>     Don Bedwell,

    >
    >     Don did you get the stp file for the rotor housing?
    >     What do you think?
    >
    >     Paul Lamar
    >
    >     Paul,
    >
    >     I have received many things in the last two days but I don't
    believe I
    > have
    >     seen this. Who sent it?
    >
    >     Don
    >
    >     I did. Here it is again.
    >
    >     Paul
     Lamar
    >
    >
    >     Thanks!
    >
    >     Did you design it? Is it the latest version that Mr. Lin is using?
    >
    >     Mazda designed the rotor housing. They cost about $400 new from your
    > local
    >     Mazda dealer.  One of our subscribers did the 3D model. Yes it is the
    > rotor
    >     housing Charles Lin is using.
    >
    >     I have others as well.
    >
    >     Here is just the end housings less the rotor
    >      housings.
    >     These are incomplete but useful for components inside cowl 3D's.
    >
    >     I also have an aluminum version of just the back end housing.
    >
    >     Paul Lamar
    >
    >
    >
    >     Paul,
    >
    >     I am trying to get just what Charles wants me to do. Will you send me
    > any
    >     and all of the solids that you might have for the EzyCopter airframe
    > and
    >     existing design with
     engine plus any other rotary models that you
    > might
    >     have?
    >
    >     Don Bedwell
    >
    >     I have no solids for the EzyCopter airframe.
    >     I am sure Charles has some or perhaps just 2 D drawings.
    >
    >     I did some aluminum end housing for Charles and he has them.
    >     His property.
    >
    >     The main problems are building up a one rotor engine, installing
    >     the engine in the airframe and test flying it. Do you have an airframe
    >     or can you build one? If not Jerry Hey can help.
    >
    >     Paul Lamar
    >
    >
    > Hey all,
    >
    > Just to note on the rotor housing part file. I have found some errors in
    > the surface that will cause huge problems if someone tries to use this
    > for machining. The rotor housing surface is not a series of
    > discontinuous curves. The dimensions should be 240mm and 180mm if there
    >
     was no offset and 246mm and 186mm with an offset. I don't have a
    housing
    > to measure but I am pretty sure that a Mazda 13b engine uses a offset
    > rotor housing surface and a non offset rotor surface. This means the
    > dimensions should be 246mm x186mm. By offset I mean a=3mm.  Maybe that
    > is why the tension bolt holes don't look centered in the water
    channels.
    > If this is wrong then the rest needs to be view with skepticism.
    >
    > Rob Woods
    >
    > I don't think it was intended to machine rotor housings Rob.
    > It was/is cheaper just to buy what Mazda offers.
    >
    > Paul Lamar


    Rob,
    Intent in performing the exercise, was to have an accurate model of the
    rotor housing for modifying existing Mazda housings, not for manufacturing
    new housings from scratch (but I could get them accurate enough for
    that....). If you would care to do your math and use a CMM, you will
     find
    the rotor internal dims are actually within .005" in all areas of the
    model
    referenced to the actual part. The arcs used to represent the housing
    internal area were used as this was done in SW2008 and it did not support
    using equations for curves.
    The water hole offset appearance is actual in the part (and not an illusion,
    as the minor errors in the inner surface are not enough to cause an
    illusion), and all positions are located within the accuracy of the CMM. All
    external areas are also quite accurate.
    So before you bash.... do your homework, as I had no requirement to provide
    these models to the group.
    Merry Christmas,
    Larry



Larry,

My intent wasn't a bash at all. I did put a statement in there that i
didn't have a housing to verify against and that it was my understanding
that Mazda did there design a certain way. I wasn't bashing your model.
I was just stating to the possibly uninformed that it is not wise to
just ask for a solid and run off to the nearest machine shop and say
make this. Cardinal rule in solid modeling is not to trust hand me down
work as a basis for your own work without thoroughly checking it out.
Exception is obviously for a person just sending an RFQ to machine shop.
In that case the client can eat any shit sandwich that they made for
themselves. Thats what the get for avoiding in house engineering fees.

I ran the actual equations and that is what my comments were based on. I
attached my spreadsheet to show what I am speaking of. This is right out
of the Yamamoto book. No matter what rotor and housing combination you
use there has to be an offset of some amount. The 13B has a 3mm offset.
So that means it must be "Parallel Trochoid Curve"/"Equation of Inner
Envelope" or "Equation of Peritrochoid"/ and a negative a offset
"Equation of Inner Envelope" In a numbers case the "Parallel Trochoid
Curve" is 246mm x 186mm and the "Equation of Peritrochoid" is 240mm x
180mm using a=3mm. You stating that the housing is 240mm x 180mm which
means the rotor has to be a negative offset of an inner profile that the
book math doesnt support.

So this has me confused now. I dont discount the possibility of error on
my side but I have looked into this a whole bunch and I dont think I am
wrong. Again my comments were not meant to bash anything you have done
and I personally appreciate you putting this out. But as an experienced
CAD guy I always check things I come across and inner surface of the
rotor housing was one thing I had verified with the math and didnt line
up with what you had.

Rob Woods

Rob,
I haven't had time to study the math on the actual shape the housing should
be. The new housing I  have here does measure 179.984 x 239.674 mm (within
some measurement and manufacturing tolerance). So somewhere the 3mm offset
is different than you anticipate. To my knowledge, these dims haven't
changed since I started working on Mazda's back in the RX2 days..... But now
I am dating myself.
Any models I pass on to Paul for use by members can be counted on as
accurate for it's intended purpose and usually with more detail than most
people need. Eventually, we will have this level of detail on all rotary
engine parts, as that is the starting point in engineering any new parts for
the system or engineering modifications to the existing parts.
Larry