=================== Joe Nichols, Jr wrote:
> A working stamp mill in Colorado? Is it still there and open for tours?
> Is there a website? This sounds like the start of yet another scratchbuilding project
> and research trip! (for after the layout tours for the NMRA convention...)
> Any info would be great.
While I can't answer the questions, I can provide the following stamp mill info, as I've been doing quite a bit of research for my build of a 32-stamp mill that will live on my 1870 Gilpin County HOn3 layout.
The first question to consider is number of stamps per mill - the stamp mills in Cornwall from the middle 19th century have 4 stamps per mill and use a drop order (IIRC) of 1-3-4-2 and this is what early mills in Colorado appear to also use (as they were built by Cornish immigrants). Later mills went to a five stamp per mill configuration where the drop order was (again IIRC) 1-4-2-5-3.
The other important thing to consider is where the mill would have been located and what type of rock it would have been crushing. Mills that crushed rock with a low concentration of pyrites (i.e. what was found in California) used a rapid, shallow drop approach - the stamps would drop over 60 times a minute and the depth of the drop would be of the order of 4" or so. Because of this, the depth of the mortar box to the discharge point would be similarly shallow.
OTOH, mills that crushed rock with a high concentration of pyrites (i.e. what was found in Gilpin County) used a slow, deep drop approach - the stamps only dropped 30 times a second and the drop depth was around 18". Because it was necessary to keep the pulp in the mortar box for a longer period of time, the mortar boxes were deeper, with a discharge depth of (IIRC) 12" to 14".
I mention all of this because if you go off and buy one of Durango Press's DP-35 gravity mill kits, you'll be getting a five stamp mill that is configured for shallow drops. I had to custom make the cams and mortar box to get a mill that is prototypical for what would have been found in Gilpin County.
Gilpin bumping tables are a subject for a whole 'nother discussion.
Hope this helps,
Ryan Moats, MMR