Best Prop Theory for Stabilazation

[Bad Mosquito]

A friend and I have been discussing the best blade size for stable video and we have read different things and both of us are new enough to multirotors not know the difference, so I was hoping someone could steer us right.

For videography, what's best practice for stable video via prop size, large or small? Or is it more about the right combination of the whole machine?

Thanks for helping.

 

[hjls3]

depends on payload - depends on how you wanna fly it - depends on tons of things.

 

[Motopreserve]

@hjls3 is spot on. There are many factors. Not least of which (to twist the real estate phrase) is balance, balance balance!

The "best " prop for a given machine will be the one that provides the most stable flight for the payload - which of course has many factors contributing to it. If you figure out the total system you'll be getting airborne, you'll then be able to hone in on a couple different size props that provide needed thrust, and then choose from there based on needs (smooth for AP/V, flight time etc).

Good luck and fly safe!

 

[Bad Mosquito]

I figured as much, so discussing prop size is pretty pointless until you know how much you're carrying.

But I think it's safe to assume most AP/AV systems are heavy payload and thus require more thrust so bigger props?

So for example, the craft I'm planning on building (this is to start with): A custom built 450 Y6 frame machined to be much like the OPQ (I know, don't make your own frame for your first multirotor - let's not argue - I'm just that guy.) with ESC's and the rest of the guts and intended to carry a gopro and gimble.

Just on a hunch, since it's a 450 carrying six motors and a GoPro set up I'm thinking 10in blades, I know there will be some trial and error here as I'm working with a custom frame, but does that sound about right? (Let just go with your best rough guess at this point... you might win me a drink from my friend.)

Thanks again.

 

[Carapau]

Your props need to match your motors. That's the critical thing. Too large a prop on too small a motor and you get over heating, loss of efficiency etc. Too small a prop and efficiency also goes. What I have found works well is to guestimate your all up weight and then look at motor spec charts. So Tiger show what thrusts can be achieved by each motor with a range of props on. They also include efficiency data. KDE do the same. Clearly they are manufacturer's data so perhaps not 100% bang on but certainly in the right ball park. Of course there is also eCalc to help you decide.

 

[Bad Mosquito]

Your props need to match your motors. That's the critical thing. Too large a prop on too small a motor and you get over heating, loss of efficiency etc. Too small a prop and efficiency also goes. What I have found works well is to guestimate your all up weight and then look at motor spec charts. So Tiger show what thrusts can be achieved by each motor with a range of props on. They also include efficiency data. KDE do the same. Clearly they are manufacturer's data so perhaps not 100% bang on but certainly in the right ball park. Of course there is also eCalc to help you decide.

I just found eCalc and I'm glad I did. Very helpful little tool. Helped me understand how every little detail determines efficiency - which I'm sure will help determine vibration.

 

[Carapau]

eCalc wont determine vibration at all. All you can do is minimise the sources which is simply ensuring good balance of both motor and blades. Balancing motors is a real pain in the butt which is why quality motors are worth buying.

 

[Bartman]

resist the urge to oversize the motors....the tendency is to buy too much motor and then to have them running big props at low power settings. this leads to heli's that are hard to tune and too floaty to handle even light winds.

determine what the goal is and then design to that goal. very few heli's will handle everything from very light to very heavy payloads so the more you can refine your real-life goal the better the outcome will be. i like to design to have a new heli hover at about 60 to 65% throttle, fwiw.

 

[Bad Mosquito]

resist the urge to oversize the motors....the tendency is to buy too much motor and then to have them running big props at low power settings. this leads to heli's that are hard to tune and too floaty to handle even light winds.

determine what the goal is and then design to that goal. very few heli's will handle everything from very light to very heavy payloads so the more you can refine your real-life goal the better the outcome will be. i like to design to have a new heli hover at about 60 to 65% throttle, fwiw.

Uh oh, I think that's exactly where my brain was heading. Here's my eCal for a custom Y6 build I'm musing over. The weight is a straight guess as I'm not sure what the frame will weigh yet - it's still in the blueprint stages - and I'm guessing eCalc thinks I'm building a hex and not a Y6 hence the prop size warning:

Basically, I want to be able to build something I can start learning AP/AV work on. I have a 450 Y6 frame much like the OPQ, little bigger, same plastic, same one piece concept. I thought that would get me started with the right FC, ESCs and rotors. Then I would strap a GoPRo and FPV unit and start practicing my maneuvers. Eventually getting to bigger models with bigger cameras. (I'll probably stop with a Sony A7 or a Canon 5d that can shoot raw.) That's the eventual plan, but I'm pretty new and I need something I can feel comfortable crashing before I strap on a $5000 camera and lens.

 

[violetwolf]

You WILL crash while learning. That's a certainty . So make sure to build cheaply with cheap props and booms that are easy to replace.

I saw that you were asking about flight controllers in the other thread. I would strongly suggest trying out the Pixhawk system. Highly professional (the best there is IMO)and very reasonable pricing. I use the RcTimer "Fixhawk" version exclusively.. Coupled with Taranis radios, truly high end professional functionality throughout the system. Open source rules the roost in this game.

 

[violetwolf]

Oh and make sure to leave the WiFi off on the gopro. There is evidence that it will interfere with GPS signals possibly causing fly-aways