First look at these monsters coming soon!
My dream of an airbot-hammock might just come true after all...
Here is the request for input on developing a new line of motors "tailored for UAV applications"
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I think he was referring to the problem of physically balancing them. It's a lot of props!
Gary, yes, I understand what you're saying. The issue is boiled down to this: The area (and thus roughly speaking thrust) increases with the square of rotor diameter, but the inertia of the prop goes up with the 4th power of that diameter. So as you increase prop size, you reduce your ability to respond to changing thrust needs. But, as you say, the larger the machine, the less fast it *needs* to respond. So, somewhere around here there's going to be a sweet spot, beyond which the equations I think will result in a knee-curve where the ability to make larger fixed pitch quads will start to fall apart.
Where is it? I dunno. It'll take brave people to experiment and find out.
I'd argue against the idea that a VP quad is simply or more reliable than a helicopter. Both machines have 4 servos. The quad has many more drivetrain compoenents (assuming a central power plant). And in my experience, tail pitch sliders (what you'd use on a VP quad) is less reliable than the swashplate. The swash plate and head assembly looks scary, but it's really not that bad. Especially with flybarless helis. "DFC" heads are even simpler, but I'm still not sold on the concept.
Helicopters also have some ability to not crash if they have a mechanical failure. A VP quad, I'm not so sure.
>"I'm ready, just not looking forward to balancing all those props."
U sure? As we known, dodecacopters not have such problems, and can't see any reason why they should appear at the octodecacopters (t.e. volocopter). There is no nedd heavy math. =)
Volocopter -- I'm ready, just not looking forward to balancing all those props.
Gary, can't wait to see your results.
And yes, convergence. We're currently jumping to hyper-time, seatbelts and tray tables everyone!
Hi Joshua,
Should have four 4 blade props awaiting pickup at local hobby shop for prototype QuadroQuad.
I do believe it is going to make a good video filming platform.
All the preliminary tests with a single additional horizontal prop have shown excellent stability.
Got to admit when I first saw those motors the first thing I thought of was brushless bicycle motors, convergence I guess.
Hi Robert, A
as an engineer, I understand that the bigger and more massive the copter, the less you need to accelerate and decelerate the motors to stabilize it.
Basically since the copter has a higher mass relative to the relatively fixed density of the air stream, the less it is disturbed by gusts and the longer it takes to displace the copter.
Sort of inverse Liliputian effect. (Why bugs can jump so far).
But definitely a slower moment of response (acting and acted upon) in any case relating to increasing masses in a fixed environment.
Of course may not balance out and could hit the limits of this thesis.
There is another BLOG about a KickStarter quad that they are trying to build that uses 2 gas motors geared to drive 4 rotors on a quad and they are using variable pitch.
Yeah it's more complex, but at least they don't need to mix in cyclic which makes the whole rotor thing a lot more robust and simpler, not as simple as our nice fixed blade copters, but still better than a traditional heli.
I don't think we need or want variable pitch on our electrics, but for a fuel multicopter it does make sense.
I do think there will be a limited hobbyist use for motors over a kilowatt, but there will probably be good commercial uses for them and prop efficiencies generally actually increase with diameter as long as you keep the tip speed subsonic.
It's will be open road to create new aircraft type like volocopter etc.
Renato,
Good point, although I wouldn't want a rolling shutter or my IMU anywhere near my electric bike motors : )
Those big motors above make a dramatic image for sure, but I assume most of our builds will stick with the smaller sizes. As Robert mentions above, any craft using differential thrust to maneuver -- needs to keep the inertial loads under control.
Of note: Gary McCray is working on a control method that doesn't have this concern.
Back to the electric bikes for a moment-
My latest e-bike build is a cargo hauler with a 2kWh LiFePO4 battery pack @ 50V. This will be used to get my flying gear onto location for mountain bike filming, and power all my ground station needs while shooting. I'm also going to incorporate a small folding PV array into the mix. I'll make a post about it soon.
I think such motors ARE already in the market... the electric bike motors, have pole count in the same ballpark, and direct drive a 26" wheel.
@R.D.
I think its a smart move for the company to not assume it knows what the people want, but I think a few hours on RCGroups could give them all of the infor they needed. Right now there are a quite few active threads on rewinding motors for various uses.
Basically the company is saying they are not going to try to determine the operational characteristics of undesigned aircraft - 'tell us what you want, we will build the motor for it'.
Most end users (media applications) would specify flight time and payload lifting ability. Everything else, to them, is just details.
It is interesting that the design group would cast their net to the community at large. Is this smart management or something else? All the parameters to crunch the numbers are in motor design software. They just want to know how many motors they can make at that size. Is there a real market for them?
-=Doug
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