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The basic skeleton of the apparatus is six long pieces of angle iron drilled and bolted together. A pivot cap is needed for the top of the pole where the whole thing hinges for the up and down winter/summer adjustment. Three small angle pivots are needed for the daily orbital swinging of the array. Four rough oak 1 x 4's act similar to roof purlins and allow for the mounting of the panels themselves. Finally, a hand winch is attached to the base of the pole, and cables are run to allow the whole thing to turn on its hinge points when the winch is cranked and the top of the pole is guyed off to the ground for stability in wind.

Materials

A straight 30-foot-long locust pole from a tree felled while clearing for the garden was our choice to hold the array. Choose a pole length that optimizes your sunlight potential—either a wooden or metal pole will suffice.

A few bags of concrete are needed to set the pole in the ground; you need enough to fill two-thirds of the hole around the pole with concrete.

Aside from the photovoltaic panels themselves, the most expensive part of the array is likely to be the angle iron. Most areas have scrap yards, and it's hard to say how much you might have to pay for the pieces. Purchased brand new, the galvanized angle iron for this project would cost about $100, but there are bound to be sources for scrap in the immediate vicinity.

Lag bolts, bolts, cable, and even the winch (refer to materials list on page 88 for numbers of each) should be available from most building or farm supplies. A catalog company called Northern Hydraulics (2800 S. Cross Dr. West, Burnsville, MN 55306, 800-222-5381) also has such supplies at a reasonable cost.

Construction

Much of the initial work involved in this project is drilling bolt holes through the angle iron pieces. A drill press and sharp bit helps speed up this task, but it can be done with an electric hand drill. For each hole, take your measurements, make a small indentation with a center punch at the center point of the hole for the bit to follow, and always apply light cutting oil to the bit and metal while drilling (refer to the diagram depicting each piece with size and positions of holes for layout). It helps to label each piece of angle you have acquired with its respective diagram number for reference during layout and assembly. Also, a metal cutting bandsaw, a metal chopsaw, a cutting torch, or even a grinder can be used to cut the angle iron.

The top pole pivot and the three identical frame pivots require a bit of welding. Make sure all welds are done by an experienced welder—a faulty weld could snap in a wind with devastating results. The top pivot is a piece of 1/4" plate metal (4) cut slightly larger than the top of your mounting pole, with four 12" legs (4c-4f) welded across from one another that fit over the top of the pole. Lag bolts screw through the holes into the pole to hold the unit—and pieces 4a and 4b are welded back to back on the other side of 4c. The 2 1/2" with the clips cut out and bolt holes aligned together stick out beyond the edge of 4c to allow for the hinging action of the entire array.

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