Re: media for tumbling
I am using a large tumbler made by Contempo Lapidary. The drum is 12X12 inches and holds about 4 Gal., motor is 1/3 Hp.. Several years ago Contempo was bought out by Diamond Pacific, whose model 40T, looks like the same tumbler in blue paint.
I think the Tumbler's standard Model b and this tumbler would both do better for brass cleaning if they ran faster. I have found faster rotation makes the cleaning action more aggressive, but doubling the rotation speed does not cut the cleaning time in half.
I have only found one source on optimum barrel speed; that was a forum posting that referenced a lapidary book. According to the lapidary book, the optimum barrel speed is 35 to 55 percent of critical speed. Critical speed is the RPM where the tumbling mix starts to stick to the barrel from centripetal force. Critical speed is calculated by dividing 54.19 by the square root of the barrel radius in feet. A 12 inch diameter barrel should turn 25 to 35 RPM.
Here is the tumbling mix:
Two peanut jars of media 22 Lb.
3.5 Gal water 28 lb.
Brass 6 Lb.
tumbler body 25 Lb.
As you can see, the drum is now heavy enough to cause severe injury, if you get careless in handling.
I tried 30 Lbs. of media and found that that was too much. The cleaning was not any better and the media was packed tight in the cases (223 Rem.).
Six hour run, compared to model B the results are:
amount of noise x4
amount of dirty water X4
amount of soap did not measure but estimated X4
amount of brass cleaned X4
run time same
unload time X4
load time X2
I sent Mark a 3000 RPM motor to turn his standard Model b into the high speed Model b, perhaps we can get some more cleaning reports from him.
Good Shooting!
Ron
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