More Cans = More Recycling = More Money. Make it so.

January 2, 2008 7:30 PM

I see you there. You're smart. You've got great ideas. You want to help me make the world a better place. So, help me brainstorm this contraption.

I work for a non profit. As part of our fund raising, we recycle cans. Lots of them. Hundreds and hundreds of pounds of them even. Trouble is, they don't usually come crushed. I can't afford a briquetter or a baler, so don't suggest that. We do have enough that a wall mounted single can crusher is probably not the best bet either. I thought about driving over them, I do have a double-wheel 3.5 ton truck, but I don't like that either since we're pretty public and have a gravel lot.

Last week we recycled 260lbs of cans, that was December's load. That's about to at least double in the next 2 months. Certainly not enough to warrant a bailer or briquetter.

So I'm thinking, what's the easiest way to crush these cans? My thoughts: I'd prefer a non-electric approach...or at least I don't want to plug it in. I wouldn't mind pneumatic, we do have a compressor (or we can get one).

Resources: plenty of PVC, sch 40 and 80, fittings, compressor, big truck, every power tool you can think of, wood of all sizes and dimensions, and just about any hardware you can think of. (hinges and screws to plugs and switches.) I could probably also spend another ~$200 if I needed to.

Requirements: Needs to be fast, ideally I dump a bunch of cans into a hopper and it starts crushing, or it crushes them all together. It needs to be safe and simple to operate, so that I can have volunteers and staff operate it often. Needs to be fairly small, or foldable, or suspendable. Lightweight would be ideal too, but I can deal with heavy. Also, it obviously needs to be able to deal with getting some soda/beer/whatever on it sometimes, and/or should be able to be hosed off, at least in the crushing area.

Bonuses: the tighter the crush the better. The more cans I can get in the same space the more money we make per cubic foot of storage space.

So mefites, get thinkin! Help me design my toy.

posted by TomMelee to Science & Nature (35 answers total)

I can think of two ways to crush cans: continuous feed, with some kind of roller arrangement, or in batches, with some kind of piston thinger. And whatever you build is going to need some kind of guard on it so you don't crush volunteers by accident.

How do your cans arrive?
posted by flabdablet at 7:37 PM on January 2, 2008

Do you have floor space? Or a big driveway? You could make a 'box' out of some wide boards, maybe like 6" tall, pour the cans into it, and get a piece of plywood to just fit inside.

Then get some kids to jump up and down. (For the bonus: get heavy people to jump instead of kids.)

It's decidedly low-tech, but it won't take up a lot of room. If you're doing it indoors, you could even just put a tarp down underneath.
posted by fogster at 7:39 PM on January 2, 2008

Response by poster: I like your thoughts AND your fast answers. I do have floorspace, and we've done the jump around thing, it doesn't give us particularly uniform crushes though, which while not necessary is nice.

My cans arrive in 35 gallon black trash bags for the most part.

My first thought was like a 6 or 10 foot long piece of schedule 80 that we dump a buncha cans in and go BOOM with the compressor, but I think that's overenginnering it, because it would be slow.

Keep 'em coming!
posted by TomMelee at 7:42 PM on January 2, 2008

1) Fill a metal barrel with water.

2) Seal it

3) Turn it on it's side

4) Weld a handle that connects to either end (what used to be the top and the bottom) and connects somewhere in the middle (thing lawnmower handle)

5) Roll barrel over cans.

6) Profit!
posted by Pants! at 7:43 PM on January 2, 2008

RE: Piston. Start with a pneumatic wood splitter, remove the wedge end and replace it with a flat bit, so that pushing the piston forward slides the flat bit into an open-topped box. Instant garbage masher. The speed on the splitters is fairly slow, so not too many worries about safety. A closed-top box might be safer but also harder to load and harder to gauge when to stop crushing. Build a box that matches the size of the can-brick you want at the end.

That's my two cents, anyway.
posted by caution live frogs at 7:46 PM on January 2, 2008

I'm thinking you could make a couple of really heavy duty wooden boxes, maybe eight inches tall, just a little wider than a truck tyre and ten foot long; lay them out neatly behind the truck, fill them with cans, and run the truck backwards. You wouldn't want ends on them at the front. Might need to fiddle with the slope of the ends at the back, depending on how the cans flow as the truck wheels go back over them.
posted by flabdablet at 7:47 PM on January 2, 2008 [1 favorite]

Would an old concrete mixer with a couple of big rocks in it work?
posted by flabdablet at 7:54 PM on January 2, 2008

If you're willing to consider an electric solution, then what you want is called a "trash compactor". They sell them at places like Sears. New ones cost about $500, but you might be able to get a used on on something like CraigsList for a lot less than that.

Great big hopper that you dump cans into. Close the drawer and push a button, and after a bit they're nicely flat. Dump in more, and keep doing that until the hopper is maybe half full of crushed cans. Then take out the bag and dump it.
posted by Steven C. Den Beste at 8:05 PM on January 2, 2008

Response by poster: Holy CRAP I didn't even think of the compactor. We actually have one on the sales floor. HAH. Keep feeding me suggestions though, I want to make something.
posted by TomMelee at 8:08 PM on January 2, 2008

What Pants! described is a like a DIY asphalt hand roller. It could work. I tried finding prices for used or new ones online but was unsuccessful. It may be worth it to find out.
posted by junesix at 8:19 PM on January 2, 2008

I am completely stumped for practical ideas, other than to say that I think it would be totally awesome if you found a way to tap into a completely free, unlimited source of power = human frustration/aggression. For instance, if you had a large mallet and some cans and toured them around to football games, gyms, corporate offices on lunch hours, etcetera...there would be throngs of people who would happily lose their minds for a few minutes to crush some cans or press some buttons that made stuff break and be destroyed beyond recognition. But maybe that's just me.
posted by iamkimiam at 8:25 PM on January 2, 2008

(the button pushing refers to the operation of a giant travelling can crusher. Bonus points if the button is big and red.)
posted by iamkimiam at 8:26 PM on January 2, 2008

Buildsturdy 3-sides enclosure out of wood that the a 35-gallon bag of cans will fit into.

side view:


\
..\
....\

Get a piece of heavy sheet metal that will cover the mound of cans (or a few layers of plywood). Drive the heaviest wheel of the truck over the sheet metal.
posted by porpoise at 8:35 PM on January 2, 2008

top view:

------
| . . |
|. . .|

You'll probably have to drive pegs behind this thing and in front of this thing to keep the metal plate from getting loose. Maybe drill two holes into it for a heavy rope handle on the side with the two '.'s. The height of the -----'s will probably be limited by the clearance of the truck.
posted by porpoise at 8:41 PM on January 2, 2008

Go to the local engineering school and throw your problem out there. I worked a summer in the garage at the University of Cincinnati and the engineering students built an oil filter crusher for them. Maybe they'll get some practical experience and you'll get a can crusher!
posted by cdmwebs at 8:43 PM on January 2, 2008

Why don't you shred them instead of crush them. Even your basic home-office shredder from Staples can make mince meat of pop cans -- an industrial shredder would be durable enough to handle hundreds of lbs per month without much maintenance.
posted by randomstriker at 9:03 PM on January 2, 2008

Response by poster: Thanks for more ideas. We have asphalt rollers. Trouble is that they weigh let's see, 50x8.33 lbs plus hardware and aren't intended to roll over things bigger than about half an inch tall.

I actually considered the levered sort of crusher using the weight of the truck like porpoise suggested, I'm just concerned about it being able to realistically support that much weight. 7000 lbs of curb weight is a lot to contend with, of course that's distributed across 4 points, but still...Also, I don't let volunteers drive the truck.

I might consider tossing the crusher idea to our engineering students, we typically use them for actual construction related goodies though.

I'm unsure how I would feed cans into an office shredder. Futher, shredded cans don't take up less space, which is the issue---more pounds per bag. Also, shredded metal is a HUGE safety issue, aluminum or otherwise. Ever stick your finger inside the mouth of a can and get a cut? Ouchie.

The concrete mixer idea is interesting, but it's waaaaay too slow.

I'm really hoping someone out there can help me understand how to pneumatically drive a piston down a length of pvc...or some other amazingly fun destructive way to smash a bunch of cans into the tiniest space possible.
posted by TomMelee at 9:16 PM on January 2, 2008

How about a vacuum crusher?
posted by cdmwebs at 9:20 PM on January 2, 2008

Would it be beyond your means to melt the cans?

I'm thinking of a crucible for aluminum. Then you could pour the melted aluminum into blanks.
posted by Cool Papa Bell at 9:27 PM on January 2, 2008

Could you rent/borrow an industrial roller? Or failing that, get a smaller version?
posted by blue_beetle at 9:39 PM on January 2, 2008

Here's one that looks pretty neat. The inventor has a parts list and instructions to build it. Watch the video for a demo.
posted by JujuB at 9:57 PM on January 2, 2008

Tom, where are you in the world? That will help us decide a solution.
posted by parmanparman at 10:29 PM on January 2, 2008

Here is one solution:

Can Crusher

The bike turns the crushing wheels, their mass helps crush the cans.

Elegant!
posted by robomeme at 10:56 PM on January 2, 2008

Keep feeding me suggestions though, I want to make something.

Are you really sure that's wise? Things like big rollers, and some of the other stuff you're talking about, are injuries waiting to happen. What if the roller goes over someone's foot? That was why I recommended the trash compactor: not only will it solve your problem, it will do so safely.
posted by Steven C. Den Beste at 12:24 AM on January 3, 2008

Where do the cans originally come from? If they are donated by many individuals, why not ask them to crush them before they give them to you?

Sorry if I missed the point...
posted by booksprite at 1:44 AM on January 3, 2008

What about adapting an old-fashioned mangle, something like this one on ebay - not particularly conveniently located for you, perhaps (I assume you're in North America, for some reason). Or concocting something like a cider press, but a bit more heavy-duty.
posted by ComfySofa at 3:30 AM on January 3, 2008

Response by poster: Ooh, sorry. I'm in America, along the Mason-Dixon line.

I don't think a vacuum crusher would work. Ever put a marshmallow in a vacuum? It gets bigger, not smaller. Perhaps placing them in a kevlar bag and then evacuating all the air would work though.

I thought about melting the cans, again we've got a workplace safety issue though.

@juju, I saw that one...it's slow and mechanical overkill. It is fun to watch though.

The bike powered one is sorta nifty, I like the overhead hopper idear.

@Steven, the temporary solution is the trash compactor. We build lots of fun stuff to encourage people to be greener, such as solar hot water heaters, hot boxes, compost bins, that sort of stuff. People like gadgets, and so do I.

@booksprite, we do encourage them to crush them. Nobody does.

@comfysofa, nice link. Now I know what the hell that thing in my basement is. Too bad I still have no idea what it's supposed to do. I could do something like that with one of the big honking 3 phase motors I have sitting around...that's sort of similar to the bike one above.
posted by TomMelee at 5:20 AM on January 3, 2008

This looks pretty interesting, but might be prone to breakage.

This looks like exactly what you're looking for, but might be a little more work in the construction than you want. Maybe you could talk to the guy who made this and ask him to help you with another one?

This one looks like it might be dangerous, but a lot more simple to build. Perhaps it could be modified to include a magazine system for a "semi-auto" can crusher.
posted by yellowbkpk at 6:08 AM on January 3, 2008

Log splitters can be quite dangerous... they're one of the wood tools the safety conscious Boy Scouts of America prohibits from being used in their activities (unlike say, axes... welding torches...)

"For instance, if you had a large mallet and some cans and toured them around to football games, gyms, corporate offices on lunch hours, etcetera..." And you could charge people for the privilige...
posted by Jahaza at 7:13 AM on January 3, 2008

Response by poster: That pneumatic system there is the same one someone linked to before. It's neato, but waaaay too slow. I could do it faster with my feet. I need wholesale destruction. There's a ton of videos of homebrew ones on youtube that are pretty cool.

I don't think that the sheer numbers of cans are appreciated. 24 cans equals one pound. In three weeks I had 260 lbs, and that's about to double or triple. I can't realistically drive around my box truck and get people to smoosh that many cans for me, at least not often enough to keep them under control.

Not trying to poo poo suggestions, I'm loving them. Keep on keepin' on. I'm really thinking some 12 inch green pvc could hold a lot of cans, it's sort of the issue of what to use as a ram-arm and how to actuate it...but certainly 30-50 psi would be enough for some real carnage.
posted by TomMelee at 7:28 AM on January 3, 2008

How about scavenging and recycling the crusher from an old garbage truck?
posted by acorncup at 9:03 AM on January 3, 2008

Response by poster: Lol, good idea, if I needed a thousand psi of crush force. Keep thinking though!
posted by TomMelee at 12:47 PM on January 3, 2008

12 inch PVC full of cans, heavy round wooden slab cut to fit inside PVC, heavy wooden beam between front bumper of truck and wooden slab, end of PVC against wall, drive truck slowly forward?
posted by flabdablet at 7:29 PM on January 3, 2008

What I expect this would actually do is form a wedged-in plug of crushed cans right next to the slab that eventually jams in the PVC and stops the crushing action going any further. But there might be some length of PVC below which it actually works.
posted by flabdablet at 7:33 PM on January 3, 2008

OK, I've given up on the truck for the time being. What about making up a heavy wooden box, held together with steel strapping. Put one of these inside, hooked up to the compressor. Put a floating false floor on top of that. Load it up with cans, clamp down the lid, and fire up the compressor.
posted by flabdablet at 9:43 PM on January 3, 2008