The flying monkeys got me...

Helis and fixed wing

AMA 957918
IRCHA 4345
AMA Intro Pilot Instructor

Friday, June 22, 2012

Oh... so that's how I killed it...

Its amazing when one does what one is supposed to do, what one learns from that. Its also amazing how frequently we don't quite do what we ought and get away with it...
But, I haven't been getting away with it lately. I have been burning out motors on my Eflite Stearman, which calls for a 15 sized motor. I have found that to be an adequate motor, flying 3S, but just adequate. I have learned that my particular Stearman doesn't like flying 3S as it flies sluggishly and stalls easily. So I have been flying the motor, a HURC 3542-10 with 4S, and over time the system fails. I know the motor is rated for the 4S voltage, but was pretty sure I was exceeding 40amps and 550 watts, just not by how much. I wasn't sure if it was watts or amps or both that was frying everything, or if the motor failed or if it was the ESC, because after the ensuing crash the everything works fine.
Everyone tells me I need a watt meter, and I know I need a watt meter, so I finally bought me a watt meter. On eBay I bought a Watts Up Meter from All-Battery and threw on the EC5 connectors (it does not come with connectors. You solder them on, load end with battery leads, source end with ESC leads). I plan to stick this puppy on every plane I have! I do hope it doesn't lead to having to replace all my motors... or accepting less performance from my aircraft. I wonder how I can put it on my helis? I like this meter, simple, straight forward.
Today I put it on the Stearman. The HURC 3542-10 is spinning a 12x6 APC eprop. It does that easily. The motor is rated for 550W at 38 amps for no more than 60 sec. Fired her up with the wattmeter in line, pushed the throttle to the firewall. 48 Amps and 640 watts. Well, yes. Its over amped and over powered, so that's why the systems are frying. I replaced the 40 amp ESC with the Turnigy Turst 70A last week. I just ordered a PowerUp 25 Speed motor from HURC today, rated at 50 Amps and 740 watts for 60 sec. The motor is bigger, but I am pretty sure I can get it to fit in the cowl.
Well, this brick is likely to fly much better with the 25 sized motor. When I build the stock one I have NIB, I wonder if I should power it with a 15 sized motor and just fly it 3S? I don't look forward to returning to her high stall speed and mushy performance with limited vertical... If this arrangement works out I will likely build the new one, when the time comes, with a 25 sized motor and 4S.

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