Paul, Doug, Bill, Rob, and all--when this issue of cooling related to
the spark plug boss area came up, Doug and others asked for photos and
information relating to the cooling on our Superlight prototype build in
the 1990 and developed through 1995. Sorry it took so long . Each of
these photos was taken from color transparencies so they were
monstrously large. They had to be reduced too much to send and it made
them a little ragged without enhancement. After I bring them up, a
simple double left click restores the image quality.

A few notes--

1. Most of these photos shown are of the SuperLight engine/installation
in the RV-3; two are shown with the successor conversion engine
installed in the RV-4 but others show the two engines side-by-side on
the bench. The Mazda conversion prototype was subsequently test flown
in both the RV-3 and RV-4. The conversion engine was essentially
a Mazda engine which among other things included our ports/induction
system, mechanical fuel injection, electronic ignition and internal spur
reduction gear for the propeller. Standard unmodified gen two water
pump worked very well.

2. On the Superlight, the coolant "in" is shown with the hose connected
to the center manifold on top of the engine (this engine was indexed 90
degrees). This cooling manifold had cooling jets directed at the spark
plug bosses. The return fitting and hose can also be seen. The Aeroquip
fitting on the center housing is an oil line (this was a dry sump
engine). Some photos show components partially assembled or off.

3. We made this externally mounted and routed pump on
the SuperLight from a combination of OEM parts and others we had cast
and machined/welded in-house.

4. There two water heat exchangers are shown angled up on each side in
the RV-3 installation photos. A third exchanger of exactly the same
size for cooling oil was mounted between them on the horizontal. All
three of these were identical size/model Serck plate-finned, furnace
brazed heat exchangers which are sold for use as race car oil coolers.
Very efficient. Because these have no header when used for water,
we fabriacted the one shown in the photos. It was also a tangental
swirl pot for coolant. The configuration for this was from
a declassified WWII technical paper. Worked great.

5. Included is a photo of our aluminum end housings prior to application
of the wear surfaces to give you a better idea of the cooling flow
through them.

6.This engine mount of the RV-3 shown in these photos was modified for
the conversion engine. We swapped the prototype conversion engine back
and forth between the RV-3 and the RV-4. To save work when converting
the RV-3 engine mount, we simply left the heat exchangers and baffling
used on the SuperLight installation you see here which had an aluminum,
annular-inlet cowling. It was in this form that we raced the RV-3 at
Sun'n Fun in 1997 with Alan up in time-to-climb and cross country 100 mi
race.

7. For the Mazda conversion engine, we found with sustained high power
settings without the cooling jets in the manifold shown here atop the
Superlight engine, it was necessary to modify the standard rotor
housings to increase surface area and coolant turbulence around the
spark plug bosses. And we also found the second gen water pump the best
up to that point, and adequate in a 100 mile race and other testing.
while these results were very encouraging, they are by no means was
definitive long terms at the same and/or higher power. .

8.As I look at these photos now, they reflect the observation which
Paul made a few days ago relating to the cost and complexity of altering
the basic Mazda system. Most of this kind of complex one-off stuff such
as our SuperLight has little applicability to the collective advancement
of rotary aircraft engines to the largest number of enthusiasts. Our
goal was ultimately limited production. We did most stuff in house--the
exception was some foundry work, some gear cutting, heat treating, wear
surfaces, etc. But even with doing most everything in house, it was an
obscenely expensive program, and the inherent complexity a siren's
song. We both spent ourselves into the poor house. We found we could
eventually develope these complex systems for cooling, torsional
vibration control and others work but the costs and complexity put the
finished piece(s) were beyond a reasonable point for target consumers.
That's why we ultimately focused finally on refining the basic Mazda
engine with our basic systems evolved with the earlier
prototypes. Although the Mazda iron end housings imposed some
performance penalty due to weight, but rugged as hell. We tweaked the
ports and runners and turned up the rpm and both the RV-3 and RV-4 were
faster with the conversion engine than the SuperLight. But the
Superlight was a labor of love at 167 pounds including all accessories.
But from it and other proceeding engines, we were able to develop
systems which were simplified for use on the Mazda conversion engine
with little or no performance loss.

Spending so much time and money on R&D with our earlier rotary aircraft
engine programs ultimately led us to conclude it is much more
cost-effective to optimize the basic Mazda configuration. That includes
the basic cooling configuration and components.

Steve Beckham

Steve,
Thanks for your updates! I, as all of us, love the Superlight engine. I
still think there is reason to continue that develop that engine or
perhaps a blending of the superlight and the production engine. Cooling
still presents itself as one of the problems in a high-output engine.
The aluminum side plates are a great item. Integrating the engine mounts
is a excellent bonus. The braized steel side plates might be the best,
most durable solution to the light weight side, intermediate, plate. The
work you guys did needs to be preserved so the entire design doesn't
need to be re-done from scratch. Many of these types of mod later become
the accepted practice in engine building.
Bill Jepson

I agree Bill.
What a great little power plant.
I'm still trying to work out the water flow.
It appears to me that the light version is plugs-up with remote oil
reservoir, water in the top of the rear housing going through to the front
housing and out the other side of the rear housing.
Is that how you see it?
George (down under)