Hi all, I’ve lurked for free for a long time, finally signing up so I can share this.
I saw someone on youtube present a replacement barrel for their rotary tumbler made out of pvc pipe, but they didn’t get into specifics about what or how. I couldn’t find a direct answer, so I set out to sort it out myself. (Also the day job has suddenly decided they want my hobby jewelry skills for a project, so work paid for the experiments )
But the point is, this is how I’ve answered the problem. There could be improvements! This is not time-tested BUT it did end up costing only about $10 per barrel.
I have a single barrel Chicago Electric rotary tumbler from Harbor Freight. The barrel space is enclosed on each side, so the length of the barrel is limited.
I had trouble finding 4" PVC pipe at my local Home Depot, but discovered I could order a 2 foot length of “Charlotte Pipe” via their website for $21.36. This is enough to get 4 barrels out of, even with some less-than-totally-precise cutting. You can cut this pipe with just about anything: meiter saw, hand saw, twine supposedly, probably a dull kitchen knife if you’re dedicated. It does make a massive pile of plastic snow though, so do it outside or in a space you can clean.
Total length of your barrel pieces will depend on the caps and the length your tumbler can handle. I cut my length to 4.5", and with the smallest caps they just barely fit the single-barrel tumbler.
The easiest and cheapest way to cap these barrels is with “knockout test caps” for 4" diameter pipes. They were $0.78 each when I was shopping. They fit inside the end of the pipe very snuggly. I had gutter caulking around from a previous project, and used that to permanently attach -and water proof- a knockout cap to the bottom of each barrel. I suspect regular old bathroom caulk would work, or any number of other water-resistant and hard-drying substances. The cap was very nearly water tight on its own, only had slow drip leaks without the sealer.
I also chose to use knockout caps for the tops of each barrel. This is not entirely ergonomic, as the caps are meant to be smacked out from the inside, so there isn’t a convenient handle or anything on the outside. But I was already using a metal washer to pry open the lid of the original rubber barrel, and that continues to work fine for these.
To improve waterproofing at the top, I found a “Sink Strainer Washer” which is a very large rubber gasket. I had to cut out the inside a bit to fit over the knockout cap, but for $2.40 each it seemed a reasonable trade off.
The last touch I added was some grip tape to the outside of the barrel, to help the tumbler grab it since the pipe was fairly smooth. Grip tape of the sort used to add traction to steps is fairly cheap on Amazon and in hardware stores ($7-10 for a roll?) though I imagine there are lots of other options to add a little grip to the outside.
I did experiment with a different cap, a “Mechanical Test Plug”. This is a big red cap with a wingnut on the top, and a gasket around the side. When you tighten the wingnut, the gasket expands, so it caps and waterproofs the barrel in one go and is more ergonomic than the knockout caps. Unfortunately its also much bigger: the wingnut sticks out about an inch beyond the barrel, and the plug takes up an inch of the interior. When the barrel size is limited such as for my tumbler, this results in a really small tumbling space.
Also its almost $10 on its own.
So, 4 new barrels for around $40 total, if you’re just using knockouts and washers. I don’t have to swap dry media around, and I don’t have to worry about black rubber breaking down on anything.
Again, I haven’t run these more than a a few days, this is not backed by “years of experience” or anything. But this is the answer I was searching for several weeks ago, and couldn’t find! So I thought I’d share.