Amps

[The_Dave]

Guys,

I have been reading most of the stuff published here and you guys really know your stuff.

Therefore I have a question that is not 100% jet related but I bet someone knows the answer. Here goes:

My son has a mini bee flying wing. It has a brushed 370 motor on it but my kid (9) smoked it....he has the need for speed!

Anyway, I have a BL motor I got from a friend. I don't know what motor it is but it is an inrunner about the same size as a Eflight park 400. I have a Phoenix 25 speed controller. I have a 4.75 X 4.75 prop on it and at WOT it pulls 29 AMPs as per my meter. The speed controller is rated for 25 amps continous with a burst to 35. My question is, what do I do to get the amp draw down to the 25 amp range? I know my kid and he opeates in WOT mode at all times.....

What say you guys? If you need more info, just ask and I will find it for you.

Thanks In Advance!

Dave

[LBMiller5]

The only way to get the amp draw down is to use a smaller prop. The 4.75 x 4.75 might be a little too much for that motor. A 4.75 x 4 prop will have about 85% of the load that the 4.75 x 4.75 gives, so that should get the amp draw down from 29 to about 24.5 amps. If you want a little less draw than that, a 4.5 x 4.1 prop will have about 75% of the load that the 4.75 x 4.75 had, and this will get the current draw down to around 22 amps.

Hope that helps!

Lucien

[fhhuber506771]

Better to under-porp and have some margin vs the ESC's "rated" continuous use current.

If he needs more speed/performance than the combo is giving with an appropriate prop load... he needs a bigger ESC, maybe a bigger motor and battery. (maybe a plane designed to give the performance desired....)

[The_Dave]

Thanks for the replys guys....

My story is a sad one....I built the bee to replace the Zagi that has had the living snot beat out of it. He loves to fly, so the bee was a cheep replacement. Long story short, the little brushed 370 could not take the constant full power runs and gave up the gost. So, I went to the LHS and got him a replacement motor. Mind you, I am a glow guy so motors are new to me.... Anyway one of the fellers at work tels me to run in the motor in some water to seat the brushes....so I do and promptly smoke the speed control! So, I unsolder the motor and connect it to a new speed control. Smoked it too in about 2 seconds... Ok now my kid is looking at me like I am about the dumbest guy on the planet, so I figure I will make up for two dopey moves in a row and put this BL motor I have laying around. To advoid this little 29 dollar wing becoming a two hundred dollar money pit I put the watt meter on it and thats how I know that I am pulling to many amps. I am sure he will love the perfromance the BL motor gives him once the correct prop is installed.

Thanks again for all the help!

[fhhuber506771]

The advice to run-in the brushed motor is fairly common...

The way to do it is with a single C cell battery (cheap one, not an alkaline), no prop and no ESC. Just directly power the motor with the battery.

Essentially what you are doing is "wet sanding" the brushes to match the commutator lands. About 3 min of running the little GWS IPS motors under water will turn a 1 quart bowl of water too cloudy to see the motor in the bottom. Pull the motor out (still running ) and let it "blow dry" itself.

Some say to run the motor underwater till the battery dies.... 3 min is plenty.

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DO NOT TRY THIS WITH A BRUSHLESS!