4-40 or 6-32 control arms?

[Rick Kent]

Is the failure point on these bolts always at the base where it goes into
the control surface? Never having had a failure of one, I don't know, but
physics kind of dictates that it would be.
If so, why wouldn't a socket head or other type bolt that is only partially
threaded work better, since it would remove the stress risers (threads) at
the base area, where the force is concentrated. Lop off the bolt head and
glue it in. The smooth portion of the bolt could easily be roughed up with a
Dremel sanding drum or cutoff wheel for CA or epoxy to grip it going into
the control surface.

Am I missing something obvious here with this idea?

Rick
 
-------Original Message-------
 
From: discussion at nsrca.org
Date: Tuesday, February 15, 2005 02:42:37 PM
To: discussion at nsrca.org
Subject: Re: 4-40 or 6-32 control arms?
 
Well it looks like the standard 6-32 threaded bolt from the ACE Hardware bin
is they way to go.  That is what I have been using all along I just haven't
heard the pro's and con's on the subject.    I use the flat head bolt and
counter sink the hard point.  Using the 1/4"  6-32 threaded aluminum sleeve
as a stand off seems to give them a lot of strength and locks the bolt to
the control surface.
Although I have seen them used with out this stand off too.   
 
Wayne G.
----- Original Message ----- 
From: ronlock at comcast.net 
To: discussion at nsrca.org 
Sent: Monday, February 14, 2005 11:09 AM
Subject: Re: 4-40 or 6-32 control arms?


Ive been using all thread rods from hardware store.
It's my understanding those are less likely to break than bolts.
No problems with older 1.20 YS bird or current OS 1.40.
 
Ron Lockhart
-------------- Original message -------------- 

Which brings up a good point here.
 
Do you use steel bolts or stainless steel bolts.
Stainless is a softer material and would it be prone to breaking easier?
Or is the harder steel bolt more likely to snap under vibrating conditions?
 
Wayne G.
 
 
----- Original Message ----- 
From: Rcmaster199 at aol.com 
To: discussion at nsrca.org 
Sent: Monday, February 14, 2005 9:09 AM
Subject: Re: 4-40 or 6-32 control arms?


In a message dated 2/14/2005 12:22:29 AM Eastern Standard Time,
ed_alt at hotmail.com writes:
I've been using 6-32 bolts to make the control horn arms for my 2M setups so
far.  It seems like that might be overkill and that 4-40 would suffice.  Is
it OK to go lighter like this?
 
Thanks
Ed A.
 
Ed I wouldn't do that especially on ailerons. I have had 4-40's snap off
like twigs on 90 sized models before. The vibration kills them.
 
Matt
 
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