Deleted
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Post by Deleted on Jan 26, 2017 14:33:54 GMT -5
My life devoid of such math. Not mine!
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Deleted
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Post by Deleted on Jan 26, 2017 14:38:50 GMT -5
But what is the rotational velocity? We also need a way to measure grind velocity. I propose a new unit of measure. The number of grams stone removed per hundred grams of grit. This factor can be used to measure all sorts of test parameters. Grit size comparisons, rotational velocity, barrel fill rates, slurry efficiency.... I christen this unit of measure the "Roki Factor". This in honour of the tireless testing and tumbling technological advancements originating at the Roki Shoals Tumbling Laboratory owned by our good friend Jim Price. The Roki Factor! I've been doing a lot of material removal rate experiments with a scale that is accurate to 0.01 of a gram. I'm finding that around 1.2 lbs of 80 grit removes around 1.0 lb of agate hardness rock. I am using a 15 pound high speed Thumler's tumbler. I am also finding the high speed model is significantly more efficient per lb of grit used than the regular speed, and the big 15 lbs barrel is significantly more efficient than a small 3lbs barrel. Additionally, the longer you use the coarse grit the more efficient it is, as I'm finding even after 4 days, the broken down coarse grit still has decent material removal capability. Also, initial experiments suggest the less grit you ad per charge, the more efficient the grit/material removal ratio becomes. I would have never expected a Roki Factor of .8 such as you describe. That is amazing!!! I'm super excited about your experiments. Would love it if we could crowd source a huge amount of data. Make a spread sheet and every inputs their data. Then we can compare a wide range of machines RPM, barrels does and materials... And more. Working towards pinning down the most efficient combo materials and tools.
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,179
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Post by jamesp on Jan 26, 2017 15:18:55 GMT -5
Just because I have had mostly 6 and 8 inch PVC barrels with easily variable speeds and rocks sizes and slurries and SiC sizes a mental data base is there @shotgunner. At this point SiC 30 and X amount of clay for the best slurry turned constant. Chosen size of 6" PVC = constant. Grit life almost constant.
Boils down to which speed (30 or 55) for what mix of rock sizes. And what level to fill barrel with rocks. So 3 variables.
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Deleted
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Post by Deleted on Jan 26, 2017 15:57:25 GMT -5
jamesp you have outstanding qualitative data. What I just proposed was for quantative data for all manner of barrels and sizes. We may learn that for the little lortone 3# barrels 90 grit without clay is best. We could also look for a sweet spot at certain rotational velocity (feet per minute) is a sweet spot no matter the barrel size. And that THAT number is different for rubber and PVC barrels. The point is standardising all the parameters using the ROKI Factor will allow us to crowd source quantitative data along all these parameters.
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doublet83
starting to spend too much on rocks
Member since March 2016
Posts: 118
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Post by doublet83 on Jan 26, 2017 17:25:43 GMT -5
Shotgunner, is it more or less efficient than you would have expected? I have been trying to optimize for grit efficiency by using grits for longer before re-charging, and using less grit per charge. When I started this hobby, using the lortone 33B and following their instructions, I was probably only getting 1/3 as much grit efficiency (rough guess).
Jamesp, I'm a fan of your posts. They are very informative and I've learned much. I actually haven't been using a slurry thickener. With the high speed 15lb Thumler, I find that after two days, I can no longer feel any grit, so it seems unnecessarily to use a slurry thickener. I know you have said before you feel that after a few days, the coarse grit breaks down is no longer useful for shaping. I actually find that after say 4 days, the broken down coarse grit is still effective at shaping, only around 50% slower than fresh 80 grit (rough numbers here, lots of different variables). Of course one variable could be that your use of clay in the slurry has sped up the grit break down process. I think one of these days I'll directly test material removal rates with 30 grit vs 80 grit vs 220 grit, and try to reach some more conclusive findings.
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Post by parfive on Jan 26, 2017 17:47:08 GMT -5
Cool. Next time you’re running 500, figure your weight-loss percentage after a week’s run.
You’ll probably find that’s enough to remove any 60/90 “scratches” and that 120/220 is a waste of time, money and effort.
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Post by captbob on Jan 26, 2017 17:57:51 GMT -5
IF 500 could remove 60/90 "scratches" it would probably take quite a while longer. Guess it depend on how long the 60/90 ran and how much it broke down. Run 60/90 a bit longer and it ain't much different from running 120/220. So yeah, grits can probably be skipped if the previous grit is given time to break down and do the next grit's job. Kinda a given.
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Post by parfive on Jan 26, 2017 18:17:55 GMT -5
I don’t run 60/90 longer to skip 120/220. Any rocks ready to move on are just pulled from regular 4 – 7 day runs in 60/90.
Been years since I bothered weighing a tumble. When I did, a week in 500 lost 5 – 8% and it don’t take a 5% loss to buff a 60/90 satin finish.
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jamesp
Cave Dweller
Member since October 2012
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Post by jamesp on Jan 26, 2017 19:03:36 GMT -5
Shotgunner, is it more or less efficient than you would have expected? I have been trying to optimize for grit efficiency by using grits for longer before re-charging, and using less grit per charge. When I started this hobby, using the lortone 33B and following their instructions, I was probably only getting 1/3 as much grit efficiency (rough guess). Jamesp, I'm a fan of your posts. They are very informative and I've learned much. I actually haven't been using a slurry thickener. With the high speed 15lb Thumler, I find that after two days, I can no longer feel any grit, so it seems unnecessarily to use a slurry thickener. I know you have said before you feel that after a few days, the coarse grit breaks down is no longer useful for shaping. I actually find that after say 4 days, the broken down coarse grit is still effective at shaping, only around 50% slower than fresh 80 grit (rough numbers here, lots of different variables). Of course one variable could be that your use of clay in the slurry has sped up the grit break down process. I think one of these days I'll directly test material removal rates with 30 grit vs 80 grit vs 220 grit, and try to reach some more conclusive findings. No doubt speed helps circulate heavy grit particles Like 30-46-60-80 doublet. What seems assist fast grinding is the cohesive forces of a 'sticky' slurry. Of course, rapid grit breakdown is useless if you don't recharge with fresh grit more often. If you can pick up one rock with another rock due to a coating of slurry on each rock there is a high probability they are being sucked together while moving against each other and increasing grind force. A little bit of a suction force goes a long way at 24/7. I use 30 grit. It is easy to find due to it's size doing a wash down separation. If there are only 200-300 sized particles I trash the slurry. Under the assumption such sized grit is ineffective at deep cutting. It is not an issue though, I add grit every 1 to 2 days except Friday without cleaning out for 6-7 days straight. Only a clean out each weekend. So day 1 add gets 7 days, day 2 grit gets 6 days, day 3 grit gets 4 days, etc etc. Only Thursday grit gets a shortish run. Close to zero waste. If a day or two is missed it is of little consequence.
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Post by captbob on Jan 26, 2017 19:06:08 GMT -5
I find it difficult to believe that 500 grit is aggressive enough remove 5 to 8 percent of the rock mass. That's half a pound or more on a 10 lb load. My experience is that 500 simply puts a finer (lessens previous scratches) finish on the rocks, not that it is removing that much from the rocks.
But I guess all results are not the same.
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Deleted
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Post by Deleted on Jan 26, 2017 19:56:41 GMT -5
Shotgunner, is it more or less efficient than you would have expected? I have been trying to optimize for grit efficiency by using grits for longer before re-charging, and using less grit per charge. When I started this hobby, using the lortone 33B and following their instructions, I was probably only getting 1/3 as much grit efficiency (rough guess). Jamesp, I'm a fan of your posts. They are very informative and I've learned much. I actually haven't been using a slurry thickener. With the high speed 15lb Thumler, I find that after two days, I can no longer feel any grit, so it seems unnecessarily to use a slurry thickener. I know you have said before you feel that after a few days, the coarse grit breaks down is no I think your numbers indicate a far more efficient material removal than I expected.
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jamesp
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Member since October 2012
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Post by jamesp on Jan 27, 2017 4:34:16 GMT -5
Rotary: Using math on scratches(pits) is vanity since it requires high tech measuring equipment. Sheens and reflections give a good idea of surface finish at 1000+ grit. Between 100 to 1000 finish is the tricky range. Images do not reflect off of rocks in that range. SiC actually pits more than scratches in a rotary. Looks as if grit particles roll between the rocks more so than dragging across rocks making pits more than scratches. Under the best conditions with fresh clay slurry thickener, 55 RPM, SiC 30 grit, biggish 1 to 2 inch rocks SiC 30 is like 300-500 after 12 hours. after 2 hours-surface very rough after 4 hours-surface very rough after 6 hours surface changes to what appears to be 80 grit finish after 8 hours surface getting smooth to touch after 12 hours it is difficult to say if surface is a 220-500 finish. Darn smooth... after 24 hours it still feels like 220 to 500, could be 1000. after 100 hours the rocks can be dropped in the vibe with AO 14,000 and get a decent polish. That is the real test. They ain't gonna polish w/14,000 if the coarse grit did not break way down. Point being, coarse grit like 30 or 46 can break down fast either with a fast rotary or good slurry or good mix of rocks or what ever other reason. If you feel that your coarse SiC is breaking down in 1 to 2 to 3 days take time to pull a rock out every 2-3-6 hours at start and look at the finish on them sometime. Get an idea of what is happening and when it is happening. Because a (fresh)46 grit finish is rough and a 200 grit finish is smooth. That will give you an idea of rate of breakdown for your tumbler. If you have a smooth rock after 6-12 hours then your coarse grit is breaking down rapidly. Guaranteed. If your rocks do not have a rough finish in coarse SiC during the first 6-12 hours then your grit is not circulating well and you are wasting time. Something is wrong. SiC 30 Roughest point at 4 hours. coral SiC 30 Smooth, after 18 hours. same coral Compare 30 grit from tumbler and 30 grit from 30 grit grinding wheel: 30 grit from tumbler = pits 30 grit from grinding with 30 grit diamond wheel = scratches You will get scratches if a bit of fresh SiC 46 is dropped in during a polish run. Just saying that the cutting operation during coarse grind is a pitting effect much more than a straight line scratching operation. Apparently the grit is rolling between the rocks and gouging or making tiny divots to remove material.
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jamesp
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Post by jamesp on Jan 27, 2017 5:32:59 GMT -5
The pitting from the rotary does not seem to be an efficient way to remove material. It is what it is. SiC 220 on obsidian after 3 hours: SiC 30 on obsidian after 3 hours
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Wooferhound
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Lortone QT66 and 3A
Member since December 2016
Posts: 1,426
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Post by Wooferhound on Mar 17, 2017 4:34:01 GMT -5
My Lortone 3A Tumbler uses 25 watts of electricity, The QT66 uses 52 watts for a total of 77 watts for both machines. Around here electricity cost about 10 cents per kilowatthour (KWH). So it takes 13 hours using 77 watts to use 10 cents of power.
1 hour = .077 KWH = .8 cents 1 day = 1.85 KWH = 18.5 cents 1 week = 12.95 KWH = $1.30 1 month 31 days = 57.35 KWH = $5.74 1 year = 675.25 KWH = $67.53
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huskeric
spending too much on rocks
Member since May 2016
Posts: 353
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Post by huskeric on Mar 17, 2017 10:54:00 GMT -5
>> But what is the rotational velocity? << Is that an African or European Tumbler you are asking about ? I guess my tumbler at 1 rotation per second would be 14.1 inches per second. I have great scales but never weighed the rocks. Almost did a spit-take on this one. Since you mention the weight of a rock, keep in mind, that if it weighs the same as a duck, then logically... it's made of wood... and therefore, it's a WITCH!!!
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Post by captbob on Mar 17, 2017 11:07:14 GMT -5
My Lortone 3A Tumbler uses 25 watts of electricity, The QT66 uses 52 watts for a total of 77 watts for both machines. Around here electricity cost about 10 cents per kilowatthour (KWH). So it takes 13 hours using 77 watts to use 10 cents of power. 1 hour = .077 KWH = .8 cents 1 day = 1.85 KWH = 18.5 cents 1 week = 12.95 KWH = $1.30 1 month 31 days = 57.35 KWH = $5.74 1 year = 675.25 KWH = $67.53 DO NOT be showing stuff like that to my wife. She has no idea why our electric bill is so much higher than the neighbors and I would like to keep it that way! If I quit tumbling and got rid of the iguana (heating/lighting/humidifiers/extra fridge) it would cut our electric usage by around 2/3s - ssssssh!
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