MakeShift Challenge: Dead Car Battery: “Rube Goldberg” Honorable Mention

MakeShift 01: Phil Salkie’s “Rube Goldberg” Honorable Mention
by William Lidwell
May 13, 2005

Okay, so Phil is a bit nutty. The bow-drill alternator crank? Impractical. Hanging your partner over a cliff as a counterweight? Disturbing. Despite these eccentricities, his analysis is as brilliant as it is entertaining. Congratulations Phil!

We gave Phil a “Rube Goldberg” Honorable Mention. Here’s his entry:

A Brief Meta-Assessment: First, you are not in the 48 contiguous United States. The most remote location in the US is in Yellowstone park in Wyoming, 20.3 miles from the nearest road. (see http://www.concept-labs.com/pepper/JMRemote.htm for a little page about remote places and how hard it is to be actually far away from roads and cars and such.)

Oh, and turn those stupid parking lights off now, before you forget again and doom yourselves. Close the doors and make sure the silly dome light stays off, too.

Second, you’ve got many hours of driving ahead of you, once you start the car. You’re 50 miles from a road, and you’ll need most of your ten hours to drive that distance through the wilderness. However, we still have the problem of recharging the car’s battery before you can start your trek. (I won’t even go into the whole rant about how much damage your driving has done to the wilderness.) And who “scheduled” that snowy weather in for tonight, anyway? Since you apparently live in a society with weather control, couldn’t you have asked for a nice, balmy evening?

But I digress.

In order to start the vehicle, (assuming Fall weather conditions, 60 degrees Farenheit, large toad-like SUV in newish condition, as per the picture) we will need to supply around 12 volts, 200 amps for 30 seconds or so. That’s about 20 watt-hours, or the amount of power required to run a hair dryer full-blast for a minute. That’s about equivalent to 1.6 horsepower minutes, or the work a good-sized horse can pull in around thirty seconds (horsepower was originally established assuming a horse only works 8 hours a day, so a horse can put out about 3 HP continuous. Your horse may vary.)

Now, it’s not quite that simple, because we’ve got to get more power into the battery than just what we want back out–there’s a charging inefficiency of 20% or more (plus other losses to consider) depending on what path we choose to take to do our recharging.

Since we need come up with just a lot of electrons to stuff into that battery, we’re going to take a look at our little kit of chemicals–metals, acids, hydrocarbons, et. al., and ignore them completely. Although it is possible to make a little battery by sticking dissimilar metals into those limes, and since there are dozen of them, you could maybe get over a volt each and wire them in series to produce 14 volts and trickle-charge that battery. Unfortunately, you’d only manage to get a tiny fraction of the power you require before the snow hits and you’re buried alive–park rangers would find you (and your limes) after the thaw, and snicker at your poor grasp of physics. Similarly, batteries are sealed, so don’t consider re-oxidizing the lead plates with the hydrogen peroxide–you probably don’t even remember whether it’s the positive plates or the negative which get oxidized, and you’d almost certainly wipe your face with your sulfuric-acid-covered hands and blind yourself.

Instead, let’s think of one of the most reliable, efficient, proven, general-purpose converters of chemical energy to electrical energy ever to exist on this planet–the internal combustion engine attached to some sort of generator! And you were even smart enough to bring an internal combustion engine along with you! Total genius!

Oh yeah. That’s the problem, isn’t it–can’t start the damned thing. So, let’s think of one of the other most reliable, efficient, yadayada converters–you. Yes, you (and the person who’s looking daggers at you) are reliable, efficient converters of organic food compounds to mechanical energy. So, eat that fruit, drink some cola, and let’s get down to work! First, we’ll need to come up with some way of generating electricity from mechanical energy. Fortunately, you packed along a generator system with you on the trip! What? Didn’t see that on the equipment list? Well, it’s there all right–the car is guaranteed to have an alternator. It is conveniently attached to a voltage regulation system (which ensures we don’t overcook the battery or blow up the radio), and it’s even already wired in for us! All we have to do is turn it. A lot. A whole hell of a lot. Just an amazing amount of lot.

So let’s do that! (Hey, Rocky–how we gonna do that?) Well, fortunately for you, your friend (who’s looking at you like you’re 200 pounds of cold cuts on-the-hoof) remembers that they used to use a little thing called a bow-drill to turn sticks and rocks and dried leaves into fire. Or maybe they set up an outdoor lathe as a kid, and practiced carving table legs without any power other than the work of other kids. We’re going to adapt that technology to the problem of turning that alternator a few thousand times in the next couple of hours.

We start (after our snack) by taking the tools and slipping the engine’s serpentine belt off of its alternator pulley. DON’T damage the belt–we’ll need it later. Done carefully, this should leave us with a lovely power generation system attached to a nice wide pulley. Don’t confuse the alternator for the air conditioner compressor–the alternator has a big wire coming out of it, the A/C compressor has a thin wire going to its clutch and insulated tubing containing refrigerant attached to its body with threaded fittings. (If you pick the wrong one, you’ll probably die, so choose carefully.)

Now take the strings from the tent, or cut up the sleeping bag, or determine who it was who actually left the lights on and have them donate all their clothing, or in some fashion come up with about 50 feet of fairly strong rope-like substance. It can have knots in it, but try not to make them too big–a spiral cut of the sleeping bag shell might be a good start, or the shock cords from inside the tent poles. Worst case, you can cannibalize the wiring for the heated car seats. Now, whoever’s still wearing clothes, climb up a nearby tree and tie one end of the rope to a nice, strong, flexible branch which is in line of sight to the car’s alternator. You want something with a springy strength to it–it’ll be working as a method of storing your muscle force and feeding it back to you, like bouncing up and down on a bed (only nowhere near as much fun, especially after three or four hours.) Selecting a decent branch may involve pushing the car around a bit. By preference, don’t have the branch right above the car, so that if it breaks, it won’t take out your windshield, thereby adding insult to stupidity. Take the middle section of rope, and wrap a single turn around the alternator’s pulley. Now find a nice hefty stick and tie the free bight of rope around the middle of the stick. You should now have a nice tee-handle, with a ropelike substance running to and around the alternator pulley, and from there up to a nice springy branch.

Now, all that’s left is to pull on the handle, which will spin the alternator and bend the tree branch. When you slack off on pulling the handle, the tree branch will unbend, and spin the alternator the other way, undoing all the work you just did.

What? Undoing all the work? Well, yes and no–the alternator will turn backwards, but, fortunately for you, you don’t have a generator in that car, you have an alternator. The difference is that a generator produces direct current, and cares which way it’s turning–one way gives positive current flow, the other way gives negative. An alternator produces alternating current, which is fed to a diode board, or rectifier, which converts it into direct current, and thence to a voltage regulator. Thus, no matter which way we spin the alternator, we get the proper polarity of DC at the correct voltage (assuming we’re giving it a good hearty spin) to charge the battery.

So, you’re going to find yourselves spending the next couple of hours yanking the hell out of that handle to put as much energy as you can into that battery. “But Wait!” I hear you cry, “If a horse can pull the 20 watt-hours in 30 seconds, why can’t I recharge the battery in, say, a minute and a half?” Here’s where we learn about the three laws of thermodynamics: You Can’t Win, You Can’t Even Break Even, and You Can’t Get Out Of The Game (thanks to Dr. A). And Rule #4–You’re Not A Horse (but you might be a part of one, if you’re the one who left the lights on). These rules mean that we lose some of our energy in converting the linear motion of our pulling to the rotational motion of the generator, some more of the energy in converting rotational energy to electrical energy, even more in converting AC to DC, more in regulating the DC voltage to 13.8 volts, yet more in storing the energy in the battery, and (you guessed it) even more still in getting the energy back out of the battery. If we were directly coupled to the engine’s crankshaft (like an old Model A, for example), you could have perhaps grabbed a crank and turned that engine over enough to start it, or at least enough to break your wrists. But we’re not, and only about 10% of the energy you put in is going to get stored and returned to the engine as cranking power. After quite some time, you should be able to observe voltage levels climbing as you get more charge stored away (but don’t turn the lights on–not even the parking lights. You worked hard for those electrons–don’t waste them!) In fact, I’d suggest cranking power into that battery for hours and hours. You’re going to have to put the serpentine belt back on to the alternator in order to start the engine, and that’s probably not the easiest task you’ve ever accomplished. (The answer to your inevitable question is “Because if you don’t, you’ll have started the engine in order to stop it again so that you can reinstall the belt and get the engine to turn the alternator and finish charging the battery. That would be a total waste of electrons.”) Once you figure you’ve got a decent charge on there, (now you can try the dome lights for a moment; the voltage meter shouldn’t drop much at all when you turn them on), put that belt back on and crank the engine.

If you didn’t get enough charge into the battery, repeat the handle part for a couple more hours, and try again. And remember, in a deep-woods snow emergency, your companion is edible. You even brought a stove (but no cooking pots).

(Now that I’ve cut up my shirt to make a rope, I’m gonna need that T-shirt–large, please!)

Alternate Scenario

Since you may actually not be in some kind of forest, you can get the “pulling back” effect in desert or mountainous areas by pushing the vehicle near a cliff or outcropping and dangling the lights-leaving-on member of your party over said cliff by one end of the rope. You will now be raising them up as you pull on the handle, and gravity will help you on your return stroke as the miscreant is lowered again. (Note that this gets a little hard on the rope–you may want to splice the jumper cables in for the section of rope which passes over the cliff edge.) Note that if yon miscreant complains of vertigo or a feeling of being unfairly treated, you can always say, “Well, if you hadn’t left the lights on, we wouldn’t have to be doing this, now would we?”)

OK, OK–don’t hang your friend over the cliff–it’s way too much work to haul them up and down. Just threaten to hang them over the cliff, and actually hang the spare tire over instead. Oh, and the parking brake is your friend. Really, really, really–you think you feel dumb now, how about after you pull your own car forward over the edge of a cliff?

Alternate Alternate Scenario

You’re driving an older vehicle which has V-belts rather than a single serpentine belt. In that case, your alternator won’t have a nice wide pulley, it’ll have a pulley which is designed to grip a trapezoidal profiled belt. So, splice one cable of your jumper cables into your rope so that the thick rubber insulation acts like the V-belt and spins the pulley. Also, don’t take a full wrap around the pulley; just take a U-turn’s worth–if you try to wrap completely around, the two ends will rub together and get tangled up.

> Back to analysis and winning Makeshift entries.

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