oscillating tail

[ajadda]

Hi,

I have an old micro heli 120 size with a µSpirit. The heli has main components from a Walkera V120D05. It has 4 servos and a belt, as bigger helis do. Vibrationlevel is relatively high as expected for such small helis, it is somewhere between 50 and 70%, which is not fine but should be OK. On a T-Rex 250 I had even more vibrations without any problems.

The problem is that the rudder is oscillating starting with a small amplitude immediately getting bigger and bigger, regardless of the rudder gain. Even with a gain of zero the oscillation starts when I try to lift off. With a zero gain the oscillation starts maybe 1 or 2 seconds later as when I use a higher gain. Also I played around with the settings of pirouette consistency, rudder delay and dynamic and even revomix. What ever I tried even desperately from min to max values in various combinations of the values, the only difference was that the oscillation starts a second earlier or later or the oscillation became a bit slower. It just looks like the µSpirit is acting too fast.

Before I used the µSpirit I had an old µRondo which worked fine.

What I tried so far:
- Exchanged all bearings.
- Exchanged the main shaft including rotorhead.
- Exchanged the complete tail mechanics including shaft and belt.
- Exchanged the rudder servo.
- Tried different main- and tailblades.
- Finally reset the µSpirit and the profile in the transmitter to exclude possible misconfiguration.

As the exchange of mechanics and trying different values from min to max I only could barely reduce the oscillation a very little bit, I was thinking if it was possible to check the sensor functionality of the Spirit.
Or this size of heli just too small for the µSpirit?

Regards,
Alexander

[ajadda]

no idea?

may 120 size heli be too small for the µSpirit?

[ZeXx86]

Hello,

For sure it can work with any helicopter size. For unit it does not matter how big or small model is.
What tail servo is used?
It might require to set Rudder Delay to higher number and Pirouette Consistency to low value - around 130.
Maybe you are using Bank Switching and some parameters were actually not set.

Have you tried to run model without main blades and observe tail servo?

Are you sure that the unit is holding firmly at the model?

[ajadda]

Hi,

thanks for your reply!

the tail servo ist an E-flite DS35 #EFLRDS35 and was a Walkera WK-03-4 with the same result.

I assumed the servo was too fast, so I reduced the Rudder Delay to Zero, but I will give a try with an higher number.

Pirouette Consistency was already reduced step by step down to the lowest number of 50 which did not help.

There is no bank switching used.

I don’t remember the behaviour without mainblades anymore, there were too many changes and tries... I will check it again soon.

The µSpirit is definitely holding firmly at the model, but that makes me think about the pcb inside the housing, maybe this is able to move?!?

Regards,
Alexander

[ajadda]

Hello,

It might require to set Rudder Delay to higher number and Pirouette Consistency to low value - around 130.
Maybe you are using Bank Switching and some parameters were actually not set.

Have you tried to run model without main blades and observe tail servo?

Are you sure that the unit is holding firmly at the model?

Hi,

I now tried different values of Rudder Delay up to the maximum of 30, but after a short while the tail is oscillating again.
Also lowering the Pirouette Consistency to 130 and even lower did not solve the problem.

Testing without main blades also shows the same symptoms and I also now used a new double sided tape 3M to stick the µSpirit to its place. - It is still the same...

No idea, what else I could try to solve the problem...

Any advice is highly appreciated!

Regards,
Alexander

[ZeXx86]

Could you by chance measure vibrations with Spectrum Analysis at Z axis without main blades? Plot from the measurement can help a lot.
Have you tried to connect some other servo to observe behavior at the bench?

No, microSpirit electronics can't be loose if you have not opened it in some way.

[ajadda]

Hi,

here is the requested plot of the Z axis without mainblades:

Yes, I tested another servo with the same result. The servos were different ones.
- E-flite DS35 #EFLRDS35
and
- Walkera WK-03-4

The µSpirit was not opened at any time.

Regards,
Alexander

[ZeXx86]

It looks all good. I can check your settings file. Can you share it too?
I guess that when you have vibration analysis On and you start the motor, tail servo is steady all the time, correct?

[ajadda]

Hi,

here is the settings file:

cHP120B.4ds

(255 Bytes) Downloaded 85 times

Yes, on the bench while vibration analysis the tail servo is steady all the time.

Regards,
Alexander

[ZeXx86]

Thanks. Have you tried to increase the servo frequency?
I believe it can handle at least 150Hz. Motor type is coreless so it should handle even 333Hz in theory.
Trying to put ball linkage closer the center at the servo arm can help too.