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Horrible motor noise?

#1
I recently got into the hobby and built my first plane. It is a foam pusher with a carbon fiber arrow for a tail boom. The thing flies pretty well, however the motor is a little concerning. The motor does not respond at all until the throttle stick is about 1/3-1/2 of the way up, but then everything functions fairly normally up to about 70-80% throttle. However this is when the motor starts to make a horrible grinding noise. If you accelerate the motor slowly enough though (and i mean stupidly slowly) through this throttle range the noise doesn't happen and it will hit full throttle. It almost sounds like stripped gears, however it being a brushless outrunner, doesn't have any gears... I originally just figured its the side effect of buying a ~$13 motor/esc combo off of amazon. It's an 1100 KV motor swinging a 10x4.7 sf prop. My theory is that the motor is lacking in torque and just cant accelerate the prop, but im interested if anyone else has experienced this or if there is a way to fix it.
 

PsyBorg

Fly Angry
Mentor
#2
It sounds like you need to do an ESC calibration mate. If you have done one then it might be a timing issue but since it does not spin immediately I will say calibration.

Remove the prop, Set radio to full throttle, plug in the flight pack. When the esc starts making tones drop the throttle to 0.
the esc should then automatically reboot and begin normal operation.
 

Hai-Lee

Old and Bold RC PILOT
Mentor
#3
Horrible grinding noises!
There are a few well know causes and some not so common!
The most common is that the prop adapter is slipping on the motor shaft under high throttle settings. Similarly this applies to spinners when fitted as well.
A second cause can be the failure of a motor bearing, (normally a motor that has crashed a few times. As the bearing loads up under high thrust settings the ball bearings start to try to trip over each other and grind into them selves and the bearing housing, (this one always gets worse but a little lube can help extend its life,
A third cause can be that the motor shaft itself is turning at a lesser rate than the motor "Can" and the noise is the grub screws plowing a channel in the motor shaft. Some motor shafts on the cheaper motors do not have a locating keyway ground into the shaft and so a loose grub screw just allows the motor shaft to spin at a different rate under load. This will become gradually worse and occur at lower speeds until the motor will not work under any real load. (Tighten the HECK out of the grub screws and see if the noise lessens or disappears If it continues to be a problem then you can try a drop of CA to aid the grubscrews in holding the motor shaft in position with respect to the bell).
Yet another cause can be a little foreign matter or metal shaving being held by the magnets in the motor and slowly being ground against the fixed winding part of the motor making a noise. this can also be as a result of a magnet actually becoming loose and striking the windings as the motor rotates.
A bent motor shaft or even a totally collapsed bearing will allow or cause the prop to not spin true and the vibration can shake the plane and this can be a loud and horrible noise akin to the grinding you mentioned.

Definitely calibrate the ESC and even adjust the timing to get best performance but a grinding noise is normally something physical or mechanical. Check that the motor shaft touches no other part of the plane and the same applies to the circlips that hold the motor together.

Just a few things to check, (please note that it is possible to have a motor suffering from a couple of the above conditions at the same time)

Have fun!
 

Namactual

Well-known member
#4
If your timing is off and or you put too much of a load on the motor, (over prop), it will screech like crazy. The noise is hard to explain, think Jim Carrey in Dumb and Dumber. Especially if you spike the throttle real fast. If you have a smaller prop available I would try that and see if you still have the issue. You could also try lowering your timing.

If you are using the motor I think you are using? the MFG recommends a 8x4 prop.
 
#5
It sounds like you need to do an ESC calibration mate. If you have done one then it might be a timing issue but since it does not spin immediately I will say calibration.

Remove the prop, Set radio to full throttle, plug in the flight pack. When the esc starts making tones drop the throttle to 0.
the esc should then automatically reboot and begin normal operation.
I had no clue that ESC calibrations where a thing and i just performed one as you explained. The throttle response is much better as it gets going almost immediately, and the the "horrible grinding noise" is still around at near max throttle, but is much less touchy. I should mention now, and even before, the grinding noise would go away after a few seconds which led me to believe it was just a stall and required some time to get to speed. A slow acceleration avoids the noise as well. Overall is running much better, thanks for the advice.
 
#6
Horrible grinding noises!
There are a few well know causes and some not so common!
The most common is that the prop adapter is slipping on the motor shaft under high throttle settings. Similarly this applies to spinners when fitted as well.
A second cause can be the failure of a motor bearing, (normally a motor that has crashed a few times. As the bearing loads up under high thrust settings the ball bearings start to try to trip over each other and grind into them selves and the bearing housing, (this one always gets worse but a little lube can help extend its life,
A third cause can be that the motor shaft itself is turning at a lesser rate than the motor "Can" and the noise is the grub screws plowing a channel in the motor shaft. Some motor shafts on the cheaper motors do not have a locating keyway ground into the shaft and so a loose grub screw just allows the motor shaft to spin at a different rate under load. This will become gradually worse and occur at lower speeds until the motor will not work under any real load. (Tighten the HECK out of the grub screws and see if the noise lessens or disappears If it continues to be a problem then you can try a drop of CA to aid the grubscrews in holding the motor shaft in position with respect to the bell).
Yet another cause can be a little foreign matter or metal shaving being held by the magnets in the motor and slowly being ground against the fixed winding part of the motor making a noise. this can also be as a result of a magnet actually becoming loose and striking the windings as the motor rotates.
A bent motor shaft or even a totally collapsed bearing will allow or cause the prop to not spin true and the vibration can shake the plane and this can be a loud and horrible noise akin to the grinding you mentioned.

Definitely calibrate the ESC and even adjust the timing to get best performance but a grinding noise is normally something physical or mechanical. Check that the motor shaft touches no other part of the plane and the same applies to the circlips that hold the motor together.

Just a few things to check, (please note that it is possible to have a motor suffering from a couple of the above conditions at the same time)

Have fun!
I have the prop adapter as tight as it will go, and the grub screw was already on very tight when i checked it. The noise was happening out of the box before attached to anything, even without a prop, however now that i've calibrated the ESC the noise doesnt happen without a prop on, leading me to believe that i am simply swinging too large of a prop for this cheap thing. Thanks for the checklist though, ill be sure to keep these things in mind for future reference.
All the best!
 
#7
Horrible grinding noises!
There are a few well know causes and some not so common!
The most common is that the prop adapter is slipping on the motor shaft under high throttle settings. Similarly this applies to spinners when fitted as well.
A second cause can be the failure of a motor bearing, (normally a motor that has crashed a few times. As the bearing loads up under high thrust settings the ball bearings start to try to trip over each other and grind into them selves and the bearing housing, (this one always gets worse but a little lube can help extend its life,
A third cause can be that the motor shaft itself is turning at a lesser rate than the motor "Can" and the noise is the grub screws plowing a channel in the motor shaft. Some motor shafts on the cheaper motors do not have a locating keyway ground into the shaft and so a loose grub screw just allows the motor shaft to spin at a different rate under load. This will become gradually worse and occur at lower speeds until the motor will not work under any real load. (Tighten the HECK out of the grub screws and see if the noise lessens or disappears If it continues to be a problem then you can try a drop of CA to aid the grubscrews in holding the motor shaft in position with respect to the bell).
Yet another cause can be a little foreign matter or metal shaving being held by the magnets in the motor and slowly being ground against the fixed winding part of the motor making a noise. this can also be as a result of a magnet actually becoming loose and striking the windings as the motor rotates.
A bent motor shaft or even a totally collapsed bearing will allow or cause the prop to not spin true and the vibration can shake the plane and this can be a loud and horrible noise akin to the grinding you mentioned.

Definitely calibrate the ESC and even adjust the timing to get best performance but a grinding noise is normally something physical or mechanical. Check that the motor shaft touches no other part of the plane and the same applies to the circlips that hold the motor together.

Just a few things to check, (please note that it is possible to have a motor suffering from a couple of the above conditions at the same time)

Have fun!
 

Chuppster

Active member
#8
I have the prop adapter as tight as it will go, and the grub screw was already on very tight when i checked it. The noise was happening out of the box before attached to anything, even without a prop, however now that i've calibrated the ESC the noise doesnt happen without a prop on, leading me to believe that i am simply swinging too large of a prop for this cheap thing. Thanks for the checklist though, ill be sure to keep these things in mind for future reference.
All the best!
Just be careful with that big prop, it could draw too much current at high throttle and you could end up with a smelly paper weight :-/