[TowerTalk] Yagis and Rivets

[Curtis, David B]

The real question is whether the forces on the rivets are tension or shear. 

Rivets in tension -> good.
Rivets in shear -> bad.

Rivets in antenna elements are in shear. Aluminum is soft. The holes might
expanding over time.

-n6nz


-----Original Message-----
From: Bill Coleman AA4LR [mailto:aa4lr@radio.org]
Sent: Thursday, March 16, 2000 10:22 AM
To: Dave Pomeroy; Dave D'Epagnier; towertalk
Subject: Re: [TowerTalk] Yagis and Rivets



On 3/15/00 6:07 PM, Dave Pomeroy at dave_pomeroy@yahoo.com wrote:

>  I don't know about antenna rivits but aircraft
>rivits hold forever.  60 year old airplanes still
>flying with tight aluminum rivits.

True, but aircraft generally use driven (ie bucked) rivets, not blind (ie 
pulled, "pop") rivets. And even driven rivets can work loose, due to 
stress or corrosion.

My question with the F12 rivets is are they structural blind rivets, or 
are they the "pop" variety? "Pop" rivets pull the mandrel through the 
rivet, leaving a little empty hole. So, the only thing holding the 
material together is a thin shell of aluminum left in the hole. A blind 
rivet has a mandrel that breaks off, leaving a piece of steel in the 
middle of an aluminum tube.

Given the friction of elements telescoped together, even the wimpy pop 
rivets are probably enough to hold the element in place. Just don't use 
pop rivets in aircraft....



Bill Coleman, AA4LR, PP-ASEL        Mail: aa4lr@radio.org
Quote: "Boot, you transistorized tormentor! Boot!"
            -- Archibald Asparagus, VeggieTales


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