A TRACKING SOLAR CONCENTRATOR
Provide a temporary system for controlling at least the tracking drive motor from a convenient position where the target shadow can be observed. The tilt drive can be manually adjusted if desired as it will not change during the days focusing operation, unless you have an error in the angle or orientation of the hub!! Figure 25 is the hook-up for the recommended motor. Adjust the drive systems so that the target shadow falls on your marks in the center of the array. Check out the tracking drive motors and mechanical systems and we're ready to focus.
Make up a bending tool similar to figure 24. This is used to bend the studs on the array for each mirror, making its reflected sunlight fall on the target center. You must have someone controlling the drive motor and adjusting its position every few minutes as you do this. Stay behind the array, peering at the target edges through the gaps between the mirrors. Try welding goggles if they help. Because of the intense light in the target center, you cannot see when a mirror is aligned, but you can see when the square of light is off center on the cooler edges of the target. When you think one is on target, put pressure on it to move it up, down, left & right and observe its light on the target edges. Using this system, you should be able to focus a third to half of the mirrors before the reflections become too intense. Drape the aligned mirrors with sheets or other light weight material and continue with the rest.
Steer the array away from the sun towards its limits to a position that you can bore sight it from in front of the array, if possible. The dummy target will be reflected with its edges visible in the center mirrors and gradually filling the entire array as you move away. Mis-focused mirrors will be very obvious discontinuities. Looking into a flashlight reflector gives you a similar effect. The cold lamp filament seems to fill the reflector as you move away, Both are parabolic reflectors This check is not essential if it is difficult or impossible to do.
Your dummy target got mighty hot! If you had used aluminum with an inch of fiberglass insulation behind it, it would have probably would have been destroyed. Without cooling, the targets temperature will approach 1200 F before its re-radiation losses will balance the incident energy. Obviously, now the kid will come out in you, and you'll have to play with the fire by testing a few items at the focal point. You'll find it easy to burn but not ignite materials. This is because the high temperature expands the air in the immediate vicinity so greatly, that their is insufficient oxygen for combustion.
Playtime is done, lets build a collector.
