<snip
Hi Paul and Vince,
I may be wrong here but I have the impression that a single rotor
engine
fires like a one cylinder, 2 cycle engine. If that's true, then a 2
rotor would fire like a 2 cylinder, 2 cycle engine. This is a common
outboard motor configuration. My 2 cylinder 10 hp Merc is quite old so
not representative of state of the art but it has magnets inbedded in
the underside of a hollowed out flywheel and some sort of pick-up
coils
180 degrees apart that are in close proximity to the flywheel's inner
surface.  Could these parts, purchased as OTS replacement parts, be
used
to fire a 13b? I can see where it's possible to fire 2 plugs but there
are 4 that need power. Tracy fires leading and trailing
plugs simultaneously and sees no difference in operation. Then there's
the matter of ignition timing. My old outboard has the pickups mounted
on a moveable plate centered on the crankshaft and a mechanical
linkage
from the throttle arm that rotates the entire plate. I'm not exactly
sure why this setup even works because I see no "wound coils" like
Paul's pictures show. The pick-ups appear to be a laminated metal
construction similar to what you'd find in a clock motor. If any of
this
is interesting, Vince, at least there are no coils for you to wind.
Any
thoughts?   Dave M

Sounds exactly what I have in mind.
The 2 rotor rotary fires twice per rev 180 out of phase.
No need for advance as the engine only generates significant
power from 5000 to 7500. Lots of engines are running on 22 degrees
or so fixed advance.

Paul Lamar

Dave M -

Sounds EXACTLY like the configuration needed for the rotary.  If only
minor surgery is required, then two more coils could be put
immediately after and adjacent to the existing ones to fire the
leading (lower) plugs.  Not optimal, but certainly workable, as they
will only be 10 degrees or so behind the trailing (top) plugs.

If that outboard's ignition is OTS (and cheap), it would be worth some
testing as a rotary magneto.  I like it - got pics?  Others on the
list should pipe up if they have better alternatives.

Timing is simply rotating the plate back'n'forth.  22-27 degrees FIXED
advance sounds good, according to Lynn.

I am interested in testing it/playing with it, but as I said: my
current project is the PWM EFI pump.  (Until we dismiss it's
usefulness, I hit a dead-end, or I finish and publish the results &
design.)  We still need to decide if Dave Leonard spoiled the party by
declaring that all aviation EFI systems should be return-based designs.

-Vince Orton