I did a bit of soldering last night:
Magnet wire works really well. It's insulated and just about the right thickness for this work. I tried using other wire previously and it failed miserably. Highly frustrating. Someday I'll get a hot air setup; until then, my trusty WES51 will have to do. After soldering all this stuff together, a few dabs of hot glue secured the potentiometer wires and provided some strain relief to the new resistor taps.
A video showing the servo response with changing R1 values:
I misspoke a few times during the video; the mass attached to the pitch ring doesn't change, that's just an affect of gravity vs pitch ring angle. Also, this would have been easier if I actually had a reasonable potentiometer available from my junk collection; the trimmer you see on the board is a 1k unit, and the next closest device I had was 500k (!!!). Might be time to restock.
A few updates not related to the servo hackery tangent:
- Early on, I considered using a ducted fan for the thruster; they improve propeller efficiency by reducing tip losses. Commercially available units tend to be high-RPM low-diameter units designed to mount within the body of model fighter jets and the like; they produce ridiculous thrust velocities (great for scale F22s!) but not a great deal of thrust. Also, they're loud. So I abandoned the idea, figuring that I wouldn't be up for custom-fabricating anything. Times have changed; I located a CFRP shop that owns a 9.63" mandrel and seems to like small custom jobs. I'm having them fab up a 14" pre-preg tube in that diameter (14" was the same price as 12", $120). Once it arrives, I'll update the CAD model and fabricate a few brackets for the motor mount. With luck, that will increase my prop efficiency a bit!
- I'm going to finalize the motor cooling stuff and get the files out for 3D printing by tomorrow evening. I'll tweak the venturi sizing a bit. I'm also out of TC amps (the last one got used in a toaster oven reflow project), so I'll order a few more of those so I can quantify before/after performance.
- I plan to order a beefy pillow block for my thrust testing rig this weekend. They're cheap and readily available. The hilarious DIY plumbing bearing has led a good life, but it's time to retire that unit for something a bit stronger. My 4S/5000mA LiPo arrived earlier this week and I'm dying to give it a proper test.
- I haven't forgotten about tachometers (well, I did a few times, but that happens). I'm going to order the optoelectronic bits to put these together when I have the motor mount out for cooling duct installation.
- I'll probably redo my HaD Prize video, since a lot has happened in the meantime (I was halfway through frame construction when I filmed the current one). I'll also finish up the other requirements and update the Project Details section as appropriate. 8/20 is right around the corner!
In any case, I think it's time to get access to the other tuning resistor!
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