Simple Variable Pitch for Brushless Motor

by tecdux | February 25, 2013 | (6) Posted in Projects

http://www.youtube.com/watch?v=qtwZi_2otrU

With a brushless motor and a TRex tail rotor mechanism I could assemble a simple variable pitch system. I measured and it generates 700g with the TRex 500 tail rotor blades.

I tried the Trex 250 blades from the main rotor but although they are longer the thrust is smaller, just 400g. This is probably because the motor doesn't have enough torque.

This could be used for a variable pitch quadcopter or with an airplane.

Specs:
Motor: Hextronik DT750
ESC: Plush 25A
Battery: Turnigy 2200mah 25C
Tail rotor: HK-500GT
Wood to support the tail mechanism: 38mm tall

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COMMENTS

jamiedco on February 26, 2013
I see you hit your hands a few times .
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tecdux on February 26, 2013
Hhhauhauha yes, but this happened with the fixed pitch propeller
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air on February 26, 2013
I wonder how well the mechanism will hold up at that RPM. I think the ideal blade size would be closer to the 11 inch prop it would normally run. So maybe 700/800 size heli tail blades (115-140mm).
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tecdux on February 26, 2013
yes, probably but there are some mechanical losses due the variable pitch mechanism (friction)
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apache64 on February 26, 2013
Great idea, but maybe running one motor and four Trex 450 tail booms via a gearbox would make it lighter and thus compensate for the servo weight you would need. It looks a bit dangerous doing your testing with your hands so close, those carbon fibre blades are like stell at that RPM..ask me how i know..
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tecdux on February 26, 2013
I'd say using 2 motors with 4 tail booms sounds better because if one motor failure the other one could still supply power. Have you cut your fingers with those blades?
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DaG on February 26, 2013
I like the Idea, it is so much costless than a true prebuilt variable pitch setup ? ... And please be carefull with that I was worrie about your hand too !
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tecdux on February 26, 2013
There are few options for prebuilt variable pitch. Hobbyking has one model but it costs US$18 and generates less than 500g of thrust
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Adib Vahedi on March 3, 2013
Looks great and I hope you don't chop your fingers off!

Keep up the great work!!!!!!!!!!!!! ;)
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tecdux on March 3, 2013
My fingers are better hhehehe ;) thanks!
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Aleksander on March 4, 2013
Looks like it is rotating the wrong way during spool up?
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tecdux on March 4, 2013
when I add throttle slowly to the ESC, it vibrates during start but then rotates in the right direction
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Gruardian 388 on April 24, 2013
How would you wire it up to the flight broad? Could a flight system such as Arduino or KK2 be reflash in order for it to talk to both the esc and the servo?

Other than that looks like you are on to something here. Keep testing and keep the first aid kit handy. lol
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tecdux on April 25, 2013
Hi my friend, for example, in a quadcopter you would have 4 servos to vary the pitch for the 4 motors. So, instead of conecting the 4 escs to the control board (KK for example), you would connect those 4 servos. You could use 1 extra channel from the receiver to control the throttle for all ESCs (Y cable).
Hhahuahuah thanks for the advice, my hands are much better now ;)
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Gruardian 388 on April 25, 2013
Now I feel really silly for the question I asked. lol Thank you for taking the time out to answer this. :)

The one thing the heil guys have on us is the fact their birds can do some amazing stuff (Tricks). Once this concept becomes more feasible I can see us being able to do more amazing stuff. We still got the advantage of being less expensive and more user friendly. ( I do own a 3d helicopter that one day I will master lol) Keep up the work.
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tecdux on April 25, 2013
I'd also say that multirotors are much more robust them helicopters ;) can't wait to have autorotation in multirotors
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Simple Variable Pitch for Brushless Motor