Category: Making

Projects that make or build something.

Post #1921: Psychrophilic bacteria for winter composting, setting up the experiment.

 

You might reasonably think that a post featuring my rotting kitchen scraps is a new low for this blog …

… though I’d bet there are some in the Town of Vienna who might disagree.  But that’s water over the dam.

In any case, you’d be wrong, because today I treated half that pile of rotting kitchen scraps with cold-water pond … eh … stuff.  That converts this pile of rotting (or, more precisely, non-rotting) garbage from a mere oddball gardening obsession into an exciting citizen-scientist experiment.

Anyway, as promised in Post #1917, I leveled up the two compartments in my tumbling composter and added cold-water pond treatment to one side.  This stuff:

The idea being that a big dose of psychrophilic (cold-loving) bacteria might jump-start my kitchen-scrap composting.

Composting activity has pretty much ground to a halt, due to the cold outdoor temperatures, despite my having built a little insulated solar shed for the tumbling composter.

Methods:  After leveling up the two sides of the composter, I added about a third of the bottle to one side of the composter,  in several small doses, tumbling the compost vigorously with each dose.  And added a packet of something advertised as enzymes to break down cellulose (though that seems more than a bit far-fetched to me, for reasons I won’t go into).  I’ll tumble it daily, maybe add another treatment in two weeks or so.

In a month, I’ll check to see whether or not the level of compost in the left (treatment) side has dropped materially below the level in the right (control) side.

This is my last-ditch effort to get my tumbling composter to continue working through the winter.  This pond treatment cost $30, so I figure I ought to try to get my money’s worth.  If the stuff doesn’t work for this use, at least I can affirmatively document that it doesn’t.  Hence running this as a controlled experiment, instead of just dousing the whole batch of compost at once.

I’ll be surprised if it works.  But that’s what experiments are for.

Results in a month.

Post #1917: Composter shed failure

 

Many of my readers have been breathlessly awaiting the results from my composter-shed experiment (e.g. Post 1899).

Unfortunately, that breathlessness is not explained by the stench of rotting kitchen scraps.

In the winter cold, my tumbling composter is not so much a composter as a mausoleum.  It’s the Lenin’s Tomb of potato peels.   Each time I visit it to dump in a new batch of scraps, I soberly reflect upon the perfectly preserved remains of ancient meals resting comfortably within.  I ponder what that means for the future.

Source for title photo, via Wikipedia:  By Russia, Lenin’s Mausoleum or more specifically image, Fair use, https://en.wikipedia.org/w/index.php?curid=48098730

Background

Recall the issue here:  I toss my kitchen scraps in a tumbling composter.  Three seasons of the year, that works great, and the compost is really desirable for gardening.  But when the weather turns cold, the composter stops working, for all intents and purposes.  I then have to throw my scraps into the trash, where they eventually become trash-to-electricity “biofuel” when Fairfax County incinerates them.

I refuse to heat my composter with electricity.  And I’m not going to bring it inside for the winter.  So … how about trying a solar-heated “shed” for it?

Bottom line:  Passive solar through double-paned glass, plus insulation, and radiant barrier, together, provides nowhere near enough heat to keep this tumbling composter running during the winter.

I suspect that adding more insulation would be fruitless. 

First, the shed does, in fact, keep the temperature of the compost up, when the sun shines.  But with a fairly large ratio of surface area to volume, a string of cloudy days allows this to cool right down to ambient temperature.

Second, the resulting “cold snap” kill off any insects in the compost.  I like to think of a composter as a place for bacterial decomposition of kitchen scraps.  But in fact, I’ve never really known what fraction of decomposition was insect-drive, versus bacterial.  Typically, when I open this composter to add material during spring/summer/fall, I can see insects (larvae) working on the contents.  But all it took was a few freezing nights to stop all insect activity.

My take on it is that adding an inch of foam board to the existing shed isn’t going to fix that.

What are the other options?

Psychrophilic, qu’est-ce que c’es?

Source:  All pictures in this section are AI-generated with the prompt “cold, hungry bacteria”, using Gencraft.com.

Composting small volumes of organic material in cold weather is a common problem.  Near as I can tell, the suggested solutions are:

  1. Compost a large enough volume that the pile stays warm outdoors.
  2. Store your kitchen scraps over the winter, in some location.
  3. Move to indoor worm composting for the winter.
  4. Give up.

I don’t find any of these options particularly appealing.  I don’t generate a large enough volume of organic matter for 1) above, and the Virginia climate is not well-suited to 2) above.  I can’t depend on the kitchen scraps remaining frozen, outside, in a typical Virginia winter.  And I’m not too keen on having five-gallon buckets of garbage sitting around, even if they are sealed.  I’m guessing my neighbors wouldn’t be all that keen on my digging a garbage pit in my back yard.  At least, not if they knew what I was up to.  I don’t want to get into 3) indoor worm composting, though I am finally beginning to grasp the potential advantages of that over traditional outdoor composting.

Arguably, the smart option is 4) give up, per the recommendation on this website.

(Finally, I’ve already dismissed the idea of an indoor electric “composter”, that is, combination grinder and food dehydrator. Just not my cup of tea.

My last gasp at making this tumbling composter work in the winter is to track down some “psychrophilic bacteria”.  That’s the term, per this U. Mich. website, for the cold-loving bacteria that break down organic matter even in colder temperatures.  (The same website says that a cubic yard of organic matter is the smallest pile likely to continue to hot compost in a Michigan winter.)

First, the idea of cold-tolerant decomposing bacteria is a real thing.  You can find it in the scholarly literature (e.g., this reference, for psychrotrophic bacteria).

I have no clue if spiking my compost with psychrophilic/psychrotropic bacteria will work.  (As you have probably already guessed, the prefix “psychro”- means “cold”.)  Everyone says these cold-adapted bacteria work slowly, but they do continue to work, even in the cold where other bacteria would not.

And that doesn’t matter anyway, until I can figure out where I can buy the little buggers.   

I haven’t found anything specific to composting.  Apparently the approved solution to winter composting is to have a big enough compost pile.  That said, I seem to find two plausible sources.

Pond cold-weather bacteria.  The first thing I came across is cold-weather bacteria for (decorative) ponds.  Apparently, you spike your pond with these to keep decomposition going in colder weather.  Here’s an example.  Here’s another example.  Amazon offers dozens of choices.

Main-line drain maintainer.  It also occurs to me that I can buy stuff at Home Depot that advertises that it spurs decomposition within your main sewer line.  Those lines sit at around 55F in this area (although the incoming materials may be warmer).  So it’s plausible that dumping that stuff, in my tumbling composter, might aid decomposition.

Of the two, I think the pond bacteria would be the better choice.  All of those products appear engineered to break down cellulose.  The drain cleaner, by contrast, is advertised to break down “grease, hair, paper, oil, soap scum”.  The pond bacterial additives appear to be directly targeting the type of organic matter I’m dealing with, the drain cleaners are not.

The proposed experiment.

As it turns out, I’m going to have to shell out something like $30 to buy some fall/winter pond treatment.  And my composter conveniently has two compartments.  So I might as well set this up as a proper experiment.  I’m going to mix up and level out the materials currently in the two sides of the composter.  Add fall/winter pond bacteria to once side.  And see if I notice any difference in the remaining volume of materials, one month from now.

I can’t find winter pond bacteria locally, so I’ve ordered some from Amazon.  This stuff.  Several comments attest to the fact that it works in cold weather.  And stinks.  And that’s, eh, more-or-less what I’m after.

Results in a month.

Post #1914: Pneumatic tires for wheelchair use, no good solution to the problem of flat tires.

 

This is a brief followup to the just prior post, on the use of non-pneumatic (e.g., solid rubber) tires on wheelchairs.

I’m trying to work out what I should recommend if asked to replace more wheelchair tires.  Traditional tires with air-filled inner tubes are much easier from the standpoint of the installer.  The question is dealing with the drawbacks of those from the wheelchair user’s perspective.

The only way to guarantee that a wheelchair tire won’t go flat is to use a non-pneumatic tire.  That includes solid rubber tires, and solid rubber inserts taking the place of an inner tube inside regular tires.

What I discovered in this post is that many anti-flat products available for bicyclists will not work for most wheelchairs, owing to the wheelchair’s use of narrow, high-pressure tires.

When all is said and done, between the past post and this post, I think I now have a fairly firm set of recommendations.

If you cannot tolerate a flat tire on-the-go, then opt for solid rubber tires (and not solid inserts in regular bike tires).  But mount them using the $35 steel bolt-to-the-workbench device sold specifically for mounting such tires on wheelchair rims.  Mounting them with simple hand tools is just too hard and too iffy.

If you can tolerate the occasional flat, the best option seems to be puncture-resistant tires and tubes.  All the rest of the anti-flat products available for bicycle use — chemical sealants, anti-puncture tire liners, tire “wipers, and the like — either won’t work with typical wheelchair tires, or are not available off-the-shelf in the right size or configuration for that use.

Background

Solid rubber tires and solid rubber tire inserts definitely will not go flat.  There’s no air in them in the first place.

But those tires have some drawbacks.  Per the just-prior post, both of those non-pneumatic options are difficult to install using ordinary hand tools.  In addition, solid inserts are difficult to purchase as they must match the tire fairly exactly.

Both types of non-pneumatic tires offer a harsher ride and higher rolling resistance than high-pressure pneumatic (air-filled) tires.  And there are relatively few options available in the correct size for typical wheelchair rims.

By contrast, traditional pneumatic bike tires (tire plus inner tube) are easier to purchase and install, but they have two big drawbacks.  They require frequent, routine re-inflation to maintain the correct pressure.  Otherwise they go soft, and that raises rolling resistance.  And they can go flat, unexpectedly, while you are out-and-about.

The latter is not just a problem for the high rolling resistance you get with a flat.  It’s all too easy to roll a flat bike tire right off the rim, or to damage both the rim and the tire if you keep going on a flat tire.

This post is my research into minimizing the hassle from both of those drawbacks:  routine periodic inflation, and flat tires.

Caveat 1:  In the particular case I’m looking at, my options are  24″ x 1″ or 24″ x 1-3/8″ tires.  This puts a lot of limits on the types of bike-tire solutions that can be adopted for wheelchair use.  You might have other options available if your rims can accept wider tires.

Caveat 2:  My only qualification for writing about this topic is that I’ve changed a lot of bike tires in my life.  And I happen to be friends with someone who uses a manual wheelchair.

Routine inflation:  An electric air pump can solve this problem.

Source:  https://www.homedepot.com/p/Husky-120-Volt-Inflator-H120N/325096203

Best guess, $20 and a trip to Home Depot gives an adequate way to maintain tire air pressure up to 100 PSI.

I don’t think it’s worth belaboring this.  All pneumatic bike tires lose air over time.  It’s not a leak, per se.  It’s that air diffuses through the rubber.  (The same thing happens to rubber balloons and car tires, just much faster and much slower, respectively).  The higher the tire pressure, and the thinner the tire/inner tube, the faster the tire goes soft.  There’s no way to stop it that I have ever heard of.

This means that pneumatic tires have to be topped up on a routine basis.  And in the modern world, the obvious solution for routine tire inflation is an electric air pump.

A standard full-sized manual bike tire pump doesn’t do the average wheelchair user much good for routine use.  Not only are they designed to be used while standing up, they are designed to be fast, that is, to move a lot of air with each stroke.  They do that by using a piston with a relatively large surface area.  But wheelchair users often prefer high-pressure (e.g., 140 PSI) tires, for the low rolling resistance such tires provide.  Even if a full-sized manual pump can achieve pressures like that, it takes a lot of force, owing to the large piston area.

The typical manual mini-bike-pump — the kind you take with you on a bike ride — is both slow and awkward to use.  They are slow because they have tiny little pistons, suitable for pumping tires to high pressures using only your arm muscles.  And they are awkward because they either clamp directly to the valve stem, or have just a short attaching hose, either of which essentially dictates exactly where the pump must be held, relative to the tire.  In essence, those pumps are made for emergency on-the-road use.  You can use them for routine tire maintenance, but I sure don’t.   

Compressed C02 cartridge pumps are expensive for use in keeping tires routinely inflated.  The poorly-designed ones appear hard to use, based on Amazon comments.  But even for the well-designed ones, depending on the pump and the tire, you’d be spending $1.50 and tossing away a metal C02 cartridge every time you topped off your tires.  Plus, based on what I read, C02-filled tires deflate more rapidly than air-filled tires, owing to something-something-something about the ability of C02 to diffuse through butyl rubber.  You’d turn your routine tire maintenance into a $100-a-year habit, for no particular reason.

The efficient solution is an electric tire pump. 

These days, you have your choice of 120 volt plug-in, 12 volt plug in, and rechargeable battery-operated pumps.  You only have to check a few things:

  • How loud are they?
  • Can they do high pressures?
  • How awkward are they to use?
  • How long will they last in routine use?
  • Is the battery replaceable?

And, of course, how much do they cost?  Because, near as I can tell from reading Amazon comments, the cheaper pumps tend to fail several of the checks outlined above.

I have no specific recommendation to make, other than the Home Depot offering shown above.  All I can suggest is (e.g.) reading the comments on pumps offered on Amazon.  In particular, a lot of cheaper battery-operated pumps cannot produce high pressures despite what the Amazon listing might say.  When in doubt, get one that plugs into the wall.

Avoiding flats:  Nothing is bulletproof

If you absolutely, positively must not have a flat tire, the only real option is solid, non-pneumatic tires.  In this section, I’m shooting for two things:

  1. A tire and tube setup that minimizes the risk of catastrophic flats.
  2. A simple, no-maintenance pump that can be kept on the wheelchair for emergency use as needed.

The pump is easy.  Any C02-cartridge inflator that fits comfortably in the hand should be adequate, as would a standard bicycle mini-pump with the addition of an extension hose.  Either would be small enough to be stored long-term on the wheelchair itself.

But finding a combination to minimize the chance of a wheelchair flat is hard, owing in part to the small size and high pressure of the typical wheelchair pneumatic tire.  Puncture sealants (e.g., Slime (r)) do not appear to work at high pressure.  Puncture proof tire liners do not appear to be available in the narrow widths required for wheelchair tires.  The only options that work for typical wheelchair rims combine relatively expensive “puncture-resistant” tires with relatively expensive “thorn-resistant” inner tubes.  Even with that, neither of those is likely to stand up to an ill-placed tack, nail, or screw.

So the bottom line is that there is no good anti-flat solution for pneumatic wheelchair tires. The best you can hope for is that any puncture is small enough that you can inflate the tire, on the go, enough to get you someplace where you can swap out the wheel.

Tire and tube setup.

An important restriction is that the only tires that I know will fit the rims I’ve been working with are 24″ x 1″, and 24″ x 1-3/8″ tires, designed for use with inner tubes.  These are narrow by bicycle standards, and that limits choices quite a bit.

Puncture-resistant tire liner:  No off-the-shelf option in this size. 

Source:  Amazon.com

These are (typically) just a tough piece of flexible plastic, designed to turn aside (e.g.) thorns.  Note what the original Mr. Tuffy tire liners don’t say:  Nails, tacks, screws, staples, and similar.  Given that I’ve had nails go right through the tread of a steel-belted radial car tire, I’m pretty sure a piece of plastic isn’t going to stop them in a bike tire.

But it’s moot anyway.  Near as I can tell, all the ones made for bicycles are too large for 1-3/8″ tires, and are certainly too large for 1″ tires.  For the Mr. Tuffy brand, 24″ wheel sizing starts at 1.95″ and goes up from there.

At best, I could cut them down and use them.  But I’d have to sand down the edges to be sure that the tire liners themselves didn’t cut the tube.

Tire sealants:  Dubious in higher-pressure tires.

Slime (r) does not make ready-made self-sealing inner tubes sized for a 1-3/8 tire.  That said, the original Slime (r) sealant was sold in bottles, to be squeezed into a bike inner tube after removing the valve core.  So it’s easy enough to make self-sealing 1″ or 1-3/8″ tubes from standard tubes and a bottle of Slime (r).  By reputation, this will stop (or greatly slow) leaks from small punctures for about two years.  After which, I think you have to remove and replace the old tubes.

So that’s an option.  Based on what I read on the internet, Slime works, somewhat.  Won’t stop a rip or tear in the tire.  May not seal fully.  But gives you enough sealant to get home on a tire with a small puncture.

This seemingly-knowledgeable user provides a major caveat:

Tire pressures above 45 psi are less effective at sealing, and above 60 psi, don’t expect any effectiveness at all.

Oddly, Slime (r) itself does not mention this limitation.  But now that I Google Slime (r) and tire pressure, I see warnings in multiple locations that Slime (r) and similar sealants will not work well in high-pressure tube tires.  I’m not entirely sure how accurate that is, but until proven otherwise, that’s a caveat for tires in the 100 to 140 PSI range.

FWIW, a competing product in this segment — Flat Out — specifically says “fat tire bikes” (reference).  The implication there is that this sealant would not work in (e.g.) road bikes with high-pressure tires.

Beyond that, Slime has a reputation for sometimes causing problems such as blocked valve stems.  All things considered, Slime (r) may be reasonable for low-pressure (“fat”) bike tires, but whether or not it will work well and without issues for thin, high-pressure wheelchair tires is an open question.

A final issue is the use of Slime (r) in mounted tires that might be stored, unused, for a considerable length of time.  Rumor has it that Slime (r) can “pile up” in the low section of the tire.  If you’re getting close to the point where the Slime loses its ability to flow, you may end up picking up a replacement wheelchair tire only to find that the low section of the tire (as stored) is now solidified Slime.

Puncture-resistant tire:  Expensive and somewhat effective.

As with tire liners, these aren’t a bulletproof solution.  It’s puncture-resistant, not puncture proof.  Near as I can tell, the only puncture-resistant tire marketed in the 24″ x 1-3/8″ size in the U.S. is marketed as a wheelchair tire.  Hence it costs two or three times as much as a regular tire.

Puncture-resistant tube:  Expensive, effectiveness unknown.

There are a handful of “thorn-resistant” (that is, extra-thick) inner tubes marketed in the 24″ x 1-3/8″ size.  These appear to cost about two to four times as much as a regular inner tube.  As with puncture-resistant tires, these are unlikely to stop a tack, nail, or screw.  Whether they provide any additional resistance to punctures from man-made objects, I don’t know.

Run flat tire:  No option in this size.

There are now foam inserts for bike tires that provide some degree of run-flat capability.  These are oriented toward tubeless tires typically used by (e.g.) bike racers.  Near as I can tell, there is no run-flat tire option available for something as small as 24″ x 1-3/8.

Tire wipers:  Maybe, but requires D-I-Y mounting.

A final offering for minimizing punctures goes by various names, but probably “tire wipers” is sufficiently descriptive.  These are typically wires that ride lightly on the tire, and knock off any solid debris that has stuck to the tire, including tacks, nails, and thorns.  The idea is that it typically takes several tire revolutions for such debris to penetrate the tire, and if you can knock it away, it won’t puncture the tire.  These typically mount (e.g.) the same place as the brake calipers on a bike, which means that you’d have to device a custom mounting for use in a wheelchair.

Emergency pump:  C02 inflator or Standard bike mini-pump plus long adapter hose.

Based on what I read on the internet, plenty of wheelchair users adopt standard bike mini-pumps for tire inflation.  These pumps are capable of reaching the (e.g.) 140 PSI required for high-pressure tires, but tend to be slow to inflate a tire, because of that.

The main drawback that I see, for on-the-go use, is that most of these pumps require direct attachment to the valve stem. That means that the user would have to hold the pump to the side, stabilize it on the wheel, and pump up the tire in that awkward position.

I think it’s far easier just to add a two-foot air hose, readily available from Amazon.  That would allow a person seated in a wheelchair to inflate the wheel by holding the pump comfortably in the lap, rather than leaning over to manipulate a pump directly attached to a valve stem.

But by far the most obvious solution is a C02 inflator.  These are compact enough to be held in one hand, and so should be readily usable by a seated wheelchair user to inflate a low tire on-the-go.  A single small (16 gram) C02 cartridge should be adequate to bring a 24″ x 1-3/8 tire up to a reasonable working pressure.

A battery-operated rechargeable tire pump is a distant runner-up.  Most of these are relatively bulky.  Many of the less expensive ones cannot generate high pressures.  And even with that, the batteries would slowly self-discharge, meaning that the user would have to remember to charge the pump periodically.  That’s just begging to find that the battery is dead, just when you need it the most.

Conclusion

For pneumatic wheelchair tires, periodic maintenance of tire pressure isn’t much of an issue.  Reliable plug-in electric inflator pumps capable of 100 PSI are readily available.  These can be had with reasonably long air hoses, allowing the user considerable leeway in hooking the pump up to the valve stem.  All that is required is remembering to use it on a regular basis.

The big problem is flat tires while out-and-about.  There, many of the off-the-shelf solutions available to bicyclists — in-tire sealants, puncture-resistant liners, run-flat tires, and “tire wipers” — are not available (off-the-shelf) for narrow, high-pressure pneumatic tires typically used on wheelchairs.

That only leaves puncture-resistant tires and tubes.  Those may slow down the rate at which flats occur, but neither of those will stop sharp metal objects such as tacks, nails, or screws.

I guess my bottom line is this.  If you can tolerate the occasional flat tire, then go with high-end “puncture resistant” tires and tubes.  Forget Slime (r), tire liners, tire wipers, and similar makeshift solutions.  If not, I’d go with solid-rubber tires (not inserts), along with the steel bench-mounted tool used to install those tires safely on wheel rims.

Post #1899: Composting shed, testing

My tumbling composter doesn’t work in the winter. Which is ironic, given that it was made in Canada.  But it’s a common problem.  Winter composting is a problem for anyone who tries to compost small amounts of material outdoors, in a cold climate.  Composting stops as the temperatures drop.

So I made a little insulated shed, to fit around the composter. 

The upshot is that, so far, it seems to keep the compost around 16F warmer than it would otherwise be, without the shed.  On average.

I’m not sure that’s going to do the job. Continue reading Post #1899: Composting shed, testing

Post #1897: Re-using political yard signs. Composting shed, Part 2

 

In honor of election day, I’m re-using a bunch of political yard signs to build a small outdoor shed.  The Coroplast used for high-end campaign signs is far too good to be tossed out just because somebody lost an election.

I’ve decided on the following method of construction:

  • Coroplast campaign yard signs
  • Stapled to furring strips

It’s every bit as complex as it sounds. Continue reading Post #1897: Re-using political yard signs. Composting shed, Part 2

Post #1896: On re-using political yard signs: Composting shed, part 1.

 

Today is the day when a whole lot of campaign signs go straight into the dumpster.  Along with the political aspirations of half the recent candidates,

Which is a pity, really.  (The signs, I mean.)  The best of those signs are made to last a long time.  We really ought to do better than treating them as a single-use disposable.

So I suggest that the first Wednesday following the first Monday in November be declared Campaign Sign Recycling Day.  In keeping with that, today is a good day for me to make something useful out of some dead political yard signs.

This post is the theory.  Next post is the actual assembly.

We’re talking Coroplast.

Source:  Coroplast, Inc.

Campaign yard signs come in several varieties.

Cheap campaign yard signs aren’t re-usable in any obvious way.  Some are coated cardboard, on some sort of stick.  Some are a printed plastic sleeve that fits over a three-sided wire frame.  For both of those, the metal frames (if any) can be recycled.  But the signs themselves aren’t good for much.  Far as I can tell, once they’ve served their purpose, they’re trash.

By contrast, high-end campaign yard signs are Coroplast(r).  That is, corrugated plastic sheets — two sheets of plastic bound together with thin plastic channels.  As pictured above.  Effectively, they are built like corrugated cardboard, but plastic.

These sheets — typically made from polypropylene — have a surprising amount of structural integrity.  Much like corrugated cardboard, they are quite resistant to bending or folding across the corrugations.  This means you could  use a single thickness of Coroplast to build light-duty objects, and multiple thicknesses to build heavy duty objects.

These also stand up well to being used outside.  The ones forming the sides of my oldest raised beds now have more than five years of cumulative outdoor exposure (first as yard signs, then as raised bed sides.)  Only this year did they begin to show brittleness from all that sunshine and weather.  (And if I’d cared to keep them painted, I probably could have avoided that, as most of the damage is from exposure to the UV in sunlight.)

Fastenating

I’d say that the biggest downside is that these can’t be glued together.  (Or, at least, not well, or not easily, using conventional glues).  The underlying material (typically, polypropylene) just doesn’t stick to much.  And the ink coating — the printed message — further complicates things.

Near as I can tell, most people who make DIY projects with Coroplast sheet opt for some sort of mechanical fastening.  That can be as simple as cutting slots and tabs, so that sheets fit together.  Than can include melting sheets together, in places, to form a sort of plastic rivet.  Or can include using actual metal fasteners (bolts, washers, nuts) to hold the plastic parts together.  Or staple or nail them into a wood backing.

(The big exception being model airplane enthusiasts, for whom gluing coroplast is the only practical option.  That said, after having read one or two sites discussing that use, I’m convinced that gluing up Coroplast is not something that you’re likely to get right the first time.)

There are chemical methods that might, in theory, hold these sheets together.  Some are specialized glues specifically designed for this sort of application.  All of those appear to cost an arm and a leg, at least for the quantities that would be needed to build (e.g.) a piece of furniture.  And then there’s solvent-welding the polypropylene (PP).  That is, finding a solvent that will dissolve PP, dissolving some pieces of PP in that solvent, and then using that as if it were glue.  I strongly suspect that either approach — specialized glue, or DIY solvent-welding — requires a nice clean PP surface, involving a lot of complicated surface preparation, and that the ink firmly bonded to the typical campaign sign would interfere with that.

Dare I say this?  Even duct tape is iffy.  The same factors that make it hard for glue to stick, make it hard for tapes to stick.  And surface preparation for taping is not easy (e.g., lightly torching the PP surface).  All told, taping or gluing this stuff seems like a lot of work, on the off chance that you can get something to stick firmly.

The upshot is that I’m going with mechanical fastening only.

Never in small amounts

I find most plans for upcycling or recycling of materials to be of little value.  Most involve using small amounts of materials.  Most involve creating something for which there is a very limited demand.  The results tend to be more of a novelty than a way to divert significant amounts of material from the landfill.

Contrast that with using campaign signs for the sides of raised garden beds.  That used up a lot of material, slowed down the inevitable progress toward the landfill by years, and avoided consuming considerable amounts of virgin materials.

In this case, I have a stack of roughly 35 campaign yard signs, or about 100 square feet of Coroplast sheet.  Pre-cut into neat 2′ x 1.5′ pieces.  So I’m looking for a project that will use up just about that amount of material, and give me something useful in return.

Revisiting cardboard furniture

Source:  Google search

In Post #887, I did up a quick summary of the various construction methods used to create corrugated cardboard furniture.  I’d guess that just about anything you could build as corrugated cardboard furniture could also be built out of Coroplast.

So if you are stuck for ideas, you can look up cardboard furniture plans.  As long as they don’t depend critically on glue, they ought to work with Coroplast.

As I see it, the main approaches to creating weight-bearing structures for cardboard furniture are:

Simple stacked sheets.

Source:  Homedit.com

Folded beams

Source:  Time, inc.

Structural grids (with or without surfacing materials):

Source:  Planet Paper

Totes

Source:  Storage Techniques for Art, Science, and History

It seems worth mentioning that a lot of lightweight commercial bins and totes are made from folded and fastened sheets of Coroplast.  It’s such a common use that there’s even a market for used Coroplast bins and totes.

You can find lots of different plans on the internet for constructing Coroplast totes, bins, boxes, and so on.  They all boil down to folding a sheet into a box shape, and then somehow fastening it together at the corners.  In the example pictured above, the author constructs a sort of “rivet” out of hot glue, and uses that to fasten the corners mechanically (reference).

Here, I’m shooting for something larger, to use up more Coroplast signs.

From dead campaign signs to structural integrated panels.

Source:  Builder Bill

I’m going to turn my pile of used Coroplast into some structural integrated panels or SIPs.  In this case, the SIPs will be flat, rectangular wooden frames, faced with coroplast sheets, and filled with … probably scraps of insulating foam board.

Like a hollow-core door, if you’ve ever dealt with the insides of one of those.  The entire frame around the rim is solid wood, and so has enough strength to hold fasteners and hinges.  But the broad flat surfaces are just thin, rigid sheets backed by some hollow, honeycomb-like structure.

As long as those rigid face sheets stay firmly in place, the entire unit ends up being quite strong, given the light weight.  Far more than you might reasonably expect.  This is why (e.g.) you can easily use a hollow-core door as a table-top, even though the individual face veneers are far too flimsy for that use.

I think this takes good advantage of the strengths and weaknesses of Coroplast.  And it allows me to connect the Coroplast to the structure using a (hardware) staple gun, which is about as fast and as lazy as it gets.  But all the connections subject to high point loads — the sort of connector that would pull out of a thin plastic sheet — can be made through the solid wood edges.

And it’s generic.  I’m going to use this to build a little knock-down insulated shed for my composter.  But nothing would stop you from (e.g.) building furniture this way.  Bookshelves.  A larger shed.  A lightweight travel trailer.  Anything that can be made from rigid flat panels can be made this way, within the strength limitations of the materials.

 

From structural integrated panels to winter composter cover.

At this point, putting the composter cover together is just a matter of connecting the panels made in just above.

Ideally, I’d like to have “knock down” construction — something that can be easily disassembled and re-assembled without tools.  (That way, I can store it away easily during the off-season).  But in the end, this is only going to take four long screws to hold it together.  So I’m just going to screw it together.

How this actually goes together is going to depend on what scraps of lumber I build it out of.

Conclusion

In this post, I figured out how I’m going to use up a lot of 1.5′ x 2′ Coroplast campaign signs.  My proposed method is to build a bunch of “structural panels” out of those signs.  That is, thin wood frames faced front and back with Coroplast sheets.  And then use those rigid panels to build a structure.

This approach:

  • Uses up a lot of signs.
  • Doesn’t require gluing the Coroplast sheets to anything
  • Uses (hardware) staples as the main fastener
  • Avoids putting high point loads on the plastic sheets themselves, by placing all the “structural” fasteners into wood.
  • Is flexible — just make the panels different sizes.

All I have to do now is to make that happen.

I’m now going to test that, by building a winter cover for my composter, using that “structural panel” method.  Assuming all goes well, the construction of that should be documented in my next post.

Post #1866: Winter composting, take 2, using an indirect solar air heater.

My roll-up solar air heater is putting out about 2200 watts of power, in the form of heated air, in the mid-day October sunshine, 37 degrees north latitude.

But absent some sort of magic, that’s not enough.  Not on its own, anyway.  To keep my composter working through the winter, I’d have to build an insulated box for it, and pipe the hot air into that box.

I’m not even sure that would work.  And even if it did work, I’m not sure it’s worth the effort.

Continue reading Post #1866: Winter composting, take 2, using an indirect solar air heater.