Tuesday, June 4, 2013

Redemption! - A.K.A. Rotary Tumbler Part II

completed tumbler - success!

A few months ago I posted about a failed attempt to make a rotary tumbler.  Dejected, I left the useless pile of parts where they lay and moved on to other projects.  This is part two of the saga where I build one that actually works.

One day in a desperate attempt to find more room in my garage, I decided to throw out a bunch of stuff.  One thing on the chopping block was a VITAMASTER belt massager.  Like a lot of my stuff...cool but ultimately useless.
vitamaster belt massager

I picked it up at a flea market years ago because I thought it was retro cool.  It was fun in college watching curious girls jiggle on it, but now it's just one more thing to draw blood from my four year old.  So I cued it up for the trash but soon had second thoughts.  "Heavy gauge steel pipe, I could use that.  Same with the base.  Cool enclosure I could repurpose.  Electric motor..."  Hey, wait a minute...  I opened it up and what was inside but a 1050 rpm, 1/10 HP electric motor.  Maybe this was just what I needed to salvage my failed rock tumbler.  Just a bit more powerful than the 1/150 HP of the original motor and three times more powerful than the motor in the Thumler model B that served as the inspiration for this project.  I did some quick calculations to check the final drum speed with this motor and realized that it just might work.

can I fit this...
...into this?

Go back to my original post to see the construction of the base.  Here are my revised gearing calculations with the new motor.  My drum is about 6 27/32" in diameter.  I want it to spin at 40 rpm.  My roller shafts are 0.62" in diameter (at the rubber bushings).

6.84375" (40 rpm) = 0.62" (X rpm)

Solving for X tells me I need my rollers to spin at 441.5 rpm.  This motor is rated at 1050 rpm.  If I divide my roller rpm by my motor rpm I find I need a reduction ration of 0.42.  Last time I used a 25 tooth gear.  I knew I needed a larger motor gear this time to compensate for the slower motor speed.  Luckily I had a 30 tooth gear.  Dividing the 30 tooth motor gear by the 72 tooth roller gear gives a reduction ratio of 0.42, just what I was looking for.  Check the math for the expected drum speed:

30 teeth (1050 rpm) = 72 teeth (X rpm)
= 437.5 rpm shaft speed

0.62" (437.5 rpm) = 6.84375" (X rpm)
39.6 rpm drum speed

Close enough!  Next I removed the motor from the massager and did a quick check to be sure it would fit into the tumbler base.  It looked good so I lined everything up, marked for the screw holes, and drilled.  Then I bored out the motor gear and fit it on the motor shaft with a set screw.  Luckily the drive belt still fit.  Finally I soldered the wires to the switch and power cord.

new motor in place

I filled the drum with 5 pounds of stainless pins and as much water as it could hold and placed it on the tumbler.  Nervously I flipped the switch...The tumbler sprang to life spinning the drum without any signs of hesitation.  Looks like I had the power I needed.  But...the stainless pins sat lifeless in the bottom of the drum as it spun around.  My rotary tumbler was all rotary and no tumble!  Obviously it wasn't going to polish anything that way.  Looking back at the original design, I realized that the Thumler drum is hexagonal.  The sides of the hexagon help to flip the contents as the drum spins.  My round drum simply spun around the contents.  I needed something in the drum to agitate everything.

I went to Home Depot and walked the isles looking for something I could add into the jar to act as flippers.  I found some plastic channel meant to go between pieces of wall paneling.  There was an extra piece on the channel that I didn't need so I scored it with a utility knife and snapped it off.

original channel

I cut the channel down to size and made a few relief cuts so that it would conform to the shape of the jar.  I decided to secure it to the jar with pop rivets.  I melted holes through the jar and channel with an old soldering iron.  Then I put a layer of silicone caulk on the channel to prevent leaks before riveting it in place.  I backed up the rivets with washers to keep from pulling the rivets through the soft plastic.

channel in place

inside view

Another problem that I had with the jar was a slight leak around the lid of the jar.  I tried several solutions to seal it, even including molding my own silicone lid liner.  It still leaked.  Eventually I came across a foam mat that I had laying around.  I cut it to size, placed it inside the lid, and voila!  No more leaks.  The final problem was that the rollers slipped on the jar if they got even a little wet.  I added some 3M grip tape around the outside of the jar; not very elegant but it worked.

seal for lid of jar

Finally a rotary tumbler that works!  Now to find out if it actually polishes anything...  In a previous post I tested a Harbor Freight ultrasonic cleaner for cleaning dirty brass rifle and pistol cases.  It worked pretty well on recently fired brass that wasn't too dirty.  But it came up a little short for cleaning really grungy cases.  I grabbed a handful of very dirty .45 ACP pistol cases and some fired and tarnished military surplus .30-06 and threw them in.  I added two tablespoons of Dawn dish detergent, 1/4 teaspoon of Lemi Shine, and one gallon of water.  Then I ran the tumbler for four hours.

Oooooh, shiny!
(52 rifle and 86 pistol cases if you were wondering)

Same batch of cases, cleaned ones on top (duh).

Doesn't get much dirtier than this.  No problem for my tumbler.

even the primer pockets got cleaned

inside is a little discolored but there is absolutely no powder residue

Wow!  The results were surprising.  The cases were not only clean inside and out, but shiny too.  Primer pockets, deep inside the .30-06 cases...spotless.  It even removed the red marking paint that was on the bottom of the .45 cases that the ultrasonic cleaning couldn't budge.  If it can clean these cases, it should be able to handle anything.  This will definitely be how I clean my brass from now on.  Well it was a long road, but I am glad I finally got this project finished.  My tumbler seems to work every bit as well as the Thumler and best of all it was built entirely from scrap; didn't cost me a penny.


  1. I admire your polished brass. "Curious girls jiggle/ draw blood from my four year old" line was the most poetic ever written on this blog so far. 4 stars.

  2. wait, you mean my weight loss machine is no more?!!!! : (