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| Posted: Thu Jun 11th, 2015 10:45 pm |
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1st Post |
Salada
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For anyone interested in seeing the inside of an intact mine mill, or wishing to model one, here are some photos of a small mill in working order. Little has changed inside the mill since the 1950's, in fact it is probably still looks very similar to how it would have been at the start of the 20th C.
Firstly, a remarkable survivor (not me - the "turbine") :
Photo 1 :
This is a water powered "Turgo Impulse Wheel" - an evolutionary 1/2 way step between an older Pelton Wheel and a modern turbine. This same machine was installed here, new, in 1918 & is possibly the world's oldest working Turgo still in it's original position.
These machines are still in use in some remote 'back country' mining districts (especially Africa) because they will happily run on a dirty, gritty water supply that would wreck a modern high precision turbine.
I replaced the shaft bearings in 1995 but the rotor had recently developed an ominous but hard to locate heavy rumble - hence the facial look seeking mechanical revelation ! This is the mill's second oldest prime mover, it was previously powered by overshot waterwheel only.
The "hard-hat" is for scale only, I can't stand actually trying to work in one, except in low roof mine workings. The 3" pipe leading off behind the hard-hat supplies water to the stamps from the Turgo penstock (feed-pipe). Stamps are run either wet or dry, according to the type of rock/ore being processed. The drive is via a 3 speed mechanical reduction using different sized belt pulleys (manual change only !); these pulleys can be seen upper right.
Photo 2 : The "3 speed" pulley arrangement :
The drive pulleys (left & right) have been temporarily removed from the Turgo rotor shaft to allow access to the bearings. The large, green spoked LHS pulley is for driving the stamps (1st gear !). The other pulleys are for general power, air compressor & the tramway haulage incline winder.
Photo 3 : Looking down onto the Turgo from the haulage winder drum :
The large handwheel just left of centre is the penstock on-off valve supplying the Turgo.
To the left is an early Ingersoll compressor for the rock drills. Right foreground is the incline haulage winding drum. Access to the main valve & the Turgo power/speed control valve involves squeezing along this 'passageway' between whizzing 6" heavy canvass belts & whirling drive-wheel spokes - a certain sense of balance & lack of fear (stupidity ?) is helpful !.
Photo 4 : An overall view of part of the mill interior :
Note the piles of essential stuff everywhere. Stacks of steel piping, steel props, spare pulleys, gears etc. The floor is simply compacted dirt, rock dust etc. that has become so compacted over the years it is almost solid. 'Economy' roof props, cut from the surrounding woods as required.
The Turgo can be seen at rear upper right. Elsewhere, behind the camera are fitters/mechanics benches & tool stores (the mill is also the mine engineering base) and extensive ore settling tanks set into the ground.
The chute behind the stamps, sloping down from the upper left, is the ore feed from the tram system outside the mill.
Photo 5: Partial overview from above & behind the stamps :
Right foreground is the incoming ore chute & water sprinkler bar (just below the red line-shafting. Note the 'economy' roof structure ! - no small mining concern ever wasted money !.
The vertical lever, immediate foreground, is the 'clutch' for the stamp's drive. The stamp drive belt is temporarily run-off it's pulley - it would normally pass over either the rusty crowned pulley or the green pulley. One of these pulleys is fixed to the drive shaft, the other is free to rotate. Operating the clutch lever simply pushes the belt across, via a sort of open 'banjo' from one pulley to the other. Any attempt at 'clutch slipping' for a gentle start can push/pull the belt right off so the clutch lever is thrown smartly - Zap ! Judder & the stamps start at almost full speed !.
My lack of photographic skill/knowledge has weirdly foreshortened the far end of the mill - the settling tanks, tool store etc. seem to have disappeared !
The main message is : you can't have too much clutter around a working mill, unless it is one of these new fangled, white suited, computerised jobs - & who wants to model one of those ?.
This is a hard rock, metal ore mine but NOT a gold mine, though the principles are generally the same except :
Outside : a gold mine would have cyaniding tanks* + stirrers, external ore bins, waiting stock piles of "mine-run" ore (i.e. as raised from below, awaiting grading, sorting, preliminary crushing etc. * depending on location & era.
Inside : a gold mine would have shaker tables, Wilfleys etc
- but otherwise there ain't a lot of difference in overall appearance (we ain't got no rattlers or tumble weed !).
That's all folks.......
Photos by Salada.
Regards, Michael
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| Posted: Fri Jun 12th, 2015 03:11 am |
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2nd Post |
Herb Kephart
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What HP would you estimate the Turgo to be?
My wild guess that it would have to be at least 25HP to run all that--but grist (grain) mills have a much lighter, easier to grind product, and they are the mills that I have some (little) experience with.
Herb
____________________
Fix it again, Mr Gates--it still works!"
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| Posted: Fri Jun 12th, 2015 09:53 pm |
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3rd Post |
Salada
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Good question Herb.
I have always been a bit puzzled by the actual Hp because, measuring the fall (approx but near eneough correct) on the penstock from the reservoir to the rotor jet and applying the formula I found in an old textbook, the answer comes out at no more than 5 Hp max.
When I restored the Turgo, 1995, I was almost sure it wouldn't start the stamps without some barring over but it never faltered on throwing the stamp's clutch - but they are only a fairly light 4 head set. According to winder operator winding 3/4 ton up about a 23% grade (+- a bit) at about 3-4 mph doesn't trouble it at all, even with me man-riding on top of the tram !. It will even stamp & wind together !!.
I reckon that lot together would stop a 5 Hp Briggs&Stratton dead.
I ain't no mathematicalician but I think I applied the formula the 'right way up', maybe t'formulas wrong ?.
Regards, Pysorarse - maybe that should be Pythagorass ?, or Pythagopras
--- like I said, I ain't no NumberMagician
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| Posted: Thu Jun 18th, 2015 07:33 am |
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4th Post |
Ray Dunakin
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Fantastic photos and explanations! Very interesting stuff, thanks for posting it!
I'm amazed that little water wheel can power all that equipment.
Are the surfaces of the belt system pulleys flat, concave, or convex? I can't tell from the photos. I read somewhere that they are usually convex, but that seems counterintuitive.
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Visit http://www.raydunakin.com to see photos of the rugged and rocky In-ko-pah Railroad!
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| Posted: Thu Jun 18th, 2015 05:52 pm |
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5th Post |
Herb Kephart
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Convex. (high in the center) Keeps the belt riding at the largest diameter.
Lots of theories for this, from those who think they know, but don't. It was discussed over 3 or 4 issues of Gas Engine magazine years ago, and a lot of ''experts'' contributed ''reasons'' that a 3 year old wouldn't believe. Finally, someone who knew wrote a lengthy letter involving trigonometry that made sense. The rest -- like myself at the time -- knew that it worked, just didn't know why.
The only exception to this is sometimes where two pulleys of the same diameter are next to each other on the same shaft, one spinning loose the other locked to the shaft with a key, and turns with the shaft. Belt runs through a fork close to the pair, that can shift the belt sideways. When the pulleys are flat in this case, the fork is relied to maintain belt/pulley alignment--at the expense of edge wear on the belt. When the moving belt is on the ''loose'' pulley, the shaft stands still. When shifted over to the ''tight'' pulley, the shaft is driven. This whole contraption forms a clutch-- so that the main shaft (usually in the ceiling) can turn all the time that the prime mover is running, while individual machines can be started and stopped as needed. All of this is shown, and described, at the lower left corner of Salada's last pix.
Unless the main drive shaft, and the driven one--with the clutch -- are perfectly parallel, problems with engagement and dis-engagement --as noted by Salada will happen. Difficult to maintain this alignment with vibration and frame movement, but unavoidable under the conditions shown.
Herb
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Fix it again, Mr Gates--it still works!"
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| Posted: Thu Jun 18th, 2015 10:22 pm |
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6th Post |
Salada
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Herb is correct.
The drive pulleys are "crowned", meaning they are slightly convex though normally this is hardly noticeable unless a straight edge is placed across the driving surface. Flat belts will always run "uphill" if they can, hence the crown keeps the belt running true but the Driver & Driven shafts must be parallel & in the same horizontal/vertical plane - if not the belt will rapidly climb up a misaligned pulley. On long drives belts are sometimes "crossed" into a figure of eight which can reduce drive slippage but need careful setting up to avoid the belt running 'edge to edge' and fraying where it crosses itself.
The "clutch" pulleys (or the Fast & Loose as it is known) are not crowned, as Herb says, because this would make it even more tricky to shift the belt across. The Driven pulley in a Fast & Loose arrangement is crowned, to maintain the correct centering of the belt. Setting the correct position & width of the 'jaws' of the forked belt guide is important in avoiding fraying the drive belt edges.
Regards, Michael
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| Posted: Thu Jun 18th, 2015 11:16 pm |
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7th Post |
mabloodhound
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Nice stuff Michael. I enjoy reading about historical machines and operations.
____________________
Dave Mason
D&G RR (Dunstead & Granford) in On30
“All tyranny needs to gain a foothold is for people of good conscience to remain silent.” ~ Thos. Jefferson
“Those who hammer their guns into plows will plow for those who do not.” ~ me
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| Posted: Fri Jun 19th, 2015 12:35 am |
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8th Post |
Salada
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Ray, Herb & Dave - thanks for your appreciation.
Now I know at least 3 people read my non-railroad ramblings !
Regards, Michael (part miner, part railroader !)
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| Posted: Fri Jun 19th, 2015 10:26 am |
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9th Post |
pipopak
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... make it four... Jose.
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Junk is something you throw away three weeks before you need it.
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| Posted: Fri Jun 19th, 2015 03:48 pm |
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10th Post |
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