To gear or not to gear?

After lots of measurements and flying on geared brushed motors, I feel it is time to switch to brushless. For a begining, I intend to try a 14 cell lifting 1:7 lightly built (2.5 kg total) 1.6m span semiscales.
Most manufacturers recommend GEARED motors (for this particular project Aveox recommends 1406/3Y geared 1:3.7 driving 12x8 prop,Kontronik suggests KBM52-18S geared 1:3.7, etc.).
According to rather dull tables, Ikarus would reccomend DIRECTly driven 500-4 or 500-5.
My question is: Are IKARUS motors so different from others so they don't benefit from adding gearbox? Is it possible to get maximum efficiency by just attaching prop to it's shaft!
Wouldn't 250-4 with, let's say, 1:2 gearbox do the job better on 14 cells and 12" prop, then direct 500-4?
Any suggestions anyone?
Best regards,
Mike

Aveox has a virtual motor test stand: www.aveox.com/virtual/html

This was the out put for the aveox motor you quoted. There are electric calculation software programs available that allow you to enter the motor constants manually and get the same results.

If you don't want to pay for that then I suggest carefully checking the tech specs' of the ikarus and kontronic motors and find a close match in the aveox lineup and plug in the numbers to see what you get. Then ask the vendors if that is reasonable....because they most certainly have those programs an can check for you.

Virtual Test Stand Inputs


Open Circuit Voltage 1.25 Volts X 14 Cells = 17.50 Volts
Battery Resistance 0.0045 Ohms X 14 Cells = 0.0630 Ohms
Speed Controller Resistance = 0.010 Ohms

Motor Type 1406/3Y
Motor, Unloaded 2000 RPM/Volt
Motor Resistance 0.037 Ohms
Motor no-load current 1.6 Amps

Prop Type Master Airscrew
Propeller Constant 1.31
Diameter 12.0 Inches
Pitch 8.0 Inches
Gear Box Planatary 3.7 to 1
Gear Box Ratio 3.70 :1


Outputs

Prop RPM: 7700 RPM
Current: 29.6 Amps
Voltage into Motor: 15.3 Volts
Power Input: 454 Watts
Power Output: 399 Watts
Efficiency of Motor Only: 87.8%
Current at Max Motor Efficiency: 25.8 Amps
Pitch Speed: 58 mph
Thrust at Pitch Speed: 55 oz

------------------
Robert Harker

"Facts are stubborn things"

"Flying is heavenly ...hovering divine...electric is ecstatic!