Veedubber's Tech-Line Coatings

Mr. Hoover, I've been pondering the thermal barrier and thermal
dispersants that you've advocated several times. Ponder with me for a
moment if you will.

I've got an experimental engine, with an experimental cooling setup. Do
know for guaranteed that the cooling will be sufficient, so I'll be
keeping a close eye on the water and oil temperatures. But the coatings
will cause more heat to be dumped into both. How would a typical
homebuilder know the difference between elevated temps due to a more
efficient heat transfer and inadequate cooling?

Then there is the issue of what the redline temperatures are set for.
In the rotary, it is for the main bearings. Would the barriers and
dispersants change the thermal characteristics in such a way that the
temps readings taking in the normal places look adequate, but in reality
critical parts are being fried?


--
This is by far the hardest lesson about freedom. It goes against
instinct, and morality, to just sit back and watch people make
mistakes. We want to help them, which means control them and their
decisions, but in doing so we actually hurt them (and ourselves)."

wrote:
Ernest Christley wrote:

I've got an experimental engine, with an experimental cooling setup. Do
know for guaranteed that the cooling will be sufficient, so I'll be
keeping a close eye on the water and oil temperatures. But the coatings
will cause more heat to be dumped into both.
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I don't understand the above. TBC's applied to the combustion chamber,
piston crown, valve heads and the exhaust port, tend to reduce the
waste heat that appears in the cooling system while increasing the
waste heat that appears in the exhaust. This is based on comments from
people running turbos who take a particular interest in the exhaust gas
temps and how much energy they can recover from that source.


First, the sentence above should have been, "Do 'not' know for
guaranteed the the cooling will be sufficient,"

But I understand better now. I was thinking that the inside of the
rotors and coolant passages would be coated with the dispersant to help
pull the heat out of the metal and into the cooling fluids. The fluid
temps would be higher, even though the actual metal wouldn't be.



--
This is by far the hardest lesson about freedom. It goes against
instinct, and morality, to just sit back and watch people make
mistakes. We want to help them, which means control them and their
decisions, but in doing so we actually hurt them (and ourselves)."

Jester wrote:
The fluid
temps would be higher, even though the actual metal wouldn't be.


Just a WAG, but I'm thinking that the temps would be the same because
of any thermostat, or other regulation device.

Some of us arent using thermostats in the rotaries, because they do in
fact restrict coolant flow, particularly when high flow is desired. In
those setups, Cooling is controlled with cowl flaps on the cooling
airflow exits, or coolant is pumped using an electric water pump with
temperature control.

What we are interested in is maximal cooling ability, since more than
one rotary install has fought with inadequate cooling for a variety of
reasons. In theory, coatings can decrease heat transfer to the coolant
and oil, while increasing heat discharge out the tailpipe.

Oh, the joys of a truly experimental engine install, not a firewall
forward package

Dave

Ahh, I see. Part of the job of the coatings is to reduce combustion
heat from even transfering to the engine itself? Very nice. It would be
neat to see some more testing to be done. Too bad we couldnt get some
major companies to do this. I suppose then that they would keep it
propietary. Oh well. A lawn mower or some other oft used device sounds
like a good test bed, because you wouldnt just be wasting fuel as you
would HAVE to use it. I really havent seen too many rotary mowers
though. Best of research to all.
Jesse M.

wrote in message
ups.com...

Ernest Christley wrote:

I've got an experimental engine, with an experimental cooling setup. Do
know for guaranteed that the cooling will be sufficient, so I'll be
keeping a close eye on the water and oil temperatures. But the coatings
will cause more heat to be dumped into both.
-------------------------------------------------------------------------

I don't understand the above. TBC's applied to the combustion chamber,
piston crown, valve heads and the exhaust port, tend to reduce the
waste heat that appears in the cooling system while increasing the
waste heat that appears in the exhaust. This is based on comments from
people running turbos who take a particular interest in the exhaust gas
temps and how much energy they can recover from that source.

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How would a typical
homebuilder know the difference between elevated temps due to a more
efficient heat transfer and inadequate cooling?

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I don't know.

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Then there is the issue of what the redline temperatures are set for.
In the rotary, it is for the main bearings. Would the barriers and
dispersants change the thermal characteristics in such a way that the
temps readings taking in the normal places look adequate, but in reality
critical parts are being fried?

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I don't know.

My only direct, personal experience with coatings has been with air
cooled engines. I began experimenting with Tech-Line's coatings in
2001, using a 6cid lawn-mower engine as my test bed. Most of my time
was spent learning how to apply the stuff. Once I was reasonably sure
of I was applying the coatings correctly I began trying to quantify the
benefit, if any. It took about a year to figure out affordable methods
of measuring temperature & torque.

About the best I can say is that I saw some improvement, and that the
coatings proved to be durable. On that basis I went ahead and
assembled a stock VW engine from used (but coated) parts, intending to
run it for several hundred hours, tearing it down periodically.
Unfortunately, when gasoline went above $2/gal I could no longer afford
the luxury of my experiments. At that time the stock engine had
accumulated about 75 hrs and was a perfect null, experimentally, in
that it showed absolutely no signs of wear or deterioration of the
coating(s).

My experiments with TLTD (the thermal disbursant) involved heating
coated and uncoated coupons of cast aluminum and mild steel with the
element from a 100W. soldering iron and plotting their temperature
(convection and conduction) against time.

My goal was to explore possible solutions to well known problems seen
in high-out engines based on VW after-market components. Despite being
unable to complete the full series of tests on the stock engine, I have
sufficient confidence in the coatings to apply them to several other
engines, all of higher output, which I'm in the process of doing. But
with gas now over $3 and still rising there's a good chance I won't be
able to afford running-in the completed engines, let alone fly behind
them.

I resorted to experiments because Tech-Line could not offer any advice
regarding the use of their coatings on air cooled engines. They did
refer me to a couple of coating shops but their claims were a bit
extravagant and they were unwilling to put me in touch with any of
their air cooled customers. Since you are dealing with a water-cooled
engine, perhaps you'll have better luck.

-R.S.Hoover

Interestingly, this series of postings came alone currently with a friend
attempting to introduce me to a network marketed product which claims to
gradually coat the piston tops, spark plugs, valves, and "fire deck" (which
is their name for the surface of the head inside the combustion chamber) of
an engine with a "sacrificial catalyst". My two semesters of college
chemistry caused me to dismiss that description is self contradictory (i.e.
Bunk!); however, I am willing to accept a description such as "continuously
deposited ablative thermal barrier coating".

What makes all of that interesting (to me) is that the manufacturer's claim
equates to 9% to 10% improvement in torque with the same fuel burn, or an
approximate 10% inprovement in fuel consumption. If their theory is
correct, and my recollection of Boyle's Gas Law and of the Karnot Cycle
suggests that it is, then the much more durable Tech-Line Thermal Barrier
coating should have a similar result.

I am quite curious whether your results to date pointed in the same
direction.

Peter Dohm

P.S.: There "aint no free lunch" so I would presume that the overall heat
retained in the engine would be a little less for a given output; but that a
little more heat might be conducted back to the exhaust port area of the
head from the exhaust tubing. I have no idea how much of a problem that
might be on some engines.

wrote in message
ups.com...
Dear Peter,

Coatings were originally developed as a means of prolonging the life of
the blades in the hot-section of turbines was metal spray using
plasma-arc, which meant the base metal had to withstand some
significant temperatures during the coating process.

Tech-Line's approach (and others) successfully bonds a
zirconium-ceramic alloy to a properly prepared aluminum surface at a
temperature of only 350F. Since this is clearly impossible I'm sure
most folks have discounted such coatings out of hand :-)

The thermal barrier coating material comes as a thick water-based
'paint' having unusual wetting qualities. After being sprayed or
brushed onto a properly prepared surface the stuff is allowed to dry.
The coated pistons & heads are then put into an oven, brought up to the
cited temperature and held there for a given amount of time. The
result is an apparently alloyed ceramic-metallic surface.

I don't know how it works but here are some guesses based on my
experiments.

The most critical factor appears to be the proper preparation of the
surface, which must be abraded with a sharp, relatively fine-grained
media, such as #120 aluminum-carbide. Examined under a 30x binocular
inspection scope your nicely machined surface has been converted to an
infinity of edges so fine that they refract light. (If you put an
abraded but un-coated sample into the oven for the required amount of
time, on examination you will see that the refraction vanishes; the
surface still appears abraided but is now smoother.)

Getting the coating material to 'wet' the abraided surface can be
difficult. The metal must be perfectly clean -- touching an abraided
surface with your bare hand is enough to cause the coating to fail (but
leaves a nifty metallized fingerprint :-)

The coating material appears to consist of a combination of finely
divided (ie, powdered) frits. During the heat-soak period -- after the
coated part is brought up to the required temperature -- the frits
appear to melt in a eutectic-like process, with those which melt at a
low temperature forming a solution which cascades the melting of those
having a higher melting temperature.

I can't say if the result is a true alloy or simply an exotic form of
hard-facing but the result is a durable, heat-resistant surface. You
can bend it or beat it with a hammer and it stays put. You can also
heat it with an O/A torch immediately adjacent to an untreated coupon
and see the latter melt (!) will the treated surface remains unchanged.

Obviously, impossible, right? :-)

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So what does all that mean?

According to Sir Harry Ricardo (and others) during the intake cycle the
residual heat causes the incoming charge to expand, effectively
reducing the engines volumetric efficiency. In a similar vein, the
instant combustion is initiated the surrounding structure begins
absorbing heat produced by the combustion process, so that by the time
the process ends the temperature within the combustion chamber -- and
the pressure resulting from it -- are reduced.

In the Otto cycle engine TBC's yield slightly higher torque for the
same fuel consumption. I've no idea how much of this may be attributed
to improved VE or increased BMEP -- and on a small engine, with
home-made sensors it's impossible to quantify those results -- but with
a test club turning the same rpm I've seen a reduction of fuel
consumption of 3% to 7%.

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As you've pointed out, there's no such thing as a free lunch. Thermal
barrier coatings cause more heat to appear in the exhaust port and
exhaust stack.

The need to coat the head & neck of the exhaust valve is clearly
indicated but even so, the stock VW valve is a rather dinky bit of
goods having a stem only 8mm in dia. On the advice of Tech-Line I've
treated the valve stems and guides with tungsten disulfide, a dry-film
lubricant that is merely burnished into the clean, unabraided metal
surface. I've also modified the VW's lubrication system so as to
increase the amount of oil reaching the rocker galleries by about 8x.
The valve gallery was abraided with coarse media (sand, in this case --
I was worried about media residue contaminating the oil) cleaned
ultrasonically and treated with a thermal dispursant. On the stock test
engine the oil temp was 8% to 10% higher, compared to an untreated
engine.

As for the exhaust stacks, while monel or stainless steel might serve,
my budget dictated plain carbon steel. This was treated with another
type of thermal barrier coating and held up quite well, assuming the
coating was properly applied. The tricky bit here was getting a
uniform coating on the interior of the tubes, which proved impossible
when the stack was made up of welded sections. Although unsuitable for
flight, I fell back on cheap, after-market headers and 'J-tubes.'
These are seamless, mandrel-bent tubes which were easy to prep and
coat.

(As a point of interest, the test engine had a unique 'bark' unlike
anything I'd heard before. To keep peace in the family I fitted
mufflers to the stacks.)

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Finally, as with most experiments I had more failures than successes.
But there were enough of the latter to convince me that, when properly
applied, coatings would do no harm and had the potential to provide
some improvement in the durability of an engine assembled from
after-market VW components.

-R.S.Hoover

Thanks,

Those are truly fascinating results, and I wish that your experiments could
continue. If a local EAA chapter in your area has 501c3 status, and if
enough of the lurkers are interested, anything is possible, although not
necessarily probable. That would at least allow the original goal of
determining durability to be met. Obviously the addition of the mufflers
during the experiment add a "fudge factor", but the circumstance you
described is interesting in that it suggests that the residual pressure from
combustion is higher in the treated engine at the time that the exhaust
valve opens.

All of this suggests, at least to me, that the claims made by both Tech-Line
and the maker of the MPG-CAPS applied through the fuel system are true.
BTW, I am currently trying MPG-CAPS in my car, which does appear to run
better and more smoothly at the lowpower levels at which cars normally
operate; however I doubt that I will ever be able to accurately quantify the
effect on fuel consumption. I am sorry that I don't have more training
and/or real world engine experience to contribute.

Peter