Design considerations for an aerial photography platform.

[whoisthedaddy]

One of the primary drivers in the OpenPilot project is to "get it right" and not release anything to market until it is. Being completely non-profit removes the commercial pressure to release early and use customers as beta testers. So you can be sure that when v1.0 of OpenPilot does release, it will be a highly capable and thoroughly tested piece of kit. Because of this there is no current estimate on when it will be released - just "it will be released when it's ready".

CopterControl is a sub-set of OpenPilot, a single-board product without the GPS-driven position-hold, come home and waypoint type features that the full OpenPilot product will have, i.e. it's a low-cost but very capable "manual" flight system. This is in "dev release" right now so market release should be not far off.

I have to agree with your comments on OpenPilot, it does look really interesting and in the mid to long term will almost certainly compete with MK. I would never underestimate the capability of a team of like minded, focused and intelligent individuals. (You only have to look at the success of other open source projects). At present however I had to discount it as there is no product as such, the 'Store' on the site isn't active and there is no indication of either cost or delivery timescales - they certainly aren't under any commercial pressure!! I will continue to review this as the months progress as I'm sure this will change.

Do you have any links or further information on CopterControl, I looked around the site and searched, even Googled it but nothing came up?

Thanks
Lee.

 

[Gary Mortimer]

http://wiki.openpilot.org/display/CCDoc/CopterControl+Documentation

 

[jes1111]

jes1111,
i've been through the prop-wonder analysis you've outlined and have a box of blades in the basement as a result. i've got a little project i call Son-of-Okto which i intend to finish one day but the intent is to use helicopter blades but of a slightly larger scale than we've seen with propellers.
there's a company that makes flat bottomed helicopter blade material and it's pretty easy to add the hub material but last i checked they were out of stock and i never heard back from them. symmetrical blades are an option but you have to run a higher pitch to get thrust so then drag begins to factor in more.
it's all very interesting but i suspect that until it's profitable on a large scale we'll be stuck with what we have, which isn't all bad but i'd guess it's a good percentage away from optimum.
re.: the contra-rotating props, one engine or two the dynamics of the props are the same. the lower props are experiencing a different airflow pattern than the tops and the fix is to up-pitch the props. the wiki article actually encourages having non-identical props (2 blades, 3 blades, etc) to avoid compounding the system's vibrations so if we were to apply that we'd have 2 blades on top and 3's on the bottom. with a little time i could work it out. problem is, no time. but i digress.
thanks for the update on the openpilot program. we're looking forward to hearing more as it plays out.

Interesting. So, in your view what would be the shape/characteristics of an ideal blade? It's so frustrating that we seem to be operating well below the optimum efficiency level. Try as I might, I cannot find any definitive info on what we should be looking for, though. I've received hints and tidbits from here and there, and formulated my own theories by piecing it all together - but I wish somebody more scientific than me would get on the case. I'd even consider paying for a mould to be made.

 

[Gary Mortimer]

Well as multirotors gain more traction (no pun intended) No doubt prop fettlers will come up with better designs for our purpose. Motors are already coming shorter shaft and longer lead. There will be considerable resistance from the masses about price though.

I would not be surprised in the future, many years in the future. If the CAA don't stipulate the brands that can be used. Makes lots of sense really a cheap chinese knock off can go at anytime.

 

[jes1111]

I would not be surprised in the future, many years in the future. If the CAA don't stipulate the brands that can be used. Makes lots of sense really a cheap chinese knock off can go at anytime.

I also see "must be fitted with blade guards" in that legislation.

 

[whoisthedaddy]

Agree with both, interestingly I suspect blade guards could also used be in the form of ducts to give some aerodynamic advantage and as well as reduce/eliminate tip wash and possibly increase the efficiency of the engine (and make things safer as well).

Jes1111, with reference to your earlier post on vibration I'd be interested to know which materials or setups you use to reduce vibration?

Lee.

 

[Bartman]

Jes,
I've been of the opinion that straight helicopter blades would make the most sense since they've been used on helicopters for decades and the heli manufacturers have had all the science they need at their disposal to make something different and they haven't. But there's a big difference between them and us and that is the nature of their controls. The blades on a heli turn at a constant rpm and lift is changed with blade pitch. As you know we make changes in lift by changing RPM so there's a need for the motors to have the upper hand in speeding up and slowing down the props making lighter weight props better. Longer blades with greater mass would be a challenge for the motors and we'd pay the price with shorter flight times.
If I ever get around to it my plan is a twin-motor geared drive with a larger flat bottomed fixed pitch heli blade but I need time to experiment with it and I have no time right now. Too many things going on. Just wait and see what I'm cooking up!
Bart

 

[jes1111]

Agree with both, interestingly I suspect blade guards could also used be in the form of ducts to give some aerodynamic advantage and as well as reduce/eliminate tip wash and possibly increase the efficiency of the engine (and make things safer as well).

Jes1111, with reference to your earlier post on vibration I'd be interested to know which materials or setups you use to reduce vibration?

Lee.

Shrouds do seem like a good idea, certainly from the safety standpoint. I understand there are problems, though, unless the blades are specifically designed to match. Even then (so I'm told) the efficiency gain does not make up for the additional weight. Most notably, Stanford University flirted with them for their craft and dropped them. Having said that, the Cyberquad seems to be a successful design, albeit with a very low payload.

I'm not actually flying anything yet - I'm planning a Y6 flying camera platform and have been researching my little socks off for about 9 months now :-D

The core issue with vibration reduction/isolation on MRs is mass. The vibrations we need to dampen are relatively low frequency, but so is the mass - and therein lies the problem. Referring to the chart attached, the two appropriate choices are "increase the mass" and "use softer material". Soft material generally means silicone/sorbothane/urethane type stuff, although I believe that miniature wire rope isolators are a promising branch to research. See www.gelmec.co.uk

 

[jes1111]

Jes,
I've been of the opinion that straight helicopter blades would make the most sense since they've been used on helicopters for decades and the heli manufacturers have had all the science they need at their disposal to make something different and they haven't. But there's a big difference between them and us and that is the nature of their controls. The blades on a heli turn at a constant rpm and lift is changed with blade pitch. As you know we make changes in lift by changing RPM so there's a need for the motors to have the upper hand in speeding up and slowing down the props making lighter weight props better. Longer blades with greater mass would be a challenge for the motors and we'd pay the price with shorter flight times.
If I ever get around to it my plan is a twin-motor geared drive with a larger flat bottomed fixed pitch heli blade but I need time to experiment with it and I have no time right now. Too many things going on. Just wait and see what I'm cooking up!
Bart

I see what you're saying.

I just checked back on an RCG thread I posted to a while back, and the OP has come up with some interesting stuff. I'll be corresponding with him to see where it goes. http://www.rcgroups.com/forums/showthread.php?t=1347147

 

[Gary Mortimer]

Constant speed variable pitch, Rob and I were giving it a bit of thought during a board meeting he called at The Canon NP this afternoon.

 

[Bartman]

in the wiki article i posted regarding contra-rotating props it mentions that the two props have different numbers of blades to keep the vibrations from coupling and magnifying each other (or something like that). i wonder if multi's would benefit from having combinations of two and three bladed props. for example, having two blades on the cardinal motors of my Okto with three blades on the other four motors. ??