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| Aileron axis vibration > 80%, causes https://www.spirit-system.com/phpBB3/viewtopic.php?f=20&t=1147 |
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| Author: | Jamisonchang [ Thu 21. Jan 2016 19:29:34 ] |
| Post subject: | Aileron axis vibration > 80%, causes |
Good Day, I recently activated the stabilization function on my 450 size heli with the Spirit. When activated, the model would list to the right (right aileron). I appreciates the sticky about imprecise rescue/stabilization- so, I made sure that the mounting was as square as possible and then did a vibration analysis The yaw, and elevator axes are < 30%. The aileron, as the sticky suggested was way off >80% and sometimes > 100%! The high magnitude vibrations were on the lower part of the spectrum making me think the main blades are the culprits? What else would make these vibrations so extreme on the aileron axis. Wow, at least I know why the stabilization has been not performing well Thanks |
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| Author: | ZeXx86 [ Thu 21. Jan 2016 19:37:42 ] |
| Post subject: | Re: Aileron axis vibration > 80%, causes |
Hello, you can save the plot and attach it here. I can then tell you what part may be wrong. |
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| Author: | Jamisonchang [ Fri 22. Jan 2016 0:35:50 ] | |||
| Post subject: | Re: Aileron axis vibration > 80%, causes | |||
Thanks as always for the great support. I have attached two y-axis files (only way I saw to capture them is [image] with produced a .png format. tell me if there another way to capture all the axes.
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| Author: | ZeXx86 [ Sat 23. Jan 2016 19:52:48 ] |
| Post subject: | Re: Aileron axis vibration > 80%, causes |
Thank you very much for the plot. Unfortunately it looks like all rotating parts are not in good condition. The biggest problem comes from the rudder (or torque tube). Mostly it is bent tail shaft or not balanced tail blades. I believe that when you unmount tail blades, it will be much better, than when you unmount blade holders it can be even better, etc. In this way, you can find what is source of the problem. Generally rudder vibrations are the worst. But I can see also spikes from main rotor head and also motor. In case of motor the problem is mostly bearing or too small distance between pinion and main gear. |
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| Author: | MyRCode [ Sat 23. Jan 2016 20:05:39 ] |
| Post subject: | Re: Aileron axis vibration > 80%, causes |
ZeXx86 wrote: Thank you very much for the plot. Unfortunately it looks like all rotating parts are not in good condition. The biggest problem comes from the rudder (or torque tube). Mostly it is bent tail shaft or not balanced tail blades. I believe that when you unmount tail blades, it will be much better, than when you unmount blade holders it can be even better, etc. In this way, you can find what is source of the problem. Generally rudder vibrations are the worst. But I can see also spikes from main rotor head and also motor. In case of motor the problem is mostly bearing or too small distance between pinion and main gear. How do you know which frequencies correspond to which parts? Is it dependent on the heli? |
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| Author: | Coco66 [ Sat 23. Jan 2016 23:28:46 ] |
| Post subject: | Re: Aileron axis vibration > 80%, causes |
I've read that the frequency of the vibration depends on the number of RPMs. So motor RPMs, headspeed, tail speed will produce vibes at different frequencies which you can calculate so to realize what part is producing vibes. I think it was explained somewhere on Helifreak (could not find it now though). |
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| Author: | MyRCode [ Sat 23. Jan 2016 23:38:13 ] |
| Post subject: | Re: Aileron axis vibration > 80%, causes |
Coco66 wrote: I've read that the frequency of the vibration depends on the number of RPMs. So motor RPMs, headspeed, tail speed will produce vibes at different frequencies which you can calculate so to realize what part is producing vibes. I think it was explained somewhere on Helifreak (could not find it now though). Come to think of it I do remember reading that thread on HF but didn't pay much attention at the time because I didn't have a vibe analyzer. |
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| Author: | Ben M [ Sun 24. Jan 2016 1:18:04 ] |
| Post subject: | Hz> 80%, causes |
Multiply the frequency in Hertz by 60 to get the corresponding rpm. The spike at approximately 45 Hz would correspond with 2700 rpm, which would probably be the headspeed. The spike at approximately 180 Hz would correspond with 10800 rpm, which would probably be the tail rotor speed. The spike at 90 Hz is probably a harmonic of the 45 Hz vibration. The spike at the far right is the motor. |
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| Author: | MyRCode [ Sun 24. Jan 2016 6:39:27 ] |
| Post subject: | Re: Aileron axis vibration > 80%, causes |
Ben M wrote: Multiply the frequency in Hertz by 60 to get the corresponding rpm. The spike at approximately 45 Hz would correspond with 2700 rpm, which would probably be the headspeed. The spike at approximately 180 Hz would correspond with 10800 rpm, which would probably be the tail rotor speed. The spike at 90 Hz is probably a harmonic of the 45 Hz vibration. The spike at the far right is the motor. Thanks Sent from my Nexus 7 using Tapatalk |
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| Author: | Coco66 [ Sun 24. Jan 2016 12:23:29 ] |
| Post subject: | Re: Hz> 80%, causes |
Ben M wrote: Multiply the frequency in Hertz by 60 to get the corresponding rpm. The spike at approximately 45 Hz would correspond with 2700 rpm, which would probably be the headspeed. The spike at approximately 180 Hz would correspond with 10800 rpm, which would probably be the tail rotor speed. The spike at 90 Hz is probably a harmonic of the 45 Hz vibration. The spike at the far right is the motor. Thanks! Very very useful info! |
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