MAKE YOUR OWN EMERGENCY POWER PLANT

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TWO SIMPLE CIRCUITS

All that's fine, of course, for charging car batteries... but we wanted to move on to bigger and better things, so we turned researchers Dennis Burkholder and Robyn Bryan loose on a staffer's 1978 Ford pickup to see if they couldn't coax it into giving up 110 big ones without damaging the stock equipment. What they came up with is a pretty ingenious use of about $50 worth of over-the-counter and junkyard parts... a hookup that comes close to duplicating the convenience and performance of commercial converters that are considerably more expensive!

The concept is simple enough: By switching the regulator (and thus the battery charging system) out of the circuit and feeding 12 volts directly into the alternator's field windings, you can get that tiny dynamo to eat enough Wheaties (in the form of current) to put out about 85 volts at a reasonable engine speed (roughly 2,800 RPM).

But we wanted 110 volts, and with the standard 40-amp alternator, this would have required revving the engine higher than we cared to, so we found ourselves a 2-1/4" General Motors double-grooved alternator pulley that increased the standard 2.45-to-1 crankshaft-to-alternator-shaft ratio to a steeper 3-to-1 gear-up... which ultimately allows the DC dynamo to produce 110 volts for extended periods without damaging the truck's six-cylinder engine.

Using this setup, it's theoretically possible to get over 4,000 watts' worth of power from the machinery already under the vehicle's hood. But to be on the safe side, we've been limiting our demand to 2,200 watts, or about 20 amps... still a heck of a lot more current than even the heftiest power tools would draw.

By referring to our pictorial schematic, you'll be able to get a pretty good idea of how our system's wired and plumbed. But let's walk through it just once to eliminate any confusion.

We can ignore the charging circuit, because that remains essentially unchanged. But once the 4-pole, double-throw master switch is thrown into the "on" position, the remote power system is activated, and the alternator's output goes through a pair of 16-gauge wires (almost a 12-gauge equivalent) to a set of 12-volt, 10-amp fuses and on through a pair of "extra insurance" automotive diodes mounted in an aluminum bracket. After running through an inexpensive ammeter, the current travels into a 1,000-watt resistor (simply a non-immersion heating element from a mobile home water heater fastened inside a 15" length of 2" CPVC pipe) and into a weatherproof receptacle, the opposite legs of which are grounded to the truck.

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