Re: Fifty Gold Mines Mill Car Loader, and Bumping Tables

Posted by drgwcs on
URL: http://c-sng-discussion-forum.254.s1.nabble.com/Roof-Hatches-Mill-Car-Loader-and-Bumping-Tables-tp19659p19661.html

Keith Pashina wrote

Those are nice looking bumping tables, Jim. There were many types of machines that all did similar things to separate the concentrates, yet differed greatly in their details.

The Gilpin County Bumping Table was I believe invented by MacFarlane, a Central City-based machinist who went on to construct a sizable machine shop down in Black Hawk, served by a spur off of the C&S.  There is a good description of it in the book, "Gilpin County Gold",  which discusses MacFarlane's career, and in the book, "Drills and Mills" by Will Meyerreicks (pages 206-7).

Will Meyerreicks said this about the Gilpin County Bumping Table: "The Gilpin County Concentrator... was a fine-sand concentrator using a continuous, smooth table. It was bumped about 1.5-3 inches, and from 120-180 times a minute, at the end of the table by means of a spring, cam and bumping post. The bump causes the ore to move up the slope and stratify, lighter particles moving above the more dense ones below. Water would then wash the lighter particles down slope and the heavier particles would continue up the slope. The table could treat 4-5 tons per 24 hours...Tables that used a bumping post lost favor chiefly because of the disintegrating effect of the bump on the mill building."


The Gilpin County bumping table did just that, it bumped the sloped riffled table to separate heavier particles (the metals) from the rest. I am no mining engineer, but the Wilfley tables seemed to have more sophisticated motion. The local milling men seemed to all have strong opinions on what process worked best, and especially if they were custom mills, needed to modify the combination of processes used to accommodate the different ores.

Here is an image of the Gilpin County Bumping table:



And here is a row of them in the Hidden Treasure Mill:


And in another mill (I do not know which one):



As an example of how mills may have used differing combinations of machines, a description of the Randolph Mill in Black Hawk (served by the C&S and Gilpin Tram), was that it had machinery that included: " 50 stamps, 10 plates, 10 bumping tables, and used water power.  In 1914, the  operating part of mill consisted of crusher, Challenge feeders, 10 750-pound stamps (53 drops a minute), amalgamation plates, 2 Gilpin County bumping tables, 6 Wilfey tables, and had electric power.  Its capacity was 75-100 tons daily."

I always find the whole milling process and equipment so fascinating.

I had seen that bottom photo and wondered if those might be the Gilpin model. For the equipment in the Bobtail there is no real match I have found and there is no name above the stamps (at least that you can tell from the pictures) I have seen a picture in the DPL that is supposedly the Iron City mill that may be an earlier photo of the Bobtail as the stamps look to be the same model BUT the tables are different from what I see (or at least have been heavily modified) The head mechanism appears the same but the table itself is different. I also see some differences in the walkway framing in front of the stamps. When the prospectus was printed they were in the process of moving the tables from cribbing down to the concrete floor so the fat that these are on cribbing is irreverent. What makes me suspect it is the Bobtail is that the stamps barely visible to the extreme right are further forward. This is where the tower/ central ore bin would have been. However the Iron City was also added on to. I go back and forth as to whether this is the Bobtail or not. I found it after I had already framed the back wall so my details would be incorrect. (That is OK- my stamps are a bit wide my mill is too shallow and there are several things that are not right or freelanced as there was not enough info and probably never will be)

It is at https://digital.denverlibrary.org/nodes/view/1118472?keywords=stamp+mill&type=all&highlights=WyJzdGFtcCIsIm1pbGwiXQ%3D%3D&lsk=2b61579f139a2ab1f0d4a4e2e37ad7c3
Jim