Geometry Achieved

Today was a wicked day.

Not only did I get a drive to work (instead of spending an hour walking and taking a packed van) but we basically finished the frame for the Butterfly (my variation on the Papillon) and proved the geometry is sound).

There were a number of problems that I had foreseen (weight distribution, pot placement, spaces between mirrors, mirror shading etc) and had assumed that we would be able to solve with a certain amount of elegance. Kudos to us for actually being able to.

Also, the butterfly is a test of construction precision, because unlike the other Solar Fire technologies, this one is pretty rigid. The Vesta, Apollo and Helios, however, all have movable mirrors and can be modified fairly easily. The butterfly is a one-piece reflector that must follow a pretty precise line of movement to track and reflect the sun easily. Initial indications… indicate… that we achieved an acceptable level of precision. Must be due to all the vicegrips:


And our counterweight (speaking of elegant solutions, note the paintbucket filled with rocks tied opposite the wing):

The butterfly works like this: the two wings face the sun directly, and will eventually be covered with 10cm by 10cm mirrors (like the one I'm holding)
which will reflect the sun onto the pot at the center. The paintbucket-counterweight will eventually be replaced by another wing, so the weight will be balanced. We've substituted that wing for a counterweight because I didn't know how this experiment would turn out and didn't want to make two wings if their shape/construction weren't for certain. I reverse engineered this design by looking at some pictures of the papillon, and so nothing was for sure.

The mirror angles at the edges of the wings are pretty acute, which means that we'll have to fill fairly large spaces with the woodglue/sawdust or Styrofoam mix, but luckily I happened across another type of plastic foam with better cohesion than Styrofoam, so we'll be able to cut it to fill the majority of the space without using large quantities of glue:
However well things went today, the process is nowhere near finished. Once the geometry is finalized, we move on to calibrating the mirrors. There are 100 mirrors to calibrate, which will take a solid amount of time (especially with the heat of the sun these days!). After the configuration, we'll have what we call a master mold. That is, we'll have glued all the mirrors at the proper angle, but in order to avoid having to calibrate 100 mirrors each time we want to make a wing we're going to make a mold of the original wing.

That's a pretty big mold. The parallelogram that makes the wing is short side: 70cm, long side 150cm and width 100cm. We're probably going to go for rebar reinforced plaster or cement (plaster is way easier to work with since it doesn't bond to mirrors too fiercely) but I don't know yet. If you've got suggestions on how to avoid breakage, let me know. I'm slightly worried, but have faith in the guys I'm working with. I don't have extensive materials experience, but they sure know their stuff. I'll let you know how we solve the problem (and the various ways we might fail).