Which platform?

[MombasaFlash]

I come from the single rotor AP world and am keen to explore multi-rotors. What started out as seemingly obvious has of course deteriorated into a confusing choice that puts me off getting involved with it at all !

First off there was MikroKopter. Easy! Either six or eight rotors - probably eight - since payload capacity is paramount. Then I catch inferences that more rotors is not necessarily better. For example, fewer rotors apparently have better wind performance.

Then I discover DroidWorx. They look like better frames that can have MK electronics fitted. But, it is imperative that a good gimbal capable of accommodating a 5D can be fitted and flight time has to be at least around fifteen minutes for it all to be useful.

Then I catch whispers that MikroKopter are not 100% up-to-scratch on build quality and customer support ...

Arrrgh. Okay. Let me whittle down the above to two questions, bearing in mind that pro AP is the sole use.

1. MikroKopter or Droidworx airframe and why?
2. Four, Six or Eight arms OR three or four arms with double motors for overall stability and best payload?
3. Bonus question (in character with first two?) - How long is a piece of string

 

[Stacky]

One proguy on rcgroups swears by Y6. Redundancy and handles the wind really well. He also debates the types of cameras used for AP. If doing video work he doesnt really follow the idea of using dslr's for video work. HD video cameras are lighter than a dslr which is an important factor. Ive never even seen a MK frame in the flesh but have handled a droidworx frame. Have to say I thought the droidworx frame looked great and was extremely light. I have a Hexa and a quad. I find the Quad easier to maintain orientation in the air than my Hexa. Im currently building a X8 so I get some more power, possible redundancy protection and 4 arms for easier orientation. Then I think I will try a Y6. Once thats all done I will have a better idea of what I want to use for pro use.

 

[Bartman]

One proguy on rcgroups swears by Y6.

who are you referring to? i'd like to se what he has to say.

i'm a big fan of the flat 8 for a variety of reasons and you can see my current build here

one thing to consider is the camera mount. some will say they can carry a 5D which may be true but there may be no room left over for wires and stuff out of the camera. in the case of my MKTR mount it carries the T2i i'm using but there's barely any room for wires out of the camera and the camera has to be loosened and turned on the mount to get the card out. it's a bit of a PITA.

the good thing is, whichever configuration you choose, the motors, electronics, camera mount, etc will fit on any frame so you can always transfer your components to a different frame if you don't like what you've got. before you go with a 4 or 6 rotor for your 5D on someone's recommendation, ask for pictures of their heli carrying that camera. between the batteries, the mount, the camera, plus other stuff that finds its way onto the airframe it ends up being a lot of weight to fly around.

 

[RTRyder]

who are you referring to? i'd like to se what he has to say.

i'm a big fan of the flat 8 for a variety of reasons and you can see my current build here

one thing to consider is the camera mount. some will say they can carry a 5D which may be true but there may be no room left over for wires and stuff out of the camera. in the case of my MKTR mount it carries the T2i i'm using but there's barely any room for wires out of the camera and the camera has to be loosened and turned on the mount to get the card out. it's a bit of a PITA.

the good thing is, whichever configuration you choose, the motors, electronics, camera mount, etc will fit on any frame so you can always transfer your components to a different frame if you don't like what you've got. before you go with a 4 or 6 rotor for your 5D on someone's recommendation, ask for pictures of their heli carrying that camera. between the batteries, the mount, the camera, plus other stuff that finds its way onto the airframe it ends up being a lot of weight to fly around.

I believe he's referring to RallyMatt who does get some amazing results with very basic equipment, sometimes not even using a mount, the camera hard mounted to the frame! Often times its not the equipment you're using but how you fly it that makes the difference and Matt is a great example of that.

Ken

 

[MombasaFlash]

i'm a big fan of the flat 8 for a variety of reasons and you can see my current build here

Are there photos in that link somewhere? I didn't find any.

I use a Panasonic HPX171 P2 for video normally (or a consumer HD camcorder on the smaller heli). I rather doubt that the HPX would fit into any gimbal these drones could take (without chopping off the handle) and for this reason I would use the 5D, mainly for photos but of course perhaps for video from time to time. It would depend upon how much vibration is present and the amount of 'Jello' produced.

However, my main concern is on the type of multi-rotor airframe to plump for. The various statements I have found around here commenting on the relative flimsyness of the central MK plate concern me a little whereas the extensive use of carbon fibre with the Droidworx frames impresses with an obvious weight:strength advantage.

I am quite sure that the MK is still pretty good because the marque has has already proven itself over a period of time but I am looking for some comments drawn from experience on the relative merits of the 4, 6 or arm versions - or even, as Droidworx offers, a 3 or 4 arm frame with double motors on each arm. I can understand the easier orientation with fewer arms but the MK 'CareFree' feature can remove much of that issue.

I have not been keen to get a multi-rotor before now because I have seen so many poor, bobbing-up-and-down videos but this could well be down to the pilots. Theoretically, the multi-rotor design plus the relatively advanced electronics suggest an inherent stability and are obviously attractive for camera work.

Actually, my biggest beef with ANY electric powered platform, and the main reason why I have avoided even single-rotor electrics, is the battery nightmare. I have generators to provide in-flight power that can also charge ALL batteries, i.e. 5v radio, 12v cameras & downlink etc.

BUT ... what cannot be disregarded with electric powered platforms is the relative lack of fuss getting them into the air quickly. Definitely an advantage for quick, simple jobs.


As a footnote, it is interesting to read Bartman's opinion on the currently available crop of camera mounts. PhotoShip and PhotoHigher certainly look like they are heading in the right direction but the necessity of keeping the weight down seems to result in rather light duty gimbals.

What is the general opinion on their performance, with regard to vibration isolation and camera movement?

 

[Bartman]

the general opinion is that they all kinda suck but the details are slowly working themselves out and they're improving. i don't think any of the mounts work perfectly right out of the box, they take tinkering, persistence, some creative problem solving, trial and error, etc. I'm in the process of preparing an averticalview mount so we'll see how that goes. rtryder has one flying already and he's basically willing to say it doesn't suck but that's about it and it's one of the better ones. there's progress being made but it's kinda slow.
bart

 

[MombasaFlash]

I can accept that with the camera mounts. I have had to modify the Copterworks mount quite a bit and THAT started off as a pretty professional unit.

But what about the multi-rotor drones themselves?

If a quad handles the wind a bit better than a hex or an octo but an octo has more lifting power, how does the double motor'd quad match up? Do the two motors on each arm give it similar lifting power to an octo and at the same time similar wind handling characteristics to the quad? And in what way exactly is the quad "better in the wind"? Conversely, what advantages do the flat six or the flat eight have over the flat four and double four?

What are your own reasons for preferring the flat eight? BTW, do you have photos somewhere of your 'current build'?

 

[Droider]

My take on this.. I LOVE MY Y6 Droidworx standard lift. I have flow it in and amongst trees, in high winds and in perfect conditions. In a previous life I have flown in more hele's than I care to remember.. mostly for the wrong reasons but occasionally for filming. These MR platforms are great but they aint ever going to replace a 2mil hele and a 250k steady cam.

I love the affects of flying these things at low altitude to grab 5 secs of action video, or for sticking it up at 100m and taking landscapes, sunsets, life and more. As a photo platform brilliant.. but for video they are limited. I chose the Y6 because of easy orientation, rumours of wind resistance, easy transportation and well coz I love the design. DroidWorx are the best as far as I am concerned (much to everyones belief I anit on the payroll)

I am in the process of getting the stuff together for a heavy lift... yep Y6 DroidWorx to fly my Canon 550D. My Standard Y6 could fly it and has but its right up there on its maximum flying design weight and its a hand full.. Flying my Sony Nex5 on it is a breeze as it is 500g below max flying weight.

IMO DW HL Y6 and MK for flying a 5D if its for stills.. If its for serious video (like movie stuff) then a 2 mill hele and a 250K steady cam!

 

[Stacky]

Mombasa when I first got the bug for AP 6 months ago I started messing about with RC helicopters. I quickly realized it would take me a couple of years to become good enough at flying to be able to try AP seriously. The multirotor route has meant its been a much faster progression for me but flying ability I believe is the #1 attribute needed to be successful. However what I have seen is how much more stable a big RC Heli is once the wind picks up over a gentle breeze. A few days ago I watched a company here in NZ called Media Mechanics shooting in a local park on a day which was during a week of storm activity that hit NZ. It was blowing hard and their RC heli handled it like it was a calm day.
Right now im going through the experimenting phase. I have a quad and a Hexa. im currently building a X8 and after that will look at a Y6 and also MatWelli's v-tails. I thought I could get into Pro AP relatively quickly because of the faster learning curve for flying multirotors. I had thought I would be ready within a year of beginning all of this. However its not as simple as it all appears. I think I will be ready for stills work by xmas but video work might take a year or so longer. Depending on what you want to do there are many factors to consider. Once you get the right craft and can fly it well enough to get the right shots you also need systems in place for video downlinks, camera gimbal control, camera control etc. On top of that you need to have safety systems in place , the right insurance and also backup gear.

Bartman it was RallyMatt I was referring to and the thread where he makes some interesting points about cameras is here http://www.rcgroups.com/forums/showthread.php?t=1417721

 

[MombasaFlash]

Appreciate the input guys. I have to say I do prefer the look of the Droidworx machines.

My reasons for considering a multi-rotor are to include another platform in the 'stable' as a backup, as an alternative for indoor work and for those occasions when taking the big heli out is a bit overkill. The regular helicopters can be seen HERE - and yes of course Droider nothing r/c is going to come close to a full size with CineFlex for quality footage. But then a full size with CineFlex can't get everywhere.

Does anyone have anything to say about the coax 3 boom and four boom with the double motors?

 

[Bartman]

Does anyone have anything to say about the coax 3 boom and four boom with the double motors?

you're referring to the "coaxial" config.......what I don't like about them is that when you lose a motor you're losing 50% of control and lift on that side. with a flat 8, if you lose a motor, worst case is the arm that is farthest out but there's only a 33% chance it'll be that arm plus there are two other motors on that "side" that will contribute to maintaining control. It all depends on how it's set up in the mixer tables (controls what motors do what and when) but I like to think a flat eight has better odds of surviving than a coaxial 8. i'll let you know how i do when i eventually lose a motor if it actually worked.
bart

 

[jes1111]

Hi, MombasaFlash - I just responded to a very similar question on RCGroups - my thoughts on arm count are there.

Denny (a member here) is "the man" on this subject - google "Denny Rowland" for lots of juicy info from him.

My own emphasis is on stills (which is my full-time occupation) and I'm such a perfectionist that I'm still building my gimbal - haven't even started on the Y6 frame to carry it yet

 

[Bartman]

jes
what are you currently flying?

regarding quality as a substitute for redundancy, i'm sorry but I can't agree with that. as a professional pilot i've seen all too often how quality is often overestimated and relied on when in fact it creates a false sense of security. i'll take redundancy any day.

but that's what makes the world go round so we make our decisions and move on.

what i've seen of wind effects on my flat 8 is that the position of the camera mount makes a huge difference on how things handle when the wind is blowing. if i'm shooting into or away from the wind i do fine as the MK controlled camera mount is better in nick than roll. crosswinds, where the copter is leaning sideways into the wind to hold itself, present more of a problem but since tuning my mount and modifying it the problems with roll aren't as pronounced. if i must get a shot i push the copter sideways into the wind and release the shutter so it fires continuously as the copter drifts back in a level attitude past the spot i wanted. i'm hoping to improve my camera stability by handing over the job to a dedicated, camera mount only, CopterControl board with my new heli.

frankly i haven't seen much credible testimony regarding configuration and wind tolerance.

DennyR is taking an entirely different approach to all of this and if you're not in a hurry and wish to add a bit more experimentation to the project, have a good look at what he's been up to. you can search his stuff at this site and find the first of five or so videos he's doing to explain his approach.

good luck,
bart

 

[jes1111]

I'm not flying anything yet, Bart. "Terrestrial" work is keeping me busy, but I'm currently constructing my first prototype gimbal. My philosophy is very much like Denny's - design an effective gimbal first then construct a frame around it. I agree with much of what Denny has done (and is planning) - I'm going in very similar directions in some areas and following a different path in others. My emphasis is on stills (but not to the complete exclusion of video) and my requirements for duration, performance and reliability are "challenging", to say the least. I'm also patiently waiting for OpenPilot to release Pro/INS (whilst contributing as I can to the project).

I believe that a lot of products and practices in the current MR world are somewhat derivative - there's relatively little original thinking going on (at least that's visible in the public forums or the pages of product suppliers). Fair enough, many people have little interest in the mechanics/electronics and just need/want to fly a camera. Others are obsessed with the RC side of things and mounting a camera on the craft is really incidental to their hobby. I kinda fall in between - I'm a working photographer but I have a keen interest in matters mechanical, so I'm enjoying the design/build as much as I will reap the professional benefits later.

Gimbals, for example - as you say - hanging it underneath is the worst possible idea. You can even identify aspects of the design of the now-generic underslung gimbal that are as they are simply because the gimbal is mounted in that position, in spite of the fact that, by doing it that way, you practically guarantee less than optimal performance. Roll compensation, for example. Trying to rotate a ring (or part of a ring) that's large enough to fit around the camera with a piddly little hobby servo... not a good idea! The gearing is way too high to ever achieve an effective speed of rotation. But people point to Cineflex and the like and say "well, that's how they do it" - sure they do, using heavy (and very expensive) axial torque motors - basically a brushless motor that's big enough to fit the camera inside its "hollow" shaft! Quite a different thing!

On frames - anything "open" in structure, i.e. "skeletal" - is a compromise. Once self-generated vibration is under control, the only thing that produces the rotational movement we want to compensate for with a gimbal is wind, and it's not hard to see how none of the frame options are actually "good" in terms of aerodynamics. And the translational element of wind disturbance, though less important, cannot be removed by the gimbal. So a Y6, of "conventional" construction is possibly the best compromise currently. There's probably some mathematics which could prove that the "frontal area" presented to the wind is lowest (for a given lifting capacity) with a Y layout - I'm just trusting my intuition. My first "mules" to test the gimbal will be conventional Y6's - but later (as Denny has) I'll be working on enclosed, streamlined construction.

Weight is a key factor, too. Mass will help the camera side of things but hinder the flying side - you really want the entire aircraft to weigh "as much as you can possibly lift for a reasonable time". Carbon fibre construction is entirely valid, but really only so you can allocate more of the aircraft's total weight to camera equipment, an effective gimbal and battery power. Trying to "stabilise" a 180g GoPro on a 950g quad is, frankly, pointless. In fact, I'd go further and say that cameras like Sony's NEX-5 and Panny's GH-1 are also a bit pointless as MR-AP devices - they are simply too light! As a photographer, I want to take top quality pictures so I want to fly a top quality camera - a 5DMkII. Am I worried that "it weighs too much"? Nope - I'm pleased! I stand a much better chance of isolating it from vibration and rotational displacement than I ever would if I wimped out and went and bought an NEX-5. A heavy MR is the right way to produce good results. Unfortunately, MRs above 5-odd kilograms get rather complex in terms of motors/batteries/etc. - but that's life

Oh, and redundancy - that's what insurance is for

 

[Bartman]

jes,
having had this discussion before and mostly agreeing with what you're saying, photos are much less of a challenge than video. in fact, photos are easy and you may be spending a lot of time for something you can already do today. the photos i'm doing for clients are only limited by my abilities with the camera and not the capabilities of my heli equipment. i'm continually looking for ways to improve though and the video challenge has made my photo output even better.
at the root of all this is the original question, what frame to buy? like I said, if anyone wants to claim their 4 or 6 rotor craft flies a 5D and can stay in the air for at least 8 or 9 minutes, I'd like to see pics or video of it in action. flat or coaxial, i'd just like to see the proof. obviously i think an okto is the way to go and then it's just a personal thing of making it coaxial or flat.
bart

 

[Bartman]

Oh, and redundancy - that's what insurance is for

tell that to the person whose head it lands on.

 

[Stacky]

Have you flown much jes?

 

[jes1111]

No, haven't flown at all.

The system I'm developing will be "guided autonomous flight", controlled by OpenPilot Pro/INS and a laptop/tablet. Although I'll need to master basic "manual" flight with an RC transmitter during testing phases, it will be no more than "up, click, down again"

 

[jes1111]

Camera stabilisation "done properly" (Just for reference!)

[video]http://youtu.be/JTO-BNicZyo[/video]


P.S. How do you embed a video?

 

[Bartman]

No, haven't flown at all.

The system I'm developing will be "guided autonomous flight", controlled by OpenPilot Pro/INS and a laptop/tablet. Although I'll need to master basic "manual" flight with an RC transmitter during testing phases, it will be no more than "up, click, down again"

jes,
what is your intended use? how do you plan to take the photos and what will the subject be? just curious.
bart