Paul,
When I was at the Seven Stock Show, I noticed that all of the rotors were cast iron.
Has anyone made aluminum rotors? Is there too much thermal expansion to use aluminum?
I was also thinking that the rotors could be made of a ceramic--low expansion, lighter
weight, and possibly lower cost.
Steve Brazil
I think it is a heat issue. The rotors can run 500 F or more. Titanium seems to work
but it is expensive.
Paul Lamar ...No rotor no motor.
Here is a photo of a lightened Mazda 13b rotor. It can be found on the website
http://www.der-wankelmotor.de/Motoren/Motoren_Mazda/Mazda_13B/mazda_13b.html
Does anyone know anything about this? It seems to me that not only can we make the
rotors out of a lighter, more durable substance, we can alter the construction.
The rotor does not need to be a solid. It can have just the material it needs to
have. It will be lighter and can still be reliable.
I do not read German. I do not know if the German written beside the photo has
anything to do with the photo of the lightened rotor. I have included it, just in case.
http://s12.photobucket.com/albums/a234/JacobPotts/Atom/Rotary%20Engine/?action=view¤t=LightenedRotary13BEngine001.jpg
Les Nordman
This photo only shows the cross section of a stock RX-8 rotor cut in half. As you
can see, there is not a huge amount of excess material in the rotors. The face
of the rotor must be able to hold the maximum combustion pressures with minimum
flexing in order to survive.
On the subject of titanium, I have built many race engine parts out of ti. It
is it's own animal when it comes to designing with it. Any surface that will see
any friction has to be coated with DLC (diamond like carbon) or a similar coating
to prevent galling. The apex seal area would have to have a steel insert. The other
issue would be the rotor running much hotter, as ti does not transfer heat well and
you could run into the case of the seals overheating. With enough money for building
the investment casting die, we could test this... but the question remains as to why
we need it so much lighter if we> don't plan on spinning the engine above 7500 rpm.
Larry
1. About the photo of the seemingly skeletal Wankel rotor, Larry wrote:
"This photo only shows the cross section of a stock RX-8 rotor cut in half."
Ah, so stock Mazda rotors have a solid surface on the side, but, internally,
they are hollow, with "spokes" of metal radiating out from the center to the
outer edges, just enough material in it to take the stresses. I though the
stock rotors were solid iron all the way through. Thanks, Larry, for making this clear! :-)
2. On the general topic of lighter rotors, Larry says, "but the question remains
as to why we need it so much lighter if we don't plan on spinning the engine above 7500 rpm."
Okay, it may very well be that this noob does not understand, but that is what this
forum is for, right? :-)
The noob responds, "Larry, I don't know about other contributors to this forum, but I
was thinking that lighter rotor construction, as well as lighter rotor materials,
would be part of an overall effort to reduce the weight of a rotary engine. If the
engine is lighter, we don't have to lug as much weight around up in the air. We will
go faster, turn better, get better fuel mileage, and go farther.
And yes, Larry, I am still interested in also applying this to The Dark Side of
rotary engines: a lightweight rotary engine for lightweight cars such as the Ariel
Atom and the Caterham."
(Cue Star Wars Imperial Death March)
Les :-)
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