On Fri, 28 Jan 2011 23:54:57 -0800, Winston
wrote:

Erik wrote:

(...)

Spark plug insulators are for real porcelain, and designed for such
service. To this day I have difficulty 'wrapping my head' around the
conditions they normally operate. I agree, they are one of engineerings
great, unsung marvels.

You are right of course.

They're also quite effectively heat-sunk.


I retract my statement about porcelain because it has only
'moderate' thermal shock resistance in relation to the
other varieties of vitreous whiteware which range from
'good' to 'excellent' in thermal shock handling capability.

http://books.google.com/books?id=_wlZ5LHTyBIC&pg=SA12-PA100&lpg=SA12-PA100&dq="vitreous+china"+specification+"thermal+s hock"&source=bl&ots=tHzBebCBw0&sig=8KuRI4j-HvqDs4aBB9jqRnE6f6A&hl=en&ei=XcNDTaKWH5K4sAORpsGsC g&sa=X&oi=book_result&ct=result&resnum=4&ved=0CB4Q 6AEwAw#v=onepage&q="thermal
shock"&f=false

Apparently sparkplugs are weenies WRT thermal shock.

Or so says The CRC handbook of mechanical engineering
(Second Edition, bottom of page 12-97)
By Frank Kreith, D. Yogi Goswami

Yogi Bearswami?

--
We're all here because we're not all there.