How to tell if thrust bearings were assembled backwards?

[curmudgeon]

I had a really tough time removing the screws off the spindle shaft.  I ended up using a mini torch and T-type 5mm hex wrenches.  It is the next day and my fingers are still hurting.  I am very happy that the dampers survived the torching.

I did not remove or inspected the thrust bearings.  Although I was able to remove the inner radial bearing, I was not easily able to remove the outer radial bearing and thrust bearings.  I felt that if I kept on trying to remove them, I would end up destroying them.  Also, the ability to grease the thrust bearings via the "Grease Port" influenced my decision to quit trying to get those thrust bearings off.  The head is now re-assembled and greased.  The grips move about the spindle shaft butter smooth with no slop.

Question:
Since I did not remove or inspected the thrust bearings, is there a way to test if the washers were installed correctly (large ID in/small ID out) and open race facing inward?  I assume that the Synergy folks went through the effort to ensure that these parts were installed correctly, but I would like to know if there is a way to test either at the bench or during the maiden flight.  I pulled on both grips and rotated them about the spindle shaft, and they rotate butter smooth, but I do not know if this is a sufficient test.

[Rodney Kirstine]

They will wobble on the shaft if the large ID thrust bearing is installed on the outside.  Since there's no slop in yours, it sounds like they installed correctly.

[hardsy]

One of my thrust bearings was installed incorrectly.

Im glad i spent the 3 hours to disassemble the head lol

[RichL]

This is the trick to removing the bearings from the blade grips is heat.  About two seconds with a torch or you can place them in the oven at about 350 degrees for about 5 minutes.  Once heated just tap the blade grip on a block of wood or something similar and the bearings will fall out.  If you have difficulty reinstalling the bearings place them in a zip lock bag and put them in the freezer for about 30 minutes, the bearings will easily slide into place.


Rich

[curmudgeon]

Let's say I take the head apart to include the thrust bearings.  Then I put it back together.  I assembled the thrust bearings backwards, but did not realize it at the time.

(1) What would be the detrimental effect of installing the thrust bearings backwards?
(2) When someone is checking someone else's set up, is there a way to tell if the thrust bearings were installed incorrectly without taking the head apart?

[RichL]

The effect of installing the thrust bearings backwards would be binding in the blade grips but, this would occur only under load.  If you were to fly this way the problem would show its self as vibration in the head (I'm not advocating trying this, with enough vibration your FBL unit will respond erratically and you could loose you heli.)  along with a mushy feel in the collective response (due to binding).  Detection while on the bench will be difficult but, there will be a very slight wobble around center toward the rear (main shaft side) of the blade grip.  Best advice is inspect them visually and verify the sizes using calipers.


Rich

[Greg Jackson]

Matt made a recommendation that my thrust bearings in the tail might be backwards and that is why i have the wag.  I plan to go through the tail rotor tomorrow possibly to see.  But I put everything back together the way the factory had it.  But maybe I should see if there is still wag after the other tests that everyone has suggested.  It is probably gone now.  i bet (other than the tail needing the boto sizer) the big issue is that the tail pushrod was not perfectly straight at the time, and a couple of things that have been fixed in the CC and vbar programming.
 Gotta order that vbar Pro program tomorrow to get it set up for the potential flight Thursday, if everything comes in.  But there is now a big chance of rain and cold temps.  Thought I would come to atlanta to fly with you guys but if the roads could freeze a little I won't take the chance. 

[RichL]

Yep, the thrust bearings being backwards in the tail will cause wag as Matt said but, not the wag that you described to me.  When the thrust bearings are backward in the tail the wag is very consistent side to side because the blade grip arms are binding under load.  I would try it again now that you have resized the blade pitch ball links.  I don't know how you managed to get them on the ball without sizing them.  Your ball links had to very very tight and combined with the tail pitch push rod binding would have caused the wag that you described to me.

Rich

[Greg Jackson]

Yeah the links were tight, now they are smooth like you showed me they should feel.  Also the pushrod is straight, but I'm going to keep eyeballing it to make sure.  Hope to have some servos on for testing in the next couple of days...now just have to hope the weather is right.