MOTHER'S WOODBURNING TRUCK

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1,500 miles of free-fuel driving, and there's a lot more where that came from: We were pleased to report in MOTHER NO. 68 (page 173) that our experiments concerning the use of wood scraps for motor fuel showed promise. But little did we realize, at that time, just how well the unlikely form of "solid" energy would work in a "liquid" world.

In short, for a total cost of about $125—and a fair amount of cutting and welding—we've come up with an alternative power system that not only moves our rig down the road as smoothly and reliably as any conventionally powered automobile, but does so at zero fuel cost!

A STRAIGHTFORWARD PROCESS

Here's how the system works: Wood scraps (we use chunks that are larger than sawdust or shavings, but smaller than a 6" length of 2 X 4) are contained in a modified hot water tank, and rest on a cone-shaped, cast-refractory hearth. The recycled vessel is airtight . . . except for a spring-loaded and sealed fill lid, a capped lighting aperture, and an inlet port (the last is simply a two-inch brass swing check valve, which allows the "draw" created by the engine to pull controlled amounts of air into the firebox).

Incoming "atmosphere" is directed through a series of holes drilled into one shoulder of a discarded wheel rim (which is girdled with a circular band of strap metal and fastened to the bottom of the tank), and supports combustion in the vicinity of the hearth. As the fuel in that area burns, it consumes the oxygen in the air—creating carbon dioxide and water vapor—and forms a bed of glowing charcoal, which collects on a grate sus pended from chains several inches below the hearth assembly. (Simultaneously, a heat-induced "decomposition" zone is created right above the combustion region . . . driving gases from, and carbonizing, the wood prior to its incineration.)

The mixture of CO 2 and moisture—in addition to some creosote—is then drawn through a "choker" (positioned between the hearth and the charcoal grate) and forced into the embers at the lower part of the tank before leaving the gasifier. The choke serves as an air restricter which blends the various vapors and directs them through the glowing coals, where they're reduced to the combustible gases carbon monoxide, hydrogen, and—in small amounts—methane. The final product also contains a good deal of nitrogen, along with some unconverted CO 2 and traces of tar and ash.

The carbon dioxide and nitrogen are inert, and such nonfuels pose no threat to the powerplant. However, the tar and ash must be removed from the gas, or they may produce deposits and, perhaps, result in engine damage. So, to clean the fuel, the "smoke" is first routed through a liquid-cooled "densifier" (a multitubed heat exchanger surrounded by a water jacket and plumbed into a junk automobile air conditioning condenser that's mounted in front of the existing radiator), which precipitates moisture and residue from the gas. Then it passes on to a tubular filter that's [1] packed with strands of commercial air conditioning filament, woven transport padding, or a similar material that won't disintegrate, rust, or burn, and [2] equipped with perforated flame traps at its entrance and its exit.