Separator for pulverized sod

[kfab06]

 Have built a hammer mill that will pulverize sod in place on the ground. Would like to find a way to pick up the pulverized material and separate out the grass, rocks and other debris and deposit the soil back on the ground where it was picked up. I have seen vacuum trucks for removing gravel from ballasted roofs, that have cyclonic type collectors where the gravel drops out the bottom of the collector into a truck or roll-off container.
So... with a larger vacuum device - say an 8 hp. lawn vacuum, and a scaled up version of the Thien unit, would it be possible to vacuum up the pulverized sod at the hammermill and have it drop out the bottom of the collector bin onto a series of vibrating sieves to separate it, collect the waste material and allow the dirt to fall back through the sieve to the ground?

[phil (admin)]

Wow.

I have no idea.

I suspect it wouldn't work.

[alan m]

i dont think it would work. a thien(or other ) seperater is designed to be as close to 100% efficient as possable. that would seperate out all the dirt adn grass etc and only leave the air clean.
i think i would think along the lines of decreasing sized vibrating seives. adn use air currents to blow the grass and other  light particals up into a hopper.

you could also use a large steel drum seaive (like the inside of a washing machine but bigger) . the rocks should roll around as the drum turns, helping break up the clumps . colect the rocks at the end. air again might seperate the grass

[WayTooLate]

I wouldn't give up so quick... 

Being able to suck 'everything' up and then drop it into separating sieves is a great place to start. 

All of the current Separator designs assume that the debris will not impinge the Separator itself (other than eventually scratching the plexiglas exterior ring).  Your application will have to be seriously beefy to handle rocks and 'hard' debris. 

While very different than our 'sawdust' designs, I think you could scale it to work - with a fair amount of Trial-and-Error attempts.  You have one major advantage - the mass differential between separating gravel from air is MUCH easier than separating sawdust.  I think your design challenges will be: 

• Determining how big of 'rocks/gravel' you will pull through the system.
• What pre-screening you will use to prevent 'boulders' from entering. 
• What 'compromise' of separation you will accept to let grass or other 'lightweight' debris to pass through to allow 'rocks' to drop out.

I think that Phil's design has many applications beyond what we originally needed in our woodworking shops. 
I will look forward to hearing how your attempts are succeeding. 

If you pursue it, I'd look forward to sharing some additional ideas with you.
- Jim

[Peter]

When you think about it, a Thien separator is pretty much a centrifuge: a mixture of fluid and particles (air and sawdust) is flung around a circular chamber and the big gunk falls out. Seems to me that if you mixed your soil with water and flung it around (vigorously!) inside a circular chamber that was composed of some sort of screen, the heavier stuff would drop out, as would most of lighter fluff and you'd wind up with mud on the outside. Of course, to collect all that, you'd want a second chamber, arranged annularly to the first and some way to carry off the slurry.

Gold miners have been doing something along these lines for centuries.