Building of a frame commenced. The basic idea is to use materials readily available from hardware stores, so that in the event of a tree, a head or Planet Earth intersecting with the flight path, things will be quite easily replaced, at least the frame will be one less thing to worry about.
At the hardware store I chose a meter long piece of U-shaped 1*1 mm aluminium profile, 2mm thick. I hope that this will turn out to be stiff enough for a small quad with ~25 cm long arms. For the body part I chose some plastic thingies which are normally used to apply cement to the walls to affix tiles to said walls. Nice thick, stiff but flexible plastic. Two of these were cut in squares with sides roughly 10 cm . Cutting the stuff with my knockoff fake Dremel turned out to work, sort of-ish, half melting, half cutting, it’s not going to win any beauty contests, that’s for sure.
The basic idea is to sandwich the four arms between two layers of plastic as can be seen below:
I don’t want to drill too many holes in the metal since these holes turn out to be mayor weak points in the construction. If you look at crashed quads, almost always the bent and or broken parts have failed at or around drill holes. The one hole at the (covered) begin of the arm is not a location that is going to be exposed to a lot of stress, so that one hole should be OK. But somehow the arms need to be fixed in place, and the construction should be stiffened up considerably. This was achieved by adding two screws to either side of the arm. The engines will be clamped to the other ends of the arms, so no holes needed there either.
Above the finished frame. it weighs 220 grams, this could probably have been less if the hardware store would stock aluminium profiles with walls of only 1mm (4 sided), but alas, this is not the case, so I’ll have to work with this material.
I plan on housing the avionics in an upside-down dvd spindle box, but that’s still kind of fluid, we’ll see if all of the wiring and hardware (which is mostly still on its way from Hong Kong) will fit. The box I have laying around seems to fit nicely though:
The plastic is not too hard (meaning, hopefully, that it will not shatter on impact) and it can be closed by fitting the bottom half on top of it. We’ll see how that one pans out. Next on the project list: fix the engines to the arms. But I’ll need some proper long 3mm screws for that, which I don’t have, so off to the hardware store it is tomorrow!