Portable Chunker

A very cool little chunker, can’t wait for video. Mines portable on a trailer; but it’s a whole axle assembly. You know its behind you when you tow it. Patiently waiting…Dan

At lunch time I decided to re-watch some video and look at pictures of the different screw chippers. There is a guy named Sergio on the wood gas group and his videos are very helpful in my case, but so are the others. I found close up pictures on the web today of the PS-10 chipper that I never seen before which was very helpful. I new after running yesterday and observing after plug ups that the chunks being cut were not leaving the housing but rather staying in between the flights not allowing the next piece cut to head to the discharge, that I had to shorten my cutting flight. My flight actually extended into my discharge opening. My discharge opening was also several inches from my inlet on the opposite side of the tube. After observing Sergio’s video again and the PS-10, I observed how short the housings were and that the inlet and discharge holes almost overlap each other or maybe even do. So I reasoned do you really need that much flighting? The last cutting flight in the inlet is all you need. Then also the pieces cut need to get out of there ASAP! So I cut my flight back so the flight stops just outside the inlet. I also cut my discharge hole back so it is almost starting to overlap with the inlet hole. Huge difference!!! No pieces getting stuck like they were and I can do larger limbs now with out killing the tractor. However I still can only do about a 2-1/4in round of dry limb wood. I chopped up some maple 1x3 flooring boards no problem. I did stall the tractor twice trying to do this one maple branch. It just wouldn’t do it.
So progress made. I think if it is going to do anything in the 3 to 4 in range it is going to need a gear box. I don’t doubt a flywheel would help some also. Just don’t know if it will get me to my target of 4 in stock.
I will try to get pictures up soon so you guys can see some details and the size pieces it makes. To describe piece size though…….it can take a 2in limb and shear it right off and you can have a 2x2 chunk, and if your doing flat boards or dry dimensional wood you can get pieces as small as 1/2 in thick by 2in long. It really just depends on what you chuck in it. I didn’t get brave enough to try a 2x4. Wish I would have tried.
On another note I want to pose a question and I know it has been discussed before. What effect is bark going to have in the gasifire. Also is small 1 to 2 in limb wood going to be a different fuel than say pieces out of the trunk? I guess I posed two questions. Try to keep the explanation simple for my brain :o) !
David S

Hi DavidS
You may find that wet timber will chunk a lot easier!
Bark has a higher calorific value than wood, but I have found that bark is also higher in impurities like ash. As Steve says bark is natures fire and bug protection. I don’t separate. Most of my gasifier wood fuel is the outer slabs (the bark) chunked up. I haven’t tried branches and limbs.
Thanks Patrick

Good Morning David,

I’m sure you will get all the bugs work out of your chunker soon.

On the bark question I echo Patrick’s statement . I make no attempt to remove any of the bark from the fuel.


Great chunker design David, The “flight with a bite”. The design tweaks are working, ever forward. Fine workmanship as usual.

Thanks Carl. I am going to relieve the bevel on the backside of the blade a little and try it again soon. I will keep you all posted of the progress.
David S

OK guys, I ran my chunker today.The belt slipped bad on my first try and the engaging lever seemed like it wouldn’t want to tighten the belt. Then I realized that the motor was mounted to the integral frame on 1 inch rubber vibration damper mountings that flexed when the belt was trying to tighten. I removed two rubber mountings at the lever end and bolted 'em up solid. This allowed the belt to tighten better for this second try - http://youtu.be/atyoSGEyW1s
My branches are all under the snow so I used 1x2 pine casing for this try. It appears that the little 2 cylinder motor will run this chunker just fine but the pulleys I had laying around will have to be replaced by double groove pulleys because the single groove pulleys still slip some. After watching the video I realized that I never wrench tightened the bolts on the gearbox to the frame. You can see the gearbox move under load.in the video. It appears that after a few tweaks this little light weight chunker will do the job exactly like it was designed for. I will update after these tweaks are complete.

Looks like you’ll be ready to chunk any where any time Don.

Howdy Don,
Sure looks like its doin the job.
Nice and compact… I’ll be keeping an eye for a gear reduction.
Good Stuff!
Thanks for the video!

Nice job Don. This is a great idea to have the equipment you can take anywhere. Solves a lot of issues.

Don, it’s the “Barrel-Top Chunker” or Bucket-top which is even Better!

Hi Don
That look great will like to see it chunking the big stuff.
Got me rethinking my chunker!

Hi Don, Nice chunker. Made a similar one last summer that was driven by the Gravely. It works well, but I’m a little disappointed with the processing speed. Then I saw this style of chunker. http://www.youtube.com/watch?v=5KAaABlfojc Working on making this style that will also mount on the same gear reducer as used by the rotating knife. By the way, I cut a used disc blade for the rotating knife that seems to work well.
Gary in PA

Hi Gary, what rpm does that Gravely spin that blade? Do you rev engine at full speed?
Don in MI

Nice chunker but i would hate to get caught by it !
Thanks Patrick

Nice work in both design and workmenship Don

Hey Don, The Gravely has two speeds. If cutting larger branches of hardwoods, I use the low speed. About 60 to 80 revolutions per minute on low speed. (a good guess as it has not been timed) It can handle green hardwood up to 1.5" if put it in at an angle. The engine is about half throttle. It is running on charcoal gas. I just don’t like to rev up much of anything.
The other chunker is coming together nicely. I have to cast two gears and install them and then ready for a test. Maybe next weekend.
Gary in PA

Don, what thickness is your cutter? From the picture, it looks like it is 1/8" thick, maybe 3/16"
I am in the process of building a similar chunker and fabricated a 1/4" thick knife. Hopefully, I have the same success you did. Thanks Mark

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Good eye Mark, It is 3/16" and it was cut out of a hardened circular saw blade. I broke a lot of drill bits making those mounting holes>


Hey Don. Thanks for the rapid reply. A good choice of steel on your part and I guess you did go through a lot of bits. Hard steel for sure. Another question, did you sharpen it like a knife on both sides or just on one side like a chipper blade??

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