Strange noise

[Rodney Kirstine]

That's the one bearing on the main shaft that I didn't think about, either.

[TJ Present]

After much checking and pulling apart the motor to check the bearings, turns out the problem was not enough gear lash between the pinion and main gear.  I thought I had enough but the main gear has a high spot (or the pinion does and it would create resistance and at speed a vibration. 

I also re-checked that the pinion end rests on the pinion support bearing.  That may have been a secondary contributor to the problem.  Not sure though.

So glad to have a smooth running heli at last.

Tom

[TJ Present]

On Saturday at the field, I still had the noise problem even though in ground testing it had been eliminated.  After much review with a flying buddy who is a professional aircraft mechanic here's what we found:

The main gear was pulling up under load on the pinion side (as a helical cut gear would normally do) and because there was extremely little gap between the main gear and the carbon frames the back of the main gear was grinding on the frames.  We found carbon-dust which gave it away.  In addition;

1) My main gear is not machined the same way as my friend's E7 (top bevel was not cut on mine)
So, machining error or so it appears.

2) I had never reversed the main gear hub as Matt Botos has advised on the Synergy forum. I just never saw this forum posting.  The illustration in the manual is apparently wrong and the gear was assembled incorrectly at the factory. Botos says on the Synergy forum that the orientation of the hub "may appear differently"   Mine had the round bolt heads facing up.  I switched this and of course changed the  direction of the one-way sleeve so the one-way would still operate correctly.  This seemed to provide a somewhat larger gap between the main and the frames.

3)  Adjusted the gear-lash to two Post-It note thickness (probably about 500 thousands).

4) It should also be noted that my Main gear measures thicker than my friend's. This may have contributed.

The problem is now completely eliminated although there is still some gear noise from the machining error.  I believe my kit was a first-run kit and obviously some changes were made.  I will eventually replace the main gear and the pinion, but they are running fine for now.

[Chris Sexton]

Wow sounds like a fun day at the field there! Glad you got it sorted.  It should be noted that he OWB Hub itself is completely universal. You might have been able to just move the delrin shims around to get more gap, but it certainly sounds like you have a bad cut on a 1st generation main gear. The gears were changed a bit.

[Rodney Kirstine]

Glad you got yours all sorted!

Since I destroyed my main gear this weekend right at takeoff, I'll have to wait to see how mine sounds after I get it put back together.

[TJ Present]

Matt was kind enough to review my problem and what came out of it is that there were two issues.

1) Main gear (which is a current production gear with holes in it and no ribs) was not spaced properly.  I had
two black delrin shims above the auto-hub and below the spur-gear hub.  Matt had me move one shim to below the auto hub (captured by the auto-hub sleeve).  This moved the gear up and gave me adequate clearance from
the frames.  I'm told this is the correct spacing for new style gears (with round holes) Older solid ribbed gears need two shims above the auto-hub (and below the spur gear).

2) Changed to a lower gain level (also at Matt's suggestion) on the Castle ESC governor which got rid of the chatter.  This was my main problem and the lowered governor gain eliminated it.

The problem has now been definitively eliminated.  So, yea for Synergy customer service.

[Greg Jackson]

Also, how many flights are on that motor?  If it isn't the bearings other shave listed try the motor bearings or make sure the pinion is seated correctly.

[Rodney Kirstine]

I finally got my E7 flying again, after the radio switch.  I went through everything.  I got rid of the strange noise but now I have a pretty nasty head wobble during slow descents. Haven't had much time to try and chase it down. I lowered my governor gain and cyclic gain quite a bit. I think it is a mechanical issue so I'm going to tear into it again.

[flyalan]

Rodney
I assume the head bolts are tight and the head is solid on the bench? Easy thing to miss.

Cheers
Alan

[Rodney Kirstine]

I'm not sure if this is the cause but when I took it apart I found that I had the main gear, owb, auto hub stack-up wrong.  When I put it together last night, I wasn't looking at the manual and I put two shims on the auto hub but I put them on the bottom of the main gear.  It was binding and wasn't turning freely so I took one out.  Anyway, I put two shims back in, tonight, but I put them on top of the main gear where they're supposed to be.

I did also check out the head, thoroughly.