Suggestion for 10kg total multirotor

[Alireza Mohammadshah]

Hey guys, my setup is less than 10kg in total on a "hexacopter", what do you suggest for an efficient motors, bare in mind that I am using 2*2200mah batteries (2.5kg each)

What I am looking for is “Longest flight time possible”

Motors + Props + ECS + Battery*2 + Flight control + GPS + Mount + RC Reciever + Telemetry + Frame + Camera + Camera Mount +Cables, Screws, etc

Ps:
I made my own Camera mount & hexa frame (i can use 19" or 20" props)

 

[Alireza Mohammadshah]

so far these happened:

i had some twiks on my frame and made a replica but not with carbon fiber just to make sure everything can be fit on places that i want, first i decided to go with 6 motors, but then i thought that 12 motors with double axis on same frame might be more efficient, let's say you need a huge rock to be out of your way, you got two options, hire a huge muscle guy to take that away, or lift that with more guys, it's heavy for 6 motors but i can use 12 less powerful motors with less thrust and the total of same weight

now i see this like i have 3 times more thrust to get more efficient, so around 5kg on 6 motor, or 2.5kg on 12 motors
since i can use 17" to 20" in this kind of design without losing balance, this is a good run i guess

but still no good news on choosing a motor

 

[OldGazer]

Hey guys, my setup is less than 10kg in total on a "hexacopter", what do you suggest for an efficient motors, bare in mind that I am using 2*2200mah batteries (2.5kg each)

What I am looking for is “Longest flight time possible”

Motors + Props + ECS + Battery*2 + Flight control + GPS + Mount + RC Reciever + Telemetry + Frame + Camera + Camera Mount +Cables, Screws, etc

Ps:
I made my own Camera mount & hexa frame (i can use 19" or 20" props)

I think you are going about this the wrong way. Using the motor/prop maximum thrust is totally useless. What you want to do is use the motor/prop thrust at HOVER THROTTLE (50% throttle, or MID STICK). So, what you need are motors and props that will give you a MINIMUM of 1666 grams (1.6 Kilograms) of thrust at 50% power.

Read this: (Originally posted by renatoa on RCG)

" For any platform of any size and weight, the flight time is the result of:
time = whkg / (1000*R / eff_gw) * 60, where
whkg = battery energy density, in Watt hour / kg, ranging from about 150 for the high C packs to 270 for LiIons. 10C Multistars are 185.

R = ratio between AUW and battery weight

eff_gw = motor/prop efficiency, grams per Watt, taken from mfr data.

Be aware to get from table the efficiency for the intended thrust, and for 50% throttle !
Efficiency greatly depends on load, so don't use efficiency stated for 1kg, to compute flight time of 2-3 lg platform !

Also, don't use values for more than 60% throttle, the platform will be unstable, no more room for motors to do their control job....

As I wrote, this formula works for ANY size platform and energy source, lets do the math for some particular cases:

Case I Ph2
battery wh/kg = 5.2(Ah)*11.1V/0.37(kg) = 156wh/kg
R ratio between AUW and battery = 1250/370 = 3.4
propulsion efficiency = 11g/W
time = 156 / (1000*3.4 / 11) * 60 = 30 min

Case 2 the 129 min record
battery wh/kg = 266Wh/kg - typical LiIon energy density
R ratio between AUW and battery = 3.4/2 = 1.7
propulsion efficiency = 14.1g/W
time = 266 / (1000*1.7 / 14.1) * 60 = 132 min

And finally, my 30 min case
battery wh/kg = 165, I use a Zippy Compact, having a bit more energy than the average LiPo
R ratio between AUW and battery = 0.75/0.195 = 3.8
propulsion efficiency = 11g/W - using Phantom 2 clone
time = 165 / (1000*3.8 / 11) * 60 = 28 min

As you can see from the above, reasonable precision of all estimations, proving this formula is valid for any configuration, so now you have a tool that should tell you what is wrong in your setup, and where to work to improve flight time.

The biggest unknown for most users is the propulsion efficiency, for this reason I think is mandatory to not buy stuff without manufacturer precise specification of this parameter.
renatoa is offline Send a private message to renatoa Find More Posts by renatoa"

The point here is you also need to look at how efficient a give motor/prop combination is, and the higher the g/w is the better..

I have attached a spread sheet that will do the math for you...