LOGO 690 vibrations

[doujoh]

I am having trouble with my 690. I have broken off one of the screws holding the tail boom support brace twice, in the chassi.

I flew with the vibration analyzer on today but forgot the ability to take screen shots.

The vibes are in the 50-70Hz range. While doing piros one way the vibes are the same but doing them the other way takes the vibes down quite a bit. All this at 1400 rpm. When going up to 1600 the vibes are lower and at 1800 almost gone.

Does anyone have any ideas what is wrong? And where to start looking?

[Johnny31297]

Hz=Cycles per second. Hz*60=rpm

50Hz*60s=3000rpm
70Hz*60s=4200rpm

Now you're running 1400rpm on your main rotor.
Motor rpm: 1400*(106/15)=9893.33rpm
Tail rpm: 1400*(81/17)=6670.59rpm.

None of those match your vibration frequency. I'd suggest measuring again.

At 1400rpm your main frequencies in the airframe are:
Main rotor: 1400/60= 23.33Hz
Tail rotor: 1400*(81/17)/60= 111.17Hz
Motor: 1400*(106/15)/60= 164.88Hz

Good luck.

[doujoh]

Is there any way to see the exact Hz?

[oliver1071]

Wait you say during piros are you sure you even have a problem?
I'm hitting 2100 on a heli that hovers at 300vibes and doesn't hit extreme vibs in the vbar log. When people post their vibe numbers they're talking about in a hover not while flying.

[doujoh]

My log is full of vibration warnings, and I can see them...

[oliver1071]

post your log

[doujoh]

The log doesnt say anything other that different levels of vibrations

[Johnny31297]

You can take a screenshot and count pixels to the peak, assuming the scale is linear.

[cbrkhan]

Originally Posted by doujoh

I have broken off one of the screws holding the tail boom support brace twice, in the chassi.

Happened to me ... turns out perfectly healthy looking main blades were out of balance quite a bit.

[doujoh]

I did a quick testhover today and i have not done anything to it, it was just made to see where the vibrations are.