jamesp
Cave Dweller
Member since October 2012
Posts: 36,558
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Post by jamesp on Nov 23, 2016 5:47:53 GMT -5
The rocks in the bottom of the barrel are likely not rubbing against each other at all. Only at the top left when the avalanche begins and while the rocks roll/slide/bounce down to the right side of the barrel. At 60% the grinding zone longer than 80% fill. At 100% fill there is almost zero grind zone, and little relative movement between the rocks whatsoever. With a high suction thicker slurry the bouncing and rolling action is converted to a rubbing action. Rocks that were bouncing in a watery slurry are not rubbing so much. Rocks that roll over themselves in a watery slurry are not rubbing so much. The motor has to work harder to move the rocks in a thick slurry because there is more friction. The friction caused by the slurry results in more drag on the barrel and the rocks. That drag increases grind pressure on the rocks.(a lot with a high suction slurry) At 30 RPM that works out to 43,200 avalanches per day. At 55 RPM 79,200 per day. Add 60% rock fill arrangement and thicker slurry and grind times greatly increased. Not only is the grind zone longer but a higher percentage of the rocks are in the grind zone. At 80% fill and slurry SiC 30 broke down in about 1.5 to 2 days. At 60% about 12 hours. So I fill to ~2/3 (66%) for daily grit additions.
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Post by Garage Rocker on Nov 23, 2016 14:14:31 GMT -5
Nice illustrations. I thought only school teachers could buy red ink pens.
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ChicagoDave
has rocks in the head
Member since June 2016
Posts: 720
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Post by ChicagoDave on Nov 23, 2016 14:25:33 GMT -5
hmmmmm, maybe I'm adding too many rocks to my barrel. Interesting.
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Post by Garage Rocker on Nov 23, 2016 14:31:43 GMT -5
hmmmmm, maybe I'm adding too many rocks to my barrel. Interesting. Could be slowing the action and reducing that grit breakdown.
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Post by captbob on Nov 23, 2016 14:44:30 GMT -5
Left wondering how much this applies to barrels with a shaped octogonal (or however many sided) interior.
In my Thumler's 15 lb barrels I don't believe that my rocks slide like rocks in a round interior barrel may.
I believe that a barrel with shaped sides tumbles rocks much more efficiently than a round barrel as the rocks ride up the sides better before being thrown (tumbled) back on top of the load. Therefore, a 60% full barrel is going to have much more aggressive action than an 80% full barrel as the rocks have more empty space in which to tumble.
I would never run a 60% full barrel as the tumbling action in all that empty space would beat the rocks to death. Maybe okay for a coarse grit grind where one is wanting to remove a bunch of rough (quickly) to get to a rounder shape and when tumbling a rock type not prone to bruising or fracturing. And maybe okay in a round barrel.
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,558
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Post by jamesp on Nov 24, 2016 10:14:42 GMT -5
Starting immediately with a thick slurry can prevent damage from the very start captbob. Best not to wait for a slurry for that very reason. Especially in the final coarse grit addition where you might be sending rocks to the next(220 ?) step with fresh bruises due to a watery slurry. Try to end the last coarse grit run with a longer run with a nice protective thick slurry before moving to a finer grit. I think all barrels have the avalanche arrangement. Octagonal barrels- I believe they are said to be gentler. Probably not a triangular barrel ! Either way, protective slurry should defend against damage. The way I see it, if you can have a full barrel width avalanche and benefits of protective slurry you are getting the most out of every rotation.
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,558
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Post by jamesp on Nov 24, 2016 10:23:14 GMT -5
Nice illustrations. I thought only school teachers could buy red ink pens. Mid aged men that wear serial killer glasses should not be allowed to teach young girls that attract honey bees.
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budified
off to a rocking start
Member since November 2016
Posts: 21
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Post by budified on Nov 24, 2016 11:41:12 GMT -5
To thicken a slurry, do you add more abrasive or just add mud?
I am testing a new abrasive product and have basically covered my rock in it in hopes that there would be a huge amount of friction and material removal, but I also have a bucket full of fine grind granite mud that I brought home for the purpose of using as a thickener and possible even a fine grind pre-polish media.
I have no intention of polishing the stones I tumble, but bringing them to a luster with simple mud would be an acceptable achievement.
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,558
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Post by jamesp on Nov 24, 2016 18:38:57 GMT -5
To thicken a slurry, do you add more abrasive or just add mud? I am testing a new abrasive product and have basically covered my rock in it in hopes that there would be a huge amount of friction and material removal, but I also have a bucket full of fine grind granite mud that I brought home for the purpose of using as a thickener and possible even a fine grind pre-polish media. I have no intention of polishing the stones I tumble, but bringing them to a luster with simple mud would be an acceptable achievement. Add mud to thicken. Too much grit settles to the bottom and/or gets concreted in spots it is not wanted. Good luck with the experiment.
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