Hunting Vibes On my 500 ESP FBL

[Lanman]

Hey all,
I've been chasing bad vibes on my 500 ESP FBL. It's been driving me nuts. It vibrates so much at times the skids would be a blur. There was also a spot in the rpm range during spool up that would shake the heli even more.

I have been all over this thing adjusting gear mesh, changing bearings, changing bearings again, three different tail assemblies, feathering shaft, dampers, head block, 2 main shafts, playing with the torque of various screws. New motor. New gears all the way around. New OWB. New TT. Best I could ever do was make it less bad but never able to make it right.

Tonight I believe I found the problem. One of those "I'll try this and see what happens". I removed the vertical stabilizer and the vibes were completely gone. It wasn't just an improvement. It was perfect. The stabilizer on this heli is a Fusuno fiberglass aftermarket part which is far more flexible than a carbon fiber stabilizer. I'm guessing it's flexible enough to produce a harmonic vibration and amplify the normal vibes many times over. I'll I need to get a carbon fiber vertical stab to test this theory. With the stabilizer installed, placing a screwdriver on the tail boom is like doing a drum roll. Without the stabilizer installed the screwdriver will sit on the boom quietly. It also spools up very smooth without the stabilizer installed.

Anyone experience anything like this before?
Thanks.

[RV_7A]

I would remove the pinion gear and spin up the motor by itself. See if you can feel ANY vibration. Align motors at times can be the cause. A new FBL heli should not have any vibrations unless something inadvertently is loose.


Jeff B

[Larry227]

I found the same thing when I was using the extra long version of the Fusuno stabilizer.
What also helps is do some trial and error tail blade balancing. I use about a 10mm piece of tape on a tail blade. If the vibes get worse put it on the other blade and try it. Once you find the blade that needs it then you can play with how much tape makes it better or worse.
99% of vibes on mine always comes from the tail.