Is there a good way to chop whipped cream chargers in half?
September 22, 2013 9:39 AM   Subscribe

Steel whipped cream chargers are a problem at Burning Man. Most of them end up in landfills, largely because recyclers don't want potentially pressurized containers. I've found an outfit in Reno that will accept them, but only if they're cut in half to prove that they're empty. What's the best way to do so on the Playa?

I'd like to set up a drop-off point for people to drop off their empty chargers, and then I'll chop them up and take them to the scrapyard at the end of the week. Off-the-shelf solutions are great, but I have access to a metalshop and welding equipment as well.

Volume - Though I'm only planning on a smaller pilot program now, I'm envisioning hundreds or thousands of containers. This'll need to be somewhat automated or quick.

Quiet - I'd like it to be reasonably quiet. Saws are probably out, unless we can really soundproof it.

Safe - I'm sure a pressurized container will make it in there eventually, so the setup needs to not hurt anybody.

Low power - The nature of the event means I need this to be pretty low power. Human power is OK, solar is better, but we're probably looking at a 120v generator.

Thanks awesome internet people!
posted by cr_joe to Technology (29 answers total) 3 users marked this as a favorite
 
Can you have step one be for your contraption to test the charger to verify that it's empty? This makes step safer.....
posted by bilabial at 9:48 AM on September 22, 2013 [6 favorites]


Portable bandsaws (like this one) are pretty stealthy. You could maybe rig a channel that's whippet-sized, and use a stick to push it into the blade (giving you a degree of distance from the canister.)
posted by Wulfhere at 9:50 AM on September 22, 2013


I'd make a small steel jig to hold each one, flip a cover on it, and puncture the end to make sure it's empty. Then a second jig to hold a large number of them facing the same way, in a hexagonal pattern. Hold the cylinders by the ends, and put the whole thing in a band saw back home.
posted by notsnot at 9:52 AM on September 22, 2013 [2 favorites]


They also come in 18v varieties for mobility. Still need power to charge, but less constant.
posted by Wulfhere at 9:52 AM on September 22, 2013 [1 favorite]


I think a cordless miter saw is probably the way to go, probably with a specialized cutout bolted on.
posted by supercres at 9:53 AM on September 22, 2013 [1 favorite]


(With a fine-tooth metal blade, of course.)
posted by supercres at 9:54 AM on September 22, 2013


Best answer: Build a jig to hold numerous chargers, I'm thinking two C shaped channels facing each other attached to a plate at one end with a slight gap between. Then use a battery powered portaband to cut the cylinders in half. A secured lid at the open end would prevent peices from flying everywhere if you cut through a pressurized charger.

Or possibly a jig could be made with a metal shear to secure the halves while cutting. You wouldn't need much more than a couple blocks of steel with a hole drilled to accept a charger.
posted by Mitheral at 9:55 AM on September 22, 2013


Would they accept them if they were smashed flat? The canisters would be clearly unable to hold pressure if pancaked, and dropping something heavy or putting them in a press seems like an easier way to go about this.
posted by blnkfrnk at 9:58 AM on September 22, 2013 [12 favorites]


A small bandsaw with a metal cutting blade would be very quiet, way quieter than you'd think. You're probably used to miter saws and circular saws that make a huge racket even when they're not cutting anything. You can get a dedicated metal cutting bandsaw, these are also called "horizontal bandsaws", that are made for the job. Put the cylinder in, apply the clamp, start the saw on it's way. Most of them will cut automatically - they apply pressure, usually by weight.

I'd be curious if there's any other way they'd accept them, though, such as punctured or flattened. I think you could make a hand-crank machine that could probably do either of these that might even be of enough novelty fun that you could get people to do a few of them themselves - something like a machine that flattens pennies.
posted by RustyBrooks at 10:08 AM on September 22, 2013


How about a manual pipe cutter?
posted by Mr. Yuck at 10:17 AM on September 22, 2013 [2 favorites]


You don't need to use power tools for this. Some sort of steampunk vice or guillotine powered by a hand crank or bicycle through lots of intriugingly complex greasy gears should do the job.
posted by monotreme at 10:33 AM on September 22, 2013 [2 favorites]


Best answer: Bolt cutters. Get a coupla folks with some big, long-handled bolt cutters and go to town. Should be pretty quick, quiet, and doesn't need power. Also if you get a full one and it explodes it won't ruin the bolt cutters. A bandsaw probably wouldn't hold up so well.

Or if you wanted to get crafty you could probably build some kind of guillotine around a hydraulic car jack that would cut them by the dozen.

Oh and whatever you choose, wear gloves and a face shield in case you get a full one. Don't want to lose an eye!
posted by Scientist at 10:36 AM on September 22, 2013 [3 favorites]


Moop is going to be an issue with cutting them locally. Paint chips, metal fragments...
posted by rr at 10:53 AM on September 22, 2013 [2 favorites]


I think the proper leverage-applying device in this case would not be a car jack (slow) but a sufficiently large arbor press, which can operate quite quickly. You could also build a little armored box around the point of contact, and fabricate a specialized punch for your arbor press that would close the top of the box as it descended. I'm visualizing something where you drop the canister in, operate the press which encloses the canister while chopping or puncturing it, then raise the press, exposing the chopped canister for removal.
posted by agentofselection at 10:54 AM on September 22, 2013


I like the bolt cutters idea. Perhaps two massive pairs of bolt cutters, each welded to a feed tube and hopper, with one arm of each set fitted with a pedal and the whole affair set under a bicycle seat?
posted by flabdablet at 10:58 AM on September 22, 2013


Or a custom made shear: two steel plates maybe half an inch thick, bolted together so they pivot, with a long handle welded to each one; a charger-sized hole drilled through both plates while the handles are pivoted apart, so when you push the handles together a charger sitting in the hole will get sheared as if by enormous tinsnips? You could case-harden the plates after drilling the holes.
posted by flabdablet at 11:10 AM on September 22, 2013


A bench vise and a large pipe cutter would be my choice.
posted by jon1270 at 11:14 AM on September 22, 2013


Stupid question from a total square: are these chargers resealable after they've been cracked open?

If they aren't, then a charger can basically be in two possible states: "fully pressurized" and "totally empty." That will make it much easier to weed out the non-empty ones.

(You might even be able to do it by weight or density if you're sufficiently clever or sufficiently lucky. Do some experiments! If you're really lucky, the test will turn out to be as simple as "full ones sink, empty ones float," or "full ones sink quickly, empty ones sink slowly with a trail of bubbles behind them." At that point, I wonder if you would be able to crowdsource the sorting effort — set up a sorting station and tell volunteers they can keep any full chargers they find. Like panning for gold drugs...)

But if the chargers are resealable, then you will have to worry about distinguishing between "nearly empty" and "totally empty," and that will make all this harder.
posted by Now there are two. There are two _______. at 11:46 AM on September 22, 2013


Smashing flat does seem like it would be easier to accomplish quietly and with less available power--once depressurized!
posted by AnOrigamiLife at 12:11 PM on September 22, 2013


Better than the metal shear I linked earlier would be a 3/4" rebar cutter. You'd want to construct a guard in case of pressurization.
posted by Mitheral at 12:17 PM on September 22, 2013


Best answer: Two people with a pair of yard long bolt cutters could likely do a lot of these things per hour. One person cuts and the other person sets them in the jaws. Yard long bolt cutters are heavy so I'd just stand them on a block of hardwood so the cutter doesn't have to hold the whole weight. The yard-long kind produce a lot of leverage so it shouldn't get too tiring. The other person could sit on a stool with a bucket on each side... swap out every few minutes or whatever. I cut up a lot of bicycle rims using a similar method. It's pretty tedious and boring but the only reason I cut up rims is for the aluminum which is far more valuable.

If you don't have yard-long bolt cutters already they're gonna cost more money than you'll likely get from 10,000 empty whippets at the scrap yard though. Scrap steel is worth maybe ~200$ a ton. I'd also point out that burning gasoline to recycle such a small amount of steel is probably worse for the environment than just letting these things turn to rust somewhere.

I would just cart them out of the desert and give them to a scrapper (post on CL free section) that is already going to a scrap yard and they can mix them in and nobody has to waste time cutting them up.
posted by glip at 12:18 PM on September 22, 2013 [1 favorite]


Is there a way to game-ify this process? Like, 5% of canisters are full, please blast one another to find out which ones. And, using an accelerometer, make the Popeye-style strength-testing device with the bell at the top that shows how hard a canister has been smashed. All done in proper style, of course. If you have squashed metal that is not explosive, it should have resale value.
posted by theora55 at 12:42 PM on September 22, 2013 [1 favorite]


Would they accept them if they had a hole drilled through them instead of being cut in half? Seems like that'd be easier?
posted by reddot at 4:56 PM on September 22, 2013


Or just a bite taken out of them with a miter saw, enough to expose the inside but not cut all the way in half?
posted by bink at 8:42 PM on September 22, 2013


You'd want to construct a guard in case of pressurization.

This is not likely to be a problem in practice; all you need to do is leave a few crackers sitting around and you will have volunteers willing to hang out all day screening the waste stream. They won't be very efficient, so you'll need a few chairs to go with the crackers, but they will be very, very thorough.
posted by Mars Saxman at 10:22 PM on September 22, 2013


Best answer: I would definitely go with a manual process if at all possible. Not only does that seem like the burning man way, it seems wasteful to use electricity (and thus gas?) just to recycle steel.

Bolt cutters will probably work fine. If there is a Harbor Freight (or some other cheap chinese tool importer) near you, the cost shouldn't be all that bad.

I also like the idea of the pipe cutter. If you put the canister in a vice or use vice grips, you can spin the thing around until you make a tiny hole in the canister, let all the gas vent, and then continue along pretty safely. (Although, the internet claims that the things are made of awfully thick steel, so this might take forever to cut through.)

It might also be in the burning man spirit to build up some human powered contraption that acts as a force multiplier. A lot of work can be done with leverage and the weight of a human body.

Lastly, you might be able to figure something out with the supply end. It looks kind of like there is no valve in the canisters, just an area of thin metal that gets punctured when the canister is installed in the dispenser. So it might be easier to figure out something that either nips off that end, or widens the hole enough to show that they are fully discharged. (Or a combination of the two- verify it's empty, and then smash them instead of crushing them.)

(Just thought of another idea: what if you designed something that pierced a hole in the side of the canister? I'm thinking a set of modified bolt cutters, where one side of the jaw is ground out in a circle to just hold the canister, and the other side is ground to create a "tooth" that pierces a hole in the can.)
posted by gjc at 12:42 AM on September 23, 2013


Best answer: Agreed with the pipe/bolt cutter or a custom sheering device.

Bonus points for a containment vessel that would technically allow a full one to be punctured (The danger here is actually the frozen liquid concentrate, not the metal puncturing).

A guillotine would be awesome for this.

Technically fulls/empties make different sounds I've been told weight is also another obvious way.
posted by anthroprose at 8:11 PM on September 23, 2013


Best answer: The danger here is actually the frozen liquid concentrate, not the metal puncturing

Given that these things are specifically built to discharge all of their contents suddenly into a larger container when punctured, I would be quite surprised to find that cutting a full one in half with shears that surround the halves during the cut is actually dangerous.

Drilling or sawing would certainly cause a risk of having tiny metal fragments propelled away from the cut zone at high speed, but during shearing I would expect the gas to escape with a tremendous hiss as the shears first breach the casing, and to be completely gone by the time they'd finished cutting it through.

Even so, putting some kind of cover over the business end would be prudent design.
posted by flabdablet at 10:33 PM on September 23, 2013


I know it's been a while but check this out:
http://www.frets.com/HomeShopTech/ForFun/CanCutter/cancutter.html

Guy uses a thing he built to cut spray paint cans in half. Seems like it might work for your containers, not sure how thick/solid they are.
posted by RustyBrooks at 11:11 AM on November 5, 2013


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