Axial play in tail output shaft

[Steve Graham]

Hi guys,

I'm putting my N7 back together after returning from the OHB and working on the tail I notice there is axial play in the output shaft.  Probably only about .5mm but it's noticeable and I'm sure will affect the tail performance at least a little.  It also creates excessive lash in the tail gears.  At first I thought, I needed to find a way to shim the output shaft spacer.  As I think about it I suppose it might be wear in the tail gears?  They look ok to my untrained eye.

Anyone else have an issue like this before or ever find a need to shim the output shaft beyond the width of the spacer?

[Mike Spano]

yes sir. part number 106-601 in the pic below. sometimes you may need to re position it. sometimes it needs to be behind the gear, sometimes on the spacer side, sometimes its not needed....it depends on several different things. tiny tiny tiny differences in machining add up when you are taking into consideration several parts (output shaft spacer, bevel gear, mushroom gear, output shaft, and overall tail box). tiny differences like this are impossible to prevent IMO, so sometimes you have to move your shim around.

[Steve Graham]

Thanks Mike,

That all makes sense.  I'd never noticed the play before and the N7 manual doesn't show a shim.  I'll order a couple.

[Mike Spano]

Brother, I am sorry. That is the E7SE.......I forgot the N7 uses the E5 tail box .....I am 50% sure I am running a shim on my N7 though, behind the gear.......they are all the same basic design.

[Steve Graham]

No problem Mike,

I suspected it was for a diff heli and double checked the E7 manual to be sure.  I'm gonna try the shim anyway.  I'm still gonna fly it til I get the shim.  The slop is small enough that I don't really think it's going to affect anything I'd notice anyway.  I think over time all the bits just loosened up some.  I've got a bunch of flights on this heli.

Missing the thick sea level air!  My first auto the other day with my "heavy heli" the Rush shocked me how little float I had at the bottom. 

[Mike Spano]

let us know how it goes please. and sorry for any confusion i caused by posting the incorrect diagram.

yes, the air here is nice nice and humid and cold right now though....lol

[Drew Robinson]

I have shimmed all my synergys at one time or another I typically try shims on different sides of output spacer/backside of gear until I get the best feeling mesh with least amount of play. Once the best combination is found, I usually don't have to touch it again. Also nice to carry shims in toolbox for rebuilds at field!

[Helinut]

I shim too.

[Steve Graham]

Update:

I added one shim on the left side between the bearing and the bevel gear.  Much better.

Now I just need to replace a couple of tail pitch links that have a small amount of play in them.  They still work fine but since I know they're worn my brain won't let it be till the tail is like new.