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