Hi,
     Finally, got the rotor in the mail. Thanks to Paul. (Is it RX8  rotor? I
    remember that You mentioned that pocket and faces are machined.  On this one
    pockets a left as cast.)
    I agree totally with what Paul and Rob are suggesting.
    Next steps:
    1) Disassemble it.
    2) Cut in two halves.
    3) Scan it.
    4) Create a valid 3D model of standard Mazda rotor.

    Here I will need help from Rob.
    Rob, as I understand You've got
     all the math to model the rotor faces. If I
    remember correctly You're working with Pro/E. Is it possible  that You model
    outer geometry (faces) and send me the file (native Pro/E or  any common -
    Parasolid, Step or IGES). Modeling the faces out of scan data  is not the best
    idea IMHO.

    5) As Rob mentioned "Cast Ti has anywhere
    from a 1/2 to a 1/3 less thermal conductivity versus cast  irons. 40
    percent less density, half the expansion rate, double to triple  the
    tensile strength but anywhere from equal to half the modulus of
    elasticity. If i were just looking at it, without changing any
    dimension(based on modulus vs. tensile) it would be about 40  percent of
    the weight of the rotor."

    If I remember it right Mazda rotor is made out of ductile iron.  Its properties:
    Elastic Modulus    120000    N/mm^2
    Poissons Ratio    0.31   
    Shear Modulus    77000    N/mm^2
    Thermal Expansion
     Coefficient    1.1e-005   
    Density    0.0071    g/mm^3
    Thermal Conductivity    75    W/m K
    Specific Heat    450    J/kg K
    Tensile Strength    861.695    N/mm^2
    Yield Strength    551.485    N/mm^2

    Now for the Ti cast rotor I'm planning to use VT20L which was  designed for
    extended work at 500C.
       Fe     C      Si       Mo    V    N       Al    Zr        O         H
    <0.3   <0.1  <0.15    2     2.5 <0.05    6     2    <0.15
    <0.012

    Elastic modulus    123000    N/mm^2
    Poisson's ratio    0.33   
    Shear modulus    46000    N/mm^2
    Thermal expansion coefficient    9e-006   
    Mass density    0.00465    g/mm^3
    Thermal conductivity    7.8    W/m K
    Specific heat    500    J/kg K
    Tensile strength    1160    N/mm^2
    Compressive strength    1170    N/mm^2
    Yield strength    1070    N/mm^2
    Hardening factor (0.0-1.0; 0.0=isotropic; 1.0=kinematic)     8.5e-007    N/mm^2

    Advantages that we may have:
    Strength =   134.6%
    E modulus = ~ 100%
    Density =  65.5%
    Thermal
     conductivity =  10.4%
    Thermal expansion =  82%

    More than that at high temperatures  mech. prop. advantages  will be higher.

    Anyway as Bob mentioned we can  safely assume 30% weight  reduction of rotor
    assembly. I agree with Rob that revving the engine 20000RPM may  cause all sorts
    of problems. But revving the  3 rotor engine to 12 - 13,000 RPM  sounds realistic
    to me.

    Now, what's the current thinking about feasible price for a 7 -  6.5lb
    Titanium rotor? We're not talking about mass production but  high power
    applications.

    Thank You
    Ted

Ted,

I don't like scanning either. What is inherently wrong with it is that
it only lets you copy something without having the ability to  modify it.
Point clouds to surfaces is a useless tool unless you are trying to
knock something off. Part of all or our endeavors should be to
understand what we are doing so when we want to make a logical changes
they can be done easily and effectively. I think a particular good
product would be a lower compression ratio rotor for the RX-8 for
instance which has almost nothing to do with copying the current  rotor.

I think a very good idea would to send a rotor to a material science
center, maybe the one we had at University at Buffalo, to determine
exactly what type of cast iron that Mazda uses in the RX-8 rotors.
Especially to find out what the hardness levels are at the apex seal
slots. Cast iron is such a variety metal that speculating as to  what it
is pointless. Just test it. This should be on the hot list to do.  Other
rotors don't really matter so much since the RX-8 rotors are of the
highest apparent quality/engineering. If we don't have real data on  what
we are trying to improve then it will make it harder to make the
replacement as good as it could be.

I couldn't tell you what the cost would be for a Ti rotor. I am  looking
into it and will let you guys know when I find out. Read up on the  post
up to this point.

I don't use pro-e but that is the program it looks like we will  need to
use in order to accurately model the rotor and housing. Once done in
pro-e it can be imported into solidworks.
That os fine with me for now
since the primary function is to replicate what Mazda has done but  in the
long run I want to try different configurations so a better solution
will have to be found. I hope to find a way to make a macro that will
have this functionality.

Example:

http://www.profilesmagazine.com/p33/marsalek.html

Rob Woods

Trying to get my hands around this topic, and guess I will do some
cut and paste comments and see how it goes. (Don't do that Scott. Makes
a mess down the road.PL)

"4) Create a valid 3D model of standard Mazda rotor."

by this I assume you were wanting to get the rotor drawn out as much
or as accurate as possible?  There are CMM machines or digital laser
measure devices that will do a far far better job.  You do not have
to own one of these for this as there are many folks that measure and
draw out parts. or measure and give full dimensions.  More on this
below:

"Modeling the faces out of scan data is not the best idea IMHO."

With all the work done in 3D drawings for this motor, is this to say
that the drawings for the rotors have not been done before? or is
this a special rotor?  I must be missing something here.

"Yield Strength    551.485    N/mm^2"
I wish I could remember things that good.   ;-)

"But revving the  3 rotor engine to 12 - 13,000 RPM sounds
realistic to me."

I think this must now be taking this motor out of the aviation
catagory and into racing?  but still weight savings is king in the
aviation world, thus my interest.

"I think a particular good product would be a lower compression ratio rotor for the RX-8 for instance which has almost nothing to do with copying the current
rotor."

So was the first rotor mentioned above, a new and improved one, or
different type?  just asking.

"Once done in pro-e it can be imported into solidworks."

I am not sure of what function that Pro E has that 2009 Solidworks
can not do and do faster, easier and so on. Thus less money involved
for final end product.

Well just some thoughts tossed out.

cheers

Scott- Iron Design L.L.C.
Scott Weinberg

Not to worry for aircraft Scott. We have to be cognizant of racing car needs as racing is partially responsible for keeping the RX8 alive. No RX8... no rotary.

I am happy to see we will have five or six normally aspirated RX8's in the Jan 2009 Daytona 24 hour race. Stupidly... with a mandatory red line 500 RPM under the street RX8 car red line and ballast to make it fair to Rube Goldberg piston engines. Mostly Porsche's.

http://www.youtube.com/watch?v=zMW09hKJQIQ
http://www.youtube.com/watch?v=d5-5Autjr0w
http://www.youtube.com/watch?v=Xk7hcjX8fVU

Paul Lamar