Flutterby™! : R/C living room airplane experiments

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R/C living room airplane experiments

2009-01-26 17:26:49.715897+00 by Dan Lyke 2 comments

We were in Hobby Town, buying extra batteries and a replacement rotor shaft for Charlene's Blade mCX R/C helicopter, when I noticed they had a two channel radio with battery, motor and prop behind the counter for $10. It took three visits before I finally said "I've never actually successfully flown an R/C fixed wing aircraft, a few minutes with some take-out containers and I could turn that into something I can fly and fix easily."

So I brought it home. Turns out it's salvaged from a crashed Revell Piloto, and though it had the prop motor, was missing the coil that moved the rudder. I scrounged through the parts bin, found a couple of busted headphones, stole the coils from them (it took me several passes, tiny wires break easily and are a bitch to solder) and got attraction to a little magnet.

Then, for some reason, I thought it'd be a good idea to wrap an electromagnet for this, knowing that my scrounged speaker coils were 16Ω I thought 16Ω * cross-section-area / Ρ, where, according to this page, Ρ is 1.6E-6 for copper. I found an old solenoid that I could scrounge some thin wire from, somewhere I came up with a diameter for #36 wire, which I thought the wire I was playing with was, it was smaller than #30, cooked that back into an area for the cross-section-area, ran the numbers, came up with about a meter and a quarter. Cut about four feet, wrapped it around a brad, and came up with somewhere between .000Ω and .001Ω down in the limits of my ohm meter.

So I slapped a resistor in-line, and, indeed, I could pick up small pieces of metal with it, but I then realized that I'd further mis-understood how the receiver was sending to the coil, it looks like there's actually an H-bridge over the two coil contacts, it's not positive and negative off of board ground, and went back to the coil with the magnet in the middle.

Still need to get some styrofoam take-out boxes, but with those, a little cellophane tape and some white glue I should be able to make a living room flyer. I guess we need to go out for Thai this week.

[ related topics: Aviation Embedded Devices Fabrication Toys ]

comments in ascending chronological order (reverse):

#Comment Re: made: 2009-01-26 19:06:39.757634+00 by: ebradway

While I'm also attuned to the DIY ethos, I can't help but ask "How much would Dan have charged a client to build a custom-wrapped eletromagnet and coil?"

I'm betting it's well more than the difference in price between the $10 bargain and a fully assembled fixed-wing RC kit.

#Comment Re: made: 2009-01-26 19:28:19.420857+00 by: Dan Lyke

Yeah. The device that this was salvaged from costs $39.95. As an endeavor measured in microeconomic terms versus my earning potential, it's silly, as is gluing up my own airframe. However, it's good for me to re-acquaint myself with Ampère's law, go through the exercise of thinking through how magnets react to fields, and get the practice with fine scale soldering on a device that's not a 3 week lead time one of a kind prototype.