Hi Ed,

My thoughts on making the rotor housing steel liner for a 13A/16X
size radius
would be to try to get a 13A engine. Doug, would you have any leads
on one in
Japan? With that we would have the shape of the inside. Casting a
steel shape
that is the inside dimension would help form the proper shape. We
would need a
die for the outside so it forms correctly. Figuring the inside
circumference
would enable machining a 4130 pipe ID to that dimension. Then
machine the
grooves in the OD with a tapered burr so the cast Al forms into it
and can not
come "unglued" or separated. Then forming it with the dies to the
shape. The
Al could then be cast around it and the width machined. The area for
the Pport
could be left without cooling to eliminate sealing there, and the
port almost
ready to go.

Anybody alse have an idea on this. Paul, what is the thickness of
the Mazda
steel liner?

Dale Davies

It is very thin. On the order of .065. Here is how Mazda does it.
You would be reinventing the wheel :)

Paul Lamar


Dale Davies, I don't think you need a housing to measure. There is in
the Kenji Yamagughi (sp) papers found on the rotaryeng.net
<http://rotaryeng.net> site the formula for generating the shape of the
trycoid housing. It is generated by  the path of the 3 rotor tips as
they revolve while the eccentric shaft rotates. You can generate
cartesian or polar coordinates to as many decimal places as you desire.
I think my desktop does to 27 decimal places but I have it set to 5
since that is ten times as accurate as CNC can machine and more just
increases the file size. A CMM (coordinate measuring machine) is not
this accurate.

If you change either the eccentricity or radius you will be
makeing a new trichoid shape that hasnt been produced and therefore
there aren't any parts to measure. The Lada and Chinese rotaries both
use the Mazda dimensions. Curtis Wright has a vast number of
displacements for use as both engines and pumps.Some are six feet tall
inside the rotor housing. They all seem to have the  same ratio of
eccentricity to radius. If you increase eccentricity relative to the
radius you improve torque, however I suspect it will not have as high an
RPM as the current optimized dimensions. Changing the ratio also changes
compression ratio which will require building a matching rotor with the
correct combustion chamber depression. The volume of the depression for
a given compression can be derrived from formulas posted on this site
last year. If you leave the ratio the same and go larger then the
currently designed end housing databases can be 3D scaled up in the X
and Y dimensions with the same Z  saving some design work. Several of us
have end housing databases including Jeff and myself.

 The problem with building rotor housings is the final finishing
steps. They need machined and lapped to .0001 accuracy. This is
currently done on specialty equipment and not likely possible
with normally available  CNC machine tools.

 Although scratch building a rotary engine is a huge task, by the
time you are able to fit lubrication and cooling oil flows  and coolant
glycol through the mechanical and structural elements of the engine you
will be better able to modify the available parts to suit your needs.


george grimes