h a l f b a k e r yQuis custodiet the custard?
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This device is a very simple adaption of a conventional refrigerated cabinet to be powered by the turning wheels on a cart towed behind a small vehicle. This could be any size from a small trailer to the size of a bicycle towed retail cart. The compressor is converted to be of the conventional automotive
sort with an electromagnetic clutch and a belt drive.
Applications:
A cheap butchers wagon for field dressing that does not require a 120v connection or an expensive generator. Cooled by the trip there and cooled on the way back.
A bicycle towed ice cream cart.
A cold foods delivery cart franchise for third world countries where a family may own only one moped and where that vehicle must be multi-purpose.
Parking is an obvious problem but no more critical than the problems posed by using a simple Ice box. The device should have sufficient insulation and thermal mass to function under regular usage. A thermostat could be included to allow the regulation of additional load. In addition a planetary gear-set that maximized compressor load when the tow vehicles brakes were engaged would be a substantial improvement.
Jericho Trumpet
http://www.military....asp?aircraft_id=97
And there wasn't much rejoicing ... [8th of 7, Jan 30 2010]
Aerogel
http://en.wikipedia.org/wiki/Aerogel
Really good insulation [RattyBunyip, Feb 01 2010]
No electricity air conditioner
No-electricity_20air_20conditioner_2e
Very similar concept. [bungston, Feb 01 2010]
Mauldin
http://www.dogfaces...mages/mauldin_1.jpg
Might convince a military, or ex-military halfbaker that the idea has a its own kind of elegance. [mouseposture, Feb 02 2010]
Riley XR3 Hybrid
http://www.rqriley.com/xr3.htm
Riley's been doing this for a while, making plans for stuff and selling the plans from the back of Popular Mechanics. [elhigh, Feb 24 2010]
Power takeoff adventures
http://news.google....BAJ&pg=1012,2701550
[bungston, Feb 24 2010]
Cyclofridge
http://img72.images...2/2321/dscn2178.jpg
Cyclofridge [sneakythumbs, Feb 26 2010]
[link]
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21Q the idea allows a cart to power a cooler without an additional engine with added weight and fuel consumption. If you have an alternative idea for a trailer that will keep itself cool as you move then you post it. |
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A solar system requires high battery capacity and strong sunlight. This is an idea that is practical. The ingredients for it are widely available even in a third world scrap yard. The technology is widely understood and robust. All energy is stored in a thermal gradient, no batteries required. |
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not counting wear&tear on the trailer-tires, there's still the question "is running the engine of that particular tractor harder going to be more economical than a separately powered a/c system?"... depends on the power curve somewhat eh?. |
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no, I think it's clear that an independent power plant would be better in many ways. However it has the downside of being more expensive and not a new idea. |
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Somewhere I read about a hybrid car that used this idea-- gas engine for the rear wheels; electric motor (with regenerative braking to charge the batteries) for the front wheels, and no connection between the front and rear except for the road surface. |
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//So wasteful. Such a bad idea.// Just like looking for validation by being snarky. |
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I think having something other than the driver change the load on a tire whenever it wants to is not a particularly good idea... and the stuff will bake if you're stuck in rush-hour traffic. |
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Peltier-effect heat pumps might be lighter and more rugged, and easier to regulate. They would have the advantage ov being compatible with both the motion powered generator and any opportunistic solar energy. |
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// the stuff will bake if you're stuck in rush-hour traffic //
Using regular expanded polystyrene foam, an insulated box can be made remarkably efficient - not far off that of a Dewar vessel. |
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The point about making the trailer totally independent of the towing vehicle is entirely valid - no umbilicals or connectors - and no auxilliiary engine or fuel supply. |
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[WcW] has a good idea, even if it does not amuse the efficiency experts. Especially if it doesn't (+) |
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// it does not amuse the efficiency experts // |
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Perish the thought that economic and practical considerations should be sacrificed like two helpless little fluffy mewing kittens on the cold marble altar of thermodynamic efficiency .... |
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// the sound that a JU-87 Stuka would make // |
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Actually, the trademark Stuka "howl" was produced by specially fitted ram-air turbine sirens, under the control of the pilot, used for psychological warfare. |
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// enormously detailed and lengthy // |
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... if, sadly, incomplete ... |
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There are worse things you could do with your time, [IT]. |
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It's a cool idea, but it may be easier to have a conventional A/C system powered by the towing car's battery -- electrical connections to trailers are baked, I believe. That would allow the flexibility of plugging this in when needed. |
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Nonetheless, I see the uses in 3rd world contexts (beverage cart towed by moped/horsecart/etc) where this might prove to be an advantage with its simplicity. |
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[cowtamer], there are vehicles used in the "1st world" which don't have an on-board electrical supply, you know. |
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//Using regular expanded polystyrene foam//
oh half bakery can do better than that!
Check out Aerogel.<Link> |
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// Somewhere I read about a hybrid car that used this idea-- gas engine for the rear wheels; electric motor (with regenerative braking to charge the batteries) for the front wheels, and no connection between the front and rear except for the road surface. // |
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Studying it right now in my hybrids class. Several University ChallengeX vehicles did that, but the vehicle suffers from control issues. When the batteries were low, the rear wheels would be drug as a generator to charge them even when the brakes weren't applied.
The result was a difficult vehicle control problem at low speeds, especially on gravel surfaces, and rear tires that would not last terribly long.
For vehicle dynamics reasons the industry will probably use another link between systems besides the ground. |
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I like this idea, for the most part. I would not use a piston type compressor here, perhaps a scroll one or another lower-NVH type would yield better reliability in remote locations. I haven't run any numbers but do suspect that you'll have to do quite a bit of moving to refrigerate the unit sufficiently. |
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Forget the solar panels. Too fragile of a technology for harsh climates. |
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Not terribly certain why 21Q thinks this will add any more 'friction' than any other refrigeration system. Direct conversion of rotational shaft work to compression seems pretty efficient to me. Of course it adds work to pull the cart and run the compression thermo loop, but could possibly make up for it in weight and simplicity by not having an engine or e-motor. |
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Good insulation would be very important. |
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[+] Perhaps power for the compressor could come from two separate systems, controlled by clutches. When the trailer is moving, the compressor could be powered by the wheels. When the trailer is not moving the compressor could be powered by an electric motor. |
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Powering the compressor via the wheels can be thought of as a "through the road" transmission, transferring energy from the engine to the compressor in a purely mechanical manner. |
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Powering the compressor via an electric motor can be thought of as an electric transmission. Mechanical power is converted to electricity which is converted to mechanical power. |
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Whether the mechanical transmission or the electric transmission is more efficient is a difficult question to answer. Perhaps someone should build such a refrigerated trailer, and run some tests? |
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This could have applications in horse-drawn, and human powered ice cream carts the world over. I think it's time someone did some figures, to see if this is actually bakeable. |
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I posted a similar scheme (linked) though the generated coolth was used to condition a dwelling. I could see such a device serving both purposes: popsicle cart by day, air conditioning by night. Although for the latter someone would have to stay up and pedal, but it would be more efficient with no movement required and all energy to compressor. |
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[sninctown], you may be thinking about the Riley
XR3. Riley is the same company that
recommended cutting up Triumphs for donor cars
back in the 70s to build little "Urba Trikes" and
"Urba Commuter" and Lord only knows Urba
whatever else. Anyway. |
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The XR3 has a little Kubota diesel up front, an
electric motor out back, and no way for them to
communicate but through the road. It seems a
little dodgy to me but if the builder - it's intended
as a homebuilt - incorporates the right mix of
controls, I think a savvy driver could do pretty well
with it. It requires more driver involvement than
what I think most Americans are willing to commit
to the experience, though.
I'll put up a link to it. |
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Would this have to be a trailer? If you had a way to drop a
fifth wheel on the road off the back of a pickup truck, you
could avoid the parking issues. |
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Of course, the trailer would be an independent unit that
would be really easy to take on and off, as [8th] said. |
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I still wonder why a pto does not come standard on all pickup
trucks. |
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Probably because power takeoffs are dangerous enough attached to tractors, which presumably are being used by sober people trying to earn a living. I shudder to think what sort of mayhem a standard pto would cause on pickup trucks. And I mean the literal definition of mayhem. |
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As people have said, insulation can be very effective without being expensive or exotic. But the biggest problem with conventional chilled transports is what happens when you open the door. |
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While you're moving (and the trailer is cold) the load on your refridgeration unit will be ideally nothing and practically very small. But to maintain food at the acceptable temperature range, you need to be able to kick up the compressor as soon as you slam the door. Our department did some research on crystallising paraffins to provide thermal mass at a discrete temperature, but the heat transfer was fairly rubbish. |
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Ah, energy on demand, nothing beats fossil fuels. |
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even the waste of the open door can be reduced: small sliding doors that open on the top of the container, or a dispensing system that is direct rather than indirect (like a frosty dispenser). The issue is that we need a device that can deliver cold food without requiring any fossil fuels and with a very minimal level of investment and a maximal level of recycling. An old horizontal freezer mounted between four bicycle tires powered by a Bosch automotive AC compressor pulled by a donkey that makes a weekly route on market days selling frozen treats and delivering temperature sensitive medical supplies to local clinics. Its an IDEA, not a business to make money with (unless you happen to own a junk yard in an impoverished nation, in that case please do) . I wonder if the Amish might not be interested in such a technique. |
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[8th of 7] //Antimatter ?// Does the "energy" part just fine;
the technical problems arise with "on demand." |
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The reefer could used as a form of regenerative
braking if it was adjustable or at least could be
switched on and off. Do not cool when travelling
uphill or into a headwind, but use max cooling when
coasting downhill or slowing to a stop. Thermal mass
would buffer the cooling load.. up to a point. + |
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@[mouseposture] : bricolage, what is it? |
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It's this kind of engineering: not the globally ideal or
efficient solution, but the right solution given the real,
local situation that the inventor is in. Especially, it's
ingenuity in satisfying constraints on available materials.
"Making good use of the things that we find" (The Wombles
are described as bricoleurs in one of the sources I
consulted; so is McGyver, though I haven't seen either so I
can't vouch for their accuracy as examples.) |
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The word (I didn't know this until just now) has a bunch of
other meanings, especially in art; also, the original French
word means "DIY," and apparently Claude Levi-Straus used
it in a more technical (and less flattering) sense than the
one I've given above. I was, though, able to confirm the
above definition, which I learned from Stirling's _Islands in
the Net_ as I recall. |
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The Bill Mauldin link I posted is meant to illustrate how
something can be horribly inefficient in the ordinary
engineering sense, and wonderfully elegant as bricolage. |
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Obviously, the people here "get it" -- the idea's got 23
positive votes, one of them mine (thought I'd voted for
this already, but turns out I hadn't, so [+]. |
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//And I mean the literal definition of mayhem.// |
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Honestly didn't think about that, but you're right. It would
be a huge liability, and making it safe would probably limit
the practicality of the thing. |
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I've dealt with tractors all my life, so I am not the least bit
scared to be killed in nasty ways. |
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no PTO. I don't even see the need for a differential. What I would have would be belt drive at massive multiplication with the compressor mounted to the axle and the flex lines running to the condenser and the evaporator. That way we can have a suspension without a complicated linkage. A single shaft with forward pawls should be adequate for differentiation when turning. |
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How good of an idea this is totally depends on application. If the trailer having an internal power source is perferable, or if it would otherwise draw an unusual amount of power from the tow vehicle, then this makes total sense. The typical trucking shipment, not so much. You never know when it will be parked for hours. |
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[nomocrow]//I am not the least bit scared to be killed in
nasty ways// You're wasted on farming. I can think of other
careers for which you'd be ideally suited. |
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I really like this. I really, really like [iron_horse]'s refrigerative braking. [+] |
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/edit to add/ However the cryo unit is powered (with the exception of solar), the power must come ultimately from the vehicle's fuel tank via the engine. Drivng an alternator to generate electricity is not a free ride; it results in substantial added load ("friction") on the engine. |
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Piston or turbine motion in the compressor is the end goal, so rather than converting engine rotation ->fanbelt ->alternator ->electricity ->electric motor ->compressor, you are converting engine rotation ->wheels ->road ->wheels ->compressor. As you are not changing the form of energy along the way -ie, it's all mechanical energy - you ought to suffer far fewer conversion losses. And in the case of using the compressor as a brake, you are recapturing energy that would otherwise be lost. |
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It ought to be possible with a clutch or free-wheel mechanism to drive the compressor with an electric motor as well as from the road wheels. |
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//you need to be able to kick up the compressor as soon as you slam the door.// On a delivery route, wouldn't driving away follow shortly after? |
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