KV / Gearing choices

[Procharged5.0]

What about............

Has anyone considered "driveability" or "control" differences between Kv ratings? Consider the "responsiveness" of a 1700kv motor vs a 2300kv motor or a 4600kv. The higher Kv motor would be far more reactive to throttle (or esc/trigger) inputs than the lower Kv motors.

From what I've gathered from various sources (not personal experience) the higher Kv rated motors have a somewhat higher efficiency.

Also....(although a bit off topic) How do we factor in the performance differences of using 2-pole vs 4-pole (or 8-pole for that matter) motors?

[Procharged5.0]

Maybe what we need is info like you'll find on this attached pdf of a Mabuchi 550 motor. It tells alot about the motors "personality".

[BrianG]

Originally Posted by Procharged5.0

Maybe what we need is info like you'll find on this attached pdf of a Mabuchi 550 motor. It tells alot about the motors "personality".

That would be PERFECT! It shows the various values at max eff, and max power. So, the user can decide what they feel is most important and make the decision based on specific data.

To a large degree, battery quality plays a big role. It looks like the graph assumes an ideal voltage source (constant voltage and zero output impedance). Pretty much ANY battery will sag and react to certain loads.

And let's not mention how the ESC handles itself. Ideally, its output should be stable no matter what, but some loads (particularly high inductive loads) are more difficult to drive due to the voltage and current phase shifting.

Argg! It's enough to give one a headache! There are simply too many variables! The motor selection is hard enough without the user being forced to make assumptions on battery quality and ESC stability.

[sleebus.jones]

Originally Posted by Procharged5.0

What about............

Has anyone considered "driveability" or "control" differences between Kv ratings?

Good point. The most efficient setup may not be the one that "feels" the best.

Ack!

Sleeb

[Procharged5.0]

A motor dyno would be the way to go. The graphs of the power output relative to voltage, current draw, etc plus measuring temps would be beneficial.

BUT.....

What if we could take and do an RC version of what we do in the 1:1 world?

Take one E-Revo w/4s2p Lipo's, Quark (or MM) and a Neu 1515/1Y run timed acceleration tests. For example: 0-30mph, 0-40mph, 0-50mph, 20-40mph and monitor voltage, temps, etc using something like the Medusa Power Analyzer Pro w/data logger and a Radar Gun (or maybe just acceleration for a fixed distance for simplicity) and then swap to a 1515/2.5D and re-run the tests.

Gearing swaps could be considered and several runs could be made w/various ratios and dropped into a matrix for comparison.

A major factor for me would be to see how the motor reacts/responds to mid-range acceleration. What motor/gear combo is most responsive and controlled for track use. Say your half throttle on track approaching a double or tripple jump and need power to clear it. Which combo is smoothest, most predictable and controlled? Lots of power is great but it needs to be in a useful rpm range and needs to be efficient to avoid excess heat buildup and battery drain.

that's my $3.52! Sorry for the lengthy response.