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  #1  
Old 11-20-2014, 01:31 PM
Tom Martin Tom Martin is offline
 
Join Date: Jan 2005
Location: Ontario, Canada
Posts: 1,586
Default Aileron bellcrank washer

I am making a minor modification to the aileron bellcrank installation that I present for your consideration and dialogue.
The bellcrank is installed on a 3/8" O.D. brass bushing that is captured between and upper and lower bracket on the spar.
When the bolt is tightened properly the bellcrank is supposed to rotate freely on the brass bushing with a very slight up and down movement along the bushing.
My concern is that the metal bellcrank, although it rotates on the bushing, rests on the bottom aluminum bracket. Each time it turns there will be contact between the end of the metal 4130 tube and the face of the aluminium bracket.
The addition of a 960-616L washer will eliminate this contact. The washer goes over the bushing and is free to rotate around the bushing, this can be seen in the picture below



This is one of those long term issues. I can see no problems with this addition and it has the potential to reduce or eliminate wear at this important location.
I was able to install this washer without any trimming of the bell crank or the supplied brass bushing, while maintaining the torque and "play" specified in the plans.
(maybe the engineers left the correct spacing for this washer and it somehow got omitted in the plans?)
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Last edited by Tom Martin : 11-20-2014 at 01:35 PM.
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  #2  
Old 11-23-2014, 10:32 PM
TimO TimO is offline
 
Join Date: Feb 2005
Location: Wisconsin
Posts: 647
Default Same here

I did the same here a few months ago on that. Especially with having aluminum brackets that the steel bellcrank is going to rub against, I decided not to let them rub. The RV-10 had steel brackets.
Tim
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  #3  
Old 11-24-2014, 08:14 AM
Tom023 Tom023 is offline
 
Join Date: Jul 2011
Location: Cypress, TX
Posts: 468
Default +1

Seems like a good idea. I'll be adding to mine as well in a few weeks when I get to that installation.
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  #4  
Old 06-16-2015, 07:48 PM
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KeithB KeithB is offline
 
Join Date: Mar 2014
Location: Granbury, TX
Posts: 305
Default

"My concern is that the metal*bellcrank, although it rotates on the bushing, rests on the bottom aluminum bracket. Each time it turns there will be contact between the end of the metal 4130 tube and the face of the aluminium bracket.
The addition of a 960-616L washer will eliminate this contact. The washer goes over the bushing and is free to rotate around the bushing, this can be seen in the picture below"


Tom (and others):

I have just completed this stage on my wings (and actually moved on to the fuselage kit - finally!). *I didn't fully appreciate this issue until I saw it first hand, and then reviewed the issue and your proposed solution with two of my esteemed technical advisors. *They both shared your concern, coming from building planes utilizing steel brackets.

However, a question was raised about your fix - that being that it does not guarantee that the friction and wear occurs steel-on-steel with the Bellcrank rubbing on the washer. *It is possible the washer and Bellcrank move as one with the washer rubbing the aluminum bracket, though the washer certainly increases the bearing area.

Their proposed solution is to use 2 NAS1149F0463P (or 432P) washers, one on each end of the bushing/bellcrank, this washer having an inside diameter hole matching the bolt rather than the bushing. In this configuration the bushing would pinch the washers between it and the brackets (one at each end), preventing the washer(s) from turning. Dimensions now become more critical and therefore complicating installation over your proposal, as the bushing must be shaved/shortened enough to incorporate it plus 2 washers between the brackets, and the Bellcrank must be shaved/shortened enough to prevent binding between the washers on each end. *However, this would ensure that Bellcrank movement is steel on steel, with wear measured in decades vs years.*

You probably considered this - did you rule it out as too complicated?
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  #5  
Old 06-17-2015, 11:42 PM
Jake14 Jake14 is offline
 
Join Date: May 2014
Location: Seattle
Posts: 378
Default

".. *It is possible the washer and Bellcrank move as one with the washer rubbing the aluminum bracket,..."

The way I made my installation, the washer just fits over the bolt, not the bushing, so that
when the bolt is tightened properly, both the upper and lower flanges of the aluminum bracket, the bushing, and the proposed washer are all clamped together as a single unit.

The bellcrank is free to rotate about the bushing since the bellcrank tube is slightly shorter than the bushing inside it.

(Maybe Van's would like to weigh in on this)

Jerry #140158

Last edited by Jake14 : 06-17-2015 at 11:56 PM.
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  #6  
Old 06-18-2015, 12:14 AM
Jake14 Jake14 is offline
 
Join Date: May 2014
Location: Seattle
Posts: 378
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PS. I didn't see any need to trim either the bushing or the bellcrank at the time, since the slightly increased gap between the bracket flanges caused by the washer seemed insignificant and all other dimensions stayed the same. My understanding was that the concern was just the weight of the bellcrank and attached pushrods pressing down on the bracket flange, so I didn't think an upper washer was needed.
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  #7  
Old 03-18-2016, 08:24 PM
Tom023 Tom023 is offline
 
Join Date: Jul 2011
Location: Cypress, TX
Posts: 468
Default

Quote:
Originally Posted by KeithB View Post
[i]

Their proposed solution is to use 2 NAS1149F0463P (or 432P) washers, one on each end of the bushing/bellcrank, this washer having an inside diameter hole matching the bolt rather than the bushing. In this configuration the bushing would pinch the washers between it and the brackets (one at each end), preventing the washer(s) from turning. Dimensions now become more critical and therefore complicating installation over your proposal, as the bushing must be shaved/shortened enough to incorporate it plus 2 washers between the brackets, and the Bellcrank must be shaved/shortened enough to prevent binding between the washers on each end. *However, this would ensure that Bellcrank movement is steel on steel, with wear measured in decades vs years.*
Today I implemented this change when installing the bellcranks. It was a very simple mod and now the bellcranks rotate on steel washers instead of the aluminum brackets. Maybe it wasn't necessary but seems like a good preventive approach that only took a half hour.
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