It’s a hollow axle with a built-in crimp fixing. And the axle that is supposed to fit in it should be 40mm. I happened to have that in the barn so I just have to put it in the lathe and make a bushing out of it so it takes the 20mm rebak-axle. I actually already cut the axle to length.
7 Likes
I have to apologize to you @MikeR , re-reading your post I realize that I misunderstood/misread. You said to have a slip clutch on the flywheel itself, not what I wrote earlier.
I am sorry and feel a bit stupid for not reading and understanding properly.
4 Likes
Johan,
No worries! I just know that flywheels are good and necessary. If spinning, and the driven load jams, that energy has to be absorbed somehow. If the slip is built into the flywheel hub, you could put the flywheel anywhere in the system.
I once heard a definition: An “Expert” = A Former “Drip” under Pressure! That might not translate well into Swedish, just think of a person who thinks he knows everything, and a leaking garden hose… 
7 Likes
Haha, that’s a good one 
4 Likes
Finally some updates, I was going to mill the keyholes in the axles but only got halfway when the belt broke, it was one of those rubber/plastic o-ring type of belt but the millingmachine got rebuilt with some new pulleys and two v-belts instead (a double pulley in the middle), made it slower as well while I was at it.
Anyway, my dad was kind and made a bushing for the gearbox to reduce the axle diameter since they are 20mm and the gearbox wants a 40mm one.
Picked up a side for pallet storage to make a little wagon to have the rebak on
Cut it to pieces and started mounting it on a rear axle for a Ford Escort I had lying around
Welded some 10mm (3/8”) plates together for a plate that the gearbox and the rebak will be mounted on.
Trying it out to see how it fits.
Shearing bolt in the bushing and axle.
The gearbox is already mounted with 4x 12mm (1/2”) threaded rods in the gearbox and with washers and nuts on each side of the metal mounting plate for near unlimited adjustability.
Forgot to make a pic of that.
12 Likes
Went and made a pic of the gearbox mounting
Sorry for making stuff a bit heavy and bulky, perhaps overkill. I just like it sturdy, I guess because both me and my dad has industrial backgrounds, him in the steel industry and me in paper mill/steam boiler industry.
13 Likes
Johan, I made my rebak from thin square tubing and moped parts. It has held up for 8 years now. I bet yours will be good for at least 80 years 
13 Likes
Thats good, I’m planning on driving on wood until I am about 130
13 Likes
I guess either make something that doesn’t flex or move at all to not break anything or make something where everything moves and flexes to not break anything, nothing in between
13 Likes
Is that metric or english units?
11 Likes
Not sure, whichever is the longest, that’s the one 
12 Likes
Do what you can to chunk green fuel, my chunker see’s 90% kiln dried lumber and that Dana 60 gets some SERIOUS abuse, it will momentarily stop then the axle shaft decides it’s a spring and snaps through the wood. Pretty rowdy, I soak the wood pile down with water and that helps a lot
12 Likes
Yes, the plan is to only chunk newgrowth of alder, aspen, sallow and willow. Perhaps a little birch. Up to 2 inches in diameter or something like that.
It’ll be interesting to see how long the cuts will be, I can’t wrap my head around if they will be shorter, longer or no difference with the knives off-centre.
11 Likes
Johan you could test measure it with a piece of cardboard and just spinning by hand. My guess is a 4" long piece.
6 Likes
Clever idea with the cardboard, that would work.
I just have to put knives on those knifeholders first.
When one set of knives meet and cuts the wood I believe it would stop moving until the next set of knives engage the wood again and drags it with them, I am hoping for something around 2 - 2 1/2 inches but we’ll see. 
6 Likes
It is what it is with this type chunker, but your chunks will probably be close to mine - around 2 inches long. Thinner material tends to get slightly longer - first chunk travels longer before the next set of knifes bite into the material. But that’s a good thing - makes for more uniform fuelsize.
12 Likes
Yes, It will be what it will be. I guess a set of five or six knives could be made, or three, but first try it out and dry chunks. I don’t think that any new set of knives has to be made. Your size would be good and I don’t see why it wouldn’t produce about the same size.
10 Likes
Put ears on the rebak itself to bolt on the bottom plate.
Bolted it on the bottomplate and then on the wagon
Put the motor and gearbox to try it out
Of course I made some error when marking either the holes for the gearbox or the rebak because the axle doesn’t line up with the hole in the gearbox.
Upgraded the holes for the gearbox to oval ones
Now it lines up a bit better
13 Likes
That geared motor looks enormous, if you accidentally put a (järnspett) in the rebak, it will twist the whole trailer
How many kW/hp?
10 Likes
Haha. Hopefully the shearing bolt will snap before anything else breaks, it is a 6mm / 1/4” bolt.
It is a 2,2kW motor geared down to about 73 rpm (or close to that)
However, it is a 500V motor and I am planning on running it on 400V so it will loose a lot of power, about 40% less if I remember correctly from the school years.
It had a reverse brake mechanism by the cooling fan but I removed that in case I want to run it the other way, the brake was reversible if someone wanted it the other way but I can’t see what I would run that would need a brake.
8 Likes