stunthanger.com
Electric Stunt => Gettin all AMP'ed up! => Topic started by: Robert-Jan on April 14, 2011, 01:33:16 PM
-
Dear all,
I just lost my flying field.
Ok I was flying without permission.
But the man in charge told me I was making to much noise.
The birds hat problems with the noise.
I am flying a AXI 2826-10.
To be honest it makes a lot of noise.
I was doing some measurement in house without prop but I needed earplugs.
The motor is mounted on a Cardinal so the motor is in the open.
Has anybody experience with noise reduction?
Is for instance a Scorpion a silent motor?
Please help
Greetings Robert-Jan
-
Usually when trying to reduce noise, you go to a lower RPM. I would think that most of the noise is prop noise and not motor noise.
-
What kind of noise is it? Bearing (just strong metal noise)? Resonation of bell (high frequency squeek)? Resonation with model frame (proximately frequency of the motor rotation)? or isnt it PWM noise?
As fas as I know, healthy AXI is one of most silent motors, certainly more silent that scorpion, but if you hit bell frequency, or model frame frequency, the it can be noisy, especially if bearing is already gone and shaft has already some free play.
-
I had the same thing happen - but on a scorpion motor - i had to retard the timing (thanks Dean Pappas) to get get the noise down.
Use the settings in Norm Whittles cookbook and you should be good to go. Prop noise is another consideration
my E-Legacy still sounds like an IC model -but I think it is the airframe reverberating more tha anything else
-
Thanks for your very fast respond.
The motor testing indoor was only with a very small prop (for measuring the RPM).
And even without prop it makes the same noise.
The frequency is a high frequency squeak.
I tried different frequency’s but this did not help.
The noise was there from the beginning.
There is some vibration but it is hard to quantify it.
My colleges pilots said eh electric is as noisy as IC.
I will try the different timings.
Greetings Robert-Jan.
-
I made a video.
In the back ground you can hear the radio it rather loud.
With the motor running the radio disappears completely.
http://www.youtube.com/watch?v=lhGeGC9hcKY
An other video were I put my finger on the motor.
http://www.youtube.com/watch?v=zaTpwV4R2aw
I tried differed settings:
Governor gain
motor timing
forward / reverse
PWM Rate
But nothing helped.
-
What's interesting in the video is that it starts at a low rpm and continues into full rpm. ??? Un-mount the motor - mount it to a test stand board and see if the noise is the same. Also if you have a servo tester you can put in place of your timer and run the motor at all speeds from 0 rpm to full rpm. If the noise is at a very low rpm I say you have a bad motor. If at a high rpm it could be cooling hole wind noise or bad bearing.
:! H^^
-
What kind of a motor mount do you have there? Looks metal.
As John Rist says, try mounting it on a wooden mount. Then you'll know if it is the mount causing the loud whine or not.
Searching youtube for "AXI 2826/10" finds a variety of videos and nothing I found is as loud as yours.
-
Today I did some testing.
I took the motor out and put it on a 3.5 mm aluminium test plate.
I tried my ICE 50 lite and the phoenix 45 both had a sweet spot at about 8500 rpm.
On the plane this looked like 9300 rpm.
So it seems to move to a lower frequency but it is still there.
I put the motor in the drill and measured the voltage:
Black Red 1,298 V
Black White 1,335 V
Red Whit 1,316 V
This is a difference of 5% is this normal.
I also changed from governor to aeroplane. But no result.
There is no play on the bearings only in the axe detection.
Greetings Robert-Jan
-
Robert-Jan
If you are axial mounted, check to see that the wheel collar on the back of the drive shaft is tight to the motor. The prop could be pulling the can forward and that could cause the noise. I have used these motors a good deal and they are normally very quiet. If you cannot localize it then I think it is most likely a bearing issue.
bob branch
-
It is sound of the bell, if it once starts, it will remain, It will probably need to replace the bearing, check if the roror is well installed on shaft and then to set proper amount of washers (you can find them on front side of front bearing).
It happen if your rpm hit the resonant frequency of the bell which is somewhere at 11 000rpm (for axi2826/xx) the bandwidth is very narrow. Do not run the motor at such rpm, it kills him, it makes that rpm range wider and wider, so it starts easier and easier.
-
Your noise problem is most likely as Igor says, a resonance problem amplified by the bell. You asked about the Scorpion motors, I have only one, a 3026-12 and it is very noisy. I've also noticed some at the R/C field that seem to be nosiy as well. My particular motor has a resonance at 7500 rpm no matter what prop I use, so I guess that there could be a problem with the drum balance. Other than that, it is a well-made motor and has good magnets and low resistance.
I've used a load of E-Max/Arrowind motors and they are very smooth and quiet.......and cheaper as well. Value for money and good performance is not always easy to achieve. Axi is a top quality motor and I have never heared a noisy one, so I suppose that you have a bad bearing or something. There are many videos on the net with Igor's model and many others that show that they are quiet motors normally.
Keith R
-
Igor and Keith thanks for the response.
The Resonance frequency of the motor is 8500 rpm. The band with is indeed narrow. I can’t understand why mine motor has such a low frequency. Is my bell heavier?
At a lower RPM there is some strange misfiring.
I opened the motor.
There was wear on the stator.
When I looked at the magnets I saw glue was spoiled over the magnets.
I removed the surplus of the grey glue.
Still there was no improvement.
I “painted” the stator with a marker to indicate if the magnets are still hitting the stator.
They didn’t seem to touch each other.
When the motor is running and I touch the bell at the side where the wires exit it feels smooth. However if it makes this screaming noise it doesn’t feel smooth any more.
I measured the bell and found that at the wire exit side there was a miss aliment of 3/10 mm.
I am still in the process of aligning it. It is now about 5/100 mm.
It was late so I could not test the motor (the children were sleeping.)
But when it was 1/10 mm there was still resonance.
Has anybody have experience with a misalignment of 3/10 mm?
@Igor I can feel no play at the bearings. But when I hear you I don’t thrust them. Can you feel or measure when they are worn out? Where can I order them ?
To be continued.
Greetings Robert-Jan
-
I afraid that if you found that magnets were at stator, then something happened during flight or so. Any misalignment will amplify that problem. I do not know how AIX, but MVVS uses dynamical balancer (like tires on car) I do not think you can balance it at home. I would say take another motor.
Just for info - the magnets are strong so typically you cannot feel radial free play on bearing, even if it is weared out. But you can make a trick, add thin washer, to those on front side of motor (stator side). It will do the bearing fit tight, and try if motor still does the same. If it change something, then you have free play on bearing. If not, bearing is probably OK. But do not run it long time, because that tightness can damage the bearing. However I would say that in this case the main problem is bent rod, or the bell.
-
Can someone confirm that these are the right bearings
1 piece 625 ZZ bearing 5x16x5
2 Pisces 685 ZZ bearing 5x11x5
I can also order stainless steal. But I think the are weaker.
Greetings Robert-Jan
-
I'll lend him one of mine to find out the cause.
-
Update
I bought a new motor.
First I let it run. The new motor ran very smooth without screaming points.
The I changed the bell’s.
The old stator with the new bell ran very smooth.
However the new stator with the old bell had the point where the motor was screaming.
My conclusion: the problem is in the bell.
The I took a tube and put a bearing in both sides. In the bearings I put the axe of the bell.
Then I put a rubber wheel in the drill and let the bell spinning very fast.
There ware no signs of vibration.
I did the same with a Chinese and it had a lot of vibration.
Next I put CA between the magnets and filled the spaces with balsa.
No result.
I have even checked the polarity of the magnets.
I don't know what to do next. I am stuck.
I think I will ask if I can buy a new bell.
I anyone has an idea please respond.
Greetings Robert-Jan
-
It is not very good idea, if you move bearings, or you exchange the rotor, you need to replace proper amount of washers. But yes, you are right, the problem is rotor, I would say to send the motor to modelmotors and ask to replace bearing and rotor, it is not so expensive. It could be good idea to mention that you are C/L flyer, they will know what to do :- )))))))))))) ... they know how we use those motors and also what is happening with the rotor during flight.
... or just write them http://www.modelmotors.cz/
-
I had some results by wrapping the external surface of the bell with two layers of electrical tape to act as a damper. Be careful to get it on evenly so as not to cause imbalance. However my application was a scale plane with a large, 1800W motor, and the motor doesn't get too warm. Running at variable speed the bell would resonate at certain points.
John
-
For what its worth I'm a e-carrier flyer and am using a AXI-2826/8 motor, jeti 70 mah ESC all pushed by a TP 65C TP4400-4s battery. I have always gotten a harmonic between 9.4k and 9.7k using an APC 10/8P propeller. I have 3 of these motors and they have all done the same thing. They do it a little less with the APC-11/8EP but always at the same RPM. Turns out that that is the RPM that is very close to the hang RPM so am going up and down through the harmonic quite a bit. At first I worried about it but after having no luck trying to get rid of it I just crank away, harmonic and all and have had no trouble so far (oldest motor is 3 years old and has around 1 hour on it). I know we use the motors differently than you do but think the harmonic is probably at or close to the same RPM. So far I'm quite happy with this motor other than the noise it makes. Eric
-
Hi all,
In the mean time I bought a new motor.
The old one I send it to AXI.
Today I got it back with a brand new rotor as guarantee.
Top service!!!
Now I have 2 motors :)
What to do with 2 motors.
Right I am building a twin.
The motors will be way to big.
But the I have a reverence point to buy new motors.
And later I will put it in a Vector.
Greetings Robert-Jan
-
Ok but is the noise gone?
???