Understanding the VBar EVO Vibration Analysis Tool
Posted by Razmo
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June 13, 2024 10:12AM |
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June 14, 2024 09:28AM |
Hi,
OK ... Motor, Main- and Tail-Rotor are calculated/approximated RPM, to help you evaluate from where (which frequency) vibration originate, when you look at the graph. Looks as if that selection is only available in standard.
You can always de-/select Pro, at vstabi.info/devices, Apps, for that serial no., if you want the other screen.
Works almost everywhere, whenever your transmitter has a WiFi (personal hotspot when at the field).
Still, the basics apply: a main rotor rotating at 2,000 rpm / 60 seconds will peak at 33 Hz and change (very low frequency, very little effect but may cause wobbles), while a tail rotor rotating at 2,000 rpm * 4.5 ratio (give or take) / 60 seconds will peak at 150 Hz (these are vibrations which may cause the tail fin to become blurry, or the tail boom supports), and a motor running at say 12s * 37 V * 450 kV will peak at 333 Hz (these are vibrations which you rather feel or hear already, than see). Oh, by the way, 333 Hz sounds like a servo refresh rate ... might that interfere somehow, under adverse circumstances? Hm ...
In Pro, you can also select the sensor element you want to check (Aileron is default, it's where you see most, by experience), to compare.
You can write a graph, too, which tells you the maximum G loads and maximum overall vibration levels, throughout a flight.
And you can see the detailed live values from the accelerometers, like their orientation (-1 G pointing to the center of earth, 0 G when a sensor is on knife-edge, neither positive nor negative Gs pulling), and the noise level. If the noise level exceeds 16 Gs on a NEO, for example, the red (!) will flash, indicating that the limits of the more precise, more sensitive IMU are exceeded. For the high range sensor (less precise, more robust), this indication is not deemed necessary, because 200 Gs should be way out of range. Still, you will see high values (100+ Gs, 160 Gs were measured on a 1st gen Kraken, 204 (!) Gs are a sad record on a nitro) in the graph. If so, this should trigger your internal alarm
Such high noise values will also show when higher vibration frequencies occur (from the gearbox, teeth clicking with multiple kW power, and only in one direction; you can easily see 2.some kHz to even higher, on multi stage gearboxes—these are frequencies you definitely hear as a whine, and they can even be trasmitted over the air, like, if a loudspeaker with sufficient sound pressure would point at such a sensor, the sensor would react the same way, even if it would not 'feel' the vibration through a physical connection). So, they are a good indicator for such, as a source.
Lastly, the log can already help: if it's full of high or extreme vibration warnings, even if you don't push the heli and it's drive system to the limits all the time, it's an indication that the overall vibration levels measured by the sensors inside the VBar are off.
This may or may not cause troubles, drift, tail kicks or sudden swash plate deflections, Rescue going the wrong way.
Please also refer to (?) as well as to this.
—Eddi
Born to fly ...
forced to work.
Edited 1 time(s). Last edit at 06/14/2024 09:28AM by Eddi E. aus G..
OK ... Motor, Main- and Tail-Rotor are calculated/approximated RPM, to help you evaluate from where (which frequency) vibration originate, when you look at the graph. Looks as if that selection is only available in standard.
You can always de-/select Pro, at vstabi.info/devices, Apps, for that serial no., if you want the other screen.
Works almost everywhere, whenever your transmitter has a WiFi (personal hotspot when at the field).
Still, the basics apply: a main rotor rotating at 2,000 rpm / 60 seconds will peak at 33 Hz and change (very low frequency, very little effect but may cause wobbles), while a tail rotor rotating at 2,000 rpm * 4.5 ratio (give or take) / 60 seconds will peak at 150 Hz (these are vibrations which may cause the tail fin to become blurry, or the tail boom supports), and a motor running at say 12s * 37 V * 450 kV will peak at 333 Hz (these are vibrations which you rather feel or hear already, than see). Oh, by the way, 333 Hz sounds like a servo refresh rate ... might that interfere somehow, under adverse circumstances? Hm ...
In Pro, you can also select the sensor element you want to check (Aileron is default, it's where you see most, by experience), to compare.
You can write a graph, too, which tells you the maximum G loads and maximum overall vibration levels, throughout a flight.
And you can see the detailed live values from the accelerometers, like their orientation (-1 G pointing to the center of earth, 0 G when a sensor is on knife-edge, neither positive nor negative Gs pulling), and the noise level. If the noise level exceeds 16 Gs on a NEO, for example, the red (!) will flash, indicating that the limits of the more precise, more sensitive IMU are exceeded. For the high range sensor (less precise, more robust), this indication is not deemed necessary, because 200 Gs should be way out of range. Still, you will see high values (100+ Gs, 160 Gs were measured on a 1st gen Kraken, 204 (!) Gs are a sad record on a nitro) in the graph. If so, this should trigger your internal alarm
Such high noise values will also show when higher vibration frequencies occur (from the gearbox, teeth clicking with multiple kW power, and only in one direction; you can easily see 2.some kHz to even higher, on multi stage gearboxes—these are frequencies you definitely hear as a whine, and they can even be trasmitted over the air, like, if a loudspeaker with sufficient sound pressure would point at such a sensor, the sensor would react the same way, even if it would not 'feel' the vibration through a physical connection). So, they are a good indicator for such, as a source.
Lastly, the log can already help: if it's full of high or extreme vibration warnings, even if you don't push the heli and it's drive system to the limits all the time, it's an indication that the overall vibration levels measured by the sensors inside the VBar are off.
This may or may not cause troubles, drift, tail kicks or sudden swash plate deflections, Rescue going the wrong way.
Please also refer to (?) as well as to this.
—Eddi
Born to fly ...
forced to work.
Edited 1 time(s). Last edit at 06/14/2024 09:28AM by Eddi E. aus G..
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June 17, 2024 09:25AM |
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June 21, 2024 09:15AM |
Hi Raz,
Pro came as a freebee for the first batch of VBar Control EVO, which had the distance issue between the main board and the loudspeaker
Right, the basic vibration analysis (live value, max. value) is always there, also in Express. The standard graphical display comes with Pro on the flybarless. And the extensive version is part of the Pro-/Value-Pack, for VBar Control Touch and EVO.
You're actually the first who's trying to get to the bottom of it
I guess if there had been more questions about it, there'd be more info, also in the hive mind, and maybe also a video or a how-to.
The standard tool is actually also questioned very rarely.
—Eddi
Born to fly ...
forced to work.
Pro came as a freebee for the first batch of VBar Control EVO, which had the distance issue between the main board and the loudspeaker
Right, the basic vibration analysis (live value, max. value) is always there, also in Express. The standard graphical display comes with Pro on the flybarless. And the extensive version is part of the Pro-/Value-Pack, for VBar Control Touch and EVO.
You're actually the first who's trying to get to the bottom of it
I guess if there had been more questions about it, there'd be more info, also in the hive mind, and maybe also a video or a how-to.
The standard tool is actually also questioned very rarely.
—Eddi
Born to fly ...
forced to work.
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July 23, 2026 10:50AM |
Hi Marcos,
the vibration analysis shows peaks at frequencies from 0...500 Hz or rpm equivalent from 0...30.000 Hz.
Means, you usually have three sources:
. engine rpm, usually in the 13,000-16,000 1/min range
. main rotor rpm, depending on the model, 1,500-2,100 1/min (?)
. tail rotor rpm, 4.5-5 times that, so 6,500-10,000 1/min (?)
So the highest peak is usually the engine rpm.
Now if that (or any) peak is unusually high (there's a horizontal threshold line which helps), there's something which can be improved.
All the parts rotating at the same rpm (motor, clutch, pinion, gear mesh there) are suspect, obviously.
Another thing I learned from Kyle Dahl some time ago was that the pipe and/or the gasket (also affecting it's resonance) can also have quite an impact ... but I'm so non-nitro
that I can't be of much more help here.
Best,
Eddi
Born to fly ...
forced to work.
the vibration analysis shows peaks at frequencies from 0...500 Hz or rpm equivalent from 0...30.000 Hz.
Means, you usually have three sources:
. engine rpm, usually in the 13,000-16,000 1/min range
. main rotor rpm, depending on the model, 1,500-2,100 1/min (?)
. tail rotor rpm, 4.5-5 times that, so 6,500-10,000 1/min (?)
So the highest peak is usually the engine rpm.
Now if that (or any) peak is unusually high (there's a horizontal threshold line which helps), there's something which can be improved.
All the parts rotating at the same rpm (motor, clutch, pinion, gear mesh there) are suspect, obviously.
Another thing I learned from Kyle Dahl some time ago was that the pipe and/or the gasket (also affecting it's resonance) can also have quite an impact ... but I'm so non-nitro
that I can't be of much more help here.
Best,
Eddi
Born to fly ...
forced to work.
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