Stiff (very) Elevator

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Stiff (very) Elevator

Postby BRS » Wed Aug 06, 2014 1:33 am

Today during preflight I thought the elevator seemed a bit stiff. After a short flight I decided it's actually quite stiff and terminated the flight. Upon instigation I found that the 'horn' between the push tubes (photo below) was so stiff I could hardly move it. Although the plane has been hangared it's been quite warm and humid. I'm guessing the shaft decided to rust. So much so that I was not even able to remove it - yet. The shaft seems frozen in the horn but the shaft moves in the airframe. The bubbles in the photo are penetrating oil.

Has anyone seen this happen before?
Attachments
20140805_171446.jpg
Shaft frozen in this control horn.
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Re: Stiff (very) Elevator

Postby User GDS » Wed Aug 06, 2014 5:49 am

It looks like your bellcrank is pivoting on a piece of steel tubing, I'm pretty sure mine pivots on an AN bolt. I don't remember if there is a bushing or not, but the cadmium plating on the bolt will inhibit corrosion.
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Re: Stiff (very) Elevator

Postby jak » Wed Aug 06, 2014 5:54 am

Query this forum and you'll find where I posted quite some time ago this bushing you have should have been replaced with a an6-40 bolt. This is a part you should remove and inspect and regrease each annual. Jak
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Re: Stiff (very) Elevator

Postby SheepdogRD » Wed Aug 06, 2014 8:37 am

Here's a link to the thread Jak referenced: http://www.wingsforum.com/viewtopic.php?f=218&t=18267.
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Re: Stiff (very) Elevator

Postby BRS » Wed Aug 06, 2014 1:34 pm

Thanks for the input! I knew I could get good info here.
Yes, as soon as I saw (I'm the second owner) 4130 tube in 4130 tube it was easy to see that something was going to eventually happen.

On another note. This bell-crank looks rather labor intensive to build. Seems it would be much easier to fabricate from square tubing just larger than the round tubing for the shaft. This would eliminate the welds on the ends. Just drill the square tube, slide in the round tube and weld. The notch the ends.
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Re: Stiff (very) Elevator

Postby Trilander Ted » Wed Aug 06, 2014 2:36 pm

I drill out the correct A/N bolt on the lathe down (length wise) then put an exit hole (cross wise) and tap a grease zerk thread on the hex end of bolt. Naturaly, the exit hole should be located close to the center of the bellcrank. That way, all you need for condition inspection is a shop towel and a hand grease gun plus a light. That's one of the things I would add to the kit, or at least recommend it. I found it difficult to reach through my trap door and disassemble then reassemble serious parts while on my hands and knees. Hope this helps. Ted
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Re: Stiff (very) Elevator

Postby Johnny C! » Thu Aug 07, 2014 12:49 pm

Great idea!

John

Trilander Ted wrote:I drill out the correct A/N bolt on the lathe down (length wise) then put an exit hole (cross wise) and tap a grease zerk thread on the hex end of bolt. Naturaly, the exit hole should be located close to the center of the bellcrank. That way, all you need for condition inspection is a shop towel and a hand grease gun plus a light. That's one of the things I would add to the kit, or at least recommend it. I found it difficult to reach through my trap door and disassemble then reassemble serious parts while on my hands and knees. Hope this helps. Ted
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Re: Stiff (very) Elevator

Postby Doug Baird » Thu Aug 07, 2014 1:46 pm

Here is the reference to a post I did in 2009 addressing this issue.
Fri Sep 25, 2009 7:03 am

I have made a modification as indicated above to the bellcrank bushing.
The first photo shows the installation of the bushing before drilling and riveting.
I was concerned that there was no lubrication on this and, as can be seen from the photo, the bellcrank had a quarter inch of sideways play.

The second photo shows a modified bushing with 1/16" weep holes drilled, the ends tapped with a cap in one end and a zerk fitting in the other plus two .0125" nylon washers punched to the size of the bushing.

Photo three shows the bushing (with a 90 degree zerk fitting) and washers installed.

Image

Image

Image
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Re: Stiff (very) Elevator

Postby alan » Fri Aug 29, 2014 5:39 pm

Ted,

Thank you very much for the idea of the grease zerk fitted bolt. I made one the other day and installed it today. This is a great idea and it should work well for the life of the airplane. :D

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Re: Stiff (very) Elevator

Postby Johnny C! » Tue Sep 02, 2014 1:12 pm

What are you going to sell
those for?

John

alan wrote:Ted,

Thank you very much for the idea of the grease zerk fitted bolt. I made one the other day and installed it today. This is a great idea and it should work well for the life of the airplane. :D

Alan
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flying an airplane. There is no sense in rushing any of the others.

I would much rather be looking down at the runway, than up at it.

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