I have done a good amount of research and I feel that I am starting to understand the relationship of how the power systems fit together from motor to ESC to battery.
My question: Everything being equal, why would a higher RPM motor be qualified as a "speed" motor and a low RPM as a "trainer" type motor?
From watching videos, I've noticed that David would always put a high RPM/KV motor in his planes when wanting to go fast... here's my problem. From what I understand the higher the pitch of your prop the more current (amps) are drawn through your ESC from your battery. So if I had two 25mm diameter motors... one of them was 900KV and the other was 1800KV, both have a max amp draw rating of 30amps. From my understanding the lower KV motors have lower RPMs but higher torque and the higher KV motors have more RPM but less torque. I've noticed that it is customary to put the lower KV motor on a trainer with a big aggressively pitched prop, and a for a speed plane you would put a smaller prop with less pitch. My question is... wouldn't you have the same results (air speed) if you had a low rpm / high torque motor with a high pitch prop or a fast rmp / low torque motor with a low pitched prop. If you found a prop for each style but each pulled the same AMPs on their respective motors wouldn't the speed of the plane be the same?
I'm just trying to wrap my head around the physics of it... and I think I must not be getting something. I've only messed with motor so far, but if I had a low KV motor and a high KV motor, I would hook up my watt meter and switch out props until I got up near the max amps that motor was rated for... and do the same for the low KV one. In my mind if the motor specs were all the same between the two other than the KV and I found a prop that pulled near the max amp draw for both... they should perform the same given the same work being done in relation to the prop. Perhaps I'm way off. Give me a hint please. Thank you in advance.
Brandon
My question: Everything being equal, why would a higher RPM motor be qualified as a "speed" motor and a low RPM as a "trainer" type motor?
From watching videos, I've noticed that David would always put a high RPM/KV motor in his planes when wanting to go fast... here's my problem. From what I understand the higher the pitch of your prop the more current (amps) are drawn through your ESC from your battery. So if I had two 25mm diameter motors... one of them was 900KV and the other was 1800KV, both have a max amp draw rating of 30amps. From my understanding the lower KV motors have lower RPMs but higher torque and the higher KV motors have more RPM but less torque. I've noticed that it is customary to put the lower KV motor on a trainer with a big aggressively pitched prop, and a for a speed plane you would put a smaller prop with less pitch. My question is... wouldn't you have the same results (air speed) if you had a low rpm / high torque motor with a high pitch prop or a fast rmp / low torque motor with a low pitched prop. If you found a prop for each style but each pulled the same AMPs on their respective motors wouldn't the speed of the plane be the same?
I'm just trying to wrap my head around the physics of it... and I think I must not be getting something. I've only messed with motor so far, but if I had a low KV motor and a high KV motor, I would hook up my watt meter and switch out props until I got up near the max amps that motor was rated for... and do the same for the low KV one. In my mind if the motor specs were all the same between the two other than the KV and I found a prop that pulled near the max amp draw for both... they should perform the same given the same work being done in relation to the prop. Perhaps I'm way off. Give me a hint please. Thank you in advance.
Brandon