SoilMaster 18,000 (prototype)




Introduction: SoilMaster 18,000 (prototype)

I've been wanting to build myself a composter for quite a while now. A few months ago some family of friends gave me a bunch of these 15 gallon plastic jugs, so I set about a plan to put them to use. Due to the limited volume (I certainly would have preferred 55 gallon drums), I decided it would be best to incorporate several of them into the contraption to increase output while maintaining roughly the same footprint (maybe something like 2/3s what it would have been if I'd built 3 separate units, anyway). Also, I thought this would be more fun.

Oh, so, a description...

It's a three armed composter. Each arm incorporates an independent composting unit. These arms/units may rotate as a whole as well. The idea being that when one is full it can be shifted back and allowed to cook while the next one is brought forward and gradually filled.

Step 1: Obtain and Modify Your Containers

Right, so, this step, as described, is probably fairly unique to my situation, but it's also very common sensical, so I don't think you'll need to fret much over the details.

Basically, you just need to get ahold of some conatiners of some kind. I got mine from the parents of a friend of mine who were looking for a way to dispose of them. They run a dairy farm and the detergent they use to clean out their milk pipes and tank comes in these jugs. They had 15-20 of them so I took my 10 favorites to start experimenting.

To get these things suspended and spinnable, there needs to be some sort of axle, right? And that axle should emerge somewhere near the center of the both ends of the container. Luckily, the center of the top end of these containers is well marked by a big, black handle affixed with a plastic pin stuck through a little nub protruding from the body of the container. I tried a few different techniques to remove these handles and found that a little limb saw was small and flexible enough to get at the base of the nub.

Once that's cut off I used a "hole saw" on my drill to put a hole in roughly the same spot, corresponding in diameter to the pipe I planned to use for the axle.

Step 2: Building the Hub-arm Rotating Support Apparatus

For this, I started with the hub. I knew I wanted the arms to butt against a central piece, so I worked out this hexagonal shape with 3 sides being 3 1/2 inches, and the others accommodating those in such a way that the hole in the center was equidistant from them, or something like that. Honestly, I don't really remember how I came up with the non-butting side lengths, and I'm not sure they're all that critical. Just seemed like it'd be good to put some space there to give the containers room to fit.

I made "hubcaps" based on the dimensions of the hub, I just added two inches (if I remember right), around the edges and made sure the hole was in the dead center. These were intended to add some lateral support to the arms, and keep them from separating from the hub.

The arms were easy, I just made them a few inches longer than the radii of the containers and put the holes for the container axles about 1 1/2 inch from the ends.

Possibly the trickiest part of the whole thing was trying to figure out the angles for the arm supports and getting my mitre saw to cut them. I ended up just laying everything out on the floor and tracing the angle on the peices to be cut for supports. This worked well enough, but a little additional trimming was often needed for a good fit.

Assembly was pretty easy. I again layed all the pieces out on the floor, lined up the hubcap hole with the hub hole and started tackied it into place. This held everything well enough that I could get some screws into the arms and supports without them sliding around and falling apart on me. Once those were all secure I put the other hubcap on.

This would also be the time to cut your axles. I used two different sources for mine. The central axle was made of some leftover well casing pipe (or so I was told), which was slightly thicker and of a larger diameter than the container axles. The container axels were made of chain-link fence tubing, the smaller stuff that runs along the top, not posts. I think this stuff probably would have been adequate for both axle applications.



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    16 Discussions

    Can you make a PDF version of this?

    your composter is really cool. I don't know how much work you've done with those containers in the past. I'm guilty of a considerable amount of home garden ingenuity involving plastic barrels just such as those. They are great to work with as they are clean, and easy to fabricate into something new. The down side: They do not hold up to UV exposure worth a darn. They become extremely brittle and fragile after about 1-1.5 years in the sun. However, I'm guessing you need to cover or paint your barrels with something dark in order to get the high composting temps. If that coating/covering was something that would substantially block UV it might dramatically improve the longevity of your creation. I'm interested to know how it works out.

    3 replies

    This was the first thing I've done with these types of containers. I've heard they have that problem with breaking down in the sunlight. I'm not too worried about it though, since they were free and the people who gave them to me have a couple more of them they're throwing out every month. If they degrade enough to start failing I'll just switch them out with new ones. The dark color of the barrels is something that has occurred to me, as far as getting the heat up (or blocking the bacteria killing UV light?). That will probably be the next modification I try, and you're right, it probably would even help with the longevity. I'll probably update it on this site as I go. Thanks for the word.

    I'm not sure about the shimmer part. Does that mean it's glossy? That would probably reflect some of the heat. Epoxy base sounds good. I doubt much would adhere well to that plastic. This project is sort of on hold right now though, I've found that a simple pile works well enough for me. I'm currently more concerned with building some kind of rainwater catchment/distribution system.

    I enjoyed your take on the composter, thanks for the inspiration, you got me thinking. when we lived in the city we had a small yard, I tried to have a garden, but did not have a green thumb. We did learn some thing, composting, that is we took our organic materials from the house, the grass clippings, the neighbors leaves (when in season) and composed them. To blend and mix all the materials evenly I put my weed whacker in a garbage pail then dropped in all the organic material we collected from the week and weed whacked the material into a uniformed blend. This seamed to speed up composting. To this day if I want to reduce the amount of leaf bags I use I'll still drop my weed whacker into the pail and reduce the leaves, now they are easier to compact in the bag.

    Exellent, I like the concept and the ergonomics of this, how long to put this baby together? Has this sped up the decomp in any way? Either way the minimizing of bending over to turn the compost is great.

    1 reply

    Thanks. I'd say it took somewhere around ten hours to put together, but that's mostly because I was sort of making it up as I went along and had to go back and correct a couple flaws. I think it could be done in half the time, or less, without too much trouble. Especially if you've got templates or patterns for the wood cuts. As far as speeding up the decomposition of material, I'm sorry to say, I'm not sure. I moved to a new place a couple weeks ago and have been totally neglecting my compost(er). Honestly, I don't even remember when I last put stuff in it, and I haven't checked on it for two weeks or so. I'm starting to get settled now though, and plan on getting back to it. Especially since the new place has a garden about 3 times bigger than the one I put together at my last place! Another thing which should make a difference, I ordered a mulcher the other day, so I plan to run most of my composting materials through it before putting them in the containers (some of it I'll probably just dump on the garden too). I think some of the grass I put in last time was too bushy to get and stay good and moist and rotty.

    Love it, Have a suggestion, a round piece of wood attached to one end of each barrel with a belt that goes to the center and rotates the outer drums as the outside is turned. Some of the high end composters incorporate a crank that you turn to turn over your compost and speed composting. But, great, love it, looks like it would be the ideal height to just park a wheel barrow under one of the drums, dump your compost and take it to the garden.

    I use a 25 dollar one from my citty and a trash can.

    This is pretty damn cool. Although you mentioned footprint minimization, I assume you have a reasonable amount of outdoor space. Maybe a future version of this could use piles (posts) fixed into the ground, instead of the larger triangular base you've built for this one. Any reason for the height?

    1 reply

    Thanks a lot, I appreciate the feedback. I like the idea of the piles. While building this I noticed an issue with vertical/lateral stabilization until I tacked a piece of plywood across the back of the supports (which worked surprisingly well). The embedded posts would certainly help with that, as well as saving both materials and space. One reason I designed it this way though was so that it would be more mobile. Right now, when it's empty, I can actually lift it up and move it around by myself. It's pretty cumbersome, but the whole thing probably weighs no more than 50 pounds. As for the height, there are a couple reasons. The way it's set up in the primary picture, you would be loading your compost materials into the lower container. It's right about waist height, maybe a little lower. I thought this would be a convienient height for walking up with a pail of vegetable trimmings and dumping them in, and it's not too high for shoveling either. The other benefit is that a wheelbarrow will fit beneath that lower container, so when the compost is ready you can just dump it right in and take it away to the garden or wherever.

    Looks good! I'd love to see the full build of your next version.