Combustion pressure was believed to be a major design issue. Subsequent
design modifications and dyno and flight testing helped somewhat but
ultimately we concluded that even in improved, modified form,  housings of
aluminum alloy using materials available at that time was not the best
material for long term service life.   Our experience with the Mazda factory
cast iron housings was very good in all respects except weight.  It seemed
that the rigid cast iron housings, together with the steel insert in the
throchoids, provided a very solid structure with none of the problems
involved with aluminum.  But due to the weight of the cast iron, to attain
the best compromise of power-to-weight and longevity, it was  determined
thin-wall steel housings with nitrided wear surface would be best.  We
researched investment casting of these and found it was simply was too
costly.  That is when we turned to furnace brazing.

For doing the first set of these housings test housings, design methodology
was very basic.  But Everett spent considerable time researching and
computing stress-deflection (compression) of  columns from combustion
pressure and  a stress analysis (elastic strain) of stress in the end
housing wall produced by combustion pressure of 1,000 psi.  Deflection rates
were calculated for a 1" square plate fixed on all edges and a  uniform load
over a small circular area at the center for steel .120 thick, equivalent
cast iron .200 thick and aluminum .200.

After the prototype housings were furnace brazed they were machined  and
surface lapped, then shipped for nitriding.  After nitriding we finished and
final lapped prior to assembly.

Weight of furnace brazed steel housings taken during assembly of the power
section were:
Center housing--9.75 lb
End housings--10 lb each

By comparison, our cast aluminum housing weights--
Center housing--8.75 lb
End housings 7.5 lb.

Steve Beckham.

Thanks, Steve,  for the extremely interesting account.  All of this
information would be lost without your publication of it and it points
the way for us to go onward.  In particular it is amazing that
aluminum housings only  save 5 lbs total for the single. Thin steel
brazed inserts is the practical way to go as you have pointed out.   I
wonder if some of the machinists on this list could produce them.
All we need is two housings and an eccentric for the single cylinder
to be a viable reality.  That would be a nice package to find at the
door.     Jerry

Yes Steve, great work !! Thank you !

We should realize the aluminum housings save about 25 pounds over the
stock cast iron housing on a single rotor. So, these brazed steel at 20
pounds less than stock as so close :-)

http://www.racingbeat.com/FRmazda2.htm

One thing not clear to me, these brazed steel housings - they are simply
thinner versions of the cast stock, or is there an aluminum part as well
forming a sandwich end housing of a thin steel layer next to the
combustion chamber, and an aluminum section adding strength like the
foam in a Rutan plane ? If is it only a thinner steel end plate, the
e-shaft would need to be custom made shorter ?

-dave

Guys--regarding your additional questions about construction and design of
our furnace brazed prototype end and intermediate housings,  these rotary
engine housings were not in any way copies of a standard Mazda cast iron
housing.  But they were designed specifically to accept a standard Mazda
rotor housings with peripheral ports.  The end and intermediate housings
contained no aluminum or cast iron...they were all steel except for flux and
paste.  Doug Johnson of Precision Castparts (now retired and building a
Bonneville streamliner) was our technical advisor during the evaluation and
sourcing process for both investment casting review and finally the furnace
brazing approach adopted.  The flat pieces were all lazer cut by BBC Steel
in Canby, Oregon and round columns machined prior to fixturing and furnace
brazing.  Each housing looked outwardly similar in appearance to our last
generation SuperLight aluminum housings and  the end housings were designed
to accept the one of a kind engine mount used in the RV-3,  Engine mount
ears were cast into the side of each housing. Photos of this mount/housing
configuration were distributed earlier showing this engine mount with the
all-aluminum engine installed in the RV-3.  Hope to be able to provide you
further clarification.
Steve Beckham.

Brazed steel engine blocks are not new. Mercedes used them right after WW II
in their racing cars. Crosley used the idea in its four cylinder engine
for its little sports car back in the late 40's and early 50's.
I had a Crosley sedan while I was in college.

It was also used for a short while in early Mooney Mite's. Scaled down P51s
so to speak.

http://auto.howstuffworks.com/1949-1952-crosley-hotshot-and-super-sports1.htm

"The cast-iron Hotshot/Super Sports engine, called CIBA (for Cast Iron Block Assembly)
was the successor to an earlier Crosley powerplant that was uniquely made up of
stamped steel sheets. This earlier engine, dubbed the Crosley Cobra
("Cobra" for COpper BRAzed), used 125 thin steel stampings brazed together
in a 2,060°F furnace. With its nondetachable head, the Cobra block assembly
formed a single, lightweight, layered unit."

"The Cobra engine's cylinder sleeves were iron and the crankshaft rode
in five beefy main bearings. This engine, like its cast-iron CIBA heir,
boasted a shaft-driven overhead camshaft and full-pressure lubrication.
Bore and stroke being over-square helped keep down friction and wear."

"The Crosley Cobra block and integral head tipped the scale at all of 14 pounds.
Fully assembled, the engine weighed only 138 pounds. Conceived for the military,
the Cobra four was designed to run at a constant rpm. In cars, the varying rev
range caused valve-seat inserts to crack, and the block tended to warp if the
coolant fell below a certain level. Also, electrolytic action between the steel
and copper layers could cause leaks."

It was also used for a short while in early Mooney Mite's. Scaled down P51s
so to speak. When I was 14 and learning to fly the Mooney Mite was hot stuff.

http://www.mooneymite.com/articles-history/Avweekaugust1948.htm

"Its primary advantage is its economy of operation, due to the use of a 25-hp.
Crosley Cobra engine, adapted from the Crosley automobile. Plane will be
priced at around $1600, the lowest priced airplane on today's market."

The idea goes even further back than that as the OX5 had welded or brazed
water jackets as I recall.


Paul Lamar ...No rotor no motor.

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