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Old Aug 27, 2012, 09:46 PM
Kevin Greene is online now
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United States, TN, Jackson
Joined Mar 2007
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Quote:
Originally Posted by Freddie B View Post
Amps are Amps, but remember the old Speed 400 Brushed motors on a 5"x5" Propeller ate about 11-12.5A, on 7 NiCd's or 8 NiMh and was rated at about 55%-65% efficient. They would fly a 1 pound airplane well, at about 60-67mph, but it could be a challange to get them on step (like some EDF's we have all had). That was when we needed 65 watts/lb to just stay in the air, 75 watts/lb to pull loops, and 100/lbs watts was awsome. So these were doing 100+ watts input, and say 60-70 watts out. So where did all the rest go, brushes, heat, wasted energy somewhere, eveywhere.

So I brushless, but when a tiny motor pulls 12 Amps on a 30mm fan, and doesn't put out as much thrust as other fan/motor combos, it seems it must be an effieciency issue? Right?????

But I could see a test of the cool J-Power motor on a 40mm unit, seems like it might just be a pair made in heaven. I would start with 3 cell though! But here is the question, if it's a GWS type rotor, would you go 3 or 6 blades!

Fred
Yep---It's all about experimentation to see what works in the real world or not...Sometimes we are surprised at the combos that do work...

Personally, I wouldn't bother with trying to get a 30mm fan to work with these planes...These planes work very well with the 35mm fan but on at least 3S for decent performance...Decent performance meaning that the plane will easily perform large loops from level flight...But again, I subscribe to the "more power is better" crowd...I expect a jet to perform as such, not needing to pitch the model down to gain enough speed for a decent loop...

My Art Tech 30mm Sabre flies well on 4S which is more than the 3S recommendation...If I had the fan I would upgrade to a 35mm fan for more thrust...Thrust is what is needed to get a heavy plane moving...Velocity from the fan (spinning the fan at a higher RPM) is what is needed for speed...Due to the airframe sometimes the values between thrust and velocity are a compromise...

Again, it's experimentation that allows us to see what works in the real world, or not...

Kevin
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