I am starting on a project to mix sand which
is really a modified ball mill. The design will be a rotating steel
drum which will hold 75 lbs of sand or so. Heavy spheres will be added
to the sand to help crush the chunks and get some mulling action.
I am collecting materials and working out the design. I have attached
some pics of what I have so far.
I found this gear reduced motor on ebay for $40!
I am planning to use several of these skate wheels to support the
barrel at a 30 deg angle from the horizontal. That should retain the
sand?
I made this pattern to cast a flange which will attach to the bottom
of the barrel. This will have a core and will fit over the motor output
shaft.
Best of all, I found this 30 gal barrel for $4.99
The coolest thing about this is the information stenciled on the
barrel. I couldn't believe it. If you can't read it, it reads Tracker Infrared Guided Missile!
Too bad it was empty, right? I originally planned to paint the barrel
silver but I don't think I can do that. I will just touch up the Army
green.
I am not sure what size and weight spheres to use. Any advice or conjecture
welcome. I may be able to find some shot puts. I do not have the ability
to cast an iron sphere. I have a source for hollow steel spheres which
could be filled with sand or lead shot. A bowling ball is too big
for this drum. I may try a metal cylinder like a section of pipe to
see how that moves. I may need to add small blades to the drum walls.
After a few TIG welds...
The drum spins very freely on the skate wheels. I would use them
again in other applications. The only problem I see is that the drum
is not completely round. I can work around that. I have this tilted
at about a 30 deg angle to retain the sand. I plan to put wheels on
the front so it will be kind of like a wheel barrow when I move it.
I casted the flange to drive the barrel and the motor mount plate.
Here is the flange after machining
Motor mount
Needs wheels, and paint.
I received these today (12/11/2008). I put a standard measuring
scale in the image. The larger sphere is 6" and the smaller is
3" I was impressed that these are very heavy guage steel.
I decided to fill them with sand for an intermediate density
The larger one weighs 8.5 lbs filled and the smaller about 2 lbs.
I will be trying them with sand next time I cast. Hopefully this weekend.
I searched out and found the owners manual for my mixer motor
and gearbox. It is designed to mix up to 230# of cement in a drum
at a 30 deg angle with only two other wheels supporting the middle
of the drum. I feel good about its robustness. I have decided to let
the gear box support one end of the drum by itself and use wheels
only at the other end. This will minimize geometry issues with the
drum being out of round.
I mulled 50# of sand today using the 6" round sphere filled with
sand. It worked great! In about 3 min all of the large chunks were
broken up. In about 5 min it was pretty much ready to reuse. The 3"
sphere was worthless.
I had to scrape a little of the sand off the walls during operation.
Not alot of work really but it would likely benefit from a plough.
I think I have a plan to add one that will ride at the top.
I empty the drum by pulling the pin out of the flange and lifting
it off the machine. I made a new quick release pin which I really
like. I have attached some pics to give people some ideas.
I used 1/2" stainless rod and about 6 " of stainless
TIG filler rod.
I will be mixing some more sand this week and I will play with a plough
design then. I may try it with some petrobond also.
COMPLETION:
I have some comments on this design for anyone who might want to
build one like this.
First the one major drawback that I see:
This device uses an 6", 8lb ball which obviously does not create alot
of compressive force for professional mulling action. It works great
with greensand . The barrel size will affect the size of the ball
that gives the best action.
There are several good points to this design:
It is very simple to build.
There are no bearings exposed to sand and therefore prone to failure.
It is very easy to load and unload by tilting it.
It is relatively safe to stick your hand into it while it is in operation.
(I would never do that with a regular muller.)
I built this whole thing for about $100 including the motor.
I am making magnetic blades to attach to the inside so it can double
as a cement mixer. It could also double as a ball mill very easily.
