Originally Posted by bimmerland
Going to buy a Electrostik. Have most of the stuff but need a motor.. What is an equivalent to a 42-50-800kV motor. I could not find an answer on HK or Hpartz website. Thanks
Just ran the Rimfire numbers through www.motocalc.com
Motocalc suggests running this motor at the peak currents of 80 Amps will burn it up. Even running the motor at the 50 Amps continuous rating will result in motor efficiency of only around 50%, and winding temperatures of over 400 F. It's going to get hot if you run much more than 40 Amps through it. This rimfire motors windings measure out at 0.036 Ohms. So at 80 Amps, you're loosing 230 watts in the windings alone. (P = I Squared times R)
This motors specifications indicate maximum burst watts is 1480. That is 211 watts per ounce of motor weight. IMHO, anything much over 100 watts of power per ounce of motor weight might be pushing it a little. And doing so usually results in the motor efficiency dropping like a rock.
FYI, one of my models recommended a 400 Watt or so Rimfire motor, with the warning not to touch the motor after a flight, because of the risk of burns.
As a comparison, a $$$$ Hacker A40-10S motor will run at 89% efficiency while pulling 52 Amps on a good quality 4S Lipo. This motor weighs in at 9.4 ounces, with a winding resistance of 0.007 ohms, about 1/5th the winding resistance of the Rimfire. That, just turns into heat, not turning the propeller. http://www.aero-model.com/Hacker-Brushless-A40-10S.aspx
I now have 8 of those $$$$ Hacker motors, ranging from an A30, two A40's, three A50's an A60-16M, and a new A60-5S. Every one of them performs to their specifications, and to their current and watt ratings without issue. (Just got the A60-5S, have not run it yet.)
Any good quality motor that gives winding resistance measurements of perhaps 0.01 ohms or less, with similar 8 or 9 ounces of motor weight should perform well. There are a lot of those good motors out there. Problem is, more than a few of the "cheap" motors don't provide the all important winding resistance information.