Modding a Lawnmower into a Shredder / Mulcher


Hello everyone. I have a simplelawnmower with a briggs 6HP motor. I want to use it to shred/grind aged horse manure compost in the easiest way possible. The mower has a side shoot, but it has a spring loaded trap door covering it right now. It also has a trap door for a back discharge bag, which is also closed and I don't have the bag, I have thought of 2 options for this myself.

1) Cut a hole in the sheet metal base of the mower beside the motor, on the left hand side if you were pushing the mower, so that I can shovel in the manure.. Cover the bottom of the mower under the blades with 1/4 - 1/2" hardware cloth. Elevate mower off the ground on cinder blocks over tarp. Hoping it would shoot the shredded mulch out the bottom, through the metal hardware cloth onto the tarp to be collected.

Problems I foresee : If the regular discharge outlet on the right side of the mower blows grass out, will my hole i cut in the left side of the mower suck inward, or also blow out? Obviously this wouldn't work if the area I'm trying to shovel in is blasting air out. Would the shredded compost be blown downward? It's really the only place for it to go except the hole I would be shoveling in at.

This is the simplest way I can think of. I would prefer to do something like this. Perhaps if it wouldnt work stock like this then I could maybe reverse the blade? I don't have a welder, btw.

2) Much cooler option but I dont really have the time, material, or know how would be to run a pulley to a seperate trash can with its own blade at the bottom and wire mesh under that.


Any idears?

crapflinger7 years ago
if you mounted the mower over a barrel, and cut your "inlet hole" in the top of the deck (the metal shroud around the blades), then bolt a sheet of metal (nothing major) over the two existing outlet holes (or maybe better, just bolt a sheet across the side discharge, and then put a latch on the rear discharge so you can use it as a cleanout if you need to). then you can build a hopper over the top hole, shovel your poop into the hopper and it will chop it up as it goes down through the blades. then the barrel would collect it all

you could have the whole mower assembly mounted on a wooden tower that the barrel would fit under, that way you can just slide the barrel out to use the poop
Goodhart7 years ago
focusing on the portion of your question about the exit hole.....it depends on how you angle the hole. If you look at the lawn mower, the grass discharge is angled in the direction of the rotating blades. If it faced "forward" it would tend to suck in rather then blow out.
pacwoods7 years ago
I remember a post where someone made a industrial strength mulcher with a lawn mower, They attached the mower to a half barrel so the blades were in the top part of the barrel. They cut a hole in the mower base, as you described, but attached a feeding tube like thing to the hole. Sounds a little safer. I think the bottom of the barrel was removed so essentially it was a big short tube. Actually I ran across this comment thread looking for the post I just described.
sandman420 (author) 7 years ago
I am really leaning toward the building of a pulley system to power a shaft with a custom made simple blade, or perhaps a tumbler made out of screen that would probably also work well. I was just taking a look at sheaves and they seem real expensive! Damn. Any tips on building a pulley system with v belts? I am a novice welder and was thinking that I could leave the motor mounted onto the lawnmower deck and remove the blades and handle to have a base to begin with. Then I would need to weld on some sort of base for the pulley system. still contemplating.