Trex 450L Dominator Vibration Issues

[mewsikman]

Hey guys,

After a long break of about 4 years due to perusing me gaining my commercial fixed wing and helicopter licences, I have decided to finally come back into the sport.

During those 4 years my heli's started to decay a little so for the past couple of weeks I've been slowly rebuilding them with new bearings etc, at the same time I decided to treat myself to a new Dx9 and a Trex 450L dominator 6s kit but swop out the motor for the 3s

Anyway... After a couple of days building and getting use to a flybarless system it was ready for hovering. First impressions that it was quite stable for a 450 size, blades were tracking perfectly and the tail was solid after a little reduction of gyro gain from 75% to 65%. It was then that I noticed that the skids were showing a small vibration that had got a little bigger, kind of like the old crack manoeuvres. This was happening with a flat 80% throttle curve but when I increased it up to a flat 100% throttle curve it seemed to go

I wasn't impressed when I hit the throttle hold and got it on the deck that the swash decided to go hard left tipping it over. Fortunately there was no damage apart from a tiny knick at the back of one of the blades.


I am using all the stock electrics including the Gpro with one Spektrum satellite.

I can't for some reason upload pics on here, so here is a link to them - https://www.flickr.com/gp/66876906@N06/aSkLWu

Any advice for a virgin flybarless flyer would be much appreciated

Cheers
Alex

[Gyropilot]

Alex,

Any estimates of rotor rpms at 80% throttle and 100% throttle?

Could you have been seeing cyclic wobbles?

John

[mewsikman]

Hi John,

The rotor disk looks perfectly stable. Ive increased the rotor rpm to a flat 85% and that seems to have calmed it down. I think it might have been due to the gyro gain being too high still.

I don't have a tach anymore so I can't get exact RRPM.

I had a slightly worrying thing happen with the main cyclic servos, when you held full right,left,up or down cyclic and released it back to centre then moved the pitch up and down the servo which was just held down would lag enough to tilt the swash by a massive amount

[alyon187]

As for the shakes... Cyclic gain too high? Or How tight are your blades?

[mewsikman]

No I'm running the Gpro with V1.2.

I'll have a look at what my Cyclic gain is set at. I just clicked on the beginner setup as I knew I'd be rusty

[alyon187]

See how tight or loose your blades are. Maybe try lowering your cyclic gain a few points and see if it improves. I think 80 is towards the low end for dfc so maybe a flat 85% could get you out of this harmonic vibe that you maybe getting. Sometimes just raising it a few points will do the trick.

[mewsikman]

Great stuff, thanks for the advice. Will try it out tomorrow.

Any idea what the cyclic servos are doing that I posted about? Or is that completely normal?

Cheers

[alyon187]

Was this in flight or on the bench?

[mewsikman]

On the bench

[RC/DC_5000]

You can't play around with the servos on the ground and expect them to act predictably. The flight system algorithms are engaged and making compensations. So its trying to "fly".

Its going to act very strangely on the ground. Unless you plug it into the software and go into setup mode. Then the swashplate will move directly without any compensations.

This also goes for your pitch. You can set 12 degrees of pitch in the software.. and on the ground.. it could go all the way up to 14 degrees. Its looking for a reaction. And when it doesn't get one, it can do strange things.

[alyon187]

+1

[mewsikman]

Great thank you RC/DC and alyon.

Sorry for the stupid questions, it's just been a little while and plus this is the first Flybarless system I have ever owned.

[alyon187]

Not stupid, im newer at this then you are. If you dont ask the questions then youll never get anywhere.