As far as I can tell, a tumbler is just a canister that rotates with rock and grit inside. How hard can that be? I've managed to begin construction on one for less than $20. They typically cost around $150. Mine has the advantage of being a bit of home schooling in the subject of mechanical engineering for my kids.
The tumbler design is simple. An electric motor will turn a shaft which will rotate a coffee can mounted on furniture wheels. The motor's speed will be controlled by a light switch dimmer. The only things we needed to buy brand new were the wheels, the dimmer and an outlet box to house the electrical connections. Total cost: about $12. For the motor, I went to a thrift store and scrounged around until I found an old Black&Decker corded drill. Cost: about $4. Perfect!
Once I had figured out how to open it, I had my son take it apart. At this juncture in the project, I hit upon a real brain wave. Household electronics can be picked up at estate sales and thrift stores for next to nothing. Most people are afraid to take their appliances and tools apart because they don't know what's in there and they're afraid they'll never get them back together. I want my kids to grow up without that fear.
I'm going to start buying these and handing them to my son to be totally dismantled and reconstructed after he does his best at explaining how they work. If they never work again after dismantling, the cost will be trivial compared to the education and confidence he will gain. As my daughter grows older, I'll do the same for her. My kids aren't home schooled, but modern schools miss parts of their education like this. Not many kids take shop classes any more.
Enough about home schooling. Back to the project.
My biggest technical hurdle was the drive shaft. I don't know how to weld and I couldn't figure out how to connect the coffee can to the shaft. Finding the drill was a stroke of luck in more ways than one. While at Home Depot looking for the wheels and the dimmer, I came across a turnbuckle. That solved all my problems. By using a spade bit in the drill, I could put the spade portion of the bit into the turnbuckle after having drilled the turnbuckle through the coffee can. Voila! I had the connection between the motor and the can.
We're at a standstill right now because the drill needs a couple of pieces. A pair of connectors inside the drill had worn out. I'll be hitting the local DeWalt repair place for the parts tomorrow. I'm sure they'll think me quite mad. That just adds to the fun!
Update: The HCCRT Mark I is done. See the results and definition of the acronym at this post, complete with YouTube video.
For more educational posts, visit the Carnival of Home Schooling. For more posts on saving money, please stop by the Festival of Frugality.