where is the wobble ?

[chansen1953]

Hi guys, went out to LMAC filed yesterday to maiden my new HK600..

I spend quite a few hours getting the min/max pitch and alignment right yesterday, and I had already spun her up with no blades .. and no vibrations.
I did have one blade out of balance, but I added a few wraps of insulation tape, and it seems pretty close. Main shaft is true ( an align one, as the HK shaft came "pre-bent" out of the box !!)

However, when I got out to the field and spun her up.. she had a bad vibration, and it didn't reduce even when I increased the rpm...

I shut her down and flew my other 600.. so no real issue with the day..

I am about to sit down and try and find the problem.. but just thought I might ask for a tip as to the other areas to look at as the source of the vibrations...

The only thing I do know about that is a little suspect, is the RH cyclic servo had a little bit of gear backlash.. you could move the servo arm a few mm at the tip before the gears meshed.. I will change the servo out first ( MG996R ) as it did cause some slop in the swash, which made it more difficult to get the alignment spot-on...

at the price of these servos, it is hardly worth chasing up another set of gears ..

is this servo backlash likely to cause the severe vibration/wobbles ??

Can the main shaft have a wobble that is not detectable by sight/spin up without blade

[Tomstoy2]

Your servo is your problem.

[chansen1953]

you're right tom, just changed it and at 1/2 power with blades on, in the houyse.. it is pretty steady..
so .. brand new servos sometimes come with built-in backlash !!

[Tomstoy2]

Pretty sure if you open it up you will find one missing tooth on a gear somewhere.