Hexcopter vs quadcopter - wind and motor failures - RC Groups
Shop our Airplanes Products Drone Products Sales
Thread Tools
Feb 22, 2012, 04:27 PM
Registered User
Discussion

Hexcopter vs quadcopter - wind and motor failures


Hi all,

How does a quad compare to a hex with regards to wind stability? DJI do a F450 and F550 frame. Are Hex's less stable in wind due to being wider or are they more stable due to having more motors?

Also, with a hex, can you lose one motor and have the thing still fly OK? With a quad I believe that if you lose one motor the thing will crash?

Thanks
Sign up now
to remove ads between posts
Feb 22, 2012, 04:33 PM
cereal killer
I was just about to post a question along these lines concerning redundancy in multirotor platforms. I have read a three up three down can be controlled by a good pilot if one motor goes out; same for a four up and four down. I have also seen claims that an eight up offers the best chance with the least pilot skills if you lose a motor. I have also seen claims that a six up is very hard to control if you lose a motor.

So can some of you experienced guys weigh in on what multirotor platform is the easiest to control (assume a top of the line FC like NAZA or Wookong) with all motors working along with what is the best choice if you lose a motor.
Feb 22, 2012, 04:45 PM
Registered User
The flight controllers don't know if a prop has busted or a motor is seizing up, there are no feedback sensors. All they know is the copter isn't going where the FC wants it too, so it will still try and rev up a dysfunctional motor/prop instead of taking it out of the pool of available resources.

In the future, it might be nice to build multi-copters with feedback sensors, optical, hall effect, whatever, just something so the flight controller knows the prop is still there and how fast it's spinning.

Currently, only a human pilot knows there is a problem and compensates properly. If you have a zillion motors, the loss of one or two doesn't mean much, and the dumb flight controllers can deal with that.
Feb 22, 2012, 04:48 PM
1.21 Gigawatts!
Steph280's Avatar
I don't have the specific DJI frames you are talking about, but based on my experiences with quad/hex/octo, quad is not as stable as hex or octo in the wind.

As for redundancy, not sure if hex can still fly after loosing a motor. You may still have control to land it, but to continue flying with remaining motors like nothing happened is not possible.

I posted this video on another thread, but it's basically an octocopter doing motor failure test which shows up to 4 motors being turned off, and the thing still flies.
MikroKopter - OktoKopter-Failsafe test (3 min 28 sec)
Feb 22, 2012, 07:42 PM
Registered User
Thanks for the feedback. I wouldn't be looking at 3-up/3-down but simply a 6 rotor setup and 4 rotor set up. I originally wanted an X8 but the Naza FC doesnt support X8.

The X6 looks likely to be the one in that case. So long as one motor failing doesnt mean it falls out of the sky uncontrolably then thats enough for me! I would be flying over water sometimes (for what I have planned!) so need to think of the most suitable loadout!
Feb 22, 2012, 07:53 PM
Z06 Tony's Avatar
A hex is more stable in any condition. It will carry alot more than the same size quad using the same motors as it has 50% more power. Most that fly hex's dont bother with quads for like AP. They are good for practicing on and sport flight but for stability and lifing its hex all the way.
DJI ROCKS. See my DJI Wookong-M hex->

Wookong-M Hex/Hexacopter UAV/Drone/Multirotor w/GPS Rc-Drones.Com (2 min 42 sec)


here is my buddy who never even hovered a multi. Not even before we started filming. He has flown helis though->

Hex/Hexacopter w/Wookong-M 1st Multirotor Flight EVER RC-Drones.Com (2 min 50 sec)
Feb 22, 2012, 10:11 PM
Tri-Quad-Hexa-Octo-copters!!
Under Project Quads/Hexas/Octos: in the
Quadrocopter and Tricopter Info Mega Link Index

--TIP 2: Excellent discussion on capability differences between an octo and hexa and coax and flat prop orientations: https://www.rcgroups.com/forums/show....php?t=1378824

Cheers,
Jim
Feb 23, 2012, 01:48 AM
Registered User
brianshell's Avatar
I own a quad (DJI F450) and a Hex (XA Hexa)... I can tell you the following:

1) In terms of stability in the wind, the Hexa wins HANDS DOWN. The little quad gets pushed all over the place and becomes really wobbly in high wind. The Hexa, on the other hand, remains quite stable no matter what (it just gets pushed around).

2) In terms of ability to withstand a failure, they are both terrible. The quad and the hexa will both crash immediately if they lose a motor or a prop. (I've experienced both on both).

My understanding is that in order to get redundancy, you need at LEAST Y6 (three on top, three on bottom, and a skilled pilot)... Octo is much better for this purpose.

I'm selling my Hexa to move to an Octo for this exact reason.... But I'm upgrading my FlameWheel 450 to a FlameWheel 550. (The parts will be here tomorrow). So my quad is going away completely, and I'll be left with a Hexa and an Octo when the dust settles.
Feb 23, 2012, 02:47 AM
Registered User
i have had failures on X8 and Y6 , if you have enough power you can land with both in case of motor failure, Y6 will be harder because you have terrible yaw. If you break a prop you have to be lucky to break both blades, because if you are left with only 1 blade you will have so much vibration that i doubt any board will be able to keep it up.
You can use X8 config on any board that supports X quad... simply use a Y cable to connect 2 esc to 1 motor output; board will think it is a quad. I have done it for 6 months on a multiwii board.
Feb 23, 2012, 03:24 AM
Registered User
Y6 is no more redundant than a flat 6 and is less stable and more inefficient to boot. In fact I'd go so far and say a Y6 is less stable than a quad, at least the one's I've seen were. If your gonna fly over water or crashing is more than an inconvience then octo is the wise choice.

A flat 6 will give you more stability and lifting power than a quad, and marginal redundancy as long as your just hovering around. Lose a prop or motor while flying normally with any forward speed and a hex or Y6 is unlikley to save your bacon. Lose a prop or motor on a flat octo and you may not notice till you land.

On a side note, a 10" APC prop weighs 12.6 grams, while a 10" carbon nylon GemFan weighs 8.8g. Which one do you think is going to create more of an imbalance and be more likley to take down your copter if it looses a blade?
Last edited by patricklupo; Feb 23, 2012 at 03:53 AM.
Feb 23, 2012, 04:20 AM
Registered User
i don't agree with you patrick, yes coaxial is less efficient than flat, but it does have better chance of survival in case of motor out. It is probable that flat hexa is smoother because of no aerodynamic disturbance of coaxial..
Sure flat octo is best for efficiency, smoothness and reliability... but it is HUGE... if you need to travel a lot it is a p.i.t.a to transport. I have been using a perfectly working X8 for 6 months but decided to go folding Y6 frame because of transport problems... it really depends on what your needs are.. if your average utility vehicle is a Ford F150 , then you can go with a flat octo no problem.. if you are in europe with small-medium sized car and have to bring other equipement too, then size becomes important.
Feb 23, 2012, 06:06 AM
Registered User
[QUOTE=thepelell;20831811]You can use X8 config on any board that supports X quad... simply use a Y cable to connect 2 esc to 1 motor output; board will think it is a quad. I have done it for 6 months on a multiwii board.[/QUOT

hello if you make a x8 from putting a y cable into connect 2 esc to 1 motor couldnt you do the same with a 12 motor or a hexa frame? im planing on building a hexa and your post caught my eye
Feb 23, 2012, 06:12 AM
Registered User
Quote:
Originally Posted by games133

hello if you make a x8 from putting a y cable into connect 2 esc to 1 motor couldnt you do the same with a 12 motor or a hexa frame? im planing on building a hexa and your post caught my eye
sure you can, and someone has already tried it.. but can you immagine all the hassle of getting 12 motors balanced and working good ?..
if you don't need a compact copter and you want redundancy, go for a flat octo.
Feb 23, 2012, 07:29 AM
Tri-Quad-Hexa-Octo-copters!!
Yep. Although probably the biggest factor in wind stability between a hexa/Y6 and a quad is simply the extra weight. The same AUW quad and hexa/Y6 will actually perform very similarly side-by-side in the same wind.

For anyone who wants true redundancy and does not have the multicopter flying skills of Warthox, an octo rules.
If you are flying an expensive and heavy DSLR with a hexa/Y6 then it is only a matter of time before you will regret doing so.

Also however, the one nice thing about APC props is that they will never break inflight.
Cheers,
Jim
Quadrocopter and Tricopter Info Mega Link Index
Quote:
Originally Posted by patricklupo
Y6 is no more redundant than a flat 6 and is less stable and more inefficient to boot. In fact I'd go so far and say a Y6 is less stable than a quad, at least the one's I've seen were. If your gonna fly over water or crashing is more than an inconvience then octo is the wise choice.

A flat 6 will give you more stability and lifting power than a quad, and marginal redundancy as long as your just hovering around. Lose a prop or motor while flying normally with any forward speed and a hex or Y6 is unlikley to save your bacon. Lose a prop or motor on a flat octo and you may not notice till you land.

On a side note, a 10" APC prop weighs 12.6 grams, while a 10" carbon nylon GemFan weighs 8.8g. Which one do you think is going to create more of an imbalance and be more likley to take down your copter if it looses a blade?
Last edited by jesolins; Feb 23, 2012 at 07:35 AM.
Feb 23, 2012, 07:49 AM
Z06 Tony's Avatar
[QUOTE=patricklupo;20831929] In fact I'd go so far and say a Y6 is less stable than a quad, at least the one's I've seen were.
QUOTE]
Its pretty cler you havent flown a Y6 so how could you even make a statement like this. You are so wrong.
You might want to fly a Y6 before you give people advice like this.
Last edited by Z06 Tony; Feb 23, 2012 at 09:05 AM.


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion RC plane or Heli vs wind Torch8 Electric Plane Talk 5 Oct 21, 2011 03:54 AM
Discussion Wind worthy vs. flying space 4-ch MIflyer Beginner Training Area (Aircraft-Electric) 13 Sep 13, 2011 11:00 PM
Discussion Random Motor Failures..... ? cellosid Multirotor Drone Talk 0 Jun 27, 2011 08:00 AM
Discussion ArduCopter vs. Fy91 q with their quadcopter alexciocan Multirotor Drone Talk 32 Jun 24, 2011 10:00 AM
Discussion Foamy CG vs. Wind Beachcomber 3D Foamies 18 May 14, 2011 11:16 AM