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Author Topic: Motor speeds up in flight.  (Read 830 times)

Offline Perry Rose

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Motor speeds up in flight.
« on: January 30, 2022, 11:19:37 AM »
My set up is an Aerowind 2820/7 motor, an APC 11 x 5.5, FM-0c timer, an F2B 60 Amp E.S.C., and 5 cell 3000 mAh batteries. I get the same results with an FM Hornet timer. Initial RPM is 9200. About a minute into the flight the motor increases about 200 RPM. About a minute after that it increases another 200 RPM. It does that two more times during the flight. I have tried another motor, a couple other E.S.C.'s and timers. Same results. Is this normal for this motor? If I could delay the speed ups until after the square eight I wouldn't mind.
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Offline Tim Wescott

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Re: Motor speeds up in flight.
« Reply #1 on: January 30, 2022, 12:06:54 PM »
Have the timers all been FM-0c and FM Hornet timers?  Is "F2B" a brand of ESC, and if not, what brand of F2B ESC is it?

I know that some of the Hubin timers are designed to work with a plain-old ESC without governing, and increase the throttle signal to the motor over the course of the flight, to compensate for battery sag.  I don't know which timer is which, though.

I would assume that an ESC that's marketed as "F2B" would have a governer, such an ESC already does the governing, so a timer that tweaks the throttle signal up during the flight would result in higher RPMs as the flight progresses.
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Offline Perry Rose

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Re: Motor speeds up in flight.
« Reply #2 on: January 30, 2022, 12:30:33 PM »
The timers have been those two. The ESC's are as stated, I got them all from Brodak. The larger motors, 35xx, work perfectly with the same timers, batteries and ESC's. Maybe I'll try a smaller battery.
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Offline pmackenzie

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Re: Motor speeds up in flight.
« Reply #3 on: January 30, 2022, 01:27:11 PM »
Sounds like a timer issue, programmed to speed up during flight.

See the product description on the Brodak site:

https://brodak.com/fm-9-programmer.html

"The Fm-9 system is designed to enable a single timer to be programmed to control numerous ESC's, including the Brodak Hornet Series. The programmer also enables the timer to be programmed for simple non-governing ESC's in a fixed or throttle compensation mode, like that used on our popular FM-0c.The programmer allows direct setting of motor RPM, flight duration to the second and motor start delay."

To run governor mode you don't want that feature. Get an FM9, and the programmer, and turn it off
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Offline Mark wood

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Re: Motor speeds up in flight.
« Reply #4 on: January 30, 2022, 10:14:39 PM »
My FM0c's don't do that. I have bunch of them. But I also run the ESCs in governor mode. My FM9 does to a degree but it doesn't work well with the ESC in governing mode. I left the FM9 and only run the FM0c and in the larger PA models I run the Fiorotti.
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Offline Perry Rose

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Re: Motor speeds up in flight.
« Reply #5 on: February 01, 2022, 01:07:36 PM »
I tried some 4 cell 3300's and they didn't create as much of an rpm increase.  I have a programmer coming.
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Offline Mark wood

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Re: Motor speeds up in flight.
« Reply #6 on: February 01, 2022, 05:33:08 PM »
I went out to the shop and ran the FM0c with my Oscilloscope connected and over 3 minutes the output ran a solid 1.72 ms pulse with very minor variation.
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Life is good AMA 1488
Why do we fly? We are practicing, you might say, what it means to be alive...  -Richard Bach
“Physics is like sex: sure, it may give some practical results, but that’s not why we do it.” – Richard P. Feynman

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