John, you got it right -- the designation numbers mean what the motor manufacturer wants them to mean, nothing more.
RPM/volt, continuous current (be wary of "peak" current ratings unless it specifies a minimum time), weight, etc. -- those are much more definitive. Even there, I'd expect a lot more consistency across product lines, and more of a tendency to be honest from the big name manufacturers -- there's nothing to keep someone from building a motor that'll run just short of melting at it's rated power level, and little to keep a foreign company from selling one that
will melt at rated power.
Lessee. Based on my day job, the specifications that mean something are:
- Kv (RPM/volt)
- Continuous current (read the fine print if they're specifying air flow)
- Maximum RPM
- weight
- shaft size
- stated dimensions (not funky codes)
Those are the motor specifications that you should look for; the rest has to come from computation (or copying something that works, which is more dependable even if you're a supposed expert).
Motor power is more or less a derived specification: the electromagnetic assembly generates torque according to the current, then the faster you spin the motor the more power you make, until either the ESC gets too inefficient because things are switching too fast, the motor flies apart, or the loss generated by windage overcomes the torque. If the three, the first two are the most likely.
So it's almost always true that with an electric motor, you can spin it faster and get more power. This is why you used to get fancy gearboxes for your motors a decade ago -- the motors then available were skinny little things that didn't generate much torque, and the gearbox would let the motor spin at a better power-generating speed, while the gearbox would spin the prop at a better thrust-generating speed. Outrunner motors are actually less efficient than the "inrunner" motors that you use in ducted fans or with gearboxes -- but they're generally more efficient and lighter than an inrunner motor + gearbox (although there are still high-end inrunner/gearbox combos available, I think).
Your challenge is to juggle RPM, Kv, motor cells, and prop combinations to get something that is going to take the power from the batteries and effectively apply it to the air.
Topic: a NOT so simple motor question??? (Read 1698 times)