Friday, May 16, 2014

Operable 5-Stamper, Cromwell, New Zealand

Gold Fields Mining Centre
5-Stamper Battery
Cromwell, NZ

April 7, 2014
We left Cromwell and stopped at Gold Field Mining Town. They had a stamper that operates. I talked with two workers that ran the mill and they were knowledgeable. Warren Horncastle    and David Henderson. They were very interested in Stampers and we talked about the mills in the US. The mill is a 5-stamper with an operational feeder and it worked quite well. 

I have a You Tube video that shows the operation of this stamper battery. All you have to do is click on the address below and paste into the Internet. 

The picture below is a shot from the front of the mill. It is an “A” frame design and (red circle) has a Hendy type feeder that still works. The timbers were replacements because when it was found the timbers were completely rotted away. You can see the small retort that was used to remove the gold from the mercury amalgam during operations. They ran the mill for some time and it worked very well, including the feeder, Berdan Wheel and the operation of the monitor.

The picture below is a shot of the bull wheel. It is a lot different from the US mills. Many of the mills in Australia and New Zealand used this principle. Using the two geared wheels gave the operators a greater mechanical advantage to allow starting the mill with the cams engaged. The States used a large bull wheel and also jackstand devices to start the mill with the cams disengaged and then drop one stamp at a time to allow the centrifugal force of the bull wheel to keep the speed up on the mill.  This mill was driven by a 3’ pelton wheel supplied with water from a lake about 30 meters (90’) above the mill. 

Discussions with David indicated that this stamper battery came from the Invincible Mine that is located in the Otago Goldfields Park about a 30 minute drive up Rees Valley Road from Glenorchy. There are remains of a water wheel and (7) Berdans that were used in the gold reclamation process that are shown below.

They also had a Berdan wheel in operation at the Cromwell site. There were several Berdan wheels that were used at the stamper battery sites in Australia and New Zealand. The Invincible Mine site has (7) berdan wheels in a row. This was an important part of the process with stamper battery’s.
The Berdan wheel below has a stationary slug in the bowl, but many of the original bowls had a large round steel ball that was used to crush the ore. The reason why they used the stationery slug was that it would crush the material rather than roll it as would be the case with the large steel balls. The miners liked the actions with the slug and that is why you see many modifications of the Berdan bowls.

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