Extra high vibration at high speed !

[lcc014]

Originally Posted by Xrayted

Always disconnect the tail rod from the tail slider when testing on the bench. The tail grips and blades will naturally go to zero pitch once spun up and stay there so you can check for vibrations safely. There will be no chance of the gryo causing the blades to move from this neutral position and cause injury to you or damage to anything around you of the heli were to do something unexpected as it did in that video

Are you running governed speeds during that test? If not, you are seriously overspending the tail with full throttle since there are no main blades on it to load things up and keep the top RPM in check.

There have been a few that have caused their tails to explode in this situation.

Thanks for the comment about the disconnect of tail control rod. I did not do that unfortunately. The shaking in the video was what I saw a couple days ago when I tested the heli on ground with main/tail blades on and Gov on.
I turned Gov off when testing it last night.
Based upon your comment, my test was not valid as shown in the video ?

Thanks.

[Xrayted]

Originally Posted by lcc014

Thanks for the comment about the disconnect of tail control rod. I did not do that unfortunately. The shaking in the video was what I saw a couple days ago when I tested the heli on ground with main/tail blades on and Gov on.
I turned Gov off when testing it last night.
Based upon your comment, my test was not valid as shown in the video ?

Thanks.

The tail was running much higher rpm than it ever would be in flight if you had the gov turned off in that test. Its a wonder it didn't fly apart on you which can be really dangerous. Its not a valid test of the actual rpms and vibes that would be seen in real flight under normal circumstances.

The higher the RPM, the less tail gain you need, and you drove the rpm through the roof in that test, so it started wagging like mad from the crazy high rpm and subsequent vibes.

You also want to place the heli on a folded towel or some type of padding when on the floor, as lots of vibes from the skids contacting the ground are transferred through the frame into the unit that it would never see in flight.

[lcc014]

Originally Posted by Xrayted

The tail was running much higher rpm than it ever would be in flight if you had the gov turned off in that test. Its a wonder it didn't fly apart on you which can be really dangerous. Its not a valid test of the actual rpms and vibes that would be seen in real flight under normal circumstances.

The higher the RPM, the less tail gain you need, and you drove the rpm through the roof in that test, so it started wagging like mad from the crazy high rpm and subsequent vibes.

You also want to place the heli on a folded towel or some type of padding when on the floor, as lots of vibes from the skids contacting the ground are transferred through the frame into the unit that it would never see in flight.

Thank you for the explanation. I was thinking about the shaking last night and thought about the setup of of Gov Store of my HW v3 50A ESC. Could it be gov did not setup properly and caused throttle went up to max. during spool up on ground or changing mode from normal to IU1 or IU2 ? That caused the violent shaking/vibration ? I will setup SK720 gov and retest again with main/tail blades on.

Thanks,

[georgi UK]

=] Well I think Tony covered the H&S aspect here in a modest polite way! YOU need to be in control of the throttle, so disable gov mode for now, hook up an RPM sensor to the SK, turn off gov mode, this will let you see the rpm's you are dealing with in playback data.

I'm setting up a scale 450 here, about 2kg holding the skids down, no tail, optical tach and standing well back with a finger on TH switch, these things can/do go wrong! Please take care.......

#4 HEX (1 min 49 sec)

[georgi UK]

Originally Posted by Tigron

If you remember, Georgi, I was one of the first user of SK720 and I was very pleased with it then. At that time it could make a wooden log with motor fly like a sky.

=] Yes Tigron you are a valued founder member, I just wish you'd asked for support here instead of soldiering on fruitlessly, or did you? so please get a log up on your own thread and lets look! georgi.

[lcc014]

Originally Posted by georgi UK

=] Well I think Tony covered the H&S aspect here in a modest polite way! YOU need to be in control of the throttle, so disable gov mode for now, hook up an RPM sensor to the SK, turn off gov mode, this will let you see the rpm's you are dealing with in playback data.

I'm setting up a scale 450 here, about 2kg holding the skids down, no tail, optical tach and standing well back with a finger on TH switch, these things can/do go wrong! Please take care.......

#4 HEX - YouTube

Georgi,

Thank you for the example of testing the head speed. I need to find the equivalent 2kg (4.4 lbs ??) weight on my 450L before testing. Also, reading rpm from SK log file via rpm sensor with governor disable, I don't realize that is possible. I will try again with the following setup:

1) Main & tail blades on
2) rpm sensor connected to SK720 BE
3) Governor disable in SK
4) More than 2kg of weight on skid.

For the logging, will vibration logging capture rpm data too ? Otherwise, which logging should I use ?

Thanks,

[georgi UK]

=] ironically your heli looked to be vibe smooth until it hit that "feeling lucky? RPM's so really playback is more advantageous here, what's your target 3000+?

Any sign of vibe resonance just kill the motor and treat it gradually log after log, much of what I'm doing in that vid if you look.....

[lcc014]

Originally Posted by georgi UK

=] ironically your heli looked to be vibe smooth until it hit that "feeling lucky? RPM's so really playback is more advantageous here, what's your target 3000+?

Any sign of vibe resonance just kill the motor and treat it gradually log after log, much of what I'm doing in that vid if you look.....

Georgi,

I am thinking of running this heli at about 3100, not higher than 3300. So, IU1 3100, IU2 3200/3300, Norm 2900.

Yes, I saw that in your video.

[Luvmyhelis]

I used to clamp my helis down to a 30lb rotating lazy susan wood base for all this. Super nice spool there Georgi! Wow.

[lcc014]

I replaced tail assembly in my heli and no more vibration at high speed with both main blades and tail blades on.
I went on to do maiden hover. Tail was wagging slowly from time to time. I would like to adjust tail gain but not able to find it in setup software.

I enclosed 2 pictures of the setup software as reference.

Any suggestion to address this slow wag is appreciated.

Thanks,

Ching-Ho Cheng

[dogbreath]

Try going to the preferences tab, select interface, and select advanced. That should free up all the greyed out areas. Dan

[lcc014]

PC setup program was in Advanced Interface mode. Which parameter(s) to change (decrease/increase) tail gain ?

Thanks.

[rickn816]

Originally Posted by lcc014

Georgi,

I am thinking of running this heli at about 3100, not higher than 3300. So, IU1 3100, IU2 3200/3300, Norm 2900.

Yes, I saw that in your video.

I apologize if I missed it earlier, but if you have not replaced the tail shaft, I suggest you give that a try.

Rick

[lcc014]

Originally Posted by rickn816

I apologize if I missed it earlier, but if you have not replaced the tail shaft, I suggest you give that a try.

Rick

I replaced the tail assembly and that fixed the vibration at high speed. So, it could be the tail shaft.
Now, I have this slow tail wag during hover. I try to change tail gain but I could not find the parameter to make change.

Thanks.

[georgi UK]

=] the way you are set up is adjusted using the channel trav. adj. end points, or they can be locked in the GUI with different gains in each bank...

[lcc014]

Originally Posted by georgi UK

=] the way you are set up is adjusted using the channel trav. adj. end points, or they can be locked in the GUI with different gains in each bank...

Georgi,

Thank you. I will use channel end points. BTW, tail gain value in GUI is same value as shown in Tx channel end point ?

[georgi UK]

=] In the view tab, check gains used in-flight....

[lcc014]

Originally Posted by georgi UK

=] In the view tab, check gains used in-flight....

Okay, I will check that and compare.

Thanks, Georgi.