Long duration asymmetric Tricopter 430 class with 15 inch props

[Tennessee Light]

Here is the preliminary documentation for a new idea in tricopters. My idea (right or wrong) is that a tricopter is more efficient that a quad because of the smaller number of rotors and no need for the props to change speed to yaw the craft.

It’s usually difficult to create a tricopter with larger props because of the large rotational momentum of the rear prop. With this machine, the rear (tilt) prop was considerably smaller than the front (lifting) props. The idea is that the front props provide 80% of the lifting power while the rear prop provides the remaining of the lift and all of the yaw.

This prototype project uses a scratch built frame consisting of 1/2 inch wood booms and two-level maple central frame. Everything is held together with zip ties and hot glue. This allows for cheep construction and easy replacement of the booms if necessary.

Specs:
430mm class
22 inches between front props
17 inches from each front prop to the rear prop
Frame weight is about 275 grams without landing gear
Landing gear is 1/8×1/2 aluminum

Future design could be 1/2″ cf booms and G-10 center frame.

Propulsion:
Lifting props are T-Motor 3110-26 470 kV motors
Tilt motor is RC Man Child 2212 1000 kV motor
Front props are RC Timer 15×5.5 CF
Rear prop is 10×4.5 nylon
Rear tilt and front motor mounts are from RC Explorer (David Windestal)
Rear servo is Blue Bird – BMS-210MH metal gear

Electronics:
Naze32 FC with Cleanflight
30A ESC from RC Man Child (w/Simon K)
FrSky x8R receiver running SBus to CPPM converter
FrSky voltage monitor via telemetry
Lumineer 600 TVL FPV cam from GetFPV
Video TX is TS832 600mW
Video Aerial Systems Blue Beam antenna

Flight battery can be 3s or 4s. The video demo shows 3s 4500 with flight time of about 16 minutes. With 4s 8000 flight time is about 34 minutes. With 4s 10000 flight time is 42 minutes with pack at 20% reserve. Hover at about 60% throttle. There is plenty of reserve power for a Mobius or GoPro.

All up weight is about 1800 grams with 4s 8000. Performance is ok on 3s but is much better with 4s. The motor/prop combination is optimized for 4s.

Please leave comments and suggestions for improvements! I’m calling it the Big Taz Tricopter in honor of the Tasmanian Devil cartoon.

(Cross post with RC Groups)

[donnyb]

Well before you start. .5 inch wood booms won’t work. I couldn’t even get a 12inch prop going with out twisting. On 1/2 x 3/4 it was smooth balanced but once I throttled up it was dangerous. I was only able to get 11 inch prop to work on a quad I worked on. If your looking to turn a 15 inch prop. HK has some 25mm cf tube may give you what your looking for.

[Tennessee Light]

Thanks for the HK suggestion Donnyb. I figured I’d use the 1/2″ wood booms on the prototype and then move to something more rigid and durable if the concept worked. Did you have a chance to watch the video? It flies pretty well and doesn’t appear to have any serious stability issues.

The design uses a T-copter design so the main boom runs between both front props. I think this helps reduce the flex in the frame.

Today I changed the flight control from the Naze32 to the Vector. The Vector seems to manage the asymmetry better but the default settings have induced a “wobble” into the tilt assembly. Hopefully a lower “I” value and larger “D” value will take care of it.

Time for more testing!

[donnyb]

You could be be right. But the arms on the ones in the video looked pretty thick. But my arms where a little bit longer. Maybe 18 inches. Not sure what resonate could of been a lot of things. When I moves to 11 inch props it flew like a dream. Scrapped the idea it couldn’t be efficient enough. I been working a lot on lighter frames without going to carbon fiber. But you always have give in take for weight and rigidity. Good luck!

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