----- Original Message -----
From: "Canyon" <steve.canyon@verizon.net>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Tuesday, September 16, 2003 5:22 PM
Subject: [FlyRotary] Internal gearing ...


> At the risk of exposing my ignorance I have a question.
>
> There must be a sound reason the internal gearing cannot be adapted to
> something more suitable to driving the prop.
>
> Is it economics or laws of physics or convenience or what which
> prevents this happening?
>
> And yes, I once saw the inside of the rotor housing once about 6 years
> ago now. :-)
>
> Steve
>
 Good question, Steve

    The short answer is that it would take a complete redesign of the rotary
engine.  There is a "locked" realtionship between the shape of the rotor (3
surfaces) and the 1:3 gearing between the rotor's gears and the eccentric
shafts gears.  Each of the 3 rotor faces covers 1/3 of a 360 degree circle
or 120 degrees of the circle.  The 1:3 gearing means that 120 degrees of
rotation of the rotor (one face) causes the eccentric shaft (crankshaft) to
rotate 120x3 = 360 degrees.  Comes out sort of nice and even that way.

More over, the eccentric shaft in turn drives the crank angle sensor
(distributor analog) which controlls the firing of the spark plugs.  So from
the opening of intake and exhaust ports to the firing of the spark plugs,
the timing  is controlled (and mandated) by the 3:1 gearing relationship
between the rotors and eccentric shaft. Also the eccentric shaft lobes
causes the rotor to do its "wobulation" at the proper time which if it is
off by as little as one gear tooth in syncronization it will cause the rotor
to jam agains the rotor housing and lock the engine solid!

I am no expert on the rotary and it would appear that you can have different
number of faces (not just limited to 3) and that in turn would mandate
different gearing to maintain proper timing.
On an reciprocating engine you can change the timing of both valves and
ignition by changing the camshaft profile, adjustment of the camshaft or
shifting the distributor sprocket a tooth or two one way or the other
probably without anything drastic happening.  Can't change the gearing
between rotor and eccentric shaft  it by one tooth on the rotary engine that
we love and know without locking it solid.

So I would say its all three of the factors you mentioned{:>)

Hope that helps

Ed Anderson