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Jan 23, 2008, 01:39 AM
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Martin SJ's Avatar
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500mg Radio Controlled Plane

Well, actually, 495mg. This is my old Shark airframe that originally flew at 695mg at NEAT in 2006. Last year I installed one of the new 8.5mAh batteries from Atomic Workshop, and it was down to 600mg, but it never flew very well. I have been following the thread on brushless motors in the mg range, started by Helmut. A couple of weeks ago I decided to try building one of those motors.

First attempt at a motor was so successful that I put it in the Shark airframe and was surprised to find it came in at an AUW of 495mg. Last Saturday I was in southern California, so I visited Matt Keenon at his wonderful indoor meet in Simi Valley. Time had allowed me to develop only three props before the trip, so I picked the best one and installed it. I had a wonderful time at Matt's gym, but in spite of all the help and encouragement from Matt, the Shark didn't really fly. More a powered glide interspersed with radio glitches.

On getting back yesterday I designed and milled molds for three new propellers, and one of them tested significantly better on my dynamic test rig. So I installed it for this evening's indoor meet at my local gym and took it there with high hopes. I also spent some time today checking out the radio, to understand better what configurations would give good radio contact.

The first flights were encouraging, with the plane maintaining altitude but not performing well on turning. It seemed the cg was too far back. On the second charge, with the cg adjusted, it flew steady as a rock climbing in left hand circles. So then I tried a figure eight, and it flew round a beautiful right hand circle, still climbing. After two figure eights I flew it back and caught it in my hand. The entire flight was completely under control, and met my criterion for flight, of being able to do a figure eight ending up higher than it was at the beginning.

Some specs:

Wingspan - 2.65" (6.73cm)
Chord - 1.05" (2.67cm)
Wing Area - 2.84 (18.3
Weight - 495mg
Motor - Brushless 1 phase, 35 ohms, magnet cut down from a 3.2 Shicoh (1.83mm dia, 1.63mm long), 0.01" carbon shaft, Allegro 1442 controller
Propellor - DD, 0.7"(1.78cm) diameter, 0.7 P/D ratio, 0.7 traction, carbon
Radio - Leichty micro modified to 2 channel and lightened
Actuator - 1/16"(1.6mm) ID, 135ohms, 1mm x 0.5mm magnet.

Weight breakdown -
Prop 15mg
Motor 45mg
Battery 300mg
Receiver 60mg
Actuator 15mg
Airframe+switch 60mg
At the next indoor meeting, in two weeks, I will try to get some video.

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Jan 23, 2008, 02:02 AM
Registered User
AleG's Avatar
Congratulations; that`s a new record, isn`t it?
Jan 23, 2008, 03:40 AM
Micro Jet Pilot
Chris T's Avatar
... several records! Lightest plane, first sub (half) gram brushless...

Congratultaions. Great work, Martin!

Jan 23, 2008, 03:50 AM
Be afraid!
Cuddles's Avatar
I was waiting for this...

Best regards,

Jan 23, 2008, 04:17 AM
Well done!

I don't want to sound greedy at all but can we get a flight clip
Jan 23, 2008, 04:20 AM
Registered User
Hallo Martin,

I expected the breaking of the 0.5g barrier a little earlier! But obviously your competitors doubted the performance of the little motors. I am really happy that you succeeded. Congratulations!
Your model is very close to my last estimate of 480mg.
I did not built this size model since I knew it is only a matter of time until somebody would achieve this goal.

I have the feeling that a little smaller prop would improve the performance, mainly the flight time.

Since we cant expect smaller lipos within the next future I am concentrating on solar planes. There is more weight reduction potential. Let's aim for the lightest solar plane in this sommer. Power saving and/or high efficiency are the most significant challenges.

I am eager to see your video.

Good luck

Jan 23, 2008, 05:00 AM
diy heli maker
U.S.U.L's Avatar
Wow, great work. I'm really impressed! Video would be nice.
Jan 23, 2008, 05:29 AM
My member is not
Zlatko's Avatar
Congratulations Martin!

Grat work as usual
Jan 23, 2008, 06:56 AM
Registered User
CA'ed fingers's Avatar

Jan 23, 2008, 07:52 AM
Registered User
well done

urs (switzerland)
Jan 23, 2008, 08:15 AM
Registered User

Jan 23, 2008, 08:18 AM
Micro EDF addict
metroidrc's Avatar
speechless! video please!
Jan 23, 2008, 08:27 AM
Registered User

Many congratulations.

Is the motor now permantly stuck to your metal ruler ?!

I will be happy when/if I achieve sub 1g!

Jan 23, 2008, 10:04 AM
derk's Avatar
thats a truely amazing feat Martin!
Jan 23, 2008, 10:37 AM
Registered User
excellent !

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