BACKYARD HOMESTEAD UTILITY

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When the vapor leaves the "in use" unit, it goes directly into a ten-foot-long, slightly inclined horizontal condenser . . . which [1] removes a good deal of unburnable water vapor and some residue, and [2] cools and thus densifies the fuel charge, making it more potent. This "chilling chamber" is nothing more than a series of tubes, enclosed—all but their ends—in a conduit "jacket" that's filled with water and plumbed into the cooling system of the engine.

After passing through the condenser, the concentrated gases travel into a vertical filter, which snags any remaining particulate matter in layers of woven filament and prevents potential flamebacks from reaching the rest of the system . . . by means of perforated flash traps at both its inlet and outlet. Again, both the condenser and the filter were fabricated in duplicate . . . so that there would be two separate and complete fuel-producing systems, each valved to a common feed pipe leading directly to the engine.

POWERPLANT, ALTERNATOR, AND SPEED CONTROL

Four factors were taken into consideration when we chose an engine for our plant: [1] horsepower and torque at a given RPM, [2] displacement, [3] availability, and [4] cost.

From our rough calculations, we concluded that—after efficiency losses were taken into account—the 10-KW alternator would require about 22 horsepower to operate effectively. However, because horsepower is a function of engine speed, it was important that we choose a powerplant which developed its "horses" in the mid-RPM range rather than at maximum speed, since a high-revving unit would suffer from poor fuel economy and a shortened life span. We also had to consider the fact that a woodgas-fueled engine delivers only 50 to 65% of its rated power, and that the slow-burning gas performs better with a long-stroke—rather than short-stroke—design.

Engine displacement is another important factor. Obviously, a huge V-8 would consume more "smoke" than a modest four-cylinder machine requires. And, in the interest of economy, we could see no point in using a grossly oversized engine to do the relatively small task of providing a single building with electricity and heat.

Availability and cost come into play, too. We figured it was better to utilize an inexpensive salvaged engine that came close to our needs than to buy an ideally matched—but costly— new powerplant.

Fortunately, our choice proved to be a good one. A search through the local wrecking yard turned up (for $75) a 1961 Pontiac Tempest four-cylinder engine . . . a 195-cubic-inch, long-stroke model, which is—in effect—the right half of a General Motors V-8. We fitted the block with 11:1-ratio pistons and a low-overlap camshaft, then installed a homebuilt car buretion system similar to the one on our wood-gas pickup and advanced the ig nition timing slightly. (These modifica tions were for experimental purposes the system would certainly perform quite adequately with a "box stock" en gine.) We also replaced the convention al exhaust manifold with a water-cooled marine unit, and built a water jacket around the exposed exhaust pipe in order to extract waste heat to use in a thermal storage system.

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