>> 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
Hi Steve,
In all of your weight reduction efforts, did you ever try simply
machining "excess" stock off the Mazda origional cast iron housings?
There looks to be a plethora of opportunities especially considering
only aircraft use (ie.: auto motor mount area, possible external oil
line routing, machining cast surfaces down to say .005 below the lowest
level of as cast, etc).Thanx for all your hard earned information. Dave M
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