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RimFire 65cc issues

Old 10-06-2020, 06:45 AM
  #1  
kevarc
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Default RimFire 65cc issues

I purchased this 65cc Rimfire motor and Castle 160A esc from a guy to put into a Phoenix 60cc Spifire.
My first try with electrics on this scale.
I hooked it all up and everything seemed to be working fine.
Finished the plane and took it out in the yard to do a test run.
I used a 26x12 prop and a12s battery.
Ran for a couple of minutes and the motor seemed very hot.
Hot enough it you could not touch it.
I maidened the plane and just flew it at about half throttle, because I was worried about the heat.
Flew it a second time again at half throttle, but did go to full throttle for a few seconds. I did note there was no sound change when I did this.

Got a 24x12, 24x10, and 24x8 prop to test out.

I ran the motor a full throttle for 1min and took the following readings.
26x12
This test started melting the 12 awg wire between the meter and the batteries. The 10 awg was hot . Will not use this prop anymore.

24x12
90 amps, 3900 watts, 6000rpm, 127 degrees, and used 30% battery.

24x10
76 amps, 3600 watts, 6100 rpm, 132 degrees, and used 24% battery

24x8
73 amps, 3240 watts, 6400rpm, 130 degrees and used 25% battery

Flew again testing the 24x8 prop. This flew the plane but slow. Noticeable pitch change when going to full throttle. The temp on the motor when I landed was 180.

After landing a club member turned the prop over and commented that it was very tight and should turn over easier.
I had another motor and checked the two and sure enough the one in the plane was much harder to turn over.
I removed the one from the plan and took it apart.
The stator and magnets are obviously rubbing at the rear portion of the motor.



Did I cause this by overheating the motor with too much prop?
Or was this the reason it was getting hot in the first place?
Thanks for your input!
Old 10-06-2020, 07:47 AM
  #2  
rgburrill
 
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I have always found it much wiser to use a higher voltage and reduce the current to get the same power out of a motor. It's current that causes the heat and, consequently, the power loss. And the higher voltage gives you higher RPM, therefore allowing you a lower pitch prop. Can't that Rimfire 65 handle a 16S battery?
Old 10-07-2020, 04:55 AM
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kevarc
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Looks like the motor can do 15S per the manual.

I put my other Rimfire 65cc motor in the plane and ran the same tests with the 24" props 12, 10, and 8 pitch.
At full throttle they all took about 10 less amps, 400 less watts, and all ran at about the same rpm as the old motor.
The temps were also noticeably cooler.

I did discover that the front bearings of my old motor have a fair amount of wobble. I will switch them out and see.
Old 10-09-2020, 08:26 AM
  #4  
ron_van_sommeren
 
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Originally Posted by rgburrill View Post
I have always found it much wiser to use a higher voltage and reduce the current to get the same power out of a motor. It's current that causes the heat and, consequently, the power loss. ...
For a given/desired rpm, choice of voltage does not matter:
Short flight time is killing me - RCG - post#165

Originally Posted by rgburrill View Post
... Can't that Rimfire 65 handle a 16S battery?
Brushless motors can handle any voltage in RC land, as long as current and rpm don't get too high. Wire insulation lacquer is tested up to several hundred volt.
RPM is proportional to voltage.
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Increase in current with one or two cells added, simple table - RCG

The full story:
Current drawn is proportional to pitch, #blades, voltage² Name:  eek.gif
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So even small changes in setup can result in massive changes.
Ignoring slightly higher voltage losses in battery, wiring, controller and motor due to higher current.

Prettig weekend en wees voorzichtig, Ron
• Without a watt-meter you're in the dark ... until something starts to glow •
E-flight calculatorswatt-metersdiy motor tips&tricksCumulus MFC

Last edited by ron_van_sommeren; 10-09-2020 at 08:42 AM.
Old 10-11-2020, 05:52 AM
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Foxbat711
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Like you indicated..... Bearing....

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