Paul, I have been thinking about this for some time... I really like
your idea about the aluminum side housings with the steel inserts with
the "O" ring seals. Here's an idea:
What if the stock Mazda gaskets were used and a simple steel side plate
was used with an extra side gasket with an aluminum side plate of said
thickness between the 2 center side steel plates and single end steel
plates was used ? Much simpler to cast and machine. What do you think ?
KISS :-) Seams like center and end aluminum castings plates could be
milled on a Bridgeport, save for the steel plates.
-dave
Make them three piece instead of two? It would probably work but it is
a lot of water seals. A lot cheaper than a hollow end housing. Probably
also cheaper than a hypereutectic end housing as well.
---------------------------------------------------------------
If we aluminum brazed the back piece on I think it might work.
Larry could do this in a heart beat. P-ports only which would
vastly simplify things. Heck JB Weld might even work.
REAL easy to try.
The steel wear plate could be through hardened and nitrided or porous
chrome
plated.
Paul Lamar ...No rotor no motor.
Paul,
Couple things:
I asked on an earlier email and didn't get a response. The Rotomax side
housing are det. coated aluminum. I assume that their rotor housings are
their design as well.
Question 1: Do they SIP or det. coat the rotor housing as well?
When we talk thermal expansion problems the easiest thing to do is have
a similar metal througout the entire engine to have a consistant growth
and shrinkage along with the corresponding induced stresses. Radial
expansions such as bore liners in pison engines, SIP inserts in stock
rotor housings, and expansion plugs for aerospace fluid passages are
very predicable in their growth and shrinkage which allows you to easily
control the room temp fit to reduce contact stresses.
I like the idea of a two piece side housing for its replaceablility as
well for someone like me who is interested in doing their own custom
side housings. The only worry I would have is since the insert isn't
part of the casting the thing will warp from the heat variation across
the surface and also because even though you have some sort of standoffs
under the surface, there is no clamping load to make it stay put.
This will cause variations in the clearance to the rotor I would imagine.
Question 2: How critical in the side clearance to the rotors?
The drawing you have is for the o-rings in the side housings while the
rx-8 has them switched to the rotor housings. Your drawing also shows
the coolant not being exposed to the backside of the metal insert. The
stock inner o-ring serves as a combustion rings as well as a coolant
retaining ring.
Question 3: How do you control the radial postioning of the insert if
you have an o-ring between the insert and the side housing?
Question 4: Wouldnt you want to press fit the insert into the side
housing much like a cylinder liner to close off the water passages and
use the clamping of the housings to axially compress that interface like
your pic shows and have the inner rotor housing seal on the axial face
of the insert instead of on the radial face?
I am not criticizing your idea but just wondering how you get that to work
correctly with the thermal expansion and making sure things are
clearance correctly. I saw the pic of your buddies two piece he made for
the single rotor and wondered if the ring of bolt about the stationary
gear combined with the clamping of the rotor housing would be adequate
for the job.
The other thing is how do you get this to all work for a side port
intake and exhaust engine? I have my ideas but I figured I would hear
yours before chiming in.
Rob Woods
?1. I don't know. They are not saying.
?2. It is critical down to .001. I don't know the actual clearance number
but it is probably in the shop manuals.
?3. We may use short studs welded to the wear surface that fit in holes.
?4. No press fit is needed as the rotor housing keeps the side housing
wear insert in place.
Last question. The short answer is: you don't. It will only work with
a p-port intake and exhaust. The big advantage of this system is the wear
inserts and be replaced when worn.
Paul Lamar
Paul,
Alan Tolle told me that there were some steel housings that were
machined in 2 parts for the "ultralight" engine. I wonder if Steve
knows all about that one? They were supposed to have been furnace
brazed together prior to face machining the large faces. I always
knew this would work but would love to hear any specifics.
Bill Jepson
Regarding Bill Jepson inquiry-- Everett and I did indeed build a very
light-weight two rotor engine using thin-wall, furnaced-brazed housings.
This was a prototype, direct drive rotary engine for small aircraft. I will
try to find the file with specifics but as I remember we used a 12A
eccentric shaft and Mazda rotors.
Doug Johnson (now retired working on a
Bonneville streamliner) of Precision Castparts here in town consulted on the
project. We drew up patterns and these were CAD/laser cut by BBC Steel of
Canby, Oregon. These pieces were all then fixtured together,
furnace-brazed, then nitrided for wear surfaces. We final assembled the
engine after the housings were completed, but didn't have a chance to run
the engine before Everett died.
It went with all the other Powersport stuff
when the inventory was sold after his death. This stuff also included
SuperLight engine housings for the prototype all-aluminum engine we ran for
a few years in Alan's RV-3. That complete engine and a Powersport 200
engine and reduction gear were also included.
Everything was sold to Ray
Richardson at Raytech Machine (now Powersport Aviation). I checked with BBC
Steel and they cannot find the programs that were used to cut all the steel
pieces for the furnace-brazed engine. I found just a couple of our
original notes for this direct-drive engine in the file but did not see the
detailed file notes we always kept when we assembled engines. They may be
commingled with the other files.
I did find a note for the direct-drive
engine that we did when we started work on it. We planned on using very
conservative port timing and with a single side-port to shorten intake
duration, shooting for a conservative 90 h.p. @2750 rpm. We also were
hoping to experiment with oil cooling of the trochoid housings. It was a
long shot but we were hoping it might be possible due to the lower heat flux
produced at the lower rpm and allow use of only one heat exchanger. The
heat exchanger would become the oil tank.
Target weight was 125 lb with an
installed weight of 165 lb. Will check the files again for the housing
drawings but I did find in the file numerous photographs I took as we
fixtured together all the fluxed pieces. We were concerned the housings
would "potato-chip" when nitrided but to our surprise they came out well.
Too bad we were not able to further develop this little engine. In addition
to folks who had small aircraft, some guys at NASA asked about it--assuming
it was for some possible drone application. Our intended market was for a
class of aircraft that is now LSA. And with the Rotax now costing so much
it seems it would be much cheaper to build a lightweight, simple direct
drive rotary that would be competitive on power.
Steve Beckham
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