[Vwdiesel] How to lose the thou.

[LBaird119 at aol.com]

  I like 2.08^ 10-5 notation except that it looks much better with the little 

numbers set up high and no ^.  ;-)  Don't know how to do that on a 
computer.
  Remember that those pistons aren't aluminum.  They're an alloy plus 
the top ring is in what looks like a fairly high carbon steel ring land 
as well as there being steel "wings" cast into the upper half of the 
skirts of the pistons.  (Forged rather than cast actually.)
  When I showed those specs to my machinist (he didn't believe me at 
all until he saw it) he said "they must have SOME expansion control 
in those pistons!"
  They were going to bore it to .0019 which is well over half worn out 
before you even start the engine!  It's tight but then gassers are usually 
somewhere in the .003 to .007 range I think.
     Loren

In a message dated 9/27/2004 1:50:29 PM Pacific Standard Time, 
mark at shepher.fsnet.co.uk writes:

> Coefficient of linear expansion for Al is 1/0.0000208 per
> deg C
>                     Cast   Fe is
> 1/0.0000108 per deg C
> 
> piston crown gets to 500 deg C;    so 500 x 0.0000208
> 
> =0.0104 or 1%
> piston diameter 76mm...
> 1% is 0.76mm
>              or 30 thou!!!!!
> 
> This is 30 times 1 'Loren'....(8oD)
>