4-40 or 6-32 control arms?

[ORLANDO FRETS]

The hardened bolt withstands a tensile higher than the more ductile bolt. Any eccentric loading will tend to shear or deform the hardened bolt quicker. Thus the more ductile bolt is the way to go.

ORLANDO FRETS
ojfrets at earthlink.net



----- Original Message ----- 
From: 
To: discussion at nsrca.org
Sent: 2/15/2005 3:29:13 PM 
Subject: Re: 4-40 or 6-32 control arms?


Rick, exactly right.  They will shear off at the base where the load is maximized. It's less of an issue with the case hardened bolts since there is substantial margin for error, but if that was to break, that's where it would appen.

By usingthe partially threaded bolts, the moment arm is reduced and the load at the base of the thread decreased. If it ever broke, (doubtful) it would break at the base of the thread, most likely. The core diameter is smaller there than the shank diameter. 

Epoxying the shank of the bolt into the hard point works great. 

I prefer the softer bolts because I can bend these easily with the technique I have outlined before, to bring the actuation point on the hinge line.

MatK

In a message dated 2/15/2005 2:57:25 PM Eastern Standard Time, knowhow3 at bellsouth.net writes:
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
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.f3a.us/pipermail/nsrca-discussion/attachments/20050215/5a8b3a51/attachment.html