[s-cars] Oil drain plug

mlbess at optonline.net mlbess at optonline.net
Tue Apr 13 18:17:23 EDT 2004

Metallurgist on call with an answer (of course):  
1.Coefficient of linear expansion for aluminum is about 12 microinches per in per degree F.  For steel the number is about 6. 
2.  Think of a hole as a line (or plane) wrapped around and connected to itself.  When you heat up the metal the line (or plane) gets longer (see #1).
3.  We have a fairly long distance between the drain plug and the restraining surfaces, so I would anticipate most of the expansion still occurs, plus, due to Poisson's ratio, the stresses set up due to the heating and the potential constarints would cause dimensional change in the third dimension (thickness).

Mike Bess
'95 S6
BE, MS(Metallurgy)

----- Original Message -----
From: Dave Forgie <forgied at ae.ca>
Date: Tuesday, April 13, 2004 11:59 am
Subject: RE: [s-cars] Oil drain plug

> Bob:  I know you are correct for an UNCONSTRAINED piece of metal 
> with a hole it.  HOWEVER, the oil pan is constrained (by the 
> bolts, its shape (to some degree), etc).  Where does all that 
> metal expansion go?  I contest (but cannot prove) that in this 
> case, the hole absorbs some of the expansion by getting smaller 
> and therefore tighter on the threads.  Any metalurgists in the 
> crowd with a spare oil pan, an oven and a micrometer?
> Dave F.
> >>> "Bob Rossato" <bob.rossato at att.net> 04/12/04 07:16PM >>>
> Sorry, but the hole gets larger.  Think of it as the whole thing being
> scaled up, in a minute way.
> Bob
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