Building a Compost Screener

I make 4-5 yards per year of compost from my animal and garden waste. The area I have available for building compost piles is an old gravel pad that a house trailer used to sit on. As a result, I get a lot of rocks in my compost in the process of turning it. To solve that problem, I'm building a power driven screener.

This is an overall view of the unit so far. The bulk of the materials came from my scrap pile or were scrounged from other packrats. The frame is make of 16 ga. 2x2 tubing with 3/16" plate gussets on all the corners. The screening basket is an old shelf with a 1" expanded metal "top" on a 1" x 1/8" angle iron frame. (Click on image to see a larger view)

The sides are made of plywood, with the side on the lower end hinged to allow me to flip it down to dump any rocks or sticks that are screened out. There will be a slope sheet under the basket to direct the screened material out the "rear" and into a trailer parked there for the purpose.(Click on image to see a larger view)

Here is a shot of the home made dogbones that suspend the screener basket and allow it to rock back and forth. The basket is suspended from 7/8" rod stock "axles". All pivot points are drilled and tapped for grease zerks.

The drive is an old sprocket with hole drilled through it and a bolt welded in to act as a crankshaft. The sprocket shaft rides in pillowblock bearings, and another dogbone drives the basket.

I have decided to use a small engine to run the screener, as my second tractor has been giving me fits and is unusable until I can remotor it. I have an electric start 11 horse Briggs & Stratton twin that will provide more than enough power.

The drive mechanism is a variable friction drive off an old self-propelled leaf blower (the one that donated it's engine and blower to the Binford 6000 Leaf Sucker, discussed elsewhere). I'll have to pin one axle to direct the drive to the axle with the sprocket on it.

The big Briggs has a different mounting bolt circle, so I had to build an adapter plate to mate it to the final drive.
Here's Plan C. The Briggs had too many RPM even at idle, and my choices were another jackshaft for gear reduction or a gearbox of some sort. I came across this 5.5hp Honda with a 6:1 reduction built in. This solves a whole raft of issues. At idle with the variable drive set at the lowest speed, it gives me 24 RPM at the lower sprocket or 12 at the upper. That gives me plenty of room to speed the engine up a bit and take advantage of the increased HP at higher RPM. With the integral gas tank, throttle and choke, it eliminates a lot of plumbing. Being pull start, it eliminates the battery, solenoid and cables. Sweet!
Another few months have passed (good thing I wasn't in a hurry on this project...) and I have the Honda engine mounted. After some head-scratching, I decided to mount it on a hinge. This has two advantages: It uses the weight of the engine/drive assembly to tension the chain and it makes the engine removable for winter storage.
I'll need to fab up a chain guard. The only remaining task is to install a slope sheet to direct the screenings out the back of the unit.