Bill S's little chunker

Still pushing the machinist on on grinding the shaft for the gear reducer. It appears most everything is drawn up and materials are purchased.
Here is my chunking drum.

Bill…What’s the diameter of your chunker drum?


The outside diameter is about 11 inches. I’m hoping it’s not too small.

That looks sturdy!
I wouldn’t go any bigger with your present reduction box.
Should be fine.

Thanks Terry,
Yes, I believe this diameter was decided on a Friday night Hangout with you and Marvin. I went with 3/8" thickness on both the cylinder and the back plate. The machinist friend is going to put it in a lathe and true it up. He is going to make a plate that will mount to the shaft coming from the gear reducer. That plate will bolt on to this back plate with grade 8 bolts.
I believe this will be very sturdy, I just hope the gear reducer can handle the torque.

Bill…Mine is 12 inch diameter, I think you will be just fine. Just remember the forces working against the gear box is trying to raise up and push back and away. Mine is damaged right now. As beefy as the gear box is, when chunking the slabs I pictured some time back, I broke one of the corner foot that holds it down. I knew better and should have stopped after finding out how tough and hard the seasoned walnut was. I had welded stops behind the feet to keep the gear box from pushing backwards and now wish I had put a strap over the top with a draw bolt on it to help hold it down and relieving some of the pressure from the feet. It broke plum into the gear box and started leaking gear lube. I’ll braze or weld the foot back on and install the strap. I cut 3 1/2 --55 gallon drums full of the walnut slabs up last night on the miter saw (man was my arm sore today). When I get it tore apart I’ll show you the damage. Just don’t forget the gear box needs to be built to with stand a tremendous amount of horizontal force, not just radial…

Thanks for the heads up Gary,
The gear reducer I have is small. About 70lbs. It’s 25:1. It has a 2 3/8" output sleeve opening. I’m hoping by having a sleeve for an output, by having a backstop will absorb the horizontal force.

but if you could provide support at the back end of the shaft, it should work.

Bill…That is a good gear box. They are made to hang on a shaft with a torque arm on it. We use them on augers at the refinery with a torque arm from the gear box to the frame to hold the torque of the gear box. If you have something to help on the horizontal push you should be good. Just don’t put something through it that you think is to much…like I did.


Sorry Carl…your post was made while I was typing. You said what I was trying to say with a lot less words…lol


may take some additional engineering. All the ideas are important Gary. That box that you have Bill has the driven shaft held in place by a key, and set screws, neither of which will stand much end force. I wonder now what is inside the baler boxes??

Yes Carl, it is a pretty shallow key way. That is another hesitation of mine. Green wood may be the only food this will digest.
If this fails me, I will be in search of a baler gear box. My hopes was to have something reasonably compact which may be be filed under high hopes.

Carl…Looks like it may have a taper lock sleeve assembly to hold the shaft,It is all going to depend on the size and kind of wood he intends to chunk. The little Dodge gear box Bill has, would not work on the stuff I chunk. Will work on smaller limbs and stuff but might be best to come up with a new idea before spending a bunch of time, effort, and money on something he may not be happy with. All depends what he runs through it. Just some honest things to think about Bill (figure your reading this). Get back with us and tell us what your thinking.


#1 - Why not build a rub bushing and place it 1/16" away from the outside of the wheel drum/cutter wheel. Put it at the point of maximum thrust. It will “push back” on the flexing cutter wheel and take up the overload. You could still overload the whole system - but we have to learn our limitations and respect them…

#2 - Here is what I was thinking about doing with my hay baler version:
Don’t let the cutter be on a cantilevered shaft. Build a heavy hub that slips over the output shaft and continue the shaft into a heavy pillow block so the axel shaft is supported on both ends.

The cutter wheel could be “traditional” like Mr. Waynes wheel drum design with the cutting edge on the side. Or, I think a stronger version might be: a cutter that is a heavy flat plate (supported by the heavy hub) of high carbon steel the cutting edge being cut out of the disk shape. This disc could be as heavy as you want. I’m thinking something like 3/4" plate. (The anvil is at 90 degrees from the “traditional” design.)

I think this would make an almost unstoppable chunker. It would last for a lifetime of DOW.

Al Denninger

Correct Gary. I was originally planning this to be a chunked for my miniWK. So my plans were to contact a local tree service and get the branches they throw in the chipper. My hopes is that it’ll handle 2" green stuff. But I’ll start small and see how it goes. I have been introduced to the red flags about the size of this gearbox on the Friday night hangout. But my German stubbornness pushes me forward. Mine may be the example of what not to do. I will come out a winner because I will have learned a lot through this process.
The gearbox was $200 and are plentiful online. But if this can’t even handle 1 1/2" stock, I will have a boat anchor.

Al, we are installing a thrust bearing that will go between the shaft and the back stop. It’s rated for 7200lbs and have no idea if that’s enough. I figure if I don’t try, I won’t know. If it works and is only good for a smaller stationary unit, then so be it. I’m hoping to drive it with hydraulics and pulleys. We’ll see.
I really appreciate everyone’s input here because it give me a lot to think about. I always accept constructive criticism. It’s a part of the problem solving formula.