|Jul 29, 2008, 10:30 PM|
Joined May 2005
That's fine and all, but I'd like to know how many amps particular, common (to that motor) props are pulling, and at what RPM they are spinning. This is critical information that's so hard to find. Usually I look at the comments on hobbycity's web site to see this. Would be nice to have this all in one database.
Knowing a motor's Kv is not enough. It was a revelation to learn that 2 different same-Kv motors can spin the same prop at dramatically different speeds (and thus power levels). For example, my hacker clone 20-20L spins a 10x5 prop at 7800 rpm, 14 amps. Another motor (forget which at the moment) will spin that same prop at 10000 rpm (same labeled Kv, mind you!), and at 25 amps or more. The same motor spins a 9x6 prop at 20 amps, 11000 rpm or so.
I don't always understand how the unloaded Kv, the number of poles, the winding type, and the diameter and length of the stator play into things in a formulaic way, so having empirical results gathered over time from many of us would be wonderful. Sure we have spreadsheets and motor calculators, but sometimes theoretical isn't quite enough. There is one motor calculator backed by a large database of actual, empirical results, so that's a good start. It's currently missing most Turnigy motors, though, and I don't know how to convert the specs from hobbycity's descriptions into parameters the motor calculator can accurately use.
|Apr 27, 2014, 02:20 PM|
The main reason there's a difference in R's on same kV is efficiency. Good magnets vs poor, metal losses, etc. One is just more efficient than the other for a given kV.....
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