"Tim Wescott" wrote in message
...
We have this big ol' pile of horse manure out back, which we can't spread
out in the pasture because it is full of rocks that are just about exactly
the right size for causing problems with horses feet (according to SWMBO,
at least). The sizes range from sand to 3-4 inches.

Since clean, rock-free horse manure is pretty easy to get around here, I'm
assuming I cannot give it away. So I'd like to build a sifter for the
stuff, to separate the good rocks from the good fertilizer.

I'm considering making a big drum with a 1/4" screen, rotating it with
either an electric motor or a Vibration & Stratton engine. I'll load in
dirty manure in one end with my loader, get clean manure out the bottom,
and occasionally dump slightly odiferous rocks out of the drum.

What I need to know is:

1. Is this a good approach?
1a. How do quarries sift their rock?
1b. Is there something out there that I can get my hands on that does
this task? It doesn't have to look like what I think will work, it just
needs to separate the rock from the crap.
2. Anyone have any suggestions for screen? I'm considering expanded
metal, but it looks like I can't get really thick expanded metal with 1/4"
holes. I'm afraid that the 18 gauge that it seems I can get will wear too
quickly, particularly if I get a big rock bonking around in there.

I would spread it and then run through the area with a Harley rake if you
have a skid steer or drag it with a York rake behind a tractor after it
dries. Any material that is sticky or wet, similar to compost, is going to
have a tendency to bridge and clog . If time is no object, maybe set a few
bucketfuls at a time on top of a suitable horizontal screen and let the rain
wash it through.