The problem with ceramic coatings on metal is that
they grow thermally at different rates than metals, so when things
get hot they tend to pop off in chunks.
That is a serious drawback. I just read about a group at Sydney University who
have patented a ceramic with a negative co-efficient of expansion, so it
shrinks as it warms up. If they can modify the co-efficient to track metals
that might help a lot, it just means they need to go very much in the
opposite direction.
Richard Dowling, Melbourne, Australia, 1979 XJ-S & 1985 XJ6.
The problem with ceramic coatings on metal is that they grow thermally at
different rates than metals, so when things get hot they tend to pop off in
chunks.
Readily available engine builder ceramic coatings go on in thicknesses
ranging from 0.0005" to 0.0015" (http://www.techlinecoatings.com/faq.html)
I think I recall talking to the guys at techline about 8-10 years ago about
the cracking issue. It is a vague recollection, but I think they said they
saw micro-cracking under the electron microscope, but they did not have a
problem with chipping/flaking.
Kirbert, how do you base the assertion that one must have a rather thick
coating to achieve any useful difference in thermal efficiency?
Shuttle tiles are only about 1/2 inch thick (if I recall properly) and the
white ones withstand temps up to 1,200 deg F (keeping the aluminum skin
below 350 F) and the black ones can see temperatures of 2,300 F!!!
Even if 0.0005" kept only a few percentage of BTU’s from transferring to the
engine metals, this would be a significant improvement.---------------------------------------------------------
Now on a separate issue under the same thread… no one has commented on the
pictures of the heads included with this “V12 to die for” www.rob-beere-racing.co.uk/clearance.html Anyone notice that they look
like HE heads? And that although the pictures are rather small, the Michael
May combustion pocket looks like it has had a work-over?
Now on a separate issue under the same thread… no one has commented on
the pictures of the heads included with this “V12 to die for” Engines For Sale Anyone notice that they look
like HE heads? And that although the pictures are rather small, the
Michael May combustion pocket looks like it has had a work-over?
How could you possibly see that from the picture?!?!?!?!?!
In reply to a message from Gordan Bobic sent Thu 1 Dec 2005:
Hi All
most of this thread has gone right over my head as I am still a
novice but;
I read in Brian Long’s XJS book that ‘Harry Mundy (Jaguar’s V12
engine designer) had the V12 (HE) running happily on 14:1
compression ratio on the testbed, and remarkably lean fuel/air
mixture’