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Old 12-22-2012, 12:02 AM
  #8  
Dereck
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Join Date: Oct 2005
Posts: 1,071
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HI Jed
Idle thought back on my Four Star 40 electrocution. When I did it, 600W+ electrics were still pretty rare and the motor was one of two brushless on the US market and the only one at the time that came with easily swapped gear ratios - the motors were inrunners and had to be geared - and an ESC that offered a true speed control from zero to flat out. It is still superior to anything I've had since, though that Tom Cimato, the guy behind MaxCim motors, had a little street cred in this region - some of his work in speed controlled electric motors was onboard the space shuttles.

Eventually, I did a lot of gear ratio/prop size testing on the 4*40, starting with props around 11", which is close to what the design was built around, but slimily impelled of course. Ended up with a very un-scientific decision that the best prop was a 15 x 10 doing 6800 RPM flat out with around 600W into it.

That decision was arrived at more by the ability to do a convincing knife-edged loop from level flight than any stream of long numbers and hard words

These models can manuevre extremely well, but a high top speed - forget it. The other good point was that the 4*40 also has a tendency to float on down the runway and refuse to come down the last couple of feet and stop flying. That 15" prop disc on very low revs threw a lot of drag into the equation and cured that tendency pretty much for good.

If you'd like a history lesson, the MaxCim website is still hanging out there - http://www.maxcim.com/ Worth a late night read, to make you appreciate brushless outrunners with modern ESCs all the more. Still wish we'd stuck with geared inrunners though. Much less fuss and if you bought slightly the wrong motor or wanted to use your motor with a different size of battery or prop, swapping a $5 gearbox pinion took about five minutes with two hex keys and a strip of office paper.

D
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