The flying monkeys got me...

Helis and fixed wing

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IRCHA 4345
AMA Intro Pilot Instructor

Tuesday, May 20, 2014

Don't Give Up!

I had tossed the EXI 450 Sport into the parts bin en mass after getting fed up with trying to solve the vibration problem. Last time I took it to the field it freaked itself out just sitting on the ground as it vibrated itself into havoc. I had cleaned up all the vibrations, but once the tail blades went on it vibrated finely and ended up creating gyro oscillations which lead to odd rudder inputs from the gyro.  I just could not solve the problem. So I hated on the heli and put it in the bin.

I also can't stand an unsolved problem, so today, after a couple of days of walking past the bin with agita every time I saw the heli,  I pulled it out and worked on isolating the gyro. Nothing really worked well. And then I remembered seeing a drawing on an Align gyro manual that showed various possible positions for the gyro, and I remember one in front of the main shaft rather than the traditional aft of the main shaft. This would move the gyro away from the finely vibrating boom and tail. I also changed the tail blades (weight balanced against one another) and new main blades, I changed the main and feathering shafts, and improved smoothness of movement in the tail assembly. This this is as clean vibration wise as I can possibly make it.

So, in main blades off spin ups the rudder servo was still and not being affected by vibration! I had to modify the canopy to allow the gyro forward. Tomorrow I will try hovering and possibly flying it!



If this doesn't work its back in the parts bin!

UPDATE: POS... into the parts bin. Still shaking itself apart. No idea why, done trying to find out. I have 3 other 450's to spend my time on.

UPDATE-UPDATE: So... I got to thinking, maybe its the Align 780 gyro? I threw an Assan GA250 gyro I had in the box on her and spun her up. She still has a very high freq vibration, but the gyro held and she didn't wag, nor did she shake herself apart! I plan to see what happens at the field on Memorial Day. I did order a $30 Hobby King 450 Pro V2 chassis to replace her though.

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