Subject: Twin Rotary
From: rotaryeng
Date: 8/30/2012, 10:21 AM
To: AAAA Put this in the To box 


 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
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  Hi Josh
   I also like the Idea of having 2 independent drive engines  and being able to shut
one down for cruise economy. If you use 2  contra-rotating props one driven by each
engine, what will be the  effect of shutting one down ( drag and interference of the
running  prop). This will also require purchasing 2 props but the belt drive  will
also work as a psru. have a look at this system  http://ezycopter.powweb.com/cds.htm
it is for a helo but you get the  idea, may fit with 2x single rotor engines and also
works as a psru.
   Or you could use 2 single rotor engines inline with  coaxial output  to a single
prop with a disengaging coupler for one of  the engines. I think I saw that somewhere
in the newsletter, using a  tc on the single rotor, similar to this
http://www.rotaryeng.net/RX8-TC-eng3.html , just can't find it right  now.
  Graeme Riley


Bell helicopter came out with the twin pack long ago. It uses twin engines driving a
common transmission through overrun clutches. I like the redundancy of the twins, but
the dual props would add a lot of complexity.
I think a simpler solution is twin engines input to a common psru, with a
controllable pitch prop.

Kevin Alderman

Josh,

You may be mildly interested in Soloy in Olympia, Wa which stretched a Cessna 208 and
put two PT-6s in it about 15 years ago.  They actually got it certified - I not sure
which aircraft.  I saw the gearbox cutaway shown as a feature in the lobby.  I should
have taken a picture when I was in their plant in Olympia several years ago:

http://www.flightglobal.com/news/articles/soloy-plans-pathfinder-push-37538/

This "Dual Pac" as they say, is apparently still available for certain aircraft:

http://www.soloy.com/Products/Fixed+Wing+Aircraft/Soloy+Dual+Pac/default.aspx

Cheers,

Norm DeBoer





-- 
The Rotary Engine News Letter. Powered by Linux.
ACRE NL web site. http://www.rotaryeng.net
You Tube key word PaulLamar2
Copyright 1998-2012 All world wide rights reserved.