Now is the time to make my own thread for the chunker build. I am planning to closely follow @Chris’s, @BillSchiller’s, @Dustin’s and others who have built this kind of chunker. Thanks to their pioneering work the design is already made, so all the is left to do is recreate it with the parts available to me.
Snagged a square baler gear box from scrap yard. I think it is a Massey Ferguson.
Started work on the frame. It has five mounting holes located on the side of the gear box. So I drilled some 5/8” holes in some 1/8” plate and welded them to the frame.
Decided I would use the large gear that was bolted onto the baler arm. It is about 1/2” thick so it should hold up. I plan to drill six holes into that plate a use that as a hub to bolt the cutter wheel to. The hole in the middle is already centred on the gearbox shaft so all I need to do is centre everything on that hole.
I’m using a piece of 5/16” pipe 12 1/4” OD welded to a piece of 5/16” plate. I actually cut that piece out of my fire tube top plate. It was exactly the right size. I’m hoping the cutter isn’t going to be too thick?
I tack welded the plate on then found the centre and used the same template to mark the holes. The holes were actually not exactly lined up. So I drilled two holes bolted the gear to the cutter and drilled the rest of the holes.
Picked up this motor on the weekend. It’s a 3hp 1720 rpm, 115/230v high torque motor with a 1” shaft used for farm equipment. I got it for $350 CAD. Hoping it will do the job.
Well I’m now trying to locate a belt and pulley. I decided to go with banded v belt, but I am having difficulty finding a pulley for a banded v belt.
Does someone know what they are called or what they look like?
And I’m probably going to want a larger pulley to increase the rpm’s correct?
On mine and some others I’ve observed it makes a chunk about every 1 to 2 seconds . Which for me is a comfortable speed. You will need to know the ratio of the gearbox (8 to 1) on mine and I believe Bill’s. And then you can calculate the diameter of pulley you need given the motor rpm to give you the desired cutting speed. iirc mine is about 1.6 sec a cut it gives you a little time to think between cuts. I use 2 B size v belts and a double v pulley on the motor and drive the flywheel even though there are not grooves in the flywheel I haven’t had problems with the belts coming off. Remember be safe the flywheel will make two wood cuts after you shut the motor off. You get a body part caught in this you are going to lose your attachment to it’.
Thanks Tom. I do agree these can be dangerous machines. I’m planning to put guards on and make an auto feeding system like some others have done. Would you know how to find out the gear ratio on the gear box?
Hi Rindert. That would be a good idea, but I did some checking and I haven’t been able to find a pulley. I found this that may work if it’s got the right size shaft.
For the gear ratio I’d just check the old fashioned way. Put some paint or tape on a point of the output and input and count how many revolutions of the input it takes to do one full revolution on the output.
Also you can consider your pulley sizes. Here’s a jackshaft calculator for go-karts but it works the same for belts.
I don’t know enough about your design to look any specific belt/pulley combo up for you. However the belt manufactures publish lookup tables for their products based on rpm, hp and wrap angle. I could look up a specific belt pulley combo for you if you wanted me to. I assume the belt well go around the flywheel? I could also recommend a clutch type belt drive that would allow your motor to start up without a load, which should allow it to last longer.
Rindert
Depending on the shaft size on your motor, I’ve found that if you take the pulley off of a modern alternator that some will fit pulley weld hubs. Check your junkyards. You’ll want a two or three jaw puller to yank the pulley out. Modern alternators are usually one way and have a sprag clutch and it’s just a press fit. I can’t remember the exact part number of the alternator but the 3" size pulley fit on an X size weld hub.
Then you could use a regular automotive serpentine belt to wrap around that flywheel.
Yes Rindert, my plan is to wrap the belt around the flywheel. If you can find a pulley/belt set that would give me something to look for.
The motor I have is 1720 rpm with a one inch shaft. If I could get a 7” pulley mounted to the shaft that would spin the 22.5” flywheel at 535 rpm. Using Cody’s method I tested what gear reduction this gearbox has. It is 6.66 to 1, so that would give me 80 rpm on the cutter wheel. Does that sound about right?
I can check at the scrap yard and see what I can find.
I don’t know if that is too fast for that style cutter or not. I usually try to get those types of things around 60.which is 1 per second just because my reaction has slowed down a bit. Wayne’s might be going that fast, i haven’t timed it. If you have the 7" I would say try it.
I think 60RPM is a good goal. That’s about as fast as I’d be comfortable with.
You might be able to find a 6" sheave from a power steering pump or Air Conditioning compressor, and if it’s made of steel you could weld it to a cheaper 1" pulley. If it’s not steel you’ll have to get creative.
You also may need to gear it down slower with a 3hp motor trying to push it. You might need the torque. I’m pretty sure balers needed more then 15hp at the pto. Which you didn’t have the entire baler but you do have the flywheel…
Finally decided to build my chunker on a frame instead of making a dedicated trailer for it. I’m still hoping to get a small trailer and just bolt it to the trailer to make it portable. This way I can pull off the chunker if I need a trailer.
The arm is now welded to the gear. I’ve got six grade 8 bolts, 5/8” diameter. The gear is 5/16” and the cutter is the same. I think that should hold up.
Got a piece of scrap square tubing from work. I was too cheap to spend $200 for new tubing. And I offered to pay scrap price for it but they said to just take it. So I got it for free.
Instead of using a serpentine belt I’m going with a double banded v belt. The parts for the pulley is easy to find. I guess I’m just reluctant to go through the hassle involved in trying to make something work with a serpentine belt work.
Great work Bronlin, it sure looks sturdy enough and free stuff is always nice.
Emergency stop for sure as Cody said and speaking of motor mounting, what kind of tensioner are you planning? Cradle type of motormount or tension rails, they both have their upsides and downsides.
You can of course also just use oblong holes only but it will be a bit of a pita to get the belt tensioned and the motor squared but way easier fabricating.
Personally I am not a fan of tension pulleys, they shorten the life of the V-belt bending it the wrong way (unless you payd up for a double-corded belt but who wants to do that ) plus if you didn’t write it down somewhere which belt you used there is no way to read it on the belt anymore but you do get a bit more traction on the drive. For a serpentine belt they work good.
) plus if you didn’t write it down somewhere which belt you used there is no way to read it on the belt anymore but you do get a bit more traction on the drive. For a serpentine belt they work good.