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Post by aDave on Dec 31, 2018 0:04:51 GMT -5
There have been a few threads recently related to barrel speed and rotary tumblers. I've paid attention to all of them, as my rotary tumblers have seemed to be slowing down over time. My belts seem to be OK, so I was left with if the motor was getting tired. After seeing input from a bunch of diffrerent folks, I decided to take measures to increase barrel RPMs without worrying about belt tension and such. Without trying to play with belt tension, I thought I would work on working with the diameter of my drive shaft on my rotaries. For illustration, I'll refer to a Lortone 45C. My 45C rotary barrels had slowed down to about 31-32 RPMS. Belt tension appeared to be OK, but Lortone recommends this tumbler turning at 34 RPMs. So I simply looked to build up the diameter of the drive shaft to increase RPMs- and I did so by adding rolls of electrical tape on the shafts to increase barrel RPM. I've added the tape along the shaft (about 10 wraps), and my barrels are now turning at about 40 RPMs. This is my first venture at this speed, so it will be interesting to see if I get more fractures and such. Just thought I'd throw this out there for folks who might want to get more barrel speed with an easy fix. A photo is attached.
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Post by Drummond Island Rocks on Dec 31, 2018 0:18:46 GMT -5
That looks like a great modification. If there are issues with fractures at the higher RPM then adding rocks may solve that. If you are were filling up to 75 percent bump it to 85 percent with the higher speed. Just a thought.
Chuck
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Post by aDave on Dec 31, 2018 0:43:42 GMT -5
That looks like a great modification. If there are issues with fractures at the higher RPM then adding rocks may solve that. If you are were filling up to 75 percent bump it to 85 percent with the higher speed. Just a thought. Chuck Thanks Chuck, I can also go the other route and start removing wraps if need be to slow things down a bit. It's just an experiment for now, so it's hard to say how this will go. It will be interesting to see how this works out. I have one barrel in polish and another in the medium stage with the new RPMs. Thanks for your input.
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Post by Drummond Island Rocks on Dec 31, 2018 0:49:08 GMT -5
jamesp has a lot of experience with varying RPMs. If I remember correctly back when he was tumbling just rocks he used higher rpm for coarser grits and slower rpm for polishing. Chuck
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Post by aDave on Dec 31, 2018 1:13:26 GMT -5
jamesp has a lot of experience with varying RPMs. If I remember correctly back when he was tumbling just rocks he used higher rpm for coarser grits and slower rpm for polishing. Chuck If I recall correctly, his barrel speed was far more than what I'm turning right now. I don't recall his barrel size, but the RPMs were pretty high. With all of the discussions about barrel speed thus far, I've come to the conclusion that all barrels are not created equal. Some are smooth walled, some are PVC, some are hex walled, and some are more narrow than they are wide, proportionally, when it comes to rocks that are going inside. I think all of these factors come into play at one level or another. I've really come to believe that each barrel type has its own sweet spot when it comes to rolling rocks. It just takes some experimenting to find where that spot is. I'm hoping I'm on track with what I'm doing now. It will be interesting to see what happens.
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Post by parfive on Dec 31, 2018 2:44:18 GMT -5
Amy - All 3 lb barrels, Thumlers. Model Ts - fast, 50 - 55 rpm - for coarse grind 60/90 Model AR-2 - slower, 32 rpm - for anything else Rich
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jamesp
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Member since October 2012
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Post by jamesp on Dec 31, 2018 6:36:08 GMT -5
I am all about 2 rotary speeds. ** Speeds are for all 6 inch inside diameter barrels. 85 RPM for coarse grind. 30 RPM for all other steps. The 30 RPM speed using 220-500-1000-polish steps is the standard 75% barrel fill. Right by the book. Focusing on coarse grind using 6 inch inside diameter barrels at 85 RPM: 1) Coarse grind is the longest step in about all cases except possibly softer than Mohs 7 rocks. 2) My home made machine was sorta accidentally designed for easy pulley ratio changes for different speeds. 3) Over a period of 7 years I bought pulleys to increase from 30 to 45 to 62 and finally settled at 85 RPM. 4) Keep in mind this tumbler is stout and built with heavy components and handles these speeds easily. Conclusion was higher speeds are not a problem if you increase barrel fill from 75% to 85/90% fill. The added speed simply grinds faster, uses abrasive faster and requires less run time and electricity. The key is filling the barrel higher to 85%+ meaning you are tumbling more rocks. Keep in mind a half full barrel uses more electricity than a 3/4 or 7/8 full barrel because it is not balanced(think water wheel). And this high barrel fill allows tumbling the most delicate shapes and materials because there is less fall in the barrel. And a thin slurry becomes less of an issue because of the high mixing rate at higher speed. However an overly thick slurry does become a problem so more clean outs or pouring slurry off and adding water to thin is required more often. Speaking of delicate, these are some really thin long pieces of glass that were shaped at 85 RPM. Very rarely do these break at 85 RPM/85% barrel fill. Even more delicate these glass 'toothpicks' I actually broke more long thin pieces of glass at 30 RPM when doing the SiC 500 step(I skip SiC 220). And the reason for the breakage was that the SiC 500 was more aggressive on glass than imagined. I started with 75% barrel fill at 30 RPM, after 4 days the glass had worn too much and gotten too thin and the barrel level had dropped to 50% fill which chipped my glass. So I had to stop coarse grind early to allow for the SiC 500 step to run long enough (7 to 10) days to breakdown without wearing my glass cabs too thin. But glass is soft and SiC 500 chews away at it much quicker than imagined. I have run over 50 six to twelve pound loads of glass in 2018 with the exact same SiC 60 and SiC 500 rotary recipe. Then to vibe. However aluminum oxide 500 had the exact opposite effect than that of SiC 500. It removed little material, much less aggressive.
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Post by fernwood on Dec 31, 2018 7:00:32 GMT -5
Interesting experiment. Here is a question. Why do the speeds vary so much on different brands of rotary tumblers? MY duel 3 lb. CE averages about 65 RPM's. This speed varies, depending on the weight in the barrels. When a want a faster speed (as jamesp recommended for some coarse grinds), I now place on an empty barrel. This causes both to rotate at higher speed. The full barrel is at about 85% capacity.
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jamesp
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Post by jamesp on Dec 31, 2018 7:25:14 GMT -5
Interesting experiment. Here is a question. Why do the speeds vary so much on different brands of rotary tumblers? MY duel 3 lb. CE averages about 65 RPM's. This speed varies, depending on the weight in the barrels. When a want a faster speed (as jamesp recommended for some coarse grinds), I now place on an empty barrel. This causes both to rotate at higher speed. The full barrel is at about 85% capacity. 20-30-40-50-60 RPM. Any of those speeds will do the job of tumbling fernwood. Take it to extremes, if you have a 4 foot tall barrel spinning at your 65 RPM the outside of the barrel is screaming fast. Too fast. So the tumbling speed should get slower as the barrel gets bigger. Perhaps product liability insurance comes into play if a company were to sell a 50 pound tumbler spinning at 65 RPM. If you got your finger caught in it a bad day would certainly happen. The work formula is certainly simple, just ask the boss. There is two ways to increase the amount of work you do on your rocks keeping your machine the same(except speed) and all else constant. Increase the time tumbled Increase the speed tumbled If your speed is changing with weight you may have slippage somewhere. AC motors will overheat if their 'rated' speed changes by just a few percent. I think it is about 5%.
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Post by fernwood on Dec 31, 2018 7:34:13 GMT -5
No overheating at all. Winter temps in utility room are in the upper 40's, which probably helps. Even when it was in the 90's in utility room, the tumbler ran cool.
I have taken apart the tumbler many times and checked for slippage. None present. Just slower speeds with heavier barrels. Note that I also do weekly cleaning and re-apply the turbine oil on the bearings.
Should be able to get the duel 3 lb Thumbler up and running within a week or so. Will be interested in seeing what the RPM's are on that.
With the variety of "normal" RPM's on rotary tumblers, it could cause a lot of confusion for some, especially those who are unaware of what different speeds can do to rocks.
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Post by HankRocks on Dec 31, 2018 8:13:18 GMT -5
There have been a few threads recently related to barrel speed and rotary tumblers. I've paid attention to all of them, as my rotary tumblers have seemed to be slowing down over time. My belts seem to be OK, so I was left with if the motor was getting tired. After seeing input from a bunch of diffrerent folks, I decided to take measures to increase barrel RPMs without worrying about belt tension and such. Without trying to play with belt tension, I thought I would work on working with the diameter of my drive shaft on my rotaries. For illustration, I'll refer to a Lortone 45C. My 45C rotary barrels had slowed down to about 31-32 RPMS. Belt tension appeared to be OK, but Lortone recommends this tumbler turning at 34 RPMs. So I simply looked to build up the diameter of the drive shaft to increase RPMs- and I did so by adding rolls of electrical tape on the shafts to increase barrel RPM. I've added the tape along the shaft (about 10 wraps), and my barrels are now turning at about 40 RPMs. This is my first venture at this speed, so it will be interesting to see if I get more fractures and such. Just thought I'd throw this out there for folks who might want to get more barrel speed with an easy fix. A photo is attached. My guess is that the slowing of the barrel is related to slippage. Either the belt on the pulley's or the barrel on the drive shaft. The drive shaft looks a bit polished so that might lead to slippage. Adding the tape provided a new non-polished contact for the barrel thus increasing the friction and eliminating the slippage. On my Thumlers Model B's I get a lot of Belt slippage. About once every two weeks I clean the pulleys with a bit of Acetone. When that no longer worked, I started using CRC Belt Conditioner. It may have been jamesp or captbob who recommended it to me. I keep a couple of replacement belts sprayed with the belt conditioner in reserve and when I notice slowing or in some cases, a complete stop, I clean the pulleys and replace the belt and the barrels are back to normal speed. Good luck
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Post by grumpybill on Dec 31, 2018 10:41:20 GMT -5
I simply looked to build up the diameter of the drive shaft to increase RPMs- and I did so by adding rolls of electrical tape on the shafts to increase barrel RPM. I had thought about doing something similar with heat-shrink tubing, but your tape idea has two advantages: 1. It doesn't require disassembling the tumbler 2. Easy to change the speed by removing/adding a few layers. I'm not sure of the longevity of electrical tape, so I'll use cloth tape if I try this.
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Post by aDave on Dec 31, 2018 13:21:39 GMT -5
]My guess is that the slowing of the barrel is related to slippage. Either the belt on the pulley's or the barrel on the drive shaft. The drive shaft looks a bit polished so that might lead to slippage. Adding the tape provided a new non-polished contact for the barrel thus increasing the friction and eliminating the slippage. You may have something there with the condition of the shaft. I've been monitoring belt tightness, and all has seemed to good there. In the past, If I start to get some slippage, I can usually see belt residue on the pulleys or inside the tumbler housing. There's been no residue up to this point in time. But, since you mention it, the shaft does look pretty polished, and I've flat out missed that - even though I look at it all the time. I'll let things ride with the tape right now, just to see how the loads go at the current RPMs the barrels are turning. If I find that the tape needs to go for whatever reason, I'll definitely make a point of cleaning/scuffing both the shafts and the barrels. Thanks.
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jamesp
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Post by jamesp on Jan 1, 2019 9:37:44 GMT -5
Keep in mind the grip on the barrel increases when the gap between the shafts are wider. A 7 inch barrel sitting on a 6 inch gap between the shafts has more grip than a 7 inch barrel sitting on a 3 inch gap between the shafts. Due to wedge force.
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jamesp
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Post by jamesp on Jan 1, 2019 12:05:24 GMT -5
No overheating at all. Winter temps in utility room are in the upper 40's, which probably helps. Even when it was in the 90's in utility room, the tumbler ran cool. I have taken apart the tumbler many times and checked for slippage. None present. Just slower speeds with heavier barrels. Note that I also do weekly cleaning and re-apply the turbine oil on the bearings. Should be able to get the duel 3 lb Thumbler up and running within a week or so. Will be interested in seeing what the RPM's are on that. With the variety of "normal" RPM's on rotary tumblers, it could cause a lot of confusion for some, especially those who are unaware of what different speeds can do to rocks. There has been a lot of discussion over the years about rotary problems. The practice of designing machines for limited longevity and performance is common practice. For starts any continuous duty machine designed with bushings is a dead giveaway for such unscrupulous practice. Don't shoot the messenger but it is true. There is enough complication with the tumbling process to not have to wrestle with your tumbler's reliability. Building a homemade using industrial grade pillar blocks, solid steel shafts, automotive grade v-belt, sheaves, lumber and a real motor is not so difficult or expensive. For serious tumbling folks I certainly recommend spending the time and money.
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Post by Drummond Island Rocks on Jan 1, 2019 14:37:04 GMT -5
Keep in mind the grip on the barrel increases when the gap between the shafts are wider. A 7 inch barrel sitting on a 6 inch gap between the shafts has more grip than a 7 inch barrel sitting on a 3 inch gap between the shafts. Due to wedge force. Is there a sweet spot for shaft spacing. Not my area of expertise but at some point wouldn't the wider spacing put more stain on the belt and motor?. Thinking more grip equals more stain somewhere in the build. My home made tumblers have all used Lortone barrels so I went the easy route and copied their standard shaft spacing. Chuck
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NRG
fully equipped rock polisher
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Post by NRG on Jan 1, 2019 19:50:21 GMT -5
Seems to me aDave is onto something.
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jamesp
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Post by jamesp on Jan 2, 2019 10:58:10 GMT -5
Keep in mind the grip on the barrel increases when the gap between the shafts are wider. A 7 inch barrel sitting on a 6 inch gap between the shafts has more grip than a 7 inch barrel sitting on a 3 inch gap between the shafts. Due to wedge force. Is there a sweet spot for shaft spacing. Not my area of expertise but at some point wouldn't the wider spacing put more stain on the belt and motor?. Thinking more grip equals more stain somewhere in the build. My home made tumblers have all used Lortone barrels so I went the easy route and copied their standard shaft spacing. Chuck There is a point where too much is bad for such reasons you mentioned Chuck. Prudence should be observed. But too narrow is a bad idea. Food for thought, hearing lots of slippage complaints.
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agatesrock
off to a rocking start
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Post by agatesrock on Jun 28, 2021 20:08:56 GMT -5
Amy - All 3 lb barrels, Thumlers. Model Ts - fast, 50 - 55 rpm - for coarse grind 60/90 Model AR-2 - slower, 32 rpm - for anything else Rich I would love to get in touch with this guy I have a high rpm and low for my thumlers model b and have been experimenting with agates and stage 1 and high speed.
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Post by parfive on Jun 29, 2021 1:21:30 GMT -5
Apr 8, 2009 at 3:34pm parfive said: Amy - All 3 lb barrels, Thumlers. Model Ts - fast, 50 - 55 rpm - for coarse grind 60/90 Model AR-2 - slower, 32 rpm - for anything else Rich I would love to get in touch with this guy I have a high rpm and low for my thumlers model b and have been experimenting with agates and stage 1 and high speed. Who, me? : ) Fire away, Chris.
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