Hi , I burn logs in the winter to keep our house warm .I always see abandoned pallets around , and in the past have cut them up and reduced them to firewood sticks to start my log fire off .My neighbors do the same , but handling a hand ax, unless you are an expert, can be hazardous , so I set out to make a kindler or firewood machine.This is a low cost project , in fact it wont cost you more than a couple of pounds if you source the materials like I did .
You need to own or borrow a reciprocal saw with a metal blade , and a donor electric cement mixer which is junked.
Donor Parts Purchased Parts
Pulley wheel and belt 18" round mild steel axle
Electric motor various M6 M8 nuts and bolts
double head ball race single ball race size to match
Heavy iron gearwheel for flywheel some hollow square tube that nests inside another
odd 30" scaffold tube for legs , 4 pieces
some pieces 1.5" x 1.5" square tube for frame
piece of flat plate 6" diameter
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Step 1: Setting Out the Frame
Again , this whole machine is made from off-cuts and bits of scaffold pole , I will give you the dimensions , but I made the thing up as I went along
The legs are 4 pieces of scaffold pole 30 inches long (76 cm)
the top is square box 1 and half inches square , size is 20" x24" , and the legs are welded to the inside corners.
Splay the legs slightly to give a nice look to the machine and add stability.My large pulley is 15 " diameter (38 cm)
so you are now in a position to mark a place for it on the frame.You will need the old axle to purchase a longer new axle , mine is 18" (45 cm). Weld or bolt the double race housing ,so that the edge of the pulley wheel is on the edge of the frame , and make a housing for the purchased ball race and weld that to a cross piece going across the 24" part of the frame .The centre of the axle rod is now the centre line to set up the connecting rod to push and pull the chisel ...I found the height must be the same or the chisel could sit slightly above the centre line, but not below as it tends then to bind .Another consideration would be the direction of rotation of the motor , so any nuts and bolts tend to tighten up when they revolve , and not undo.You can now determine where the motor mount should sit by slipping the belt on and blocking up the motor , I made a belt tensioner ,but thats not really necessary ,just clamp the motor in place and see that it runs freely without slippage, adding the four lower braces at the same time.I also supported the bearing housings top and bottom with strips . You can add the flywheel to the axle ,you will need to tap it for an M8 bolt , and also I found it needed "Loctite" to keep the bolt from becoming slack .
Step 2: Fitting the End Plate,connecting Rod and Chisel
I found a small piece of square walled steel in my shed , that an old SDS chisel was a hammer fit into .A slightly larger square walled tube fitted this piston and acted as a bearing , as I said before the line should be horizontal , so a spirit level is handy here to align the height of the chisel piston .The cam if you can call it that was simply a pice of plate cut roughly into a 5" disc , with a small piece of gas tube that was a snug fit over the exposed end of the axle .The plate I welded to the gas tube and drilled it and the shaft for an M8 bolt and nut . i have to go metric here because imperial doesnt quite work .I found the optimum distance from the centre of the axle to the centre of the conn rod bearing at 3.5 centimetres , I tried larger and smaller but found this is the best distance to give a back and forward movement to the shaft, we will see why later .....I would add too , when the connecting rod arm is in the 12 o clock position , it is moving at its fastest rate , and as it reaches the end of the stroke ,it slows to zero , so you need to make sure, when the chisel initially strikes the wood it is going as fast as it possibly can.....I found the best way is to make the chisel sit back maybe and inch and half from its striking position , the blade doesnt have to be woodwork sharp to cleave the wood .The chisel then can run forward, gain momentum and then strike the wood in the tray
Step 3: Making the Railway for the Wood Billets
I decided on 17 centimetres , about 6" was a good size for a fire stick ,so the railway was based on that measurement it is made from inch and half L angle iron . You can make it narrower if you like, but I would recommend 17cms is the max . Playing about with the machine , if you angled this bed down then the vibration would probably help it self-feed ! You need a push stick , and keep your fingers out of the way of the chisel , it will give you a painful pinch! I was going to guard the large pulley wheel , but if the machine does jam , due to a really nasty knotty piece of wood, simple switch off the power and retract the chisel by pushing the pulley slightly backward .It can chop 3/4 " wood with a straight grain without problem , if the chisel is sharp it may do one inch wood ..Oh the cover top is an old stainless steel kitchen cooker hood cut up a bit and pop riveted together, as the machine will stay in the garden in all weathers ..There is a little video of the machine in action .it cannot be shown here because the instructable editor is not ready to take vids , but its on my FB account https://www.facebook.com/philip.ryan.948 you are welcome to look at it there.