does lower kv mean more torque with less amps?

[Erik102696]

I have read many different sources about what size kv to use with different projects. the topic has come up that lower kv works better slower applications that need fine motor control as you need in a rov. I have also read that they need less amps but can throw a larger prop. is this true? I just purchased this motorhttp://www.hobbyking.com/hobbyking/stor ... oduct=8622 they are small and have a low kv. they are the same ones that are used on the OpenROV and they reported thrust of around 2.6lbs with it only drawing 7 amps! for my needs amp draw is an issue since my power needs to have a 25 amp fuse in line (this is for the mate competition). so what are your experiences with brushless motors? if you have use them on a rov how many amps did it draw while you where driving around? Also how many of you think I should make a project thread so you guys can follow my teams progress?


thanks-
erik

[scubersteve]

The kv rating to amperage draw thing gets rather complicated as it is largely a function of the size, pitch and number of blades of the prop you are trying to spin.
A small, two blade, low pitch prop requires more rpm to make the same thrust as a large, three blade, high pitch prop.
So for the fictitious two blade prop I just mentioned you would pick a higher kv motor than you would for the three blade.
A motor wants to spin a certain speed at a certain voltage (brushless motors call this the kv rating) and each prop has a certain speed at which it is most efficient. The key is matching them so the prop's sweet spot is the same as the motor's sweet spot with the voltage you are running.

And of course you should start a build thread.