A TRACKING SOLAR CONCENTRATOR
THE HUB
The hub must carry the entire weight of the array and provide the bearings to permit it to follow the sun. The tracking drive system will be mounted here as well as part of the tilt drive system. This chapter will define the requirements of the hub and show you how to economically assemble it from discarded automobile parts thereby eliminating expensive machine work. The following chapter will describe the the drive system.
Figure 11 shows how an old Chevy 1/2 ton pickup front wheel, hub, brake drum and spindle where used to provide the bearing system. The 15 inch diameter plate (101) is intended to mount on your support structure which should have a similar plate (201) mounted dead flat. The mirror array will have its bearing plates (008) rotating on the one inch shaft (109). This shaft should be located exactly over the center of the plate (101) in order to properly center the weight of the array.
The spindle (104) forms an angle to the surface of the Earth that is equal to your latitude. This makes it parallel with the Earths axis. The mirror array will now rotate about the spindle towards the West at 15 degrees per hour while the Earth rotates toward the East at the same rate. The result is that the mirror array remains steadily fixed upon the sun. This mounting system greatly reduces the tracking requirements.
second bearing system, consisting of the bushed bearing plates (008) riding on the one inch shaft (109) provides adjustment for the 23-1/2 degree tilt of the Earth. The array will be adjusted over this range only one cycle per year For this reason, we did not set fit to make it automatic, but a motor drive has been provided to make it easy to adjust once in a while. You may desire to save the cost of the motor drive and make it manual if the system is mounted in a convenient location.
THE HUB - MAJOR MATERIAL LIST
- Two discs of 1/4" steel plate cut and drilled per figure 14.
- scrap iron similar to (102), (103) & (108)
- Automobile or light truck front wheel assembly (104), (105), (106), & (107).
- 24"x 1" steel rod (109)
- Four bushings, (110) cut from 1" black pipe- 2" long
When selecting your front wheel assembly, you have many choices, so you'll probably do better at a scrap yard buying by the pound rather than at the auto salvage dealer. The requirements are:
- The brake drum should have flanges suitable to wrap a #40 roller chain around for our drive system per Figure 11. The old Chevy drum used on the prototype had a raised ridge that the chain rides upon just as it would on a sprocket but this is not essential.
- The spindle (104) should be designed so it is convenient to attach to the channel iron (102) by bolting. This is preferable to welding as minor adjustments can be made with shim washers.
- A six hole wheel bolt pattern is nice as the symmetry makes for less clearance problems with the one-inch rode (109) that will be welded into the wheel, but this also is not essential.
