Machining a shaft for a redneck style rock tumbler

I would also like to make a rock tumbler, like another poster. My plan is as follows.

I will use a used tire as the rotating vessel. I grew fond of used tires after my generator project.

The tire will be bolted to a large plywood ring that will have a hole larger than the internal diameter of the tire, just enough to go a little bit over the widest point of the tire.

There will be a board screwed to plywood and serving as a "diameter" of the plywood ring.

There is going to be a horizontal shaft, mounted in bearings. (see below). The shaft will be made either from a steel pipe nipple, with flanges on both ends, or from a solid 3/4" diameter piece that I already own. On one side, a sprocket will be bolted to the flange. On another, there will be an adaptre plate to attach the "diameter" board securely, but it will be removable for cleaning purposes.

The sprocket will connect via chain to a 3/4 HP 60 RPM gearmotor with a keyed shaft and another (smaller) sprocket. My friend will give me that gearmotor (I gave it to him 3 years ago, but he did not use it).

My expense will be sprockets, nipples and the shaft (maybe).

My question is about bearings. I have a variety of bearings, about

100-150 lbs of bearings. I have some sealed bearings, some needle bearings 1 1/8" ID. Huge stuff for tractors and tanks, tiny ones etc.

I also have something I like, spherical bearings 3/4" ID. They are not pillow blocks because they do not have a "base" to be screwed to something. Nevertheless, they are nice because they can survive misalignment. (I also have some 1/2" ID spherical ones, but I need a bigger shaft).

My misgiving about them is that I am not sure what shaft to use. I have a solid steel 3/4" shaft. But how would I mount a sprocket on one side, and a plate holding the wheel, on another? I can easily drill and tap a coaxial hole on both sides. But I have great doubts that the bolt's tension would be enough to hold it during days of operation. I do not have a welder.

I could try to thread both ends on my lathe, but I expect this to become a pathetic failure. And I do not think that there will be a suitable NPT flange at my home improvement store (although I am not sure).

I can probably drill smaller parallel holes and tap them and put in little 8-24 screws or some such.

i
Reply to
Ignoramus32374
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"Ignoramus32374" wrote: (clip) I will use a used tire as the rotating vessel. (clip) ^^^^^^^^^^^^^^ Would you be interested in a simpler, totally different way to use a tire? Mount a V-belt pulley your gearmotor shaft, and just hang the tire on the pulley by one of the beads. By sizing the pulley properly, you can get RPM in a suitable range. If the tire hangs too "slanty" by a single bead, you can always use two pulleys.

Reply to
Leo Lichtman

I am sorry, can you explain a little bit more in detail? I do not understand what you are proposing. I am quite open minded.

i
Reply to
Ignoramus32374

I'd say the ouside of a tire might make a good surface to run directly on a motor shaft of some sort, letting you skip all the gears and nonsense. Why does this need to complicated?

Reply to
Cydrome Leader

yhgdc "Ignoramus32374" wrote: (clip) can you explain a little bit more in detail? (clip) ^^^^^^^^^^^^ Sure. You have a horizontal shaft coming out of the gearmotor, turning 60 RPM. I visualize the tire hanging vertically from this shaft, with rocks inside, at the bottom. To get the RPM you want, you have a couple of V-belt pulleys on the shaft, turning at 60 RPM. Lets say you want the tire to turn at 20 RPM, and the tire fits a 15" rim. If the v-belt pulleys are 5" diameter, you will have a 3-to-1 reduction to give you 20 RPM. The smallelopr you make the pulleys, the slower the tire will turn. 65 The weight of the tire and rocks will create the contact pressure for the pulleys to drive the tire beads.

If I have managed to make this too confusing, feel free to ask more questions.

Reply to
Leo Lichtman

Or he could get his paws on a kiddie bike with the 12" wheels and a long chunk of all-thread. The axles in those wheels are just short bits of all-thread anyway. Remove the spokes and rims, keeping just the hubs. Screw them along the length of the shaft until they're where the beads will ride on them. One will come with a sprocket pre-installed. If he goes with a multi-speed bike instead of a single-speed he could even adjust the rpms by moving to different sprockets. Could probably repurpose the leftover frame to support the whole mess.

Reply to
B.B.

Damn Leo..thats exactly what I was thinking. Great minds DO think alike.

I would suggest a pvc plug and close nipple and pipe cap in the sidewall for fluid drainage though.

Gunner

"Considering the events of recent years, the world has a long way to go to regain its credibility and reputation with the US." unknown

Reply to
Gunner

That's a smart idea Leo. I'd like to see a tumbler built like that.

Chris

Reply to
Christopher Tidy

Good question. In my opinion, 60 rpm is too much for a used tire.

i
Reply to
Ignoramus14511

Leo, I like this idea. The pulleys will have to be big, otherwise the belt will slip. I will think about it.

i
Reply to
Ignoramus14511

On 21 May 2005 12:55:38 GMT, the inscrutable Ignoramus14511 spake:

Let's see, 60rpm too much? Take your 15" tire (Mine are 28" tall.)

1 mile is 5,280' or 63,360". One rev is 88", 60mph is 1mpm, so dividing 63,360 by 88 gives us 720rpm at 60mph. I think a used tire (even a 12-incher) can take that beating, Iggy.

But 60rpm would likely stick the rocks and all else to the drum, not allowing any movement or tumbling. Speed probably has to be 30rpm or less, lower on larger diameters due to centrifugal forces.

(Oops, I meant to say "centripetal forces." Sorry. ;)

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Reply to
Larry Jaques

Well, the actual systems in use at the rock shop were a bit different, but still a lot simpler than what's been talked about here previously. One problem with what you describe above might be excessive grit transfer to the drive system, but it's heading the right direction.

A more detailed description of a system which was in use for decades at a rock shop near where I grew up, and may yet be in use (I haven't visited recently).

A motor drives one, or better two shafts through some sort of chain or belt or gear reduction. If only one is driven, the other is an idler. The shafts are as long as you like, and may have intermediate bearings or support wheels (psuedo-bearings) as needed. The bearings should be well-sealed, and you might want to arrange covers for them, too. You may want to texture the shafts a bit between bearings, but probably don't need to. The shafts should not be too small, at least on the tire-contact area. 2" would be a lot better than 5/8", though I can't say where, exactly, it would stop working. 1-1/2" strikes me as about what the rock shop used, might have been pipe with smaller shafts welded or pressed into the ends for the bearings.

On the shafts sit one or more tires. Just tires, no seals, no plywood covers. I forget, there might have been some arrangement to help keep any drips inside the tire, but if so, it was a fixed arrangement (like a reverse fender), not something attached to the turning tire. The turning of the shaft(s) turns the tire(s). I vaguely recall that there might be a particular SFPM range that works pretty well for this (rock tumbling gets a lot of its science from ball-milling), so the same set of shafts can turn larger or smaller tires at the appropriate speed (same SFPM, different RPM for each size tire). Inside the tires are rocks and grit and water. In multi-tire systems, those can be different grits in each tire. If you want to check progress, you reach in and pull out a handful of rocks. If the rocks (or if you care to sort them, some of the rocks) are ready for the next grit, you wash them carefully and move them to the tire with the next grit.

Reply to
Ecnerwal

There is no belt. The tire rides on the pulley.

(top posted for your convenience) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Keep the whole world singing . . . . DanG (remove the sevens) snipped-for-privacy@7cox.net

"Ignoramus14511" wrote in message news:d6nb5m$o3t$ snipped-for-privacy@pita.alt.net...

Reply to
DanG

That's the idea I like..

John

Reply to
JohnM

Even simpler yet, a 5 gallon bucket sitting at a 45 degree angle. Check this link, but boy is it slow.

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Reply to
Grady

Actually, after some thinking, this is precisely the way I will do it. I decided to avoid sprockets, etc. The buckets will be easily replaceable, it will be more portable and even cheaper to build.

i

Reply to
Ignoramus14511

Surely it would, but would it do the actual job of polishing the stones, properly?

Exactly.

i

Reply to
Ignoramus14511

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