Motor rpm/volt tradeoff

[BHChieftain]

Hi,
What's the tradeoff on selecting say a 540 8XL vs 9XL? I know the higher the number, the lower the rpm/volt. Does that translate to speed vs. runtime tradeofff? Is the diff between 8 and 9 significant on any measure?

Thanks
-Chief

[Fluid]

IME there is not a lot of difference in the potential performance between the two motors mentioned. They can both give similar speeds if propped appropriately. The 9XL can swing a larger, higher pitch prop than the 8XL, so for heavier hulls the 9XL would be slightly better due to the larger prop and thrust cone. But in narrow hulls - which don't like the torque reaction of larger diameter props - the 8XL might work better. Both motors can be propped for longer run times at reduced speeds, and both can be over-propped if you want to let out the magic smoke.....





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[BHChieftain]

I'm trying to understand the principle of the differences-- so let's change the example to a 6XL vs. 12XL...

Does the delta in rpm/volt translate to speed vs. runtime, or is it more related to torque?

-Chief

[ozzie-crawl]

with a 6xl running on 3s gives you around 32,000 rpm a 12xl to get the same rpm would have to run 6s.
the 12xl running 6s would have more torque and pull far less amps.
a 8xl on 4s would also give similar rpm with more torque and less amps than the 6xl but more amps less torque than the 12xl
so basicly these 3 motors will spin the around same rpm but will require diffrent setups to do so
hope this helps

[BHChieftain]

Thanks!
-Chief