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Theoretically it should be much better. Remember that a straight swap from top to bottom mounting will likely need a re-tune of parameters since the centre of thrust will move downwards. Also watch out for the props getting in the field of view of the camera - that'll change with an underslung...

Booms under the props are also a major source of vibration which you then have keep away from the camera. Square booms will produce a higher amplitude of vibration than round ones (more surface area presented), but best of all would be streamlined (tear-drop) booms. Primary frequency of the...

"YOU HAVE TEN SECONDS TO COMPLY!" :upset:

OpenPilot is working on a purpose-designed ESC that will (among other things) feature two-way communication. It will therefore be able to inform the FC that something has gone wrong (since it could also detect a broken prop by the sudden change in load) and the FC could then evaluate how to...

Interesting figures. If I am interpreting them correctly, the top motor on its own gives 940g thrust with 10x4.5 and the bottom motor on its own gives 825g with 10x4.5 prop. But together they only manage 1420g - against a theoretical "no loss" target of 940+825=1765g. If we assume that the the...

I'm not saying that the top prop is operating in still air - just that the velocity of the air entering it is "effectively" zero - in terms of selecting a suitable propeller pitch. What percentage increase in the pitch of the top prop are you proposing?

The top prop in your video is "free-wheeling" - of course it will do that. Your proposition was that the top prop would need a higher pitch than "normal" because of this effect - I'd still reckon that's not the case. What's "normal"? The fact remains that the bottom prop needs more pitch in...

It's there somewhere - a long thread about contra-rotating motors. Somewhere in the middle some scientific bods weighed in and spelled out the theory. That sounds like the wiki article on contra-rotating props - doesn't apply at all here - that's using two props driven by the same engine. The...

Thinking some more - using only the kit you've got, you could get a relative measurement of what each motor/prop in a pair is doing by starting with two identically-charged identical packs, running at a fixed throttle position for X minutes, then seeing what you need to put back into each pack.

To measure rpm, maybe a strobe like we used to have in the physics lab at school (100 years ago) :)

I think practical experience supports the theory (well explained by Bart). Many coax machines fly well enough with identical props. I've even seen people putting higher pitch on the top and they still fly. Also seen bigger diameter on top, bigger diameter on bottom and every other variation...

I'm a registered GoPro hater :) It may be small, light and relatively cheap but that's all you can say for it. In photographic terms, as a way to capture a scene in order to create a final image, it sucks big time! Massive (and complex) distortion, horrendous chromatic aberration, vignetting...

You've referred to the "suction" that the bottom blade would exert, but in reality the effect would be negligible - the bottom blade is not pulling air down in a straight-sided vertical column, but rather pushing the air that it encounters downwards - the "void" so created is filled from every...

Very interesting - but the actual "resolution" doesn't seem to be outstanding, judging by the examples on their site.

Cut & paste from a thread I started on the OP forum some time ago:

I'm guessing, but the only negative I can think of is the possibility of uneven left/right yaw response due to the likely difference in thrust between top and bottom. The OpenPilot CC configs have the Y6 props this way, but the X8 alternating, but nobody could tell me why when I asked. I agree...

Denny - Admittedly I haven't tracked back over every post you've made in the last few months but I'm puzzled: I recall reading a very enthusiastic post from you, reporting that CC had "great" potential as a dedicated IMU. What changed? Also, every report I recall of CC board "natural death"...

Go for it! The latest batch of OpenPilot CopterControl will go on sale within the next few days. Much cheaper than Hoverfly (less than €100) (and better IMO). Watch here for news.

Dirk is using them on his big-*** Droidworx-based heavy lifter: http://www.multirotorforums.com/showthread.php?862-And-my-knees-go-weak-again-the-new-Droidworx-airframe&p=9452&viewfull=1#post9452 I'm guessing, but I'd say you'll get a fairly unstable machine with small motors and those big...

Honesty of the ratings, higher mass (but same outer dimensions), design of the airflow through the motor, quality of the aluminium, quality of the copper, temperature tolerance of the magnets and their glue, etc. Lots of possible reasons. China does skew the price/quality equation somewhat, but...