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Old 04-02-2016, 02:23 AM
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Join Date: Apr 2008
Location: Wisconsin, USA
Posts: 8,952

Originally Posted by Ron View Post
Motor prediction programs are at best a semi educated guess. If it is the opinion of the guy writing it that you need 1000 watts per ounce to fly, the program will reflect that in every combination. I know for fact that a lowly Eflite Power 160 on ten cells using a 20X10 prop works well..****calc says it will burn up the motor on 9 cells at a ridiculously high amp draw......which I know from tests conducted on my own setup, is way off base.
like 25% high. another program I have tried is similarly inaccurate.
IMHO, a lot depends on the type of model being flown with a particular power setup. E-flite indicates their Power 160 can handle 60 Amps continuous and 78 Amps peak for 15 seconds.

Put that power system in a very fast streamlined model, and the current drops way off at high speed. Put that same power system in a big slow flying Piper Cub, and that is a much different application.

Motocalc suggests that the current pulled with a 20X10 prop and a 10S LiPo will result in a current level of 78 Amps. I've got three giant scale models, two with Hacker A60 series motors, and one with a Rimfire 50cc electric motor.

The motocalc predictions on the Rimfire 50cc motor and my 12S3P A123 battery pack, installed in a 20 pound 95 inch wingspan airplane are pretty close. Motocalc was within 5% on RPM and current pulled by that Rimfire motor. But as usual, motocalc, and other computer programs are only as close as the motor specifications provided with the motor.

This is the main reason it is almost mandatory to backup what ever predictions a particular computer electric motor program are with a wattmeter.

(PS, I've been flying electric models for 33 years!)
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