I have seen this video already a while ago but now, Infinity Hobby has it in their product news. Apparently, some company is making propeller hubs to use heli blades with multirotors.

That allows using of ridiculously big propellers, leading to very efficient setups. Additionally, heli blades are dirt cheap, compared to multirotor blades and with the adjustable pitch (!), there's even no searching for pusher-props any more.

Can't wait until this is actually available!

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Comment by Rob_Lefebvre on August 9, 2013 at 9:28am

Interesting development, but I'm not so sure it's a good idea.  I'd like to see some test data.  To me it seems like combining the worst features of the platforms.

Theoretically, large, slow turning props are more efficient than faster smaller props.  However, the blade profile of helicopter blades is not as efficient as multi-rotor props. So overall, is this more efficient?  I don't know, but I doubt it.

Then you have to consider the problem of control. Using props this large, you start to have a serious problem with being able to speed up and slow down the props fast enough to achieve attitude control.  Large props like this have much more inertia, so they can't respond as fast.  The video showed a few places where it seemed like the quad was unstable.  Helicopters solve this with variable pitch which can respond faster than variable speed when using props of this size.

Comment by HeliStorm on August 9, 2013 at 9:39am
I don't see a way for controlling pitch, so this seems like it would not be very efficient, compared to blades optimized for fixed pitch operation. Variable pitch quads do interest me some, but I am not sure how this setup is advantageous. I wonder if it could auto rotate though. That would be interesting.
Comment by Alexsey Novik on August 9, 2013 at 9:54am

I like the idea of adjustable pitch and cheaper props!

Comment by Rob_Lefebvre on August 9, 2013 at 10:36am

Nope, no autorotation.  You need to reverse the pitch for that.

Comment by HeliStorm on August 9, 2013 at 10:46am

No, my thoughts were slightly disjointed. I was wondering aloud if a variable pitch quad could auto. Not this exact configuration.

Comment by Stefan Gofferje on August 9, 2013 at 10:49am

Robert: not necessarily. Fullsize helos can't reverse pitch :).

Comment by Gerard Toonstra on August 9, 2013 at 10:49am

Unfortunately they don't say anything about the duration.

5kg for a quad without payload is an enormous amount to lift. From the specs I gather that they put on 6S and 220kV motors in an attempt to increase efficiency, but then undo the entire effort by adding 4 blades instead of 2 and variable pitch hubs which in the end aren't used and set to "max pitch". If they had limited the weight for the entire setup they could have won a lot more. It could have been an endurance quad with FPV equipment capable of aggressive manoeuvers, probably around 25 mins. flight time or it could have been a 5-8min. heavy lifter.

Comment by R. D. Starwalt on August 9, 2013 at 10:55am

The fellow at 0:54 has a lot of guts to walk under that machine. Talk about a flying lawn mower!

The heli blade is not a new idea at all. I just finished reading 'Fascination Quadrocopter' by Roland Buchi . He discusses a similar setup using heli blades. In his case, he used blades from a Coaxial bird (or two?) with homegrown hub adapters.

The innovation here is the hardware. It looks like a variation of the 4 blade hardware seen on scale helis but with a manual pitch adjust. Clever.


Comment by Josh Potter on August 9, 2013 at 10:56am

Stefan:  Well any heli that's airworthy has to be able to auto rotate.  If they can't reverse pitch they're going almost negative and using the rotating mass to keep the main blades spinning. 

Comment by Austin Suhler on August 9, 2013 at 11:05am

If variable pitch in flight heads come to multicopters, what's the first thing someone is going to do? Is it:

A) Fly gently and carefully.

B) Fly as fast as they can into a building.

C) Make it fly inverted as often as possible and post as many youtube videos as possible about it.

D) Give up, because variable pitch is too much to handle.


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