Paul,

 Years ago there were two brothers from Venezuela with a Cozy powered by
    two
 Suzuki Swift engines that were Siamesed together.  They didn't share the
 same prop, but instead used two counter-rotating props.  The prop shafts
 shared the same centerline.  In cruise, they could shut down one engine
    and
 greatly reduce the fuel burn.  I don't see why this idea couldn't be
 applied to the rotary using two 13b engines.  It would require the use
  of
 belt drives.  I believe Wankel GMBH developed one along these lines they
 called the Wankel Twin-pack.  (discussed in your YouTube video)  I
  always
 thought that would make a great package for a larger plane if someone
 wanted to spend the time and money to work out all the details.
  Mark
  I've been tossing this idea around in my head, and I really like it.
    (This is why I was asking about reverse rotation and 3d models a few
    days ago).  It seems so neat to be able to have an almost completely
    independent twin setup in a single engine sized package.  The only
    interlink really is the sharing of the engine mount and perhaps some
    bearings in the prop shafts.  Both of those can be designed to a very
    low failure rate.
 I've roughly sketched out a few things, and it seems to me that the
    best way to go about it would be to face one engine forward, and the
    other backwards.  The backwards engine would drive a countershaft off
    the similar to some supercharger setups except off the flywheel side,
    and the forward facing engine could drive the external co-axial shaft.
 I think Mark was right that a belt drive setup would be best.  This
    setup has a couple of benefits over facing both engines the same way.
    First is that you can have the plugs all facing inwards and the
    exhaust and intake facing outwards.  This will make mounting of coil
    packs a bit easier, and will prevent exhaust from one engine heating
    the other up.  The intakes could possibly share a common filter and/or
    plenum depending on how you set them up.  Depending on the mounting
    setup, you may be able to keep the engines a little closer together.
    The countershaft could also provide a great moment arm to resist the
    bending moment from the props
 If one did want to keep both engines pointing the same direction, a
    gearbox type setup with a reverse idler would certainly work.  I think
    it would be more expensive to do that way, and possibly a little
    heavier as well.  You'd have to worry with oiling too.
 Anyone have any thoughts?
  Josh
 Are you talking about twin engines driving a single prop, or a twin setup
   with independent engines, props, etc?

   Kevin Alderman
 I'm talking about twins driving separate contra-rotating props.
  Basically everything would be independent. It's all the advantages of
  a twin in with single engine drag, no yaw on engine out, and no torque
  steering on the ground... like the Cessna 337 except both engines and
  props are at the same location.

  Joshua Jacobs


  The engineering has been done- find any Volvo boat outdrive from the last
  20 to 25 years- they have been using counter rotating props on the same
  shaft for decades.
  The design is simple- the shafts are one inside the other. The main input
  shaft has a single gear on it and the shaft drive gears mesh with this
  drive gear. Since the drive gear is being tapped for power from both
 sides,
  the shafts rotate opposite directions.

  Lately Mercruiser/Cummins have partnered to make a diesel powered unit
  similar to the original Volvo unit.

  http://www.marinepartsexpress.com/vp_sch_fs.html

  Kevin Alderman



 There have been contra-rotating prop aircraft since ww2.  The guys mark
 mentioned did
 it with two suzuki engines.  It's not a new concept by any means, but to my
 knowledge
 no one has ever done it with an engine as compact as the rotary.  It may be
 more
 simple to add a turbo or another rotor, but with twins you get redundancy.
 With the
 co-axial props, you get no adverse yaw. It's a win/win the way I see it. I
 suspect
 cooling two engines in a single engine cowl could become a problem, but not
 an
 insurmountable one.

 Josh

 There is room for two engines in a lot of six cylinder cowls.
 500 HP anyone? You can almost get two 3 rotors in some six cylinder cowls.
 750 HP anyone?

 Paul Lamar

Paul,

I set two rotor housings side by side (plugs to plugs) allowing just
enough room to get the spark plug boots on the plugs and it looks like
it would fit in a space 32" wide.  The Lancair ES fuselage is 48" wide
at the firewall... more than enough room.  Heck, there's even enough
room for a pair of T04's.  This would make a great package for a
Lancair IV-P.

Mark


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