windmill composter

[StoneHeartFarm]

Why would backwards be a bad thing? We're makin compost here. If the agitator fins inside the barrel (we really gotta make up some names for these parts) are shaped right, the barrel could rotate in either direction and still function properly.

How about an old lawn mower transmission? The small light aluminum jobbies that fit in your hand? They're small, lightweight, and can turn 3600 RPM into what? 100 or 200 RPM? Good torque. I don't know how fast the anemometer would spin at max RPM. Probably wouldn't want the barrel to turn all the time anyway. Compost might not compost if constantly spun. Think REAL OLD Mother Earth, back when they showed you how to build tractors and cars and stuff. (Oldest I've been able to collect is issue #3, anybody seen an older one?)

Or, How about a bicycle transmission? ie, 10 or 18 speed gearing and chain set up. Again, in low gear they can move a lot of weight with relative ease. Somewhere I have a bicycle book from Mother Earth. It shows how to hook up generators and such. Believe it or not, they've got a set up you can use to plow a field!

I like the anemometer idea. Would it have enough power to run something like this?

Also, we need to consider the maximum speed (Is that overrunning?). So the darn thing don't get turnin so fast it spins the barrel off.

A slow turn is probably better. 24 hours to make a complete turn might be just about right.

SHF

 

[toddler]

SHF,
I thought backwards would be bad because after a gust of wind, it would only go backwards until the heavy compost turned the tumbler (new word) back to where the compost is at the bottom. I was picturing it just ratcheting along until the compost had to fall off the side of the barrel/tumbler and aerate itself. The fins I picture would just be to stop the mix from sliding backwards. They wouldn't have to run the length of the barrel, they could be a few inches each and we could stagger them. If they spiral around the inside, then we would only be lifting a portion of the mix at any given time. Less torque needed.

Lubrication I hadn't considered. Trying to follow the KISS philosophy, maybe we can avoid it. Could we use a plastic spline(?) like the pull cord on my old yyz toy cars 20years ago. One turn of the worm gear there would only rotate the barrel a few millimeters.

Todd

ps)anenometer, huh? so that's what you call the thing. nice to have a name to put with my mental image.

 

[RPM]

We'd definitely need some kind of mixing 'fins' inside the drum -- think of what the inside of a concrete mixer or even a front loader washing machine looks like.

Toddler - I think that the plastic spline/worm gear (the worm is the screw part - the wheel is the normal looking gear) would wear too fast. There's a lot of heat generated where the worm and wheel contact ...

Also on the windmill idea - if you were using a worm gear the vanes would never blow in the wrong direction - you wouldn't need a ratchet. All you need is the resistance to rotation in one direction due to the gearing - and eventually the vanes will blow in the right direction (if you use vertical vanes rather than 'cups').

By the way, was thinking about this some more this morning (going through a very boring time at work - busy, but boring). Operating on the KISS principle - perhaps the quickest way to do this would be to knock together a device with a cheap plug-in 110V timer, a car battery charger / jump starter - and a starter motor from a junkyard. Just set the timer to activate the jump starter for a minute each day (probably all the starter would handle) and crank that motor. Would still need a frame and a couple of rollers for the barrel to lay on, but the motor should have enough torque to turn over the barrel (espec. if you get one from a truck) without needing extra gearing - just a shaft coupling.

I know this approach doesn't have the ecological appeal, but would probably be the most simple after doing it manually. Next step up would be the windmill I guess.

One last thought - anyone considered doing this on a larger scale? I know that most compost piles are turned with a loader - but what about getting hold of an old 500 gallon propane tank and using that as the tumbler (after some suitable mods) - would get a useful amount of compost out of that!!

 

[RPM]

SHF - only problem on the two gearing mechanisms is that the reduction isn't high enough. 36:1 may sound like a lot for a reduction (for a mower) - but it would probably still be too stiff for wind power to rotate a barrel. Bike chain wheels probably produce of the order of 10:1 at most.

Typical worm gear pair can produce of the order of a couple hundred to 1 ratio. Some will go up to 1000:1 ...

My warped mind also had another idea (first stage of a good design is to brainstorm right?) - you could power the rotation of the barrel off the water flowing through a downspout if your area of the country has sufficient rainfall. Sort of a mini water-wheel. Wouldn't work for everyone but it might be good for some.

 

[RobS]

Speaking of drums with fins, and wanting to handle a larger volume... How about a retired concrete mixer body? The drum supports are already there, as are the fins and such. The drive mechanism could be geared down sufficiently to allow a small motor (or windmill) to drive it and with some additional inventiveness it could probably be made to run in reverse at "normal" speed for unloading.

It wouldn't look very good, but with all that compost a few arborvitae would grow up around it in no time /w3tcompact/icons/smile.gif

 

[StoneHeartFarm]

Concrete mixer might work, or at least something on that design. Been putting some thought into this (making my head spin), and thought that the less compost that can be turned at a time, the easier it would be to turn it.

Question: Is it easier to turn the drum, or turn the compost? ie an internal "mixing" fin set that would rotate around inside the drum. Downside would be corrosion of the internal parts.

A starter motor might not be that bad of an idea. Power generating windmills are all DC. A low power draw DC motor could even be hooked up to a solar panel. Use windmill/solar panel to charge battery. Timer kicks in, rotates drum.

I doesn't have the romantic appeal of an old time windmill pumping water, but...

SHF

 

[RPM]

<font color=blue>Question: Is it easier to turn the drum, or turn the compost? ie an internal "mixing" fin set that would rotate around inside the drum. Downside would be corrosion of the internal parts.</font color=blue>

Answer: It would be easier to turn the compost from a weight perspective - but easier to turn the drum from an overall design perspective.

 

[toddler]

RPM,
I agree. I'd stick with turning the drum. It might actually be harder to turn the compost, given the static friction it would have against the drum, assuming the drum is on bearings or such.
Todd

 

[StoneHeartFarm]

The drum could be rotated on a pair of rollers similar to those in a copy machine. Basically steel bars with a rubber coating for grip. Kinda like the roller (platen?) in a typewriter. Problem would be driving this roller.

I'm thinking the overall RPM would have to be REAL slow. A fast turn, say once every 24 hours might effect the microbes ability to decompose the material. With wind, this might not be a problem unless the composter was in a really windy location where it was getting wind everyday. The system would need some kind of brake built in for high wind situations.

SHF

 

[RPM]

Well ... you could always have two worm-wheel pairs back to back. If each had (conservative) gearing of 100:1 then you would have a total of 10,000:1 with the 2 of them.

Add to this the fact that the roller rotating the drum would probably be of the order of 1/10th the diameter of the drum i.e. one rev of the drum for each 10 revs of the roller.

Total reduction would be 10,000:1 stepped up by 10:1 ratio to a final gearing of 100,000:1.

That's pretty slow.

If, on a windyish day (just guessing), the vanes rotated at 250 rpm all day long (just over 4 times a second) then we would calculate the total revs of the barrel as:

(250/100,000) revs per minute = .0025

(250*60)/100,000 revs per hour = .15

250*60*24/100,000 revs per day = 3.6

Hmmm, might need another reduction gear in there. I guess it depends on how often you get windy days.