - this mill was a modern operation!
Remnants of a cone classifier by the Pittsburg Mill (about 1/2 mile south of Central City)
TROMMELS AND CONES
The next refinement was to mechanize the shallow conical table, so that it slowly spun clockwise while the slurry was run down over its center. By shallow, I mean the table sloped about 1½” per foot, and speeds were very slow, between 1 rotation per minute to 1 rotation per hour! Buddles would be a piece of equipment easy to model.
Other equipment used, particularly at the large Frontenanc/Iron City Mill, were cones and trommels.
Cones were similar to a funnel, and separated out heavier particles from lighter particles. Trommels were essentially a cylindrical rotating screen. This equipment would be interesting to model, although I have no idea how I would build a trammel in HO – trying to model realistic sized screen would be tough. I have seen no commercial models offered for this equipment.
Example of trammel