A TRACKING SOLAR CONCENTRATOR
THE HUB - FABRICATION
The brake drum will be used as a sprocket for a #40 roller chain later. This saves us the expense of mounting a large sprocket. It works great without teeth because it will rotate considerably less than a full turn and so the chain can be bolted into the drum. Of course this trick won't work if you live far enough North where the Summer days get very long. To clear the chain you'll have to take some metal off of the back rim of the wheel. The sketchs and photos show both rims cut off, but this may not be necessary
The hub requires some customized design to suit your latitude and the wheel assembly that you have salvaged. The ultimate requirements are:
- The spindle must form an angle to the horizontal that is equal to your latitude, Therefore the channel iron (102) that it mounts upon must form an angle of (90-latitude) with the steel plate (30.1).
- The one inch shaft (109) must be directly above the center of the steel plate (101),
Obviously the place to start is with the 1/4" plate (101), figure 13. Might as well make the second plate (201) at the same time and set it aside for attachment to your support structure. Because the hub must be oriented exactly in a North-South line, the mounting bolt holes are elongated to allow for later adjustment in case you are not a precision surveyor. You could get by with square plates of about 12" x 12" if you can get them sheared to save labor, but the lay the bolt pattern out in a circular form so that some rotation is possible later.
Make up items (102) and (103) and weld them at the proper angle for your latitude onto the plate (101). If you're handy with angles, I need say no more, but if trig' makes you nervous, use a carpenters framing square and the chart in figure 12. Item (102) should he no wider than is necessary to mount the spindle as the space along side it will be needed later for the motor drive. If you prefer to do careful planning and layout and are working with a drill press instead of a portable drill and cutting torch, you may prefer to delay the welding of these pieces until all the holes are cut for the Tracking Motor Drive described in the next Chapter.
With the wheel (107) off of its hub, notch its face about a half-inch deep so the one-inch shaft (109) can lay into it. Select a piece of pipe or pipe coupling (108) large enough to clear the hub (106) when the wheel is in place, but small enough to avoid interferance with the lug nuts. continued on page 24
