Periodically these can be found on Ebay. There is a guy that makes them up
quite a bit cheaper. 3 low speed gear motors on hinged springloaded arms.
The cups are mostly made up of pvc. You have to have a mechanism to drip
grit and water on them. Seems like the gear motors were around 60 rpm or so,
and some guys were using clock motors to drive a twisted piece of flat metal
that ran horizontally through a container. The grit would get on this like a
screw and slow sprinkle out the far side. Pretty nifty, I almost made on
myself. I think there are some yahoo groups pertaining to what you are after
if memory serves me correctly.
"Charles Spitzer" wrote in message
...

"Ignoramus32374" wrote in message
...
On Fri, 20 May 2005 17:33:25 GMT, Gunner
wrote:
He takes a chunk of rock, sorta kinda knocks the corners off with a
saw, and then turns them into highly polished spheres using a wierd
looking but really neat grinding arraingment of motorized cups and
grinding media.

Like these

http://www.therockshed.com/spheres.html

That's most interesting. I would like to learn a bit more about that
process...

i

using one of these
http://www.covington-engineering.com...e_machines.htm

regards,
charlie
http://glassartists.org/chaniarts

Snip
It took me a while to work out the motor speed as I
sold my tachometer when I needed some cash. So I put a sticky label on
the shaft and held a pencil against it so it made a clicking noise. Then
I recorded the sound on the computer and looked at the waveform, and it
turns out the motor runs at 1425 rpm. I took a picture of the motor and
put it online:


That's ingenious!

On Fri, 20 May 2005 17:39:33 +0000 (UTC), Christopher Tidy
wrote:

Gunner wrote:
On Fri, 20 May 2005 16:26:31 +0000 (UTC), Christopher Tidy
wrote:


I woke up in the night and it occurred to me that a stone
polisher (or rock tumbler as some people call them) would
make a great home shop project.

I figure I can make a drum (probably cube-shaped) from
welded 1/4" plate. The drive is going to be more of a
challenge (I don't have a great deal of cash to spend on
this).

I remember seeing plans for a DIY rock tumbler many, many years ago in my
childhood subscription to Popular Mechanics. But there's a huge price
difference between consumer commodity products of back then and of today. I
strongly suspect that you could buy a decent-quality used one off Ebay (or a
cheap new one for $20 from Harbor Freight) for the same amount of money --
or less -- than building one yourself (by the time you factor in the costs
of all the materials, parts, and fasteners -- not to mention your time and
labor). Unless you are really looking for a new home project to undertake.

If you do decide to build one yourself, you won't want to make the drum out
of steel (or any other metal) and you certainly don't want it to be a cube:

1. Steel is too hard and would cause the stones to fracture and scratch.
2. Aluminum also would not provide enough cushioning (and might get embedded
with abrasive).
3. Even if breaking and scratching is not an issue, a metal drum would be
very noisy.
4. A cube shape is too "angular" a geometry: the stones would tumble too
violently and fracture or scratch.

Ideally, what you want is a rubber drum that has an octagonal profile. The
stones should be rolling and sliding against each other (not dropping and
crashing), with the octagonal sides providing just enough tumbling action.
If you must make a drum out of metal, you'll probably want to glue rubber
sheet all over the inside. (Of course, then you have to worry about abrasive
getting trapped in the seams. Remember, you will need to progress from
course to medium to fine to polish.)

Even if I were going to make my own tumbler base station, I'd probably still
buy the hard rubber drum.

Btw, tumblers can also be used for deburring, derusting, and cleaning small
metal parts.

Thanks for suggesting eBay. I just had a look at a few machines on
there. The way in which the drum is supported on smaller rollers solves
the gearing problem rather neatly.

Chris


A local gentleman uses a 55 gallon drum with flanges welded inside to
provide a tumbling action, sprayed with bed liner for longevity. He
has it attached to the counterweight arms of a pumping unit here in
the oil fields. He can tumble a **** load of rocks at one time, for
little or no money G

Rather impressive how well it works.

Nice idea. Do you have any pictures of the contraption? I'd love to see.

Chris


Ill see if he has a run going this weekend and take some pictures.

He also makes spheres using home made Stuff.

Thanks. Would be fascinating to see. What kind of spheres does he make?

Chris


He takes a chunk of rock, sorta kinda knocks the corners off with a
saw, and then turns them into highly polished spheres using a wierd
looking but really neat grinding arraingment of motorized cups and
grinding media.

Like these

http://www.therockshed.com/spheres.html

Very neat. Must have taken some ingenuity to build a machine that can
grind those.

Chris

http://www.cyberrockhound.com/spheremachine.htm
http://www.cyberrockhound.com/images...re_machine.jpg

They are actually not that hard to do. Shrug

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

Gunner wrote:

On Fri, 20 May 2005 16:26:31 +0000 (UTC), Christopher Tidy
wrote:


I woke up in the night and it occurred to me that a stone
polisher (or rock tumbler as some people call them) would
make a great home shop project.

I figure I can make a drum (probably cube-shaped) from
welded 1/4" plate. The drive is going to be more of a
challenge (I don't have a great deal of cash to spend on
this).

I remember seeing plans for a DIY rock tumbler many, many years ago in my
childhood subscription to Popular Mechanics. But there's a huge price
difference between consumer commodity products of back then and of today. I
strongly suspect that you could buy a decent-quality used one off Ebay (or a
cheap new one for $20 from Harbor Freight) for the same amount of money --
or less -- than building one yourself (by the time you factor in the costs
of all the materials, parts, and fasteners -- not to mention your time and
labor). Unless you are really looking for a new home project to undertake.

If you do decide to build one yourself, you won't want to make the drum out
of steel (or any other metal) and you certainly don't want it to be a cube:

1. Steel is too hard and would cause the stones to fracture and scratch.
2. Aluminum also would not provide enough cushioning (and might get embedded
with abrasive).
3. Even if breaking and scratching is not an issue, a metal drum would be
very noisy.
4. A cube shape is too "angular" a geometry: the stones would tumble too
violently and fracture or scratch.

Ideally, what you want is a rubber drum that has an octagonal profile. The
stones should be rolling and sliding against each other (not dropping and
crashing), with the octagonal sides providing just enough tumbling action.
If you must make a drum out of metal, you'll probably want to glue rubber
sheet all over the inside. (Of course, then you have to worry about abrasive
getting trapped in the seams. Remember, you will need to progress from
course to medium to fine to polish.)

Even if I were going to make my own tumbler base station, I'd probably still
buy the hard rubber drum.

Btw, tumblers can also be used for deburring, derusting, and cleaning small
metal parts.

Thanks for suggesting eBay. I just had a look at a few machines on
there. The way in which the drum is supported on smaller rollers solves
the gearing problem rather neatly.

Chris


A local gentleman uses a 55 gallon drum with flanges welded inside to
provide a tumbling action, sprayed with bed liner for longevity. He
has it attached to the counterweight arms of a pumping unit here in
the oil fields. He can tumble a **** load of rocks at one time, for
little or no money G

Rather impressive how well it works.

Nice idea. Do you have any pictures of the contraption? I'd love to see.

Chris


Ill see if he has a run going this weekend and take some pictures.

He also makes spheres using home made Stuff.

Thanks. Would be fascinating to see. What kind of spheres does he make?

Chris


He takes a chunk of rock, sorta kinda knocks the corners off with a
saw, and then turns them into highly polished spheres using a wierd
looking but really neat grinding arraingment of motorized cups and
grinding media.

Like these

http://www.therockshed.com/spheres.html

Gunner

"Pax Americana is a philosophy. Hardly an empire.
Making sure other people play nice and dont kill each other (and us)
off in job lots is hardly empire building, particularly when you give
them self determination under "play nice" rules.

Think of it as having your older brother knock the **** out of you
for torturing the cat." Gunner
The term is PREFORM the chunk of rock. The two 'cups' of cast iron turn
against each other, keeping the rock between - once cranked together. If
the chunk is caught it might cut a ring. So one must pay attention and aid
the auto movement of the chunk. The cups typically crank in and out on threaded shafts
to match the diameter of the work. The one I used didn't change the angle, but
I figure large balls might require larger cups and different angles...

I suspect a Single cut pointing up can be used for hand use - a cup lap is what
it is. But that is hand work then... :-)

Martin

--
Martin Eastburn
@ home at Lion's Lair with our computer lionslair at consolidated dot net
NRA LOH, NRA Life
NRA Second Amendment Task Force Charter Founder

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