The trouble with any kind of wear coating on bare aluminum is there
are only a couple of molecules between you and disaster. It is
extremely sensitive to any kind of foreign particles. The only kind
of tried and true, robust and reliable wear surface for piston
engines and rotary engines is a hard steel steel liner.
Paul Lamar
Paul, earlier you said that the steel liner increased thermal
efficiency, would putting a 2 or 3 times thicker liner in, make a
significant difference?
Dave James
I think it would as heat transfer is a function of the distance it
must travel. Everything I have learned on this subject in regard to
the rotary has to do with keeping the oil working between the apex
seal and the wear surface. That is what the cooling system is
required to do.
In that case just using synthetic oil should cut the cooling
requirements. I discussed this with the Mazda factory several times
and their attitude was we did not try Mobil One so it is not
endorsed one way or the other. However the large Japanese oil company
Idemitsu sells synthetic oil for the Mazda. I use it in my RX8.
So far I have not seen a tech paper on this subject where synthetic
oil was tried back to back. It should be investigated with both iron
and silicon nitride seals. The question is: What temperature can the
wear surface be and still work?
Perhaps Frank Herfert can help in regard to a tech paper on this
subject. Here is some info from Rotary Engine.
This is relevant to piston engines as well.
Paul Lamar
This is an interesting chart from Heinz Heisler book Advanced Engine
Technology. You can see how the oil film would cool the apex seal.
Organic oils break down around 250 F so the OMC was designed around
that factor. Synthetic oils help a lot.
The apex seal takes the brunt of the heat as it sweeps all the hot
gas stagnant film in front of it. The steel wall temperature is
quite low. My guess is 300 F.
Silicon Nitride seals are a major advance and should be used in all
rotary aircraft engines as they will tolerate 1000 F.
Paul Lamar
Paul,
Mazda went trough hell and high water to solve the chatter problem.
Since then 2.5 million steel lined chrome plated rotary engines have
been sold. All others have failed.
Henry Ford said : "Show me a pioneer in technology and I will show
you candidate for bankruptcy" . Or words to that effect. I agree with
Henry :-)
If it were me I would copy Mazda with regard to the wear surface.
Paul Lamar
Nice Paul, good info on the apex seals.
The chrome plating of the rotor housing is the same technique used
for Chrome plated piston cylinders?
David Mikesell
Yes. I would think any chrome shop could do it. I think they reverse
the current for a short while after it is done to get a bit of
porosity on the chrome layer to enhance oil wetting. This would be
far less expensive than any other kind of effective coating on
aluminum. 2.5 million rotary engines prove it works.
I think they can mask off the surfaces that do not need to be
chromed.
My name for the all steel new design is "Unsymmetrical Rotary"
Copyright Paul Lamar 2016
I will scale it up to Mazda size and determine the weight. I'll bet
it is not much more than a stock Mazda rotor housing. I was right!
The stock Mazda ( mostly aluminum) rotor housing weighs 6.5 pounds.
The Unsymet all steel water cooled weighs 7 pounds. Plus or minus a
few ounces.
It is all that useless junk on the cold side of the Mazda rotor
housings.
The air cooled Mazda version would be about the same weight.
The way to make the aluminum heat sink fins is gang slitting saws.
This is the way P&W and CW did it in the old days on radial engine
cylinders.
The way to get rid of most of the material in the big block of steel
is drill a trochoide pattern roughly in the center. Then band saw it
out. That is the way the Wright brothers built their first crank
shaft. They drilled a big block of steel then they sawed it to rough
shape.
Anybody for an air cooled one rotor Mazda size rotary engine
weighing 70 pounds and putting out 130 HP ?
E-shaft and rotor the same Mazda parts.
Of course :-)
Paul Lamar
Anybody for an air cooled one rotor Mazda size rotary engine
weighing 70 pounds and putting out 130 HP ?
Paul Lamar
For sure, can the original rotor housing be modified to attach to
"new design" side housings
Steve Carlisle
Maybe but I don't think so.
Here is what it looks like with the off the shelf heat exchangers.
These are far lower cost than if you made them your self. They are
extrusions and the fin thickness and spacing is far far better than
the OMC cooling fins.
Green is steel and blue is aluminum.
The end p[late are chrome plated to reflect the heat which is an
improvement over the Mazda.
Paul Lamar
Paul, can the side housings be designed to captivate the heat sink,
and rest on the rotor housing ?
Steve CCarlisle
I am not sure I understand what you are purposing. The heat sinks
must be held in firm contact with the steel rotor housing for good
heat transfer. I intend bolting them in place with 10-32 screws.
Paul Lamar
And some heat sink compound.
Mark LaPierre
Just curious, how do you seal between the center housing and the end
plate? That may be a bit of a challenge. Nice design, though!
Gary Knutson
Metal to metal. The same way Mazda does it. No head gaskets.
There is a silicon rubber O-ring that keeps cooling water from getting
into the combustion chamber. We don't need that here as this engine
is air cooled. There are thousands of pounds of clamping force
due to the 17 tension bolts in the stock Mazda. In this case a couple
of dozen 10-32 screws
Prior to about 1974 the O-rings were neoprene.
Early engines when overheated would melt this o-ring. The engine did
not stop running but it was hard to start the next time due to coolant
in' the combustion chamber.
Everybody thought it was an apex seal failure and the car manufactures
heaved a sigh of relief and piled on. People still ask me about it. At
that
time Mazda was selling 300,000 rotary powered cars a year and the other car
manufactures were really worried.
Then came the fuel shortage and Mazda came under criticism
for burning more fuel. Anything to get rid rid of those damn Mazda's.
The power to weight ratio of my 12A RX2 was extraordinary for the
time. 130 HP and 2000 pounds so we drove the heck out of them because
it was so much fun. Using the power burned the fuel. I raced an Opel GT
across the Ohio Turnpike back in 1973 and the Opel engine blew up
before we both made the state line :-)
Mazda rotaries started dominating road racing. They won the Datona
24 hours more than an other brand until they were handicapped by
being forced to carry several hundred pounds of ballast.
Paul Lamar
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