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Old May 30, 2012, 06:50 PM
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Originally Posted by JetPlaneFlyer View Post

PS.. 608W out and 646W in for the Vox 13x5 would make the motor 94% efficient, not 80.16%
No, if you are spinning a prop at a specific RPM and on a specific number of volts, then the KvE is determined by the difference in RPM, not Watts. All the numbers there for KvE are calculated by volts, Kv, and RPMs and not Watts, and seem to be correct.

Also, if you think the 12x6 spinning 10,650 RPMs should use less current than the 13x5 Vox spinning 540 RPM less, then you may have a good argument, but if these numbers were read correctly, I don't really see any reason for there being a problem with them.

It may be the APC weighs more than the Vox and the added pitch and RPMs is causing the additional Amps, and not the additional diameter. It could happen. There is definitely more work as far as RPM and the static thrust calculator backs this up by saying that it would take 14 more Watts to turn an APC 12x6 the additional 540 RPM than an APC 13x5 540 RPMs less if there was such a prop. So the evidence is at least leaning in the direction that the bigger diameter with the lower pitch rotating slower draws less current. If the Vox was less weight, it should close the door on this, IMO.
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