laminated shims and housing seals

[Randy Strock]

Hi Guys - just thought I'd share and ask a question at the same time. I had noticed a repetitive "knock" in the tail rotor area and of course began to investigate. found that the backlash is out of whack in the lower or intermediate gear box at the tail end of the ship. To fix this, I have to utilize a laminated shim, part # 251-1, and a dial indicator to get the backlash setting correct. The housing cover and gear body are a metal to metal boltup with the laminated shim in between which is supposed to provide the seal for those two surfaces. I'm not a fan of metal to metal sealing even if they are perfectly machined. does anyone have any experience with anaerobic sealants or is there a particular type of sealant used by the Brantly community that works in these areas. I've had a small amount of oil seepage in this area and would just like to take care of it when I'm setting the tolerances between the gears. Thanks for any input. Randy Strock ship N2297U ser.470

[bryancobb]

When I did my T/R boxes, I went EXACTLY by the book with a little coaching from Doyle and Big John at the factory. Never had a leak after. The laminated shims are layered aluminum (I think) and the seal real well if the box and its' cover are clean and smooth.

It takes A LOT of patience to do this task correctly. Be prepared to take apart/put together several times to get it right.
I you are done and it's noisy, it's wrong. Take it apart again.

[Randy Strock]

Bryan
thanks for the comments. I understand the patience and trial and error part of setting the backlash, not a problem. just as an observation, i'm impressed with the simplicity of the "oil pump" arrangement. do you know whether they are hdpe or nylon? just wondering. also.....how did you hold onto the head of the bolts that are in the tail end to which the strike plate tubing bolts to? I got lucky and one side came apart easily so I was able to simply leave the other bolt alone and just rotate the entire strike assembly out of the way. but tightening them up may become a problem........perhaps a crows foot wrench end? this is one of the maddening things about the Brantly. Doesn't seem like maintenance got any priority when they were assembling this ship. ah well. just have to deal with it.
The benefits are worth the aggravation.
Randy

[bryancobb]

Randy, I'm trying to understand what you are calling the strike plate?

I don't remember anything being called a strike plate or strike plate tube?

[bryancobb]

Oh.. I guess you're calling the Tail Rotor Guard, the strike assembly.

The 2 AN-4 bolts that insert from the inside of the tail-cone were a little hard to get to but I bent an open end 7/16 wrench so it was almost like a 1-piece crow-foot wrench. That worked.

Then when I put new bolts in, I glued them with ZAP C/A glue to hold them until I got them tight.

Bryan

[bryancobb]

The oil pump parts are probably not HDPE. That's a fairly new high-tech product that I do't think was manufactured in the early 60's.

They are probably just nylon. Mine looked brand new with 2200 hrs on them. Were yours in bad shape?

[Randy Strock]

everything inside of the housing looks brand spanking new. really pretty impressive when you consider the number of times they've turned 'round and 'round. both the oil pumps are in excellent shape also. even the oil was still very very clear. sorry for not using the proper terminology regarding the tail rotor guard. on the bottom of mine is a small skid plate and I just pulled the label out of thin air. I've ordered the laminate shims from Gary and am now killing time waiting for them. Thanks for your interest in answering my posts. Randy

[Ron Spiker]

Randy, most of the T/R gears and shafts in yours are new. They were replaced two owners ago. I wouldn't expect more than a hundred or two hours on them.

Ron

[Randy Strock]

Hi Ron - hope you're getting better.

well, that explains a lot. no wonder everything looks so good. It's just the backlash tolerance that was out of whack. thanks for the info. I guess I should dig back into all of the old paperwork and look it over. I knew that someone had worked on it from the notes in the o&m but didn't realize that it was not that long past. I don't suppose you know who did the work? thanks again. Randy

[Ron Spiker]

Yes, I know who did the work. I'll talk to you off line with that info. It should have been roughly 2006 - 2007 that it was done.