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[johnredearth]

Hi


Not sure where to drop this.  I may put one in brushless also.

http://www.scratchbuildwithjohn.com/public/brushless-verses-brushed-verdict/

[HMS Invisible]

John, ministeve said to me that he needed to be able to turn a prop at 15 rpm (one rev every four seconds). He can do that running brushed at 2kHz. At 2kHz you get a much better slow speed control than you can with old brushed speed controls at 50Hz or at frame speed for 40 & 27MHz radios.

In your comparison you are running with a reduction gearbox and you don't say what pulse frequency the brushed controller runs at.

You can also get 75% efficiency with a 555 motor @ 1 amp. That's about right for your test boat and on a par with the brushless motor.
So the arithmetic shows it would be wrong for anyone to conclude from your test that you can get the same power out and cut the input power by a third.

On the size comparison, you could have use a fully electronic 40amp brushed esc at one sixth of the volume of that electromechanical speed control.

[johnredearth]

Mike!


Nice to hear from you!  My comparison is certainly not meant to be definitive; I just told it like it was, and I had absolutely no pre conceptions. 


BTW my Nautilus is now running with one of your speed controls and two 555's off a lipo, and it is magnificent.  Just a perfect combination. 


The old electronize is featured just because it is the one that was in there.  The slow speed demo is just that, a slow speed demo.  In the comparison it works just as well in that boat, with 4x1 reduction, as the brushed motor.  And in this test, the result is just what it was. 


Cheers  John

[HMS Invisible]

John, low rpm brushed losses are worst case with older frame-rate or 50Hz controllers. Losses markedly reduce with high frequency rates as the current ripple declines.
Brushless efficiency also differs with rpm. I'll leave prospective testers to see what happens at very low speed and find out why. :)