Repairing a difficult hole in a compost tumbler

A few years ago an upstairs neighbor built this compost bin out of a food shipping barrel. It works fairly well. Rats chewed a hole in the door, which I repaired by bolting on some aluminum sheets. But then this autumn, rats struck again, this time chewing a hole in one of the most obnoxious possible places: Just below the axle.

Photo of compost tumbler, a plastic barrel on its side
       with a metal pole stuck through the axis; the pole is resting
       on crossbars, keeping the barrel off the ground. The pole goes
       through a hole in the center of the plastic lid, but there's a
       6 cm tall expansion gnawed into the plastic, running
       downwards.

Mechanically, this wasn't awful. I could still turn the tumbler, and halfway through the rotation it would drop a few centimeters, then drop again when turned all the way around. The plastic is astonishingly sturdy, and hasn't buckled much at all over the several years it has been sitting under load. No, the real problem is that now the rats can get in. I don't have anything against rats, per se, but there are a lot of good reasons to keep them out. (Additional future damage; rats bringing plastic bags in as nesting material; city fining us; available food leading to more rats; etc.) So the hole had to go.

Photo of the lid lying on the ground along with all the
       materials and most of the tools I used for the job. Tools shown are
       needle-nosed pliers and tin snips.

Normally I'd just patch this up with some hardware cloth (galvanized wire mesh). But it needed to not just keep out rats, but also support the weight of the barrel every time I rotated it. Hardware cloth would just buckle and warp under that kind of load. The solution I came up with was to first lay down a square of hardware cloth with a hole cut out in the center for the axle, drill four small holes in the lid, then lace heavy (1.6 mm) galvanized steel wire through the holes and form a cradle out of it. The wire punches in and out of the plastic a few cm higher than the axle and about 6 cm away, wraps under the axle, and back up again on the other side where it punches back through the plastic. I tied the loose end around the axle for good measure. (Probably pointless, but might have some load-spreading effect? Might just add unwanted friction.) I roughly twisted the ends together to secure them and tucked it into the mesh.

Photo of the plastic lid covered in hardware cloth, a 0.5
       cm metal mesh. The axle protrudes through a hole cut in the
       mesh. Heavy wire supports the axle so that it can't push into
       the rat-chewed hole.

Now the rats can't chew on the plastic, because of the hardware cloth. The wire keeps the hardware cloth from flopping around but also keeps the axle (really, the weight of the barrel) from crushing the mesh. I also cut radial slots and bent the mesh up and over the edge to keep it tidy and close-fitting. But there's still a lot of unwanted mesh protruding over the edges, flopping about. It's actually quite sharp, and I use the edge of the lid for turning the barrel. However, I also wanted to cover as much plastic as possible to keep the rats away. How to finish off the edges? It also wasn't clear at first how to secure it—staples? rivets? wire twists?—but my partner suggested using a trick from a previous project: Stitch with wire. In the photo, you can see more of the wire being used to secure the mesh. I drilled holes in the plastic on either side of each radial cut in the mesh, and stitched the wire over-under through the holes, with the "over" part covering each cut. This probably uses more wire than just tying short sections of wire through each pair of holes, but it's faster and leaves fewer sharp ends.

Photo of the edge of the lid, with mesh protruding over
       the edge, and wire periodically coming up through the plastic
       and mesh and down again a few centimeters farther around the
       rim.

Finally, I trimmed the mesh just to the very edge of the rim, and bent the pointy ends down into the groove there. Most of them stayed in place. I suppose I could come back through with caulk or something if I wanted to cement them in place and make them more hand-friendly, but I'll wait and see if it becomes a problem first.

Closeup photo of rim, with cut ends of mesh bent down into
            a small but broad groove.

The final result looks fairly nice if you don't look too closely, and seems to function well. I don't think it would be wise to leave the barrel rotated upside down for any length of time, since the weight might pull on the cradle wires hard enough to cut the plastic. (Perhaps there should be metal sleeves of some sort where the wires go through the plastic. Or just more wires, to spread the load to more than just 4 points.) The cut ends of the mesh are hidden away well enough that I haven't gotten scratched up. The hole I cut in the mesh for the axle ended up off-center, leaving a gap where a rat might be able to wiggle through, but it's mostly covered by the cradle wires. If needed, I can simply lace some wires across, anchored only by mesh—these wouldn't need to be structural.

Photo of reassembled compost tumbler.

I think if I were to redo this project, one change I would make would be to trim the mesh 2 cm out from the rim, then bend it under itself before stitching; this would get rid of the vast majority of the sharp bits, and would have been somewhat less labor. And of course the whole thing could no doubt have been done more professionally or efficiently. But in any case, the rats have been excluded and I still have a working tumbler, and that's what matters.

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