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Washer usage

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Ken

Joined: 06 Jun 2008
Posts: 15

Posted: Thu Oct 01, 2009 3:53 pm Post subject: Washer usage

What are the rules regarding usage of flat washers on the AN bolts?  I assume you must have one under the nut so you don't scuff the metal it is tightening against (when you tighten it)?  How about the other end, is it necessary or even required by FARs?



How about on the rudder pedal where you have a bolt going through a clevis that attaches the cable?  Is a washer under the castle nut enough or do you need one under the head as well?



Thanks in advance.

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Thruster87

Joined: 16 Apr 2008
Posts: 193
Location: Australia

Posted: Thu Oct 01, 2009 9:15 pm Post subject: Re: Washer usage

 	  Ken wrote: 	
		  What are the rules regarding usage of flat washers on the AN bolts?  I assume you must have one under the nut so you don't scuff the metal it is tightening against (when you tighten it)?  How about the other end, is it necessary or even required by FARs?



How about on the rudder pedal where you have a bolt going through a clevis that attaches the cable?  Is a washer under the castle nut enough or do you need one under the head as well?



Thanks in advance. 	
Washers are there to spread/transfer the loads  and secondary for scuff marks.You can use just one under the nut  or max two under nut one under head.Usually with clevis pins you only use one for the split pin end as the head is already against solid metal.  Hope that helps Cheers

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bryanmmartin

Joined: 10 Jan 2006
Posts: 1018

Posted: Thu Oct 01, 2009 9:57 pm Post subject: Washer usage

See AC 43.13-1B, paragraph 7-37. The maximum combined height of  

washers that should be used is 1/8". Since standard AN washers are  

1/16" thick, that usually means no more than two washers can be used.  

1/32" washers are also available. You should have one washer under the  

nut, you don't usually need one under the bolt head. An additional  

washer can be used, if necessary, to keep the nut from bottoming out  

on the shank of the bolt. The additional washer can be placed on  

either end of the bolt. If more than two washers are needed to keep  

the nut from bottoming out, you should use the next shorter bolt.  AN  

bolts are available in multiples of 1/8".



On the cable attachment to the rudder pedals, the nut will not be  

tightened. The nut will be left loose enough to allow the parts to  

move freely, which is why a castle nut and cotter pin is required  

here. You will probably need a washer under the nut to keep the  

threads from bearing on the moving parts. You may not need a washer  

under the bolt head. Only the unthreaded shank of thethe bolt should  

bear on the moving parts of the cable connection.



On Oct 1, 2009, at 7:53 PM, Ken wrote:



 	  Quote: 	
		   



 What are the rules regarding usage of flat washers on the AN bolts?   

 I assume you must have one under the nut so you don't scuff the  

 metal it is tightening against (when you tighten it)?  How about the  

 other end, is it necessary or even required by FARs?



 How about on the rudder pedal where you have a bolt going through a  

 clevis that attaches the cable?  Is a washer under the castle nut  

 enough or do you need one under the head as well?



 Thanks in advance.




	


-- 

Bryan Martin

N61BM, CH 601 XL,

RAM Subaru, Stratus redrive.

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_________________
--
Bryan Martin
N61BM, CH 601 XL, Stratus Subaru.
do not archive.

klaus(at)utdallas.edu
Guest

Posted: Fri Oct 02, 2009 5:43 am Post subject: Washer usage

Hi Ken,



The general rule is that a washer must be used on both sides. The reason

is not just to prevent the head or nut from damaging the surface

during the tightening, but also to prevent dangerous corrosion. 

The cadmium plating of the washers is

attacked by any corrosion first and thus prevents corrosion at the head

or nut, where corrosion would be dangerous. 



Happy flying,



Klaus

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z601a(at)anemicaardvark.c
Guest

Posted: Fri Oct 02, 2009 6:15 am Post subject: Washer usage

On Friday 02 October 2009 08:37, Klaus Truemper wrote:

 	  Quote: 	
		   



 Hi Ken,



 The general rule is that a washer must be used on both sides. The reason

 is not just to prevent the head or nut from damaging the surface

 during the tightening, but also to prevent dangerous corrosion.

 The cadmium plating of the washers is

 attacked by any corrosion first and thus prevents corrosion at the head

 or nut, where corrosion would be dangerous.



 Happy flying,



 Klaus


	


A delimma I've found is that Zenith doesn't always supply, or call out, bolts 

that allow the use of two washers. I've also found that some of their photos 

and drawings do not show the use of washers. 



I think this is a mistake, and that Klaus is correct: it is very desirable 

that there be a washer under both the head of the bolt, and under the nut.



Another rule of thumb I see ignored in the parts supplied, the drawings, and 

the photos is the number of threads showing beyond the end of the nut. I 

think I recall AC 43-13 requiring a minimum of one thread showing, and a 

maximum of three. Of course, additional washers, up to a maximum of three, or 

a maximum 1/8", may be added to achieve this.



I again emphasize that AC43-13 does not apply to experiemental aircraft, but 

that's a good guideline. You sure don't want installed bolts that don't have 

less than a thread showing beyond the nut.

-- 

=============================================

                Do not archive.

=============================================

                Jim B Belcher

    BS, MS Physics, Math, Computer Science

                  A&P/IA

     Retired aerospace technical manager



     Mathematics and alcohol do not mix.

         Do not drink and derive.

=============================================

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carlossa52(at)gmail.com
Guest

Posted: Fri Oct 02, 2009 8:23 pm Post subject: Washer usage

There is a good summarized Standard document in the ZAC web site.



I don't know if it is still pointed to by any ZAC web page. If it is, I could not find it. But I do have the direct link to the document:



 http://www.zenithair.com/pdf-doc/zenair construction standards draft 1-07.pdf



 It does not replace AC43-13, but it is a pretty useful summary.

 I believe it is also provided in the CDs that ship with the kit.



Carlos



2009/10/1 Ken <hror1(at)pld.com (hror1(at)pld.com)>

[quote] --> Zenith-List message posted by: "Ken" <hror1(at)pld.com (hror1(at)pld.com)>

 

 What are the rules regarding usage of flat washers on the AN bolts?  I assume you must have one under the nut so you don't scuff the metal it is tightening against (when you tighten it)?  How about the other end, is it necessary or even required by FARs?

  

 How about on the rudder pedal where you have a bolt going through a clevis that attaches the cable?  Is a washer under the castle nut enough or do you need one under the head as well?

 

 Thanks in advance.

 

[b]

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