Wind Powered Composter - the Green Twist , Exactly





Introduction: Wind Powered Composter - the Green Twist , Exactly

About: I'm a senior at Florida Tech studying Ocean Engineering (making wave and wind generators at sea). I'm into electronics, chemistry, all the sciences, alternative energy, welded steel art and lots more. To s...

This is my Epilog Laser Cutter entry so please Vote if you think the idea is unique and worth supporting.

Composting is the easiest thing one can do to help your community. With a wealth of good soil you, your neighbors, and everyone else is stuck with the predictament of what to grow. Imagine such a world.

The problem is that the standard composter doesn't turn itself, and the average human is too everwhelmed with life's callings to take the time to turn the composter once a week.

Hence the self turning composter, wind powered so no additional power is needed.

I just added a laundry basket to the inside to help churn the soil. It was turning a 3/4 full load with no problems at all. I had to empty it out to paint it black, but once the winds pick up I will post a video of it turning soil.

The gear drive supplies more torque than it would ever require, I used vise grips and tried to stop it turning but could not. I estimate that I applied about 150 lbs with a moment arm of 8 inches and still it didn't stop! The gear ratio is 1255:1.

You will need:

A drum, or other round item that will server such a purpose. Note that I did not have a drum but I did have a large bucket I bought for 3 bucks at walmart.

Plywood-depending on how big you want to go will determine how much scrap you need. I used about a half a sheet of 1/2 inch ply for the turbine but I think twice as many layers would be better.

2x4's or 2x6's-The frame and upright uses about 2-8ft lengths of one or the other.

Screws-get a box of 3in deck screws, they last forever and are very strong.

A junk gear motor with a high gear ratio is also needed.

Tools-I used a drill press, angle grinder, hammer, screw driver and jig saw. My advice, you can never have too many tools.

Time: It took about a day to make this. I actually did it over the weekend but actual time was about 12 hours.

Step 1: First Cut Out the Layers for the Turbine

The Vertical Axis Wind Turbine (VAWT) is made up of many identical layers of plywood. First, I cut out a template from foam and used it to mark scrap plywood for cutting.

Step 2: Cut Out the Many Layers of Plywood

Unfortunately it takes a insane number of layers of plywood to make up the turbine. Well actually it takes only 20 or so, but after cutting out 15 or so, you may go insane. Use the guide to mark up plywood and begin cutting. I attempted to cut 3 layers at a time using a jig saw but the progress was too slow so I ended up cutting one out at a time.

Step 3: Drill the Shaft Hole

After you cut them out, stack them up and use a drill to make the shaft hole. You can do this individually or all at once if you have a drill press and a really long drill bit. You don't need to be super accurate at all really since the turbine turns slowly and you will be grinding away a lot of material later on.

I used a 1/4 inch drill bit since I used 1/4 inch thread stock for the shaft. However, in retrospect I could have used a larger drill bit (1/2 inch or so) for the same shaft since the layers are compressed together with the end nuts. This would allow for easier re-alignment of the shaft had I poorly drilled my hole to begin with.

Step 4: Decide on Your Rough Shape

Once you have the layers drilled out and stacked on the shaft, you can play around with the final shape by twisting each layer a little bit forward from the one below it. If you make up a test rig you can experiment with the different shapes outside in the wind to see which one works best. I chose the simple spiral since it was pretty.

Step 5: Make Your Layers Smooth

Take an angle grinder and some sanding disc and begin sanding the layers into a smoother form. This is more art than science, so enjoy the task, and where a face mask if you are smart......note my lack of one.

By the way, this is my first attempt at hand grinding the shape and I think the final form turned out very well.

Step 6: Find a Good Gear Motor

In order to turn a heaping pile of compost it takes a lot of torque, therefore a gear motor is used to convert the low torque the turbine provides to high torque at low speeds. So I went to Astro 2 in Melbourne, Florida, a local surplus store and bought a gear motor for 10 bucks. It has a gear ration 1250:1 so it should provide lots of torque.

Step 7: Hack the Gear Motor

The motor is not what we need, we just need the gear reducer. Instead of taking just the gear reducer, it is smarter to just disable the the motor and use the whole device as it is. This lets us use the bearings and original weatherproof housing as well.

First take the gear motor you found apart. Gut the electrical parts (the rectangular brushings, and remove the magnets with a hammer). You don't care about the motor being a motor and these components only cause friction. Be careful not no damage bearings as you need this running smoothly.

Step 8: Mark the Shaft for Drilling Out

The motor will have a drive shaft running into it, thus we need to have access hole in the housing and a shaft hole. Use a center punch to insure a good shaft hole.

Here you see me attempting to hold the center punch and camera at the same time. The center punch indents the metal when hit with a hammer. This dent will guide the drill bit so your shaft hole is about as perfect as can be made without a lathe.

Then drill the housing with a larger diameter hole so the shaft doesn't rub.

Step 9: Drill the Marked Shaft

The center mark we made before really makes drilling out the shaft easy and near perfect (given you marked it near perfectly!).

If you do happen to miss align the center point mark, you can move your mark a little bit closer to center by angling the centerpunch in the direction you want to move the mark and hammering again. Once the mark is reset, give it a couple of taps of the hammer vertically to clean up the dents.

Now, to drill. I wanted to drill and tap the shaft in place but I didn't have the right tap. So, I drilled the hole to the size of the turbines shaft (1/4 inch) and used a wrap of friction tape to make the connection lock together. The hole I drilled was only about half of a inch deep, but you can pick whatever depth you need per your supplies.

Step 10: Drill the Cap

Like before, the cap needs to be drilled out so our turbine can spin the internal core. I used a 5/16 drill bit but you can use whatever as long as it is larger than your shaft diameter. Making it bigger is a good idea so you can have plenty of wiggle room for murphy and his law.

Step 11: Now Make the Composter Frame

Given that I do not know which motor you will find, I will just give a overview of what you should aim for. Basically, the drum will roll on two tires at one end and will ride on the gear motor on the other end. The motor output shaft is set in a disc of material of your choosing and this disc is bolted to the drum. The purpose of this disc of material is to spread the load over a wide area, since the plastic most drums are made of is usually very thick. I had a 1 inch thick lexan disc from another project so that became my disc. You can achieve the same results from cutting a disc from a 2x6 or some other lumber.

Now make a frame with two tires attached to one end, and a upright on the other end that leads to the gear motor.

The composter rolls on these two tires.

Step 12: Assemble the Beast

Use lag screw or deck screws, or whatever you have around and scrap a test rig. Test for alignment of the shaft with the turbine and see if bearing are needed. I ended up using some old bearings from my inline skates and would suggest there use in furture projects. They are cheap and weather resistance.

Once the frame is prototyped, secure tacks with lags and give it a try. My final design sorta took a weird path of development but that is like my life. Depending on resources, your project may or may not look like mine, and that is a good thing. I would rather have it not look like mine since I truely value innovation over replication. But either way take a look at my result and try to do better!!\

I should note, the gear motor was attached to the barrel via a plate with a keyed hole in it. I failed to note that earlier.

Also, I made a video of the system in operation but I had the camera on it's side. I will post a less neck paining clip tomorrow as well to show it operation.

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    I don't get a lot of breeze where I live, but I do get plenty of sun. Do you think there's any way to use solar energy to power the turning mechanism? And if so, how much power would I need? I think the size of the thing seems perfect, since I have a very small amount of space, but get fed up of throwing away so much, and then having to buy compost!

    Hey thanks for stepping in and answering sangretoro's question for me! Your answer is exactly right.

    4 replies

    No Problem!
    You stated that you picked up the motor for next to nothing at a local shop in FL, but I am not finding anything in TX. I've searched online, but the only things I've found are either dissimilar to your or very pricey! Is there an online store you might suggest, or any other advise you might give me and others to find a comparable motor?

    try surpluscenter DOT com

    first I'd lookup surplus stores or junkyards. If you go to a junk yard then try and find a windshield wiper motor since these usually have a worm gear reducer. However, you should be aware that a windshield wiper worm gear set only reduces the rotations less than a 1000:1 so the output torque won't be as high as my setup. But if you take this output and attach it to a bike spocket you can reduce it further with a bit of chain and a larger spocket attached to your composter. If you get my drift just nod. Basically just McGyver the hell outa it. That's what I did, my way isn't the right way, it is just a way.

    Thanks for the response. Yeah, I'll take a look at windshield wiper motors. I know it's no science, but I am finding nothing above 1:100. I had considered bike chain and sprockets. I'll give it a go!

    Can you give us a few more specs on how powerful a motor you suggest? Can this turn slowly but still strongly?

    1 reply

    1250:1. That is the strength of the motor. For every 1250 rotation input, 1 rotation is output. The fact that the output is turning so slowly in comparison to the input, makes it very strong! He also states that he feels it was a bit more than required to turn the barrel, but I'd suggest not straying from his choice too far.

    Awesome! Ok - like others I am looking for a gearmotor to build one of these. Are windscreen wiper motors from cars geared down enough to work? Has anyone used a windscreen wiper motor sucessfully - or can anyone answer this question for me before I go out and buy one.

    1 reply

    well if you can't find one gear motor to do it you can always connect two gear motors into each other. I don't think windshield wiper motors are geared down enough tho, they are usually single stage worm gears which are only 100:1 but.....two wiper gear sets in series would work.

    great idea and done very well. Just two remarks (no criticism) The bin is kinda small for most gardens compostable material yield and i found the easiest way to compost is still to just leave it on a heap, no turning whatsoever. It will compost the way nature has always done it without the help of men.

    That said: a great project

    1 reply

    Thank you very much for the input! I really have been lazy on that project and I think I need to get back to it. I have a new design that has a scalable capacity. I need to find the research paper I once read about the rate effects of these rotating composters. Somewhere on the interwebs is a whitepaper that quantify this value. BUT, I never did similar research so now I guess I have a fun fall project. Indoor controlled enviroment, of course. ;)

    I know its been a while, but I was wondering if you may have some ideas. I have a bunch of grass clippings left after we mow the lawn and it would be nice to compost at least some of them. The problem with that is that I would need to contain like 3 to 6 months of clippings. Do you have any ideas for big versions, and also how do you compost just grass. I was wondering if it was necessary to contain or of you can build some kind of box with a stirring device. Obviously this would require a much larger turbine, but that is fine.

    Ahh, I like this a lot. Very nice build. It looks nice spinning in the wind like a lawn ornament. HEh Nice to see some one els in the area on instructables. I am in Sebastian.

    Just saw this video on Catapult Design's vertical wind turbines. One metal & canvas design was specifically cited at costing $100, and the blue one is a looker...

    1 reply

    Thanks for the are right it does look nice. I really hope to post the new version soon....but I have a idea for the gulf oil spill I'm working on right now and that is taking all my time. Again thanks for the research

     That would work great, and it looks very mobile.

    1 reply

    Thx, I hope to begin making the final version soon.  It will look much nicer and will be easier to build.

    This is really great. Good luck with the next model.


    Can anyone provide more information on step 6 - Find a good gear motor? I tried to find something online but I couldn't find anything with such a high ratio (1250:1) What was attached to this gear motor? Essentially, I'm just trying to find out what to ask for at a local surplus store or search for online. Any suggestions, model numbers, keywords? Thanks!