Fred! Thanks for the offer... I'd like to spin up a smaller frame (like really small) after I finish my bigger frame. Would it be OK to laser cut polycarbonate with your cutter? Pololu won't do it because they say the fumes are too bad.
Just FYI, I have your frame all setup and have spun up the motors. I get vibrations on two of the four, but I need to make sure the motors are torqued down enough. I did have to move them because if how I wired up the connectors. I'm just gun shy about screwing down the motors from the last experience (felt bad about cracking them with my usage of the thread lock). I just wanted to get my latest software releases out before I start playing with it again. I'll take pictures and post here and at RC Groups.
I also got my latest prototype in... it looks great, seems stiff enough to fly... but is a bit heavy.
Fred or any other mechanical engineer types, what's the best plastic to use that is light, stiff, but can take the impact of a quad crash? I've used acrylic and ABS plastic so far. I accidentally bought Lucite before... it's VERY stiff but ultra heavy. Besides polycarbonate are there other good plastic candidates to try?
I could try cutting polycarbonate on our cutter, but I am a bit hesitant to do it. I have only ever tried very thin polycarbonate, but I wasn't too impressed with the results. The edges tend to be rough and burned.
Don't be too afraid to tighten down the screws as much as you need to. It should be fine now that the material hasn't come in contact with a solvent, and if it does break, then I need to look more seriously into another material.
As for plastics, I have done a lot of looking into this, and have quite an extensive Excel sheet that I compiled. Here are my top five plastic choices, with their advantages and disadvantages:
1. Hydlar Z
-Advantages: Light weight, extremely strong and stiff, quite impact resistant.
-Disadvantages: Pricey! Very pricey! Also, gets much of its strength from kevlar fibers, which makes it slightly more interesting to machine, as it requires all carbide bits. (Hydlar Z is a kevlar reinforced nylon.)
2. Polycarbonate
- Advantages: Light weight, reasonably strong and stiff, extremely durable and impact resistant. Easy to machine using physical processes.
- Disadvantages: Susceptible to solvents, doesn't laser cut well.
3. Noryl
- Advantages: Lighter and stiffer than Polycarbonate, still very durable.
- Disadvantages: Susceptible to solvents, somewhat expensive.
I'm not sure if Noryl can be laser cut or not.
4. ABS
- Advantages: Very light, durable, and inexpensive. Very easy to machine or laser cut.
- Disadvantages: Not particularly stiff.
5. Glass filled Polycarbonate or Noryl
- Advantages: Much stiffer than either of their unfilled varieties, without being much heavier.
- Disadvantages: Much harder to machine, because the glass is very wearing on tools and tends to get everywhere.
I also noticed that pyjamasam mentioned plywood. I have to agree with him that Baltic Birch plywood is a good option. It is lighter than the lightest plastics, while still being very stiff and durable. (About as durable as ABS, but much stiffer and even lighter.) It also laser cuts easily. I would like to do a little looking into this.
Also, I might try my hand at a laser cut quadrotor frame. It is looking fun!
