The World's Only Operating Hydraulic Compressed Air Plant

| July/August 1978

  • Ragged Chute Air Plant

  • Ragged Chute Air Plant

New Ashford, Massachusetts 01237

The town of Cobalt developed in the center of a booming silver mining area from about 1900 to the late 30s, about 80 large and small silver mines were in operation. Natives tell the story of the 'Million Dollar Sidewalk', a rich vein was found under one of its sidewalks, it was quickly relocated and a million dollars worth of ore was mined from that area. Today one can see idle mine heads or hoists and tailing or spoil piles in every direction. As the high grade ore ran out, mine after mine closed. Today, 1976, only four are active. Now that the price of silver has gone up making the mining of low grade ore profitable, plans are in progress for reopening several of the old mines.

Back in 1900 this was a sparsely populated area without any rail service. Worse, it is hard rock mining so a source of power was a dire necessity. Plenty of wood was available, so steam boilers and engines to operate compressors and hoists were hauled in. However, cutting and processing the wood required manpower badly needed at the mines. At this point a Mr. C. H. Taylor, a Montreal engineer, was called in to investigate and produce a central power plant as coal or rail transport was not available. This ruled out steam-electric plants. On the other hand, plenty of lakes and streams are to be found suitable for hydro-electric plants. This required extensive dam construction and importing of complicated generating machinery, both difficult at the time. To utilize the readily available water and construction techniques of the mining type; shafts and tunnels, Taylor designed a huge 'Tromp.' This is a method of producing compressed air by utilizing the gravity flow of water in a pipe formed like a large flat bottom U or what is called an inverted siphon. Iron workers in the early years of the iron age knew the principle and used this method to make air of 1-5 pounds pressure to fire their small forges. It is simplicity in itself, is fully automatic and available as long as one has a flow of water. We can see the principle every day. Note the water draining from a quick draining household sink or tub. It forms a whirling, funneling action that sucks in air as it flows downward. Now if this is run horizontally in a size larger pipe and then upward in the same size pipe as the down pipe it will form an air cushion in the top section of the horizontal run. If one taps this section, the air can be drawn off and the flowing water will release more air while passing through this section. The volume of air is relative to the head or height of drop. The height of the riser and the volume of water while the ancient users were working with a 10' head 2' and 3' pipes and an 8' riser, Taylor's design used 9' in diameter head shaft and over 300' of head follow the schematic drawing starting at point A. Twin 16' in diameter heads consisting of 72-14' pipes draw in the water and air. They are held at the right distance below the water surface by a pneumatic lift. The two heads are connected to a 9' diameter head shaft, 351' deep. The enlarged tunnel at the roof section slopes upward to 42' in height at the top of the air received (see 'B'). It then drops down to tail shaft diameter, thus the height of water in tail shaft locks in and controls the psi. of air roughly .434 pounds per foot of height. The difference in height between A and C is about 50'. This is to expedite the flow of water through the plant. When the initial flow was started the top of tunnel and receiver section were pumped full of air to form the first air cushion. Then as the water rose in the tail shaft it locked in the air and started working. Since shortly after 1900 this plant has been in continuous operation to present time.

Now here is where air for steam comes into place. This air was piped in a 20' pipeline (20 in air at 1.25 psi equals a lot of air) a distance of 8 and miles all laid on top of ground with an expansion joint every half mile, then in 4 or 6' feeder lines to the various mines. It was used direct to power the jack hammers and used to power steam engines to operate winches, hoists, stamping mills or other mine machinery even belted to generators for lighting. This only required some minor modifications to the lubricating system of the engines. Today air motors would be used, but this was before they became popular. We all know air will run a steam engine but not as efficiently as steam, so to compensate for this, they just used a larger size engine.

Today a modern electric plant supplies power for the entire area. The mines that are operating still use the hydraulic air for modern air tools and drills and electricity for the rest of the modern mine machinery, while the plant goes on making compressed air. It is checked once a week, mostly for debris removal at the intake and the area has so much air. If a pipe leaks, they do not bother to fix it. A little escaping air does not warrant the time required to fix the leak.

In this day of energy shortages, perhaps this method could be revised. For instance, a city water supply could be utilized by simply passing it through the right type of head and an inverted siphon. It doesn't in any way change the characteristics of the water, thus it is used twice to make air and supply domestic water.


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