Friday, October 8, 2010

Swivelling foot mirror idea

Mirrors here are shown tilted
for winter performance.
Red lines are swivel controls.
Blue lines midday sun angles.
8 Oct '10: I am sufficiently convinced by the performance of the mirrors in the last 3 weeks to take this further.
   I told the guys on the N-tron forum that I would probably fit foot mirrors next Spring equinox to bounce summer light upwards. I have access to cheap metals, so if an idea is possible, cost is not an issue about trying it out. Once an idea takes hold it is difficult to postpone it, and during a lecture, I started doing sketches for a swivelling foot mirror that could be workable for winter and summer. Once the sketch is done, the details of swivelling and control begin to crystallise. So why not do it in Winter? That is the time when I am seeking gains, even if only marginal gains. With my collectors arrayed horizontally, heat and foot mirrors will help, side mirrors will do nothing useful.

  The Top mirrors are not adjustable, because I didn't think I could make an adjusting mechanism that wouldn't rattle on windy nights or require more drilling of holes in the wall. So they are at a fixed angle of 60º, optimised for Winter sun. They are not useless in summer as the sun is only at 60º at midday, and there are times either side of midday when the sun will be lower and will bounce downward.

  The Foot mirrors would be best to be sloping about 10º forward in summer, so the 60º midday sun bounces back up onto the front glass. For winter it needs to tilt further forward to bounce heat upwards to the centre height (but not too high, to avoid reflection off the front glass). As the range from winter to summer is 46º, I suppose that the mirror angle should vary by 23º from one season to the other = 10º, 20º and 30º.
  Tilting the mirrors slightly back would be better on cloudy days to improve the daylight into the two bedroom windows below. I have shown the mirrors above as being TWO louvres, with a hinged control mechanism below, but this is a lot of work to make in detail.
  Next, I need to make a 3D model to test out the idea, and forecast sizes and swivelling modes.


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