I still believe that alfa beta Ti alloys are best for this purpose :) Also casting (IMHO) is the best way to have desired complex internal geometry.
  We have to look at alloy mesh properties at working temperatures - Al is not up to the task - at elevated temp they loose strength very rapidly. Alloy that I suggest is designed for use at 400-450C without loosing its strength. Even being higher dencity material it leads to even lighter than aluminum rotor which is much stronger and reliable. Having high surface hardness It eliminates the problems with seal slots wear etc., etc. It's not a cheapest option thought but sertainly best aside from most exotic materials. That's what I want to see in the engine of my rotary supercar project :)

All thus IMHO.

Thank You
Ted

      So does anybody have a drawing or better yet 3D model of standard
      rotor? If not than we'll have to wait for Paul to produce one.
                  Thank You  Ted

      Does anybody know how to calculate the radius of the rotor face?

       Paul  Lamar



         Hey all,

         Here is the excel file I have been working on. It is not finished and I
         am still sorting out a couple errors here and there but it is getting
         there. Eventually the thing will be all correct and allow you to change
         the
          variables and do all sorts of neat stuff. I just got laid off
         recently from Delphi (note: F*%k the American auto industry) and have
         been busy with finding a new job so I will get back on it when I get the
         chance. Paul, note that the rotor equation never nets a constant radius.
         This data while representative of the the points cannot be used in a
         machine shop environment. This is where my questions of Solidworks 2009
         came from as you would need to graph the sketch of the equation and not
         a spline of a number of points. I checked with NX3 platform and SW2009
         and it looks like they are too simplistic to do what pro-e does. Who has
         pro-e that we can test out? I can gpo
          more into it at depth but will
         only do so if there are serious questions about it. Here are a couple
         things that will show you whats up with what I mean. I am working
         diligently to get this worked out because if my plan for a lightweight
         all steel
          brazed rotor works out then I can move to the next step which
         is increasing the capacity of the engine and and having the weight of
         the rotor as the cast iron version for the larger capacity engine be the
         same as the 13b/renesis. 8500rpm to 10000 rpm limit on a 1 liter rotor.
         That sound intersting to anybody?

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

         http://esoxrepublic.com/blog/category/geometry/splines/

         http://www.adras.com/SW2009-Equation-Driven-Curves.t8302-83.html

         Rob Woods

         If I am understanding  you correctly you are saying the face of the rotor
     is a
         not a circular arc?

         Paul Lamar


     Paul,

     The statement I made before is true.You can see by looking at the
     graphical output on my program that the curvature in somewhat flat in
     the middle where the combustion chambers are in comparison to where the
     apex seals are where the equation starts to take a swooping turn which
     increases the curvature. There isn't a solid radius arc anywhere in that
     equation. Kenichi Yamamoto wrote the book with all the derived and
     integrated formulas that net the equations of the inner housing and
     rotor. If it was a simple as drawing three circles and trimming the
     outside stuff I think it would have been written as such. Any attempt to
     look at it so simplistically without actually taking the time to work
     out what he provided us is a fools quest to put it lightly. So sagitta
     has nothing to do with this. This all comes back to what I have been
     speaking about. I can set up 1080 points or many times that number and
     import that into solidworks and run a spline through it all. A curvature
     comb placed on it will show all sorts of weirdness going on. Getting an
     accurate cad profile is priority for this since any custom housings or
     rotors need to be spot on for any number or reasons. There are a couple
     programs that can do this and with some resourcing I can get the
     profiles into Solidworks.This board is one of the resources I have and
     hope that someone can work something out with this. Or someone who is
     much better/smarter than I in programming Macros I can install into
     Solidworks. I have one so far but havent verified the accuracy yet.

     One thing that I think might be a constant arc is the side seals. They
     are not an offset of the rotor profile which makes me wonder why for one
     and also because how they might manufacture them. Constant section large
     diameter that gets cut into three pieces maybe? Is that the reason for
     not being a offset of the rotor surface?

     Rob Woods

     You are absolutely right. My mistake.
     I have no doubt what you say is true. I happen to know however the rotors
     have been machined three at a time on a turn table. I have a picture around
     here someplace of the machine. I think it was a Curtiss Wright machine. This is
     what fooled me.

     Obviously Mazda is not doing it this way unless there is something hiding
     behind the turn table. I did not see the machine used when I was in the factory
     but Mazda would not let me take pictures of that part of the plant anyway. It is
     not an NC machine as the plant was built in 1969.

     I laid a rotor on a piece of paper and traced the face curve.
     An arc with a 9.15 radius comes pretty close. Here is a scan of the paper.
     My 715 mm (28 inches) radius number was way wrong. I am not sure why. The arc
     radius is more like 9.15 inches. This is something everybody can try.
     This also proves your contention.

     Here is the fly in the ointment. All these engines require a depression
     in the face of the rotor to form the combustion chamber. What only matters is
     the exact path of the apex seals. I contend a pure triangular rotor with
     straight sides would work. The compression ratio would be too low but the engine
     would run. I contend an arc of some radius with a combustion chamber depression
     would be close enough.

     Interestedly enough here is a patent on a CW rotor face that did not come close
     to an arc.

     BTW Ansdale published the math in his book "The Wankel RC Engine" in
     1969.

     Paul Lamar


Paul,

Looking at that patent he is showing a knife edge apex seal that will
never work. Interesting shape but I would always stick to the math. All
of the work in Kenichi book is all dependent on each other as far as
calcs go so I would mess with anything. One thing to note on my
spreadsheet is that I will eventually replace the constants(all of the
2/3, 9/2 and such)in the equations with variables so we can visualize
lobe and housing number bigger that two and 3. It is a work in progress
and it is important to understand everything in and out before solid
design decisions are made.

Rob Woods

Thanks for doing all this work Rob. I am sure it will be useful when it comes time to machine some rotors.

I see what you are saying but I think the guy drawing the patent just got lazy and did not draw an arc on the apex seal. The apex seal had nothing to do with the patent anyway. If you want the complete patent I have it in a pdf.

I found that dwg on how to machine  rotors faces in the 1969 Kenichi Yamamoto book on page 119 and pagwe 120. Here they are.

There is one other thing going on and that is crevasses that store unburned hydrocarbons are not good. The side seals should be out as far as possible. I think the side seal slot is an arc on the current rotors so an arc along side an arc would work best. What Mazda is doing now is filling that gap with Teflon which must be pretty expensive.

I am still thinking about how to best machine this thing out of one piece and get some cooling fins inside for oil cooling. Steve Brazil's two piece idea welding  them together is the best idea so far. The face of the rotor must be supported by ribs the same as the bearing support. Rotor faces have been known to collapse. It behooves us to use the stock phasing gear and all the stock side seals if possible. I am open to suggestions. The Curtiss Wright method is a bit heavy. Perhaps we should not go for the lightest configuration at first but develop the optimum aluminnum rotor one step at a time.

Paul Lamar

  I still believe that alfa beta Ti alloys are best for this purpose :) Also casting (IMHO) is the best way to have desired complex internal geometry.
  We have to look at alloy mesh properties at working temperatures - Al is not up to the task - at elevated temp they loose strength very rapidly. Alloy that I suggest is designed for use at 400-450C without loosing its strength. Even being higher dencity material it leads to even lighter than aluminum rotor which is much stronger and reliable. Having high surface hardness It eliminates the problems with seal slots wear etc., etc. It's not a cheapest option thought but sertainly best aside from most exotic materials. That's what I want to see in the engine of my rotary supercar project :)

All thus IMHO.

Thank You
Ted