The Moth
The Moth is essentially a cut-down Piccolo. It has smaller blades, paddles, tailrotor, undercarriage, tailboom and tailskid. John Kallas of California did the experimental work and the plans for the conversion, unfortunately his web site isn't online now, but with his permission, here are the necessary files:
Moth instructions.doc Moth blades.jpg
Back in 2001 I came across a link to this cute dwarf version of the Pic, and as soon as I could, I got hold of a new Pic kit, less the onboard electronics. I intended to put together an experimental version, using light weight separate components for the radio control. I already had the recommended motor at the time, a Mabuchi 180, a slender and quite high revving device. Mine was the Tamiya "black" motor label. Here are a few pictures of the early days, click for bigger pictures:
Note how few bits there seem to be! The right side view is particularly clean.
I had a few problems with this setup. The speed controllers needed calibrating to run smoothly, they had an odd habit of not running properly until they had seen full throttle, though they had already set themsleves a working range based on the "low" throttle position. They were small, light and not expensive. I had to sort out a mixer for the tail control, so that it ran up the tail motor as the main motor did. Eventually I had to use my Multiplex transmitter as the mixers are more flexible than my old faithful Fleet transmitter can manage. The main motor seemed to "hog" the current from the battery whenever the battery was not peak charged. More battery volts seemed to be the answer to the latter and I eventually tried 9 cells. The basic heli seemed quite controllable and stable, I did like seeing it in the air.
Eventually for reasons I forget, I decided to use the airframe to run my cdrom trial in. I used a Jeti 06 controller, which had come with my Astro 01 brushless motor, it proved to run the cdrom motor though still had the annoying coarse throttle action. This meant the heli either sat in a slow descent or a slow climb, nothing in between.
I also changed the tail controller for a JMP which has a fixed throttle range. To my surprise and delight the main motor ran really well, plenty of power. Unfortunately I couldn't live with the Yo-yo hover, and at least twice the tail controller cut out on me. I decided to tackle the problems one at a time. The main controller was changed to a Castle brushless controller. This did some odd things and proved to be faulty, repaired without question by Castle. However, it didn't like the cdrom motor. Time went by! I couldn't use my best Schulze controller, I had been warned they got upset in this application. Anyway, I eventually found a likely reason, weak magnets on the cdrom motor. My motor was quite an old one, from a 32X drive or less. I heard of a few suitable small magnet types/suppliers, and sent 20 Euros off to Supermagnete.ch in Switzerland. My order found its way back through a postal strike and I epoxied 12 of these little beauties inside the motor. Eureka! Epoxy barely dry I threw the rest of the gear back on the Moth and went off to the village hall.
Here is a picture of the magnets, already being glued into a second motor:
If you are getting this the same resolution as I am 1024 x 768, then that thumbnail view (pun intended) will be about life size.
Running on 3 x 1200 Kokam pack, which is way too heavy for a Moth really at 71grams, the motor lifted the heli easily into a solid hover, only minor trim required, phew! The tail controller seems happy too, maybe the controller had been objecting to the motor and doing strange things to the supply volts? Flight characteristics - Confidence inspiring, easier to hover than a stock Pic, but more agile too. The following weekend we went to the Harrogate show to do some indoor demo flying and the Moth was flying nice stable circuits in the small conservatory, and chasing Nigel Ling's infra red control tank around the floor as he attempted to bring his gun to bear on the heli. I was flying tiny circles, stop-start sprints over the top of the tank, various strange pirouette manoevres without giving it a second thought; marvellous! I only erred once, resulting in a harmless nose down landing, ending with the heli back level on the skids.
Next outing - Halesowen December '03 indoor fly. Hehe, my other helis didn't get flown! Moth was hurled up and down the hall, despite carrying some draggy Christmas decor, and flew brilliantly. The transmitter was passed to at least 4 people, all were able to cope easily with the nice steady flying characteristics. Eventually Moth Pilot went into banzai mode and diced several times with walls, floors and finished with an ear-to-ear grin. I had to pack my gear away in haste, the nice chap from the sports centre wanted to put the table away.
I've flown the Moth outdoors today, light breeze falling away to calm. The turbulence at first made accurate hovering hard work, but Moth went well, and proved capable of straight runs up and down the field, plus circuits and eights. Hovering was best done nose into wind, the low-ish tail power made tail to wind and side to wind hovers hard work. Forward flight required some forward pressure on the stick, but not much. Hovering descents need some care, as with any fixed pitch, so as not to lose the headspeed.
Here's a movie of the Moth in our local village hall, sorry about the quality, it was taken on a stills camera, in dodgy light, by my good mate Kevin (thanks buddy!): Moth.mov 3.7Mb Quicktime movie
Weight: 138g without battery.
Motor: at present, cdrom motor from (I think) 32X cd drive. 15 turns of 0.4mm wire. 12 of 5x5x1mm N45 square magnets. Two3x9x4 ballraces, 3mm steel shaft salvaged from the rest of the cd drive.
Gearing: 10/96 using a metal ECO-8 pinion. Small metal shims inside to make up the 0.2mm difference in diameter.
Controllers: Main Castle Creations Phoenix-10, tail JMP HF9-32Heli.
Receiver: ACT micro4 (less glitches than the original GWS pico)
Servos: JP Supertec Pico 6 gram
Rotor span: 402mm (stock is 528)
Flight time: Typically 24 minutes on the 1200 packs. The main motor runs just barely warm, the tail motor warm to the touch. I run a home made battery warning light - RiverRider's DIY Liposafe light from the Ikarus Piccolo bulletin board.
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