notjustone
spending too much on rocks
Member since January 2017
Posts: 426
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Post by notjustone on Mar 26, 2017 12:26:51 GMT -5
I finally got around to bringing home a tach and checking my barrel speed. disappointing 25 rpm. forgot when I was calculating for my puleys I had added some extra to my shaft for hose. I was guessing at hose thickness and shooting for close to 40 rpm. od of hose was a little smaller than my guess. sleaved it now running 37 rpm for 8 inch barrel. sound about right?
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Post by captbob on Mar 26, 2017 13:07:24 GMT -5
To ME that sounds great for coarse grits. I prefer slower (20 to 25max) for fine grits and polishing. If used for fine grits, I would cushion the heck out of the load with plastic beads.
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notjustone
spending too much on rocks
Member since January 2017
Posts: 426
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Post by notjustone on Mar 26, 2017 14:06:21 GMT -5
I'm still trying to decide if i want to build some more barrels and run the 3 step ao80 process or stick with just useing it to feed my 2 hf tumblers. ill probably do that for now and switch over when one of the hf tumblers dies.
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cabjunky
has rocks in the head
Regency Rose Plume
Member since November 2008
Posts: 683
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Post by cabjunky on Mar 26, 2017 17:12:55 GMT -5
Mine are running around 25 rpm on my contempo and lortone running 15 pound thumlers and 12 pound lortone barrels (respectively). Seems to do just fine through all stages.
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Post by youp50 on Apr 1, 2017 16:44:45 GMT -5
RPM confuses me. It seems to me I need to be more concerned with the speed of the tumbler. Rim speed? A 4 inch barrel is running approx 35 % slower than a 6 in which is 23 % slower than an 8 in barrel, all driven at the same rpm. How fast in feet per minute should one design for?
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Deleted
Deleted Member
Member since January 1970
Posts: 0
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Post by Deleted on Apr 1, 2017 18:17:02 GMT -5
RPM confuses me. It seems to me I need to be more concerned with the speed of the tumbler. Rim speed? A 4 inch barrel is running approx 35 % slower than a 6 in which is 23 % slower than an 8 in barrel, all driven at the same rpm. How fast in feet per minute should one design for? Like a saw blade, surface feet (inches?) per minute. I would agree. 37 RPM 8" barrel. 77ft/minute 64 RPM 6" barrel. 100ft / minute jamespDrummond Island RocksJugglerguy
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Post by Drummond Island Rocks on Apr 1, 2017 20:05:27 GMT -5
RPM confuses me. It seems to me I need to be more concerned with the speed of the tumbler. Rim speed? A 4 inch barrel is running approx 35 % slower than a 6 in which is 23 % slower than an 8 in barrel, all driven at the same rpm. How fast in feet per minute should one design for? Like a saw blade, surface feet (inches?) per minute. I would agree. 37 RPM 8" barrel. 77ft/minute 64 RPM 6" barrel. 100ft / minute jamespDrummond Island RocksJugglerguyI went the lazy route. I use standard lortone barrels and run my homemade tumbler at stock lortone RPM. Figured that was safe years ago when I built it and it has not let me down. Chuck
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Deleted
Deleted Member
Member since January 1970
Posts: 0
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Post by Deleted on Apr 1, 2017 20:07:14 GMT -5
I went the lazy route. I use standard lortone barrels and run my homemade tumbler at stock lortone RPM. Figured that was safe years ago when I built it and it has not let me down. Chuck Would you share those values? Your success is notable and those values important. Please and thank you.
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Post by Drummond Island Rocks on Apr 1, 2017 20:12:33 GMT -5
I went the lazy route. I use standard lortone barrels and run my homemade tumbler at stock lortone RPM. Figured that was safe years ago when I built it and it has not let me down. Chuck Would you share those values? Your success is notable and those values important. Please and thank you. I am at bowling tournaments with my kid all weekend but will report numbers when I get a chance. Did you ever request the speed calculator I made in excel? Chuck
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Deleted
Deleted Member
Member since January 1970
Posts: 0
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Post by Deleted on Apr 1, 2017 20:49:30 GMT -5
Would you share those values? Your success is notable and those values important. Please and thank you. I am at bowling tournaments with my kid all weekend but will report numbers when I get a chance. Did you ever request the speed calculator I made in excel? Chuck I did not. I used less specific ones online for my purple machine.
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Post by Drummond Island Rocks on Apr 1, 2017 20:54:32 GMT -5
@shotgunner
I made that document to be rock tumbler specific. If I want to know what happens when I change from 3/4 shafts to 1" I just change one field and get an instant final barrel RPM. I only used one time to build the tumbler but I like the challenge of doing stuff like that in excel.
Chuck
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notjustone
spending too much on rocks
Member since January 2017
Posts: 426
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Post by notjustone on Apr 1, 2017 22:06:31 GMT -5
I saw it looking through the archives but couldn't use it because I ran a double sheave reduction pulley {jackshaft type concept) to knock down speed before going to the shafts. so I could keep my shaft pulleys small enough for a positive drive. going from motor straight to the shaft would have been a bigger diameter pulley than I could have done on my little jet lathe.
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,159
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Post by jamesp on Apr 2, 2017 1:19:53 GMT -5
I finally got around to bringing home a tach and checking my barrel speed. disappointing 25 rpm. forgot when I was calculating for my puleys I had added some extra to my shaft for hose. I was guessing at hose thickness and shooting for close to 40 rpm. od of hose was a little smaller than my guess. sleaved it now running 37 rpm for 8 inch barrel. sound about right? I run 30 RPM and 55 RPM on an 7.5" barrel. 7.5" barrel has thick walls(pipe plus coupling) and only a 6" opening(6" PVC pipe). So the inside surface speed of the barrel is 6/7.5 (80%) slower than the outside of the barrel. 30 RPM is fine for finishing and coarse grinding, 55 RPM only for coarse grind for above barrels. 20 -25 RPM is better than 30 RPM for finishing larger rocks. Barrels like the Thumler with raised edges and thick walled barrels have about 75-80% slower surface speed at rock zone. Unlike Lortone with thin walls.
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Post by youp50 on Apr 2, 2017 20:07:42 GMT -5
Would you share those values? Your success is notable and those values important. Please and thank you. I am at bowling tournaments with my kid all weekend but will report numbers when I get a chance. Did you ever request the speed calculator I made in excel? Chuck I think there is an error here. By my calculations you are much closer to 37 rpm at the barrel. When figuring pulleys and speed you need to use pitch or datum diameter. Going to Grainger catalog, I find a pitch diameter of 1.05" for a 3L belt and a 1.5 inch pulley. A 10 inch pulley shows 9.55" for the same 3L belt. Plugging 1.05 for drive and 9.55 for driven I get 190 rpm (rounded up) barrel shaft speed. 190 rpm at .75 onto a 3.875 barrel results in 38 rpm (again rounded up). Not being a tumbler very long, but currently recuperating from hernia surgery gives me time to glean much information. I would venture a guess that a 38 rpm 3 7/8 inch barrel would increase the time needed to properly shape stones with coarse grit. I believe you are vibrating your final steps, but to follow through. A slow speed rotary tumbler should give a nicer polish if given the time needed. Might I suggest a 2 in pulley at 1.55 pitch, again the same 3L belt, to achieve 54 rpm drum speed. I chose the 3L belt for these calculations because there seems no need for a heavier belt to run a tumbler. Using a 4L belt changes things.
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