I recently came across this patent application.
Apparently several people are making apex seals using the
EDM process. Any metallic material will work.

One can start with chrome molly 4340 pre hardened steel or any
other cast iron or steel alloy. Even some of the new high temp NASA
cast aluminum or BeAl alloys might be used and MAY work.
Don't breathe the fumes. The problem is the seals can run
over 500 degrees F destroying the lubrication. They must be
kept cool by an adequate quantity of oil. This is the
main reason charged cooled rotors don't work in heavy duty
rotary engines. The rotor temp. can run up to 650 F.
http://www.rotaryeng.net/OMC-heat-release.pdf
This is probably what caused the demise of the charged cooled
Rotamax engine.

I can see two problems with home made apex seals and I noticed
this with after market seals I have inspected with a mass
spectrometer and a microscope.

Problem number one: Mazda stock apex seals have a slight crown.
Read http://www.rotaryeng.net/seals.html Hard to do with EDM.
The first thing you will notice is a reduction in compression
pressures. This is because the seal is leaking.

Two: The finish on the seal is not mirror smooth as it
is on the stock seals. Stock seals are heated with laser
and chilled in liquid nitrogen. A less than mirror finish
in conjunction with hard steels is death on rotor housings.
EDM does NOT give a mirror finish.

Acicular cast iron used by Mazda is porous and retains lubrication.
Mazda spent millions on apex seal R&D so my advice is to stick
with the stock seals.
http://steel.keytometals.com/default.aspx?ID=CheckArticle&NM=21

Paul Lamar


I wonder what Aixro is using as apex seals, other than the ceramic
model.

Marc Joseph

Hi Paul, zorbi here...!
I have a enquiry about the metal for apex seals...!
Recently i was experiment with stainless alloy of steel with titanium,
that one have more possitive (about ours job) advantages...!
It was lighter

It was strong more than the steel of apex seal, i destroyed 2 noses of
drills to make a small hole and i destroyed zero drills to make home
to original apex...!

I was heated to the same fire both of them and with the same duration,
the apex was more brighter than the titanium who was more red light...!
After burn the apex lost the shine mirror look and never took it buck
but the other alloy steel was the same before and after, except from
some nuances in the surface...!

I do not have the opportunity to investigate more about that (what
about oil and the surface in microscope)
I thing it is good start or bud start but all the manufacturing
community will judge it...!

I was start searching because my renesis engine destroyed too early
from broken apex seal (i will send photos) and during the
investigation found that is missing a trird oil beck, at the middle of
the surface of apex seal was scraching but not the edges...!

At my opinion the original apex seal it is well enough for their own
use but not as 2 pieces (the driangular edge of 2 pieces style not
withstand at pressure) and with third middle oil beck will be more
reliable...!
My renesis work at 0.9 bar pressure...!

Regards...!
zorbi from Greece...!

The piston engine people found out over one hundred years ago
that cast iron was the best material for piston rings.  Mazda, after
trying everything under the Japanese sun, found out the same thing
for apex seals. Everything else chattered. The only thing proven
better than cast iron  so far is silicon nitride ceramic.

http://www.rotaryeng.net/history.html

Contact Francesco Iannetti <iannetti@pop.mindspring.com> for ceramic
apex seals.

Mix 2 cycle oil with the fuel and forget the third oil injector.

Paul Lamar