Hi All, Just pulled this image in from SUAS News (Thank you Gary) to illustrate a few really good concepts that it incorporates and talk about better Multicopter design a bit.

This copter has a lot of things right and is really a study in design excellence.

1. Most obvious is a sliding ball full enclosure camera Gimbal, very pro and really something we should be striving for.

2. The motors are on the bottom under the arms: More aerodynamically efficient with no prop wash interference and very little intake interference. Noticeably increased flight times and greater lift capability and much quieter.

3. Large slow high efficiency props and pancake motors: These are way more efficient than faster motors with smaller diameter more conventional props.

4. Carbon fiber aerodynamic frame arms: Again more aerodynamically efficient, light and strong.

5. Fully enclosed framework and a simple spring loaded landing gear that provides as little interference with the prop wash as possible.

Basically this quad incorporates the best design features I have seen so far and definitely provides food for thought.

I thought it might be worth soliciting comments and other thoughts about optimal multicopter design techniques.

Best Regards,


Views: 26535

Comment by Gary McCray on January 22, 2014 at 12:59pm

Here is another picture of it from a different perspective:

Comment by Carles Gelada on January 22, 2014 at 1:19pm

i think it costs about 50k so, it better have the best design :)

Comment by Gary Mortimer on January 22, 2014 at 1:35pm

I wonder if anyone has a paper on increased efficency for unobstructed props. Logic says it must be better. I flew alongside the earlier version, the scout once, they were very nice folks.

Comment by Euan Ramsay on January 22, 2014 at 1:51pm

Immediate thoughts:

- Motors have no cooling on this one. As we progress towards bigger motors, they will need active cooling at some point. Foxtech are already there with the W61-35.

- Upside down motors will get damaged more. On a tip over, there is a chance a conventional layout will tip over onto the arm first. Upside down, this impact is guaranteed.

- Those arms are not aero, and any efficiency gains there will be minor. 

- However, the unblocked prop path will definitely improve matters. This is a good thing.

The frame is not aero either - but it is "clean" - no wires etc. And nowhere to mount stuff? Where are the antenna? This looks like the MR version of a concept car...all nice to look at, but someone forgot about the practical stuff. Which is why your concept cars never make it intact into production.

- The plastic ball gimbal...at what price comes the cool look? Weight? Complexity? Public fear? At least with current gimbals, they don't look so "sinister". Grouse House has the right idea - reducing weight, improving stability, and serviceability. That ball in plastic will be expensive to mold, and weight at least 150g.

- The legs are good, but again - more moving parts = more chance for failure

Personally - as I am doing airframe design - I feel the following is the way forward in the 2-3 year time frame:

- more adoption of standards. Size of arms, Screws sizes, mount sizes (gimbal, motor etc). We're definitely getting there; M3 & m2.5 screws are everywhere, arms are down to 4 diameters in the majority now, 4 post or 2 rail mountings are becoming the 2 main mounts, and motor mounts can take practically any motor these days.

- more structurally efficiency. More stiffness, with less weight. Expect the bigger players to adopt F1 style dynamic stress modelling techniques. I'd love some - my frame could probably lose a lot of weight before integrity is affected.

- more stability through better design of vertical CoG, motor dihedral

- more aero efficiency though faired designs. See Microdrones latest model.

- more flexibility in missions in one direction, more specialisation in the other

- cleaner builds via better design of cable paths, and panelling. See Sky Hero and to some extend Steadidrone QU4D.

- better battery payloads

 - better packing options. Say what you will about DJI, but their ability to get an S800 into and out of a case in practically minutes is the way forward. Other manufacturers are starting to make arms completely removable as well.

- FPV as standard

- common bus technology to simplify wiring, while allowing flexible components options

- Some unification of functions to save weight. See Hobbywing 4-in-1 ESC.

- Components to require less soldering (see standardisation above).

- More circuitry built into the frame. I suspect TBS' Core is just version one, and their Disco pro has the entire alexmos built in as well. This will only continue. See common bus technology above; with a universal - secure - connector, barely any soldering will be needed.

- The OP is correct about one thing - the trend to big props and pancakes will not stop. Aerodynamics and electro-magnetic motors concepts are well known after a hundred years of research and the methods are mature. I expect evolution rather than revolution for the foreseeable future, with an ever decreasing rate of returns. There's no Moores Law here.

- And pull it altogether are the Flight Controllers...*this* is where the real advances will be made. Quads/hex/Octo's will all look the same for at least the next 5 years...but what they can *DO* will just blow our minds.

Comment by Mustafa TULU on January 22, 2014 at 1:55pm

I don't think the number 2 is intent to do so, for me the reason why motors are facing downwards is allow it to fly at bad weather conditions like rainy, dusty or snowy since this is a military purpose - standard drone.

Comment by Gerard Toonstra on January 22, 2014 at 1:56pm

There are some guesses by people that it saves 5% or so. I think the vibration is also a lot less because the prop doesn't push the propwash against the arm. That same pressure temporarily increases the weight. Not sure about the impact of sucking in the air from above though. It's the same experiment where you have a truck full of birds not noticeably making a difference in the weight when birds fly around:


Or... you could say that the air pressing down on the bottom is the same as the weight of the vehicles in the air. So if you obscure an arm's width under the prop, it'll (theoretically) have plenty of impact.

I fly with inverted props on my hexa and get 39 minutes flying time. After I get the mounts done, I'm also going to see the impact of high-pitched props, which according to theory should be less efficient. The judges are out on that too apparently, since others having really good results utilize as high-pitched props you can get.

Comment by Gary McCray on January 22, 2014 at 1:59pm

@Gary, As per Brad Hughey's Blog: http://diydrones.com/forum/topics/the-case-for-large-scale-electric....

Dr. Paul Pounds, University of Queensland (now Yale I think) who really has one of the definitive works on Multicopter design says that motor and prop underneath is always considerably more efficient.


The props on top cause the prop wash to directly impinge on the frame arms which effectively reduce the thrust by their equivalent flat plate area plus any generated turbulence and counter pressure.

With the frame arms on top, interference with air intake is more complex but seems to be always considerably less than frame arms below.

@Carles There are a lot of them out there with worse design that cost more, but this design has some features we can replicate for a lot less and end up with something we can actually use.

Really just a sign post for excellence and appropriateness in design.

Comment by Euan Ramsay on January 22, 2014 at 2:09pm

There are a lot of them out there with worse design that cost more, but this design has some features we can replicate for a lot less and end up with something we can actually use.

Agreed, but so far, all I can see as the props being upside down as the only "advancement" this airframe is making. The rest is just complexity and weight, but then again - we've not seen the inside. Those arms definitely look removable in the DJI way, and that's a good thing too. Folding arms are all very well, but "Clunk Click" components is a much better consumer proposition.

Comment by Quadrocopter on January 22, 2014 at 2:28pm

If it folds, it vibrates. Yes it does :-)

Prop are on the bottom, test this yourself, you will LOOSE 5-10% of efficiency. The ONLY adavantage is keeping the front boom away from the camera.

More vibration from slower turning props, Hard mount a GoPro to your copter, eg. use 13x65 props, Jello will be seen.

Use 11x65 props, motors spinning quicker less Jello.

+1 for the gimbal and the frame.



Comment by Stephen Zidek on January 22, 2014 at 3:13pm

"Prop are on the bottom, test this yourself, you will LOOSE 5-10% of efficiency."

That seems counter to what most others are saying.  Can anyone cite some examples?


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