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