Truck Powered Chunker, would it work?

I’ve been kicking this idea around for a while now. I want to be as safe as possible. This isn’t a treadmill, which I understand are dangerous. I know how to brake the only the wheel on the other side so it would act as a safety slip clutch. This seems simple and low cost so I have to believe that people have at least thought about it. Has anyone tried this?



This is preety much exactly the same idea that dr Larry presented last year on Argos.

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I wish I could talk to him.

You’d want some kind of flywheel.

Stopping one wheel doubles your speed and halves the torque. All the strain goes on the spider gears, you could blow up that diff on a hard chunk of wood.

That framework looks difficult to install. Is this a permanent conversion or one you want to drive afterwards? If it’s dedicated to chunking, weld the diff, add a flywheel and slip clutch to the input driveshaft.

I pursued engine > transmission > rear axle chunking, briefly. Turns out there were enough issues that I abandoned it in favor of the baler gearbox style.


Dr Larry allso proposed the chunker being powered by rollers. Imagine a dynamometer thats runing a gearbox and a chunker. Its safe as the wheels can slip, it doubles the grip being powered by 2 wheels and you can drive off it in literaly seconds. Its not portable thugh… but l like the concept anyway.


Hey K
I think it could be portable If you built it on stout enough of a trailer, but it would be heavy. When I was out there Dr Larry and I did a little playing around with this. the main Idea to avoid the slipping diff problem would be to build a steel pipe on a set of bearings mounted to some really stout hinges that would swing down when you wanted to chunk, to lock the two wheels together. Then to mound a dual wheel hub on a single wheel pickup and use the outer rim to mount your cutter head on to and build the anvil inside the side of the bed. I would probably do a flat cutting disk on it line BobMack or Jan just built one with the same style. The reason being the room they take up unless you want this thing sticking way out the side of the vehicle yo are working with a very limited space.
I would be concerned if you are doing this on a light pickup truck. I believe Chris is right you have to do it properly or it will destroy a diff in no time.


What about a chunker from a PTO off the transmission?

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Thanks!!! That’s exactly the kind of thing I wanted (and needed) to know. I suppose Wayne’s diff doesn’t blow up because it’s from a 3 ton truck?

if this were to happen the way I imagine, setup and take down might each take an hour. If I were to chunk up about a ton of wood I would probably then be able to drive for 4 or 5 thousand miles. Two hours spent setting up and taking down doesn’t seem that bad.
So far I like the gear boxes from those old square balers best. They had to be stout to pack that hay the way they did.

I like the concept too. But I once saw a shifter cart, much like this one, break loose from a chassis dyno, because of extreme vibration straps wear out very fast. It went right through a corrugated metal wall. Many stories like this, very dangerous.

Thanks Chris, and everyone.


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I have kicked around the idea of a portable chunker, but I think for weight, cost, and ease of use, a inverter ran off of a second battery in parallel so it would be charge off the vehicle , and a chop saw would be more convenient.


What about making a pulley system that hooks on the engine pulley, turns a pto to get a few feet away from the engine then run the circular saw from there?


I’ve thought about those things. I chunked about 1500 pounds of wood last winter using a chop saw, 2 pound hammer and a wedge. I didn’t regret the exercise. LOL But it took 11 days. I want to do it in 1 day. And I want a chunker, not a saw, partly because it crushes and tears the wood. Somewhere in HWWT Wayne said he could process enough wood in a single morning to drive from Alabama to California. That’s the kind of productivity I want. :grin:


Wayne has a welded diff.


Why isn’t anyone talking about using a standard transmission? Hook it to a PTO or a small engine. Put a fly wheel with a clutch on the input shaft TomC


Errr, I read that in HWWT too. But something has to be spinning in there or how would he be transferring power around a right angle.
And I think lightly applying the parking brake on the opposite drum would allow the driveshaft to keep spinning even if I jammed the cutter with an extra hard piece of wood. Not?!!!

Learn about how a differential works:

The two small spider gears only spin during cornering, and transfer very little power. When one wheel stops, all the power from the engine must transfer through them to one wheel (double their normal design load). Their bearings are smaller and not made to take that pounding. And, as I mentioned the wheel speed doubles and torque halves (not what you want for a chunker).

Wayne welded the spider gears to the side gears, making it one solid chunk. But the big ring gear still turns, and the axle bearings themselves take the abuse. Full torque and lower speeds.


Okay Chris, This is very productive. You are making me think. Thanks.
However, I think about the shock loads my diff must take when I’m spinning on ice and then suddenly hit a dry spot on the road. I can even apply the brakes and let my foot slide off the clutch so it snaps into engagement in first gear. The engine will stall but the diff won’t break. My 1991 Ranger has been out there for 29 years, 400k plus miles and has probably seen just about everything. At this point I don’t see how the kind of duty it would see as a chunker would be all that different.

My 91 Mercedes has a electronic diff lock. Anyone knows how this works and if it culd be usefull here?

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The style of shearing chunker head you pictured develops a tremendous amount of axial thrust in force.
Your c-clip retained light duty Ford Ranger axels will fail at this c-clip groove/retainer lip area.
A true truck rear wheel drive axle will have thust capable opposing tapered roller bearings on each side. The axle is retained on it’s forged outer flange end by many bolts to the heavy cast bearings hub.
So “maybe” begins at true F250/2500 axles.
With for sure at the proven much larger, lower geared truck&bus full floating axles


I suspect this will make your rear end behave like a ‘solid axle’. We used to call this Positraction, and more recently ‘limited slip differential’. None of these things are exactly the same but will all give you more traction on snow or other slippery conditions. I don’t see how that will be useful here.

Yup, those Timken tapered roller bearings sure are nice. They take both axial AND radial loads. I might look into that c-clip groove/retainer lip thingy. But I can remember hauling flagstone. I did didn’t go extra fast but I wasn’t a traffic hazard either. I just know that going around corners had to generate some big thrust loads. Hard for me to imagine that chunker doing worse than that.

So i was just doodling. I think if I actually build an elevator I’ll tear up an old treadmill and reuse the electric motor so it would be independent of the truck and speed controllable. But wouldn’t something like this be nice for filling bulk sacks and storage silos, putting the chunks on a trailer and things like that?

I wasn’t meaning as your only chunker, I meant on the fly if you were away from home, and need some fuel along the road.