I'm designing a new quad or hexcopter, Ive got my basic design and I know what autonomous flight controls I will be using. I'm having issues figuring out what motor, prop efficiency. Ive searched different discussions on the matter, but they way it is explained is as though they are speaking to people that have been in the hobby for a while. I basically need heavy lift capable and longest flight time possible. I'm not so much looking for speed, or agility really, but that would be a nice feature. If anyone out there can help me figure out my power thrust needs, I would greatly appreciate it
- What are you calling heavy lift capable? 4 pounds, 8 pounds, 16 pounds?
- Long flight time and heavy lifting are almost polar opposites, something to consider because trying to do both makes it a very expensive idea.
Max efficiency is going to come from high voltage low kV motors, plan on 6s systems if not higher.
A good place to start is figure out how much weight you want to carry and with how many motors.
Say you want to carry about 3 kilos of payload with a hexacopter. (assuming you know this)
Say your frame is going to 1.6 kilos and can spin 18" props (assuming you know this)
Your RX,TX,Controls is going to be another 0.6 kilos (assuming you know this)
Lets figure a 6s 22,000 mah battery to add another 2.6 kilos (This a guess that may require you to come back and change after picking motors)
So before you have motor and esc weight you are at 7.8 kilos. Let use minimum of 2:1 thrust to weight for final build, so lets assume 4:1 off the current weight of 7.8 kilos because you don't know motor weight yet. This puts you at 31.2 kilos of thrust or 5.2 kilos per motor as a goal.
So jumping over to KDE site for some quick motor numbers, the first motor I clicked on is a KDE 5215XF-330kV. On a 6S system, with 17" prop, the motor is rated at 4.6 kilos of thrust at 30 amps to give you a max thrust of 27.6 kilos. This is close enough, the motor is capable of more but we will start here.
Motors and escs add another 2.8 kilos, so your take off weight is up to 10.6 so lets assume 12 kilos for whatever I am missing.
At 12 kilos weight, 27 kilos thrust, you would be running 2.25 Thrust to weight which might fit the bill perfect for you and your frame/motors leave some room to get up to about 2.75-3:1 by changing props and/or battery.
These numbers may not even be close to what your looking for but you didn't give much to go on. If this fit the bill for you, you then go into the above mentioned ecalc and estimate your flight time. Flight time comes back at x, is this acceptable?
Yes -done.
No - you can try getting there with more battery, but you will also have to look at bigger props most likely to counter battery weight, if you max out prop size for frame, then you looking for a bigger frame....and the cycle starts over.