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Spirit 2 - Goblin Nitro - Head oscillation.
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Author:  Jay23 [ Sun 19. Jan 2020 18:57:08 ]
Post subject:  Spirit 2 - Goblin Nitro - Head oscillation.
Hello,

I having a real issue with the head on my Goblin Nitro shaking violently when setting the head speed to anything over 1450rpm. When i engage the gov to set the head speed to 1900rpm the head sakes violenty, it does this at any rpm faster than 1450, here is a list of things i have tried:

Different blades - no diffence
different ball positions on the servos horns - no difference
new head dampeners (b) - no difference
adjusting the head gain by 5 points each time until its at its lowest setting - no diffenece
adjusting the tail gain and gain multiplier - no diffence
adjusting cyclic feed forward - no difference
adjusting cyclic rotation speed - no difference
adjusting cyclic sensitivity - no difference
setting 6 degree cyclic to 5.5 degree - no difference
running the engine leaner - no difference

i have stripped the transmition down and checked everything, the mechanics on the heli are sound, cyclics are new and set correctly on the fbl. The spirit to fixed using 1 3m pad as per manual.

Please please help, all my other helis are running spirit pro, im wondering if this spirit 2 unit has a fault.

Thanks, Jay
Author:  ZeXx86 [ Sun 19. Jan 2020 20:15:06 ]
Post subject:  Re: Spiri 2 - Goblin Nitro - Head oscillation.
It will very likely happen with any unit.

The problem is probably in the head dampeners. Helicopter is simply oscillating on its own, which is independent of settings or FBL unit.
The only thing that could help is to change Center of Gravity downward (skids more heavy) or to change dampeners. Possibly there is a bigger play in the head.

Possibly it is also due to a servo issue - servos might pick up some noise from the ESC. Then you can also do nothing with FBL settings. Lower BEC voltage might be helpful.
BK servos? :)
Author:  Jay23 [ Sun 19. Jan 2020 21:23:23 ]
Post subject:  Re: Spiri 2 - Goblin Nitro - Head oscillation.
Thankyou for such a quick response,

I have totally re-built the head, the dampeners are new and the standard ones that came with the original kit, i replaced the old ones which were very hard Lynx dampeners, i have also shimmed the head as per the Goblin manual with 1, 1mm and 1, 0.2mm shim on either side,i have checked the trust bearings, re-greased them and installed them back correctly, there is nothing wrong with the head i can assure you.

I am not using an esc i have a 2s Lipo plugged diectly into the spirit so there will be no noise from any esc, this is a NITRO helicopter. The servos are all new, they are high voltage GWD servos powered at 7.4v.

Is there anything else that i can check? I'm not new to setting up and flying heli's, i have been through the machine from top to bottom and its perfect.

Thank you Jay
Author:  ZeXx86 [ Fri 24. Jan 2020 9:32:12 ]
Post subject:  Re: Spirit 2 - Goblin Nitro - Head oscillation.
Hi,

could you please check what will happen when there are no main blades and motor is running at the head speed that is problematic?
Is there some servo movement visible? All servos should be steady even when motor is running.
Author:  Jay23 [ Sat 13. Jun 2020 9:55:25 ]
Post subject:  Re: Spirit 2 - Goblin Nitro - Head oscillation.
An update to my post, finally got the Heli flying, it turns out one of my servos wasn't centering properly and causing the head oscillation, I tried a Vbar and had the same setup problems.
So for those who might be getting the same problem double check your servo centering!
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