How important is redundancy?

[Blacksails]

I'm in the process of planning a medium lift hexa/octocopter. I have decided that the multi will be powered by the dji wkm, radio link will be via EZuhf and It will also be carrying a Sony Nex 5n as payload.

My budget allows for me to build a HEX with top quality components, or I could build an octo with slightly lesser motors/esc's etc. What would you guys advise, as I have no experience with hexacopters and octocopters.

I understand that if a hex looses a motor/esc it WILL kiss the ground (unless its a Y6), where as an octo has a higher chance of staying aloft. But is redundancy as important when using high quality motors/esc combos such as AXI's and Maytechs? How often do these fail? I have flown a multiwii powered tricopter on cheap £6 motors now for around a year and have not had a motor/esc fail on me.

Cheers Guys

Alex

 

[Bartman]

Hi Alex,
I'm a big believer in using multiples of components to make the overall system more reliable. Having said that, and fully expecting the simple is better crowd to weigh in, it should be noted that the DJI WKM appears to lack the ability to compensate when a motor is lost thereby negating any redundancy you may have been relying on to get your craft back on the ground. I'm not reading the DJI board as much as some others likely are but that's how it was the last time I visited with them.
We have at least three examples at this point of MK guided craft maintaining control after the loss of a motor or prop on Okto's, FWIW.
Welcome to the site!
Bart

 

[Blacksails]

Thanks Bart

So, considering that the DJI lacks the ability to compensate when a motor is lost i'd be best off just going for the hexa equipped with better components then?

Should I be too worried about flying a camera over water etc on a system with no redundancy, or am I just being overly pessimistic about it?

Cheers

Alex

 

[DucktileMedia]

No, that means octo minimum for redundancy. I have only seen one hex video recover and fly normally without a motor and the way the FC achieved this was by killing the opposite motor making it fly as a quad. I can't believe that the DJI isnt capable of handling a motor out. but that seems to be the general consensus.

You might do yourself a favor and buy one of Bart's XY8 frames as that will give you the best of all worlds.

 

[Mactadpole]

This might help answer your question:

Coax motors in my format of choice now! Shawn

 

[Blacksails]

Thanks Shawn, impressive video!

I don't understand how the wookong cannot offer redundancy, these things only get off of the ground because the IMU is constantly correcting for pitch and roll.......if they dont then there is no stability. Not that I don't believe you guys, I do, I just cant get my head around how it refuses to compensate for a dead motor when its main job IS to compensate for variances in lift for each motor on craft.

Really stuck on what to do. I want the WKM as it seems to best every other controller I have looked at in terms of stability and functions......but I wont have a redundancy safety margin even with an octo.

Shawn, how do you like your RC carbon frame? Whats the quality like? CarbonCore sell them over here in the UK (hes the original designer) and i've been looking at their octo kit.

 

[Mactadpole]

Thanks, those were some scary moments. I feel much better now days knowing that I at least have a chance.

I really like the RC-Carbon frame but I definitely had some problems with it and they do have some cosmetic issues since it is hand-made for the most part. The original motor mounts were crap and I had to order their new motor mounts out of durobond that are great. I have heard they now mount the arms with the wide side vertically oriented which would also help with prop wash hitting the wide part of the arm like it does on mine. The fact that the arms are foldable is a huge plus. I did have to custom drill holes for mounting things like the Droidworx landing gear and mounting for the MK okto xl distro board. If I were to be in the market for a new frame I think I would wait to see what the Droidworx ECM frames are like that should be coming out soon: http://www.droidworx.com.au/ECM.html. Of course I would want one that is an X8. :frog: If you have not flown multi's yet then I would get one of Rusty's frames at AGLhobbiesLLC.com and start with that. I keep going back to his frames for new builds because their just so durable and utilitarian. Plus they are pretty cheap!

 

[homer911]

I am stuck in the middle in relation to this. I want to buy a Droidworx octo HLE ECM when I comes out soon. But I am a little worried about the redundancy. I havent heard of many events of people recovering from an engine failure etc with the WKM.......

They are only bringing out hexa and octo ECM so the coax is not on the cards :upset:

How about a HEXA COAX ECM. I'm sure it would work.... It would just eat batteries I think.

 

[EgonW3]

I am going to buy HL frame for aerial photo with heavy cameras. Now we have following options for HL frames:

1. Mikrokopter with BL-CTRl 2.0 or Aerodrive or Herkules II limited to ca 35A per motor but with redundancy
2. Wookong-M with PWM ESC in fact without any boundary for motor current, but lack of redundancy and limited telemetry
I've sent inquiry to DJI about redundancy or plans to implement it. I consider their lack of answer as a negative answer....

 

[Bowley]

Anyone know how Ardupilot Mega handles a motor out on Hex and Octo.

 

[iscorama]

doesn't you need I2C Octo Isolator R3 for reducancy to fork with mk eletronics?

 

[homer911]

Thanks, those were some scary moments. I feel much better now days knowing that I at least have a chance.

I really like the RC-Carbon frame but I definitely had some problems with it and they do have some cosmetic issues since it is hand-made for the most part. The original motor mounts were crap and I had to order their new motor mounts out of durobond that are great. I have heard they now mount the arms with the wide side vertically oriented which would also help with prop wash hitting the wide part of the arm like it does on mine. The fact that the arms are foldable is a huge plus. I did have to custom drill holes for mounting things like the Droidworx landing gear and mounting for the MK okto xl distro board. If I were to be in the market for a new frame I think I would wait to see what the Droidworx ECM frames are like that should be coming out soon: http://www.droidworx.com.au/ECM.html. Of course I would want one that is an X8. :frog: If you have not flown multi's yet then I would get one of Rusty's frames at AGLhobbiesLLC.com and start with that. I keep going back to his frames for new builds because their just so durable and utilitarian. Plus they are pretty cheap!

@Shawn I'm thinking of getting the ECM 918 OCTO when it comes out soon and converting it to a coax 4X. What props are you using for your coax mentioned above Shawn?

 

[DucktileMedia]

Before anyone goes spending a huge wad of cash on a new heli, inquire with Bart about his new XY8. I really think he is on to something here. So far the majority of us have it engraved on our minds that the only professional rig is the cinestar and droidworx frames. but there is an even better configuration that no one seems to have done yet. Bart has taken the MK based X8 and went one step further. The frame is a 120 deg "x" instead of a 90deg "x." This means you get the Field of view of a Y6 with the lift and redundancy of an octo and it is small enough to fit in any back seat! What makes this even better is that his custom camera gimbal can not only look completely straight down but it can also look up over 20 deg and NOT see any prop! I can;t think of any other configuration that would give all these benefits in one package. I think even if you are stuck on DJI the unit will still be controllable. I have personally landed my DJI hex when a prop nut came loose without crashing. This makes me feel pretty confident that the X8 or flat octo would still fly with 1 or 2 motors out.

Bart would you get off your butt and start letting people know about your frames? Let's see some top secret teaser pics at least. Not only do I want one but I feel pretty confident you got the next best thing out there. better do it before the Chinese steal your hard work.

 

[homer911]

I was thinking of doing that exact thing Iris. Copying Barts XY8 config with the ECM Octo frame. The ECM has the foldable booms aswell. I would also have the option to convert back to a straight octo if I wanted.