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Author Topic: How do I stop a full-throttle screech?  (Read 309 times)

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Online Frank v B

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How do I stop a full-throttle screech?
« on: November 24, 2019, 10:08:57 pm »
Calling any and all Techies:

I tried to fly the DeNight Special twice and twice at full throttle just after breaking ground the motor screeched and stopped working.  It would then power up fine afterwards in the pits  This happened twice to me on two separate days this summer.

The motor is a Turnigy PropDrive approx. .50 size on 5 cells swinging a 13.5 x8 Graupner prop with a 70 amp Opto ESC and a separate 4.8 volt RX battery pack.

The sound is not bearing related but appears to be timing.  How do I fix it?... pretty please.

Frank



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Offline bweaver

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Re: How do I stop a full-throttle screech?
« Reply #1 on: November 26, 2019, 08:33:34 am »
Calling any and all Techies:

I tried to fly the DeNight Special twice and twice at full throttle just after breaking ground the motor screeched and stopped working.  It would then power up fine afterwards in the pits  This happened twice to me on two separate days this summer.

The motor is a Turnigy PropDrive approx. .50 size on 5 cells swinging a 13.5 x8 Graupner prop with a 70 amp Opto ESC and a separate 4.8 volt RX battery pack.

The sound is not bearing related but appears to be timing.  How do I fix it?... pretty please.

Frank

While not being a techie, I have two comments. 

1) Sounds like many situations I experienced when flying glow fuel airplanes.  This is why I switched to electric.

2) Sounds like it's broken.  In my technical view, I would replace something. 

Maybe a true techie will have some real advice.   ;D
« Last Edit: November 26, 2019, 08:38:54 am by bweaver »

Offline battlestu

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Re: How do I stop a full-throttle screech?
« Reply #2 on: November 26, 2019, 02:19:46 pm »
had this problem some time ago... you'll need to change the timing on the ESC (assuming you have a programmer for it)
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Online Frank v B

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Re: How do I stop a full-throttle screech?
« Reply #3 on: November 26, 2019, 06:02:16 pm »
Bruce: re  In my technical view, I would replace something.  ...like the pilot??  ;D

Greg:If it works fine up to 3/4 throttle and screeches only at full throttle, does that mean the ESC needs to be programmed to a higher frequency?

Maybe I should just replace the ESC or increase the size of the prop to reduce the RPM on the motor.

Frank
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Offline pmackenzie

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Re: How do I stop a full-throttle screech?
« Reply #4 on: November 26, 2019, 10:41:58 pm »
Screeching is usually caused by the ESC losing "sync" with the motor.

Try a smaller prop, or adjust the timing on the ESC.

ESC frequency does not usually affect this.
This frequency has to do with how fast the current is "chopped" at part throttle. At full throttle there is no chopping going on, only commutation.

Pat MacKenzie

Online Frank v B

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Re: How do I stop a full-throttle screech?
« Reply #5 on: November 27, 2019, 12:07:17 pm »
Pat,

Thank you.  I was hoping you would weigh in on this.  Will do all this next spring knowing what to do now.

The electric guru has spoken.... and I have listened. ;)

Frank
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Online davidk

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Re: How do I stop a full-throttle screech?
« Reply #6 on: December 01, 2019, 11:53:33 am »
Is it possible that there are wires in the mix that are either not the same length... or too long?

I've been reading lately (dangerous pastime) and it's been suggested that motor wires of difference length could cause a timing issue... and that too long a wire length between the battery and ESC could cause a timing issue.  Even that too short a wire from battery to ESC will cause problems.

Since you're seeing odd behaviour at full throttle, when more juice is used, maybe something electrical (spikes) is happening.

Online Frank v B

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Re: How do I stop a full-throttle screech?
« Reply #7 on: December 01, 2019, 03:55:30 pm »
The leads are the same length.  The only thing "short" is me on technical experience. ;)

Frank
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Online davidk

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Re: How do I stop a full-throttle screech?
« Reply #8 on: December 01, 2019, 04:06:22 pm »
Me too!  :D