FPVManuals Delrin Tricopter

I was interested in experimenting with multirotor aircraft, but wasn’t sure if it was something that I’d want to get deeply into. They certainly have limitations as compared to fixed wing, especially when it comes to flight times. A 10 minute flight with a multirotor is doing pretty well. OTOH, they can get into places and do things a fixed wing can’t. So maybe. I figured my cheapest option would be a trirotor as that’s about the minimum number of motors you have have and be a multirotor aircraft.

I later read online that someone called trirotors the retards of the multirotor world (I’d rather just say they are “special”). The main reason for this is in the case of aircraft with 4, 6 (hex) or 8 (octo) rotors, turning is accomplished by slightly spinning up or winding down opposing motors. This works with an even number of motors but is problematic with three. To to pull off a turn with a trirotor the rear motor (yes, there is a definite rear to this thing) is actually on a pivot and is tilted left and right by a servo. This weird moving part can introduce complexity into the design of a trirotor and result in fragility in the inevitable crashes. The upside is that you can have an aircraft that flies like a bat outta hell. Now I did not know this latter part. I thought I was getting a somewhat docile trainer.

I eventually selected a kit called the Delrin Tricopter by FPVManuals. It’s an elegant design, with replaceable wooden arms. I mentioned replaceable, didn’t I? Good. I did it a lot. Turns out they end up being the weak point in crashes and are wonderful at absorbing impact.

All multirotors need some sort of computerized flight controller to keep them in the air. There would be no way to fly the damn things otherwise. Basic flight controllers have gyros and accelerometersn to keep the craft level and doing what the pilot wants it to do. More advanced flight controllers can have magnetic compasses for direction, barometers for altitude,  and GPS to find its way home and do completely autonomous flights. Since I was just dipping my toe in I cheaped out and got a KK2.0 flight controller from Hobbyking for $30. None of that fancy stuff, just enough smarts to level out of the aircraft when the pilot does something stupid. I also added a Swann HD sport camera (sorta a FauxPro) and a 5.8 GHz ImmersionRC video transmitter.

FPVManuals Delrin Tricopter kit, as embellished by moi.

FPVManuals Delrin Tricopter kit, as embellished by moi.

I had a few problems with the trirotor. First, it flew like a friggin’ sports car and I was a beginning pilot. It is unseemly for a man of my age to be climbing trees to retrieve an expensive tricopter. But it was sorta fun and nobody was looking. Also, since it had only a basic flight controller, there was no “altitude hold” function to maintain a constant hover. If you nudged the throttle stick just a little too much, it shot off into the sky. It wanted to be free….or something. And this introduced the final problem. With such a small cross section, it was often difficult to tell which way the damn thing was pointed after it became a spot in the distance. My international orange paint job on its ass end was an attempt to improve this situation. It helped, but not enough.

I had been flying the thing only a couple weeks, slowly expanding my comfort zone, when I decided to fly it out a bit and higher, doing a large orbit of the lot I was flying it from. This was somewhat working out until it flew behind some Eucalyptus trees in the foreground and I momentarily lost sight of it. Well, I shouldn’t say momentarily, as that implies I caught sight of it again. I didn’t, it had gone on walkabout.

I panicked somewhat, knowing I had hundreds of dollars and many hours of work hovering somewhere high in the distance. To make matters worse, I had included my expensive HD camera on the trirotor for this flight. I “guessed” which direction it might have been pointing in and spun it around what felt like a proper amount to point it back to me, then pushed the nose forward. I was hoping it would move closer to me and I’d eventually hear the thing. No luck. I kept looking off to the west, the direction I had lats seen it, and manipulated the controls in a vain hope that it might move in my direction and I’d see or hear it. Finally after a few minutes I throttled it back and started looking.

Much of the area I was flying near is under the control of the Evil Empire, uh, I mean Irvine Company, and is a mixture of agricultural fields, avocado orchards and temporarily mothballed building pads. I knew if it had drifted into the dense orchards I’d never see it again, but if it went down into the fields or building pads I had a chance. So the trespassing commenced.

It took 45 minutes, but eventually I saw a piece of international orange leg sticking up out of the grass. It was almost a half mile away from its launch. Although it was in pieces, the actual damage was three broke wood arms, and two props. The camera had survived it all and was still running. The video was rather entertaining as the aircraft spins around in response to my efforts to figure out where it is. At one point I can be seen far below in the distance looking in the wrong direction. The final part is wonderfully grim as it rapidly descends, completely level, from several hundred feet. Here’s the Youtube video:

The result of the tricopter doing an uncontrolled descent from around 400'. One broke prop, two broke legs, pretty cheap! Lesson learned, don't let the damn thing get out of eyesight.

The result of the tricopter doing an uncontrolled descent from around 400′. One broke prop, two broke legs, pretty cheap! Lesson learned, don’t let the damn thing get out of eyesight.

So after that, I thought, “Damn…I need a quad…..Yeah, a quad, with GPS and a ‘return to launch’ function”. This multirotor stuff was actually a lot of fun and held out the ability to image a lot of interesting sites.