Anyone who has tried to garden in rocky clay-based soils knows the challenge: you need to add organic matter to encourage both water drainage and retention. We needed an easy way to remove the rocks from the ground, as well as process the large amounts of compost necessary to build healthy soil. We built a DIY rotating compost screen that is robust enough to sift the soil and also doubles as a workbench.
It can be built in under two hours – and there is only one step that requires an extra pair of hands. Most of the components are stainless steel or aluminium, so it can be kept outdoors. Feel free to save money where necessary if you do not live in a coastal region. If you want a motorized or two person sifter, this tutorial is not for you.
DIY Rotating Compost Screen Tutorial
You will notice some measurements are imperial and some are metric, this is due to what is available in the Caribbean – adjust accordingly based on what is available to you.
Tools:
* Screwdriver + drill bits and bit to match your screws
* Adjustable Wrench x 2
* Miter Saw, circular saw, or hand saw with miter box with a 22.5 degree guide
* Power Drill
* Wire Cutters
X Frame Materials:
3 8′ lengths of 2×4 (A finished 2×4 is actually 3.5″ x 1.5″) Under $20
16 3″ Stainless Steel Screws – 2.5″ will work
1 Pine Shelf board 1m x .5m (Optional – must match length of threaded rod)
1 1m (Must match length of your threaded rod) length of square trim approx 1.5″ x 1.5″
2 Mending Plates and 4 1″ screws or 2 6″ screws
X Frame Method:
1) Cut 4 identical lengths of your 2×4 with a 22.5 degree cut to the bottom and top. The easiest way to do this is cut your first 22.5 degree angle, measure 3’11” and cut your second 22.5 degree angle, continue until you have 4.
2) Cut your 2 shelf supports, again with a 22.5 degree angle.
3) Cut your 1m 2″x4″ brace and your 1m 1.5″x1.5″ shelf brace
4) Cut 2 3.5″ squares to support your threaded rod.
5) Use a straight section of your house to form an x with two of your 2×4’s. The bases should be about 2’10” apart and the top of the X should be about 3’5″ away from the wall. Pre drill 2 holes in the top board at the X, and screw the two together. (Pre-drilling helps pull the two boards together.)
6)Choose your shelf height, and use two screws to hold it in place. (Again, pre-drill to help pull the two pieces of wood together.) Finally, pre-drill and screw the angled edge of the shelf bracket into the x frame. (Or use a mending plate.)
7) Pre-drill and screw the 3.5×3.5 piece onto the inside of the X to support the threaded rod. You can adjust the angle of your tumbler by lowering or raising this block.
8) Arrange your second x frame in mirror image to the first.
Putting It All Together:
1) Call in your second pair of hands – hold the two x/frames 1m apart using the counter top or threaded rod as your guide. Attach the 2×4 brace about 1′ high on the back side. Initially pre-drill and use one screw each side. Add the second screw to each side after checking for squareness.
2) Finally, brace the two shelf brackets together on the underside with your 1.5″ x 1.5″
Rotating Drum:
2 discarded bike wheels of equal size
We used 26″ Bontragers with a quick release axle – FREE
1 meter length of Stainless Steel threaded rod to replace the bike axle (A2 grade of stainless, aka 304, is adequate)
We used 10mm A2 – Under $10
2 stainless steel nuts to fit the threaded rod
1 10′ x 3′ hardware cloth with 1/2″ openings Cut to approximately 8′ x 2’8″ (You could use a 10′ x 2′ roll to avoid cutting) Under $10
24 Bolts, 24 Nuts, and 24 Fender Washers to fit where the spokes are in your tyres
We used #6 machine screws x 1-1/2″ Under $10
3 Bolts, 3 Nuts, and 6 Fender Washers to hold the steel mesh closed.
We used #6 machine screws x 1″
Method:
1) Loosen (but don’t remove) the nuts on each axle, using both adjustable wrenches. Clean and lubricate as needed.
2) Remove every 3rd spoke from both wheels. You can cut the wire with an angle grinder, wire cutters/secateurs, or unscrew the spoke nut. Remove the spoke completely.
3) On one wheel, remove 10 spokes in a row. This is where you add material with a spade.
4) Thread a nut onto one side of your threaded rod.
5) Carefully remove the nuts from one side of the axle. Insert the threaded rod as you remove the axle so you don’t drop any bearings in the process. Repeat with second bike wheel.
6) Put the threaded rod and wheels onto your frame so you can work comfortably standing. Wrap your hardware cloth around both bike wheels. Remember do start and end at the opposite side of the wheel to your opening so gravity holds your sifter in the right position.
7) Trim the hardware cloth as needed, leaving an overlap. We used about 8′ x 2’6″. Fold cut edges under, or use duct tape to cover the sharp edges.
8) Attach the hardware cloth to every third spoke hole using the bolts, washers, and nuts.
Using Your DIY Compost Sifter
1) Position wheelbarrow under the screen.
2) Add Dirt to the high side.
3) Turn before it gets too heavy.
4) Enjoy fine compost and lighter soil!
Try out different methods – screen compost into a wheelbarrow, onto a tarp, or directly into your new bed. Play with the angle of the screen – You can rest the threaded rod in different positions. Rocks only need a tiny angle to drop out the low side. Compost needs a bigger angle.
If you need a sturdier workbench, replace the 2×4 brace with a x-shaped cross brace or a 1″x6″ board. We kept it simple as we want to be able to take it apart easily to pack away into the shed.
Click here for the full series on composting
