Make a Rotating Frame for a Solar Furnace

Assembling the base, the gimbal frame and the mirror frame for the solar furnace.

| March/April 1979

If you read Make a Solar Furnace you're probably familiar with the name Charles Curnutt. Mr. Curnutt—a designer and manufacturer by trade—had come up with a singular apparatus to catch the sun's rays and put them to work. His design was unique not only because it afforded an almost unlimited number of possibilities (from heating water to driving a steam engine), but also because it required an investment of only a few hundred dollars. Best of all, Curnutt's unit was compact enough (10' X 15' X 16') to qualify as a "backyard" solar generator!

These factors alone made Charlie's rig worth looking into, but he really "put the icing on the cake" by allowing MOTHER EARTH NEWS' researchers to take his design, improve upon it, and make it available to anyone who cared to use it!  

Well, we've been working up our own version to share with you. In Do-It-Yourself Solar Tracking System we showed you how to construct a sun-tracking system. Now, here's the second part of this long-awaited backyard solar project: setting up the furnace's rotating frame.

Essentially, there are three main parts to this assembly: [1] the base, [2] the gimbal frame, which pivots right and left (to track the sun across the sky during the day) and also supports [3] the mirror frame (this structure holds the 10 rows of mirrors in position and is additionally adjustable on a horizontal axis to compensate for the changes in the sun's height during all four seasons).

All three sections of the furnace frame use either rod, tubular, or angle steel, which are all available from any steel supply house. In addition, the mirror frame is made with common electrical metallic tubing (E.M.T.), which can be purchased at your local electrical contractor's supply store. (Of course, if you already happen to have a large assortment of steel on hand, or if you don't mind bartering with your friendly neighborhood scrap dealer, you can save a tremendous amount of money on this project by using salvaged metal.)

Getting Down to Brass Tacks

Before you begin this project, you'll need to get hold of some basic workshop tools: a power drill with an assortment of bits, a hacksaw, a 25-foot measuring tape, several C-clamps, a hammer, a square, a vise, and a pair of pliers or vise-grips. You'll also need a welder (either gas or electric)—since this isn't a "bolt together" project—and a posthole digger if you plan on mounting your solar furnace on an unpaved site.

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