Hi All
I would like to have a Quadcopter that would carry a GoPro (preferably with a brushless gimbal) and try and get close to the hour mark in flight time.
Does anyone have an airframe/spec that get even above 30 mins and would they mind entering into some Long Distance R&D with me to try and spec something up.
Tried a lot of innovations with frames, props and motors but not got past 25 mins mark myself
Thanks for any replies/specs
Cheers
Ewen
Replies
Hi Troy,
The larger diameter the prop the higher the actual efficiency, normally also slower moving at hover which is where it counts.
That is a pretty immutable fact and is the single most important factor in efficiency.
However, big slow moving props do introduce other problems.
The bigger and slower they are the more a "quadcopter" tends to actually teeter around according to current asymmetrical prop Blade alignment / misalignment with each other.
With faster props this teetering is nullified or barely noticeable, but as the props get larger and slower it actually becomes a noticeable effect.
Also, big slow motor / prop units tend to respond to application and removal of throttle more slowly so it introduces sluggishness.
Also current blade position when throttle is applied or removed can actually introduce additional asymmetric trust offsets.
The net result is that copters with big slow props tend to be less responsive to flight command inputs (pilot or automatic) and tend to have more problems in gusty winds.
You also don't want to get prop blade tips too close together because coincident prop tip turbulence can induce vibration and "choppiness".
My Hoverthings Flip Pro FPV with extended arms exhibits all of these phenomena with 14" props (about 1/8" tip clearance).
My friend Oliver"s identical quadcopter with 13" props does not and fies smoothly through a very wide range.
I will be going back to 13" props myself because of this phenomenon even though it will result in a 5 to 10% loss in efficiency and endurance.
Best Regards,
Gary
Hi Gary,
Thanks for your response.
Do you think that having another blade on the propeller might solve the teetering caused by "asymmetric thrust"? Having another blade (or two) might average out that effect similar to how it's averaged out with fast turning props.
Perhaps an X8 configuration would solve that problem as well. What do you think?
Troy
Hi Troy,
My freind Oliver tried 3 blade props and I have a set myself (Master Airscrew).
They did not actually work very well,but it may well be that their skinny blade design is at fault, more of an airplane prop than a multirotor even though claimed to be multirotor.
I think the qualified answer is that with the right prop and under some circumstances they could probably work better.
As for X8, it is a good way to stuff a lot of thrust in a relatively small package, but you lose 15 to 20% efficiency through the coaxial dual prop design, period.
There is no way to eliminate that loss, even with top and bottom prop sizes and pitches optimized.
It is possible that it could still be more efficient than a roughly equivalent Octo however because the Prop diameter could be considerably larger.
So it is a trade off more smaller props versus Coaxial loss.
A efficiency optimized quad with optimal propeller diameter and motors will always beat either an "equivalent" X8 or an Octo though (or Hex for that matter because of the smaller propeller diameters or coax loss.
Hex's and octo's are smoother than big quads and an X8 can be used to lift a heavier payload.
You really need to design your copter for what it does, Hexs and Octos are popular for big camera craft because they fly smoothly because of the more small props.
Generally Coax's are pretty smooth too.
So its a choice - maximum efficiency = quad with biggest possible props.
Smoothest flight = Hex or Octo or Coax X6 or X8.
Best,
Gary
Excellent summary, thanks!
Not sure what you mean, maybe you are refering to quads only. Octos, and hexes to some degree, are known to easily survive the loss of a motor. I fly octocopters (X8 and flat 8 configurations) exclusively for higher end copters, for that very reason. Loss of a prop or motor is no issue, in fact it's barely noticeable in flight. Depending on which ones, even the loss of two motors or propellers, with Arducopter or DJI, does not lead to crashes on octos.
I've always been a bit on the fence with helis, mostly because of their mechanical complexity (compared to multirotors, vibration and noise, and their dangerous long blades. Especially gassers. Also lack of redundancy at the motor/propeller level. But I've got to say that as the required size for multis for long flights goes up with props in the 18"-29" range, helis seem more and more attractive on a relative basis, especially with the availability of TradHeli.
But while I know it's definitely possible to build helis for very long flight times, and there are records out there that go well beyond the one hour mark, are there actual, reliable "production" (for lack of a better word) helis out there carrying a reasonable payload (e.g. suitable for mapping) that fly, reliably, for forty minutes, one hour, or more?
Multirotors dont have redundancy with their spinners either. If one motor dies or a prop breaks up, your flight controller will get confused and the thing will spin and crash into the ground almost as fast as if everything turned off.
Steadidrone X quad.
http://www.steadidrone.com/drones/steadidrone-x
Hi,
What's the long flight time needed for? Just out of curiosity.
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