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Posted in response to Large homemade tumblers- anybody seen one? from Mike H on February 19, 2010 at 08:38:32:

Re: Large homemade tumblers- anybody seen one?

Remember Mike: most anything can be made larger or smaller, providing the concept is sound. Some variations or adaptations might have to be taken into consideration; but for the most part, smaller can usually be made larger. With the plans listed below, I would probably use a 55 gallon drum to knock of all the large sharp corners, go through all the stock you prefer to tumble at this relative size, and then start over, like a regular tumbler; reducing the grit size and etc. Here's an example I found online. http://tomaszewski.net/Kreigh/Minerals/Homemade.shtml His plan calls for a small barrel. Modify the plans to enlarge foe a 55 gallon drum, and a motor that can how many pounds of rock you can fit into it.


Make Your Own Open Top Rock Tumbler

Above I covered the traditional tumbler that has the barrel rolling on its side laying on shafts that support and drive it. This posting will cover the more difficult 45 degree tumbler. With this tumbler you can use an open top barrel making it great for schoolrooms (add some Plexiglas guards over the moving parts for safety in a classroom).

In this type of tumbler the shaft is attached to the bottom center of the barrel, and the barrel and shaft as a unit are tipped to a 45 degree angle, shaft down - open top of barrel up. The shaft is supported by a base block. The motor shaft has a small wheel on its end that rides on the bottom outside edge of the barrel to drive it. It can be made to spin faster by moving the drive wheel closer to the center of the barrel bottom or enlarging the size of the driving wheel.

The barrel and shaft are really a single unit. For a small tumbler you could use a large plumber's helper (plunger) - the type that is shaped like a wine glass instead of a cereal bowl. For a big tumbler a steel shaft with a floor flange on one end, a circular plate attached to the floor flange, and the barrel base attached to the top of the plate. Fastening a holder (large bucket?) container that your bucket just fits into on the top of the plate is an easy solution and makes the barrel removable for cleaning. The plate will be used as the drive surface. For the plunger you need a washer shaped plate and a floor flange that you can slide down the handle and fasten on. It is important that the drive plate be at right angles to the drive shaft and be rigidly attached (and thick enough not to flex) - plywood works.

Get a motor, wire, plug, and switch so you can hook it up, plug it in, and start or stop the motor. You need to be able to fasten a small wheel to the end of the shaft. Alternately, the wheel can be on one end of another shaft that is pulley/belt driven by the motor - and this actually helps since most motors you will find are probably a little fast unless your drive plate is larger than the barrel by a few inches. The drive wheel and the plate make a pulley system, so you can figure a reasonable speed ahead of time and make your drive plate large enough, or reduce the speed with pulleys by using drive from the second shaft.

The end of the barrel shaft is going to support weight and needs a thrust bearing. The top end of the shaft can use a regular bearing. If you are making the plunger type you might be able to do without a bearing if you drop a large marble or ball bearing in the support hole before putting in the shaft (and lubricate the shaft with bar soap). Make sure the barrel shaft is long enough to support the barrel weight; its a lever and probably should be near the height of the barrel.

We're going to need a large cube of wood. Your shaft will need to be about the length of the diagonal of a face. Stacked 4x4s with side bracing can be used in place of a block of wood. For something large, you might want to use a concrete base with a 4x4 embedded where the shaft will go. This base block will be fastened to one half of a board twice as long as it is wide (and at least as wide as the support block). The barrel will hang over the part of the base not covered by the block, which is there to keep the whole thing from tipping over.

With the base assembled, the shaft/barrel assembled, and a motor we're ready to put it together. One side of the cube rises up from the base at its center. At the top center of this edge we're going to drill a hole 45 degrees downwards to the center of the bottom edge that is at the outside of the base. Don't drill all the way thru if making a plunger tumbler and make sure the shaft just fits the hole; otherwise drill a hole large enough for the shaft, mount the bearings (thrust bearing at the bottom, regular bearing at the top), and line them up with the shaft. The drive plate should be a little ways above the block when the shaft is inserted. If you are not using bearings, make sure the hole is smooth and closely fits the shaft - drill a smaller pilot hole first.

Mount the motor so that the wheel on the end of the drive shaft pushes up against the bottom of the drive plate at its edge. The axis of the drive shaft on the motor should point at the center of the barrel shaft. As the drive wheel turns, friction against the base plate makes it turn.

Hook up the motor, put on the barrel, and start tumbling. Don't fill your barrel too full or it will splash out the top. If the barrel has a small neck, like a wide mouth mason jar, that is a good thing.

And if you want to see one of these built by Bruce Mitchell on an industrial scale, check out the monster tumbler at Machine Intelligence.

I've never posted a picture before, but I'll see what I can do.


Mike Gramlich

From Mike Gramlich - February 21, 2010 at 18:21:49
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