motor/Prop selection hmmm....

Blackbicbiro

Blackbicbiro

New Member
so im going to build my own quad for fpv. i been going though tons of web pages and reading up about it as much as possible. i have come up with the following set up

Frame: reptile 500 v3
flight control: apm2.5
telemetry: 3dr air to ground
RX: Orange 8 channel
battery: 4s5000 or 3s5000
motor: ntm prop drive 28-26 1100
props: 9x6 for 3s or 8x4 for 4s
ESC: Q brain 4x25Amp
camera: Go pro
gimble: not selected but aveage weight around 250g
FPV tx: not selected but average weight 30

My issue is with the frame full loaded with a 4s battery i am looking at 1770g and i not sure the motors and props will be enough.

with 4s and 8x5 prop i will get 3.3kg of thrust. flight time would be quite short with the bigger battery and prop

3s battery and 9x6e prop will get 2.9kg of thrust. this would not be double the overall weight

what do you guys think on this or do you think it will be ok to run 3s battery or 4s battery set up?

i tried putting the info in to ecalc but hobby king has no resistance values for the motors

Help would be much appropriated
 
I came across this somewhere else and it's put pretty well:

As a general rule you want a 2:1 thrust/weight ratio for a standard quad and 3:1 or higher for something acrobatic. 1.5:1 has been known to fly.
Click to expand...

Why not go 4S with 9x6 or even 10 inch props and a lower kv motor?

Hobbyking does prop tests on a lot of their motors, including the 28x26 1100kv

Code: 
8x4 - 11.1V / 100W / 9.1A/ 0.54kg thrust
8x4  - 14.8V / 116W / 14A / 0.82kg thrust
9x6   - 11.1V / 149W / 13.6A / 0.73kg thrust
9x6   - 14.8V / 285W / 19.6A / 1.05kg thrust


Or go with these guys with 4S and 9x6:

http://hobbyking.com/hobbyking/stor...s_28_30S_900kv_270w_short_shaft_version_.html

Code: 
Prop Tests:
13x4E - 11.1v - 194W - 17.4A - 1.04kg thrust      
12x6E - 11.1v - 195W - 17.8A - 1.01kg thrust             
11x7E - 11.1v - 188W - 17.0A - 0.89kg thrust
10x5E - 11.1v - 133W - 12.0A - 0.75kg thrust
  9x6E - 11.1v - 120W - 10.7A - 0.68kg thrust
  9x6E - 14.8v - 234W - 15.8A - 1.05kg thrust
  8x4E - 14.8v - 159W - 10.6A - 0.75kg thrust

Same thrust, less watts, and getting KV down cuts down on vibration.
 
Thanks for your help MM

will properly end up going for the 28-39 900k as you said now. dont want it being under powered. my only concern is flight time. i looking at 5000mah maybe have to try was trying to put the info in to ecalc but they dont have the values for the 28-30 900k so i cant put a custom motor on. might have to just suck it and see.
 
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