For a sight increased cost, if you're ever planning to get near the max size of that 4", and you have enough tractor to drive something bigger, bigger is ALWAYS better on a
chipper. Make sure it has a big ol' fat flywheel because that's what does all the work. The 4" might be all you need, but if you're feeding it water oak brush or anything of similar species, you will regret not having the larger opening. I have a 3" Briggs powered
chipper, and that thing will work you to death. Between all the extra cutting and poking the stuff in the
chipper, yep, wore out gloves, killed my wrists and shoulders, and constantly fought clogs when I fed it birch, despite the flails in it. A 3"
chipper won't take much of anything over 1 inch, unless it's REALLY straight.
Dried material will ALWAYS be harder to chip, and hard on the hands. UNLESS, you get a hydraulic or manual feed. Poke the brush in the rollers, and let them do the work. NEVER, but NEVER put your hands past the mouth of the chute. Besides that, you'll find the chute is sized pretty much where you cannot reach the rollers without doing silly things. Most, as the OP pointed out have a safety bar. If you hit that bar, it actually reverses the feed rollers because it thinks you're trying to change your number base by removing digits if not appendages. They really are pretty safe, though, if you treat them like there are four very sharp knives whirling around on a 200 pound flywheel. I ain't no rocket scientist, but I do understand Darwin's theory of selectivity. I actually do have an engineering degree, but it doesn't take that much education to just not put your hands in places you shouldn't. Anyone with a girlfriend or wife should be familiar with this axiom. Most of these monsters can be fed from quite a way back from the hopper if your brush is long enough. If you got a large enough
chipper, your brush should be long enough. There's less need to cut things up with a larger infeed. Stick the butt of a 6" tree in an 8"
chipper, and let the big dog eat. The WM-8H, WM-8M, WC-68 all will run just fine with 19.5 PTO HP. I just had this discussion on another forum that I frequent. The WM-8M is a little less costly than the WM-8H because of the lack of hydraulic pump. It's a mechanical (belt driven) infeed, and is geared to feed the beast at 50 FPM. The WM-8H, being hydraulic, with it's own pump and reservoir (also belt driven) can be adjusted from nearly 0 up to whatever max feed rate is (75 FPM if I recall). Depending on what you're chipping for what purpose, you can vary your chip size. It also lends itself to running it with smaller tractors by slowing down the feed rate on larger material. If you want big chips or to find out if you can stall your tractor, crank up the feed rate. The WC-68 is a 6"W x 8"H infeed chute. The WM-8H/M are both 8"W x 8"H (slightly larger) infeed. WC-68 has two driven rolls, the other two have one driven roll, if I remember what I read correctly. The pricing is all very similar on this frame size (8"), and if I had a hybrid of the Woodland Mills machine and the
WoodMaxx machine, I'd be happier than a pig in slop. Right now I have my little 3" Briggs/Murray. But I also just bought a Kubota LX-2610-SU that needs something to do. I have plenty to feed a
chipper and will have some very happy nightcrawlers to invite fishing with me when I'm done. I'm thinking slow feed rate, small chips, faster decay/mulching. Though listed as Made in Canada, they're all actually Chinese knockoffs of the Wallenstein. Hate to burst your bubble, but that's the way of it these days. The Wallenstein requires more PTO HP for their 8" model, and it's a monster to move. It also requires about 20% more cash for the purchase. Personally, I'm leaning toward a clamshell design for knife/cutter access. I don't care how good a
chipper is, if you feed it the right material, you will choke it up. In my case, it's burch and elm. That stuff has some stringy bark.
Every owner of any brand that I've researched says their
chipper is the best thing since sliced bread and handier than a shirt pocket. Some are built harder than woodpecker lips, some not so much. But even a cheap
chipper can last quite a while and take a beating if you service it and keep it maintained. You're going to find something you don't like about any brand, and a lot of things you like about every brand. If you want it to cut, keep the knives at peak sharpness. For maintenance sake, I recommend a clam shell design simply because knife access is a lot easier. When you can see what you're doing, you're less likely to remove your fingers. If you start to see smoke coming out of the flywheel housing, even if ever so slightly, or smell something like burning wood when cutting fresh brush, it's time to flip the knives over. Just remember you did that, because next time, you'd do well to have a second set on hand to just swap while you send the first set to the sharpening service of choice. Some manufacturers will not sharpen knives from other products (probably avoiding liabilities more than not knowing how). There are a few sharpening services that will sharpen any knife from anything. Consumer beware. I sharpened my own knives for my little guy. Who cares if it's a polished edge if it cuts? You're making CHIPS. I have a small bench grinder with a fine grit wheel in it that won't overheat the knives. If you want a clean edge, then consider using a machine shop to mill the knives for you. Keep the bevel angle close to original, and Bob's your uncle. As massive as these things are, tiny weight differences are not going to matter much, but it's probably a smart idea to keep them as close as possible to the same weight. They don't turn super fast, and I doubt you'll ever see any more vibration than that from the PTO driveshaft. Some of the belt drive models step the 540 RPM up to something around 1100-1200. The faster machines will be more sensitive to smaller weight differences.
