Replies to This Discussion

Permalink Reply by Jose Luis Cortes on February 4, 2011 at 10:00am

Hello Ying, you need good controller-motor-propeller efficiency to keep a plane in flight with 200w and 7kg, I think this motor is big, it get maximum efficiency with more than 15A.

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Permalink Reply by Calvin Lee on February 6, 2011 at 9:51pm

Yes, I reckon that I need good motor and propeller efficiency but I am could not find materials on motor sizing for this application. Thus, I am hoping to gather some good resources or experience from fellow forum-ers.. 

 

For the propeller sizing, we purchased a good number of them of varying diameters and pitches to select the better one. Controller wise, I didn't take note of the efficiency side of it. Perhaps we should do that now too..

 

We were aware that the maximum efficiency is above 15A. We chose this as it is the 50 series motors which reflects maximum efficiency having lower range limit (15A in comparison to higher ones in 40s/30s/20s series). There are 50s series motors with maximum efficiency lower range limit of 8A but that is unavailable when we were purchasing.

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Permalink Reply by Ground Loop on February 4, 2011 at 10:21am

With the heavy plane and 200W peak output, you might want to consider pairing the fuel cell with a LiPo battery.  The idea would be to use the LiPo to supply additional current during peak draws (climb) and then recharge off the fuel cell during lower demand.  I imagine some cell management electronics would be required, and then the weight added is also a concern, but it would widen your power envelope quite a bit.

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Permalink Reply by Jose Luis Cortes on February 4, 2011 at 11:00am

It seems Aeropak is a "pak" with all included, it seems it comes with stack controller, valves and a small lipo battery (1350mAh), seems to be nice product, but very expensive for me.

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Permalink Reply by Calvin Lee on February 6, 2011 at 9:58pm

The 200W would be continuous output. The peak output is 600W.

The design comes with an inherent lipo battery attachment to cater to the purging of the fuel cell to remove the generated water. We are in view of using another lipo battery for the same purpose of climbing. 

 

However, we need to up the thrust produced by increasing the efficiency of the controller-motor-propeller combination and my main suspect is that the motor is not exactly compatible/efficient...

 

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Permalink Reply by bGatti on February 4, 2011 at 10:44am

motors are rated at RPM per Volt. as you have High voltage, you'll generally want a slower motor; I'd also consider a geared motor to help reduce speed and increase efficiency.

 

Here is an interesting option:

http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=...

 

it's a dual motor, but your problem is still high voltage - so you may need to rewind the motors.

 

 

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Permalink Reply by Calvin Lee on February 6, 2011 at 10:09pm

Hi! May I understand the relationship of high voltage with slower motor..? 

 

meanwhile, i will check out geared motors and hopefully thats increase my efficiency..!

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ModeratorPermalink Reply by Graham Dyer on February 4, 2011 at 12:25pm

200W / 7kg is 28W a kilo, low powered efficient gliders can fly on as little as 60W per kilo, 28's going to be pushing it a bit. You'll need a highest quality competition motor with 6:1 (or higher) gearbox and massive propellor to get any results. Kontronik and Hacker brands come to mind.

 

Something like the Kira 650-11 with 6.7:1 gearbox might produce some thrust at that wattage with a very large prop (Kontronik Kira 650-11)

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