"Rod Richeson" wrote in message news: firstname.lastname@example.org...
I have previously found a site showing a home made chipper, but it was not that big. From memory it was a larger version off a small domestic chipper, running of a single cylinder petrol engine (between 5 and 8 hp possibly).
There are several different forms of chippers. The type you would probably be most interested in, would be the most common version off industrial/arboriculture chippers. These consist off a flywheel, with 1 or more blades mounted on them. The flywheel is normally constructed from 2 discs off steel, joined by strips of steel welded radially from the centre out, so as to create a centrifugal fan. The blades are then mounted in cut outs on the face off one off the discs. On basic chippers, the blade is simply mounted onto the face off the disc, whereas a reasonable chipper, the blade will be mounted onto an adjustable block, as the distance off the blade edge from the disc face, is the main factor in chip size. Around the outside off the flywheel will be fingers, which can either be an extension off the radial strips holding the two discs together, or seperate blocks welded on. These fingers pass through other fingers mounted on the inside off the chipper body, and serve to break up the chips (explained further down). The chipper body, consists of some form off feed chute (can be either self feeding or powered). At the end off the feed chute (where the cutting blades pass), will be mounted a solid steel plate (the anvil), which supports the wood as the blades cut the end off. There is also the exit spout, which normally comes up vertically from the body, and has fingers (essentially strips off metal mounted so as to follow the circumference off the flywheel) which prevents long pieces off wood from exiting the chipper.
A brief explanation of how it works. Wood enters the chipper from the feed chute, where it will hit the face off the flywheel. As the blade comes round, it will force the wood down onto the anvil (if it's not sitting on it already) and slice a section off the end. This section will then be forced to the outside edge off the flywheel, where it will be caught by the fingers on the flywheel. The section off wood will then be fragmented between the fingers on the flywheel, and the fingers mounted on the side off the chipper body, as they pass through each other. At this point, the wood chips should be small enough to be blown up and out off the chipper, however, if they aren't, they will be picked up by the next set off fingers on the flywheel. The set off fingers mounted on the bottom off the spout, prevent any large sections off wood from exiting the chipper, causing them to be knocked back down into the flywheel fingers.
I could supply pictures off this type off chipper if needed. The main problem with this chipper, would be getting the right size off flywheel. Too light, and the cutting shocks/stresses will be transmitted through to the tractor, which could quite easily damage the tractor. Too heavy, and you may have problems getting it started, although once running very few shocks would be transmitted through to the tractor. Also too small a diameter, and you won't create enough draft to expell the chips (which could be counteracted by increaseing speed off the flywheel), and too big, there might not be enough power for the blades to slice through the incoming wood. Then there is the problem off balancing the flywheel.
There are other types off chippers. There are ones (small domestic type) that consist off small teeth mounted on counter rotating drums. Wood is simply passed onto the top off the drums, and as the centre off the drums turn into each other, wood is gradually chipped off, and discharged below. The problem with this design is on a larger scale, you would have a major problems with wood chips being thrown back out the feed chute due to the forces, and also the drums and mounting would have to be off a suitable construction to prevent them being forced apart when larger pieces off wood enter. Also, should any solid material enter this, it is far more likely to be blown apart. Although there are newer versions off this design which use diamond blades, so as to be less effected should metal enter.
There are also ones which use disc cutting blades, although I've never seen one up close to tell you how it works.
On Fri, 4 Feb 2005 21:07:04 -0000, "Moray Cuthill" vaguely proposed a theory ......and in reply I say!:
remove ns from my header address to reply via email
You left out the hammermill style. These are simply flails, on a spinning frame, that thrash the wood to pieces. They are incredibly noisy, but are very tolerant of dry wood and stones etc. Get a piece of gravel in a disc or drum cutter and you have a major sharpening job on the blades.
They work much like a sort of multi-layer, multi tine lawnmower.
Some of the largest mulchers have gone to this style, as have many garden ones. The main advantage is sheer toughness. I have dropped a
3/8" hardened steel chain into a tractor-driven one, and it broke a belt, rounded the flails a bit, filled my undies, and completely destroyed the chain. The machine still works, although not as well.
Also, all blade style chippers need to be kept very sharp, and are best given only green wood. I have a drum style one, and when it's working we spend nearly as much time sharpening as chipping, to keep the thing easy to use and efficient. We used to sharpen every couple of truck loads.
All chippers are extremely dangerous. Hydraulic feeds seem to help, but in many cases have actually dragged people in anyway, in spite of stop bars etc. Hydraulic feeds certainly lower operator fatigue (DAMHIKT) but are costly and complex.
Anyway, all of this says that there is more to making a chipper than meets the eye. They need to be well-balanced, very strong and with very hard yet tough cutting surfaces of whatever sort.
Actually, talking of lawnmowers, a nice mulching tractor mounted mower may do the job.