If you are talking about small ones for the garden then I have gone through a couple, I would get another one if this one broke and I only really use it a couple of times a year when I do a blitz on the pruning.
There are a couple of types, some have a pair of blades spining on a horizontal plane, much like a lawn mower, avoid that type, they throw sticks out the top and gunk up too quickly, the blades also need replacing fairly often.
The second type has a big cog which grabs the wood and shears it off against a metal plate, doesn't need sharpening and there are no blades to replace. This one is the one to get, quieter too.
Neither of them do too well when you use a metal bar to push the branches through.
It has a direct drive (NO BELTS!), attached to a 70lb flywheel. I primarily use the chipper part of the machine, and hardly ever use the shredder part. If the wood fits down down the tube, it will chip it. I used to think my last drops of fuel would be used with a chain saw, not anymore. My last drops of gas will be used on my chipper. I can replace my chain saw with a bow saw. Nothing could effectively replace my chipper.
A few years ago we harvested some large maple trees. Now they coppice out every year, and in two years I have perfect sized poles to run in the chipper. If the coppiced poles get larger than 3 1/2" in diameter, I cut them into 4' poles for my rocket stove.
Someday I will figure out how to run the chipper on wood gas, using what else, but chips of course. Yes I would strongly recommend a chipper, but invest in a good one like the Patriot.
Cliff (Start a rEVOLution, grow a garden)
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