Received: from hplms26.hpl.hp.com by opus.hpl.hp.com with SMTP (1.37.109.8/15.5+ECS 3.3+HPL1.1) id AA04022; Wed, 14 Jun 1995 14:47:50 -0700 Return-Path: <Francois_Jouaux@NeXT.COM-DeleteThis> Received: from NeXT.COM by hplms26.hpl.hp.com with SMTP ($Revision: 1.36.108.11 $/15.5+ECS 3.3+HPL1.1S) id AA078876471; Wed, 14 Jun 1995 14:47:51 -0700 Received: from aulait by oz.NeXT.COM (NX5.67f1/NeXT0.1-Aleph-bf) id AA18800; Wed, 14 Jun 95 14:43:57 -0700 Message-Id: <9506142143.AA18800@oz.NeXT.COM-DeleteThis> Received: by aulait.next.com (NX5.67e/NX3.0X) id AA01832; Wed, 14 Jun 95 14:43:56 -0700 Content-Type: text/plain Received: by NeXT.Mailer (1.118.2) From: Francois Jouaux (Contractor) <Francois_Jouaux@NeXT.COM-DeleteThis> Date: Wed, 14 Jun 95 14:43:48 -0700 To: wind_talk@opus.hpl.hp.com-DeleteThis Subject: Re: Broken Universal & Rescue (l References: <199506142055.AA071043356@hplms26.hpl.hp.com-DeleteThis>
>>Since that I don't trust any universal pin that is less than 1/2''.
>Don't all the stainless steel pins narrow down to 1/4" to thread into the
>bottom of the universal joint itself?
>The pin I broke off 3rd Avenue was 1/2" in its exposed part, but became 1/4"
>in the hidden part that threaded into the bottom of the universal.
In this rescue I was talking about an F2 base type of pin that is (used to be
?) narrowed down to 1/4'' on about 1/2'' outside the UJ.
My own North pins uses the 8mm bolts I think.
Anyway you just have to be unlucky enough and use a pin with a tiny bubble or
micro crack inside : that's where it will snap. Or given time, the water &
salt corrosion will develop the micro cracks needed.
You can't even see them at this point. The smaller the section, the worse the
shear. The shear is a function of the tangential force applied (which is most
of the force transmitted from the sail to the board). It is also an inverse
function of the section area (or something like that).
There is already so much shearing force in this little piece of steel that
not much default is needed where the diameter is reduced to make it MUCH
weaker.
That's what I remember from structure/metal corrosion classes...
-Francois
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