Thanks BgCatfish1!

If I only know the unloaded rpm per volt, how do I know either the power (watts) in or out? If I knew the power in, I could make some assumptions about the efficiency and the power out. It seems the spec tells me the point where the back emf equals the voltage in but I still don't see what that does for me. Also, why the letter k?

Just getting into this area of the hobby but I do have an electrical background so I shouldn't be too snowed!

Paul