I have a Multiplex MiniMag which I've been flying for some time with the following setup:
HiMark 2815 brushless inrunner
7x5 or 8x6 APC E props 3 cell 2250 LiPoOriginally I had a Castle Creations 25A ESC running with the 7x5 prop. The ESC used to cut out until I realised mounting it directly to the foam fuselage (a great insulator) was not a good idea. Since letting it 'float' within the vented fuselage all has been well.
I changed the ESC to a 40A Turnigy unit as the original 25A was pretty much at it's rated limit.
A friends E-meter showed I was drawing upto 60A+ with the 7x5 prop. Changing to the 8x6 dropped that to 50A.
Question 1: Why would a larger prop spinning at roughly the same RPM draw less current? It doesn't make sense.
Question 2: Why would a 40A ESC deliver more than 50A (static) without getting hot or cutting out? It doesn't make sense.
Question 3: Why would a 25A ESC run perfectly if there is a 50A draw?
Anyhow, multiple flights later the motor quits. Inspecting the motor and testing the ESC shows the motor is burnt out.
Question 4: Why would the motor burn out? Yes, I was doing some full throttle runs whilst towing a small glider (Alula under 400grams) which it handles with ease.
Question 5: The HiMark motors are very good and fit the plane perfectly. Should I fit another and be a little cautious on throttle application and duration?
Question 6: Any other suggestions as to why I'm drawing so many Amps and how I can keep that within the ESC's rating? Is it a matter of bigger or smaller props?
All constructive comments and suggestions welcome.
Regards