Mother's Heat Grabber Is Back

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MOTHER's second generation Heat Grabber is simply a weather tight wooden box that's insulated on the bottom and topped with single strength glass. Inside this box, an insulated divider is mounted just about halfway between the glass and the container's bottom, with a small airspace left at the foot of the box for circulation.

The divider itself is additionally separated into two parts: the main body (which serves as a partition between the upper and lower chambers of the collector) and the airflow passages (which are located on the top side of the divider under a black aluminum plate, and which-in effect act to increase the surface area of the collector).

The divider is then brought out the upper end of the box where it forms part of a "lip" that hooks over a window—sill (so the window can be pulled down snugly against the top of the collector's frame and the glass) ... leaving the main part of the collector leaning against the outside of the house at about a 45° angle.

When the sun is shining, its rays pass through the glass on top of the collector and heat the black aluminum plate mounted on the upper surface of the divider within. As the heat radiates from the aluminum, it [1] warms the air between the plate and the glass, and [2] at the same time raises the temperature of the air In the airflow passages underneath the aluminum plate. This heated air, then, naturally rises up the face of the divider and in short order begins to pour out of the opening in the top of the Heat Grabber and into the room.

Of course, as the hot air rises up and out of the box, it pulls cool air from the foot of the container ... which, in turn, draws more cool air from the lower opening in the top, or "head" of the collector . . . and the cycle repeats itself as long as the sun continues to shine. And if the sun isn't shining? Well, then the air in the box cools and sinks to the foot of the collector ... where it prevents any reverse circulation within the box. In other words, the Heat Grabber will feed hot air into a room when the sun shines but won't pull heat from the room when the sun goes down.

MOTHER NO. 47 (1977 September/October Issue) featured a very Interesting little solar furnace. The unit could be built in less than two hours for just $2.56 a square foot ($32.18 total). It fit right into any south-facing window that could be opened. And-all by Itself-it could heat a reasonably well-Insulated room almost anywhere on the continent on almost any sunny but otherwise frigid day.

And it still can (which is why so many hundreds of people here In the U.S. and In Canada have constructed and are using the MOTHER-designed project).

The only real trouble with that original Heat Grabber, in fact, is the Celotex Thermax TF-610 that MOTHER's researchers specified as the major material for Its construction. Dang It! The highly insulative and easy-to-work construction board simply Isn't available in many parts of the country. And when it Is available . . . well, we've had reports that various suppliers aren't above charging double for what little TF-61 0 there is to go around.

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