Could use some help diagnosing head "wobble" on N7 ...

[Chief58D]

Morning all -

I've also posted this on Helifreaks;
anxious to get this ironed out and get some more quality blade time!!

Could use some help diagnosing the head "wobble" on my N7 ~

I currently have 15 flights on the new N7.
Governor speeds (Normal / Idleup 1 / Idleup 2) are 1550 / 1850 / 1900.
Since I'm still (re) learning, I've been taking it easy on my flights, and spending the majority of my time in Normal doing basic circuits and hover practice.

Initially, there was a very slight wobble in Normal, which pretty much went away after a few flights.
Blade track & tail were very smooth. Wobble was a bit more pronounced in Idleup, but seemed to smooth out when transitioning into forward flight.

Decided to try a low hovering auto yesterday, and unfortunately I rolled the N7 on touchdown (note to self - keep the frickin' cyclic steady when touching down from an auto!! ). No apparant damage other than some dirt on the blades; checked everything out, and flew it again.

I now have a VERY slight, continuous vibration in Normal hover, with a very slight but noticeable difference in the blade track. However, when switching to Idleup 1, the vibration levels increase rather dramatically - enough that I didn't even try switching to Idleup 2. Crap! Switching back to Normal reduced the vibration levels back to where they were before switching flight modes.

So, I figure I have some teardown work ahead of me, and could REALLY use some pointers on where to begin! Keep in mind that I did not build this one - the heli team at a LHS took care of that for me - but I figure I might as well dig in and start getting my hands dirty!

Any pointers, lessons learned, etc. would definitely be appreciated -
Thanks in advance!

RR

[Jason Cummings]

Sounds like you you probably bent the spindle. Remove one of your blades and put an Allen key in the spindle bolt and turn the spindle and watch for movement in the blade grips

[Jason Cummings]

Also it wouldn't hurt to bump up your head speed while the dampeners break in. 1850-1900 would be good place to start

[Chief58D]

Appreciate the feedback, Jason -

I hope to tear into the N7 over the next night or two and start evaluating everything in detail.
Question concerning parts -

I just glanced briefly at the Synergy store, and didn't see any head components listed for the N7.
Where is the best source to get those particular components?

I would really like to get everything together & test flown in time for a heli fun fly in my home town Memorial Day weekend.

[Richard Rollins]

The best way to find parts in Matts Store is to do a search for the part number from the manual. There are many parts that are used for all the Helicopters so one part may be listed in the E7 section or any other heli that the part may be shared with the n7.

Hope this helps,

[Chief58D]

Definitely helps -

Thank-you Rick!

Randy

[Kevin Dalrymple]

Hey Chief. Always wanted to say that. What shims are in the head? If they are from the stock kit they should be 1mm. In the Synergy store you can .5 and .75 mm head shims. Put the .75 in and take the 1mm out. You will use just 1 per side between the blade grip and dampener.  Don't forget a little lube on the spindle and the dampener.
Bump up your normal mode to 1750 or higher like posted above. If you still have the wobble remove the .75 and install the .5mm shim. As the dampeners break in over time you will need a thicker shim and will have to readjust. 

[Chief58D]

Good timing -
I'm just getting ready to place a parts order!

I'm running the stock shims right now, so I'll add those shims to the list.

Thanks!

[Chief58D]

BTW -

I just created an account on the store;
How long does it generally take for the "approval pending" status to clear so I can place an order?

[Kevin Dalrymple]

Minutes.

[Chief58D]

Cool -
Appreciate the assist!

Randy

[Chief58D]

I have the shims and feathering shaft changed out (it did appear to be slightly bent), but so far everything else still appears to be aligned.

My only concern now is the vertical "play" in the main shaft (it may have always been there, but since I didn't do the original build, I hadn't really noticed  ...)

The main shaft shim is installed between the jesus bolt collar and lower bearing block, but there was still some noticeable vertical movement (estimate around 2-3mm vertical movement). I was able to "take up the slack" using the upper main shaft collar, but now there is actually a slight gap between the jesus bolt collar, shim, and top surface of lower bearing block.

Provided verything is still aligned, should this be of concern?

Thanks!

[Chris Sexton]

2-3mm is quite a bit of movement, check to be sure that the raised boss side of the collar is against the shim on the lower main bearing block. If that collar is upside-down you can have excessive movement.

[Chief58D]

Thanks Chris -
I'll go back and double-check that this evening.
I "thought" it was installed correctly, but I may have overlooked something.

Anything else I might want to check that could contribute to the vertical movement?

[Chief58D]

So I went back through everything, and it looks like the vertical play is actually only around 1.1mm, and that is with the shim installed and the lower collar oriented in the correct direction.  I couldn't find anything out of alignment anywhere else.

So, it looks like my options might now be -
1) Just live with it "as is"
2) Take up the slack using the upper collar; this leaves the lower shim "floating"
3) Stack additional shims between the lower main bearing block and jesus bolt collar.

Suggestions / other options I haven't considered?