Re: O.T. Found some interesting old letters


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Posted by David Sherman [216.18.131.163] on Wednesday, January 06, 2010 at 13:23:13 :

In Reply to: Re: O.T. Found some interesting old letters posted by Dave Royal [76.182.149.93] on Wednesday, January 06, 2010 at 12:40:56 :

Machinery was generally not supplied with a prime mover (motor) back then. Small machinery came with a belt pulley. Bigger stuff was direct-driven or with a rope drive (we're going to restore a rope-drive compressor for the Mine Heritage exhibit), but the machinery maker did not supply the power source. The companies that made machinery were not the same companies that made prime movers (Westinghouse, General Electric, Stanley for electric motors, Pelton for water wheels, and a hundred small and large shops all of the country for steam engines) and the idea of a "unitized" compressor hadn't appeared yet. I suspect that a 500 hp compressor just by itself took a major feat of expert rigging to get from the rail siding and onto its footings in pieces, and to do it as one assembled unit on skids, complete with motor, without the benefit of a diesel/hydraulic crane, would be insanity.

Around here, a compressor was most likely driven by a Pelton wheel, such as the Morning mine's unit at a place that's still called "Compressor", complete with a freeway exit sign. Compressors aren't very picky about speed and so the Pelton wheel could usually just run flat-out without any speed regulation other than that inherent in the head of water. Under runaway conditions, a Pelton wheel inherently governs itself to no more than twice its design full-load speed. Steam was never used for power around here to any major extent as near as I can tell, possibly because water was available, coal was far away and timber was needed underground. You can still see the remains of some of the flumes and pipelines that carried water to the mills. I remember the old Hercules mill's Pelton wheel before the EPA "remediated" the whole place into oblivion.

Electricity was used very early on, especially underground. One of the first long-distance power lines in the country was built by Washington Water Power from the Spokane Falls and Post Falls plants up to the Coeur d'Alene mines, and the Hercules mine itself paid to construct a line over the mountains from from Thompson Falls, Montana. Electricity was the most expensive source of power back then, but it had such huge advantages underground, as well as for running the actual hoist machinery, that it was worth the cost.

I doubt that a 500 HP compressor would have been run off an electric motor unless the compressor was itself to be located underground, which is unlikely. Running an air line down from the surface is cheaper than running the kind of power cables that a 500 HP motor would need. They did (and still do) run heavy electric power underground when a shaft is sunk starting from a deep underground level and the hoist machinery is installed in a big cavern above it. About 6000 feet is the practical limit for a single hoist, so to go deeper, they need another shaft that starts well underground. Also, they might want another shaft to access a good deep ore body that might be a mile away from where the main shaft was sunk.



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