View Full Version : Shim up the main gear?

06-20-2009, 10:18 AM
:thinkingHas anyone else had to shim up the main gear on an intrepid to meet up with the tail rotor drive gear?

06-20-2009, 11:05 AM
:thinkingHas anyone else had to shim up the main gear on an intrepid to meet up with the tail rotor drive gear?

you should not have to shim the main gear up,one thing to check is loosen the two silver collars that are in between the upper and lower bearing blocks and grab the head and pull up and then while holding the head up make sure the bottom collar is all the way down and tighten the bottom collar first and then tight the top one and then you should beable to set the gear mesh on the tail transmission.

06-20-2009, 12:19 PM
Thanks Todd, I gave it a shot and the brass sleeve on the auto hub is all the way up, and touching the bearing inside the block, I'm still shy of making contact with the main gear. Also loosened up the bolt that carries through the front of the tail trans and tried to push it down to make contact but again came up a little short of pos engagement. The main gear is on top of the alum. ring on the auto hub, looks the same as the pics on the build up disk. :thinking Do you think the shims would hurt anything?

06-20-2009, 05:39 PM
I found while building my EB that there was a little movement available by slightly loosening the top collar & lower bearing block then pulling the whole head up. After doing this my tail mesh went from "sloppy, chew up crown gear in a couple of flights" to "pretty much perfect, no binding, no backlash"

While I haven't been able to do that much flying, the mesh has stayed exactly the same.

06-20-2009, 09:21 PM

You also need to loosen the back 4 bolts that mount the tail transmission ,,,as they will sometimes keep it from moving down to mesh right . I had one that needed the front bolt of the main shaft bearing mount loosened to let it drop into mesh .

Finally ,,, sometimes the locktite gets into the slots of front tail transmission mount and fills the slot up and that will keep it from moving down ,,,take the tail transmission out and clean the slots out good and try it again .Also make sure there are no burrs on the main shaft block or the transmission mount where they slide together .
Good luck

06-20-2009, 09:27 PM
Do you have any pics of the tail transmission. Make sure its the correct way round. You should not have to shim it to make contact with the tail drive. Is it a driven tail or non? Please post pics so we can help.


06-20-2009, 11:08 PM
Ensure that the lower main shaft bearing block is not installed upside down. The open bearing side should face UP.

As Dale said, some pics may help with diagnosis...:)

Due to the frames being tight around the cage of the transmission, sometimes (well, almost always) it is necessary to tap the front of the cage down using a driver and a small tapping tool (some call it a hammer) to get it to move.

The "ears" of the cage should be at least flush with the top of the bearing block where they dovetail together.

06-21-2009, 10:45 AM
Thanks for the direction to look in. I have some pics- kind of hard to tell but it looks like the arms leading from the front of the trans box are flush with the bottoms of the upper frames just above the rear of the main gear, also the bearing block is installed the same as the pic of the upper block with the orientation possibly asbackwards. I have the suface of the lower bearing block that accepts installation of the bearing, facing the main gear, so the smaller hole is facing up, on the upper block the smaller hole is facing down. You can see about one mm of the lower flange from the auto hub sticking out of the main gear from the shims. I am pulling them back out and inspecting the mounting holes for locktite, and correct orientation of the blocks and trans before re-installing. I thought it looked the right way round when doing the build:roll: but- well, y'no.

06-21-2009, 11:32 AM
It looks to me at least the top block is upside down, can't see the lower block.
I say this from looking looking at the build diagrams..

06-21-2009, 12:32 PM
Yep, got it apart and checked the drawing again, turns out I had both the upper and lower bearing blocks in backwards:smokin:. Fits together fine now! Appreciate the info and concern. The only other grey area I had was the new head dampners versus the two piece O rings. I have installed the new one piece ones with the one .40 shim on each side. I prefer a softer feel on the head, not really much 3-D goin on over here. I have a very small amount of lateral play in the assembly. Had a tough time getting more than one set of shims on, so just went with the one. Any suggestions on compressing the rubber to squeeze one more set of shims on, or really not necessary?

06-22-2009, 08:39 AM
If you like a soft head, then certainly try it the way you have it. If you feel that it is too soft, then add another shim, using the blade grip to press the circlip in to the groove.

06-22-2009, 08:57 PM
Thanks Chris, I ended up pulling it back apart and getting another shim in. :thumbup: