[SEL] Re: Rotary & Impulse Mags

[Arnie Fero]

Hi Andy,

Since I just have the two engines with rotary mags, my experience here is
limited.  But let me tell you how I start both.  After the normal prep
stuff, both are given a priming charge and are turned back against
compression at the end of the exhaust stroke.  The reason for that is to
get maximum turns on the flywheel before you get ignition.

The two engines are a 5 hp Petter M and a 7 hp Crossley 1070PE.  Each is
started with a hand crank.  The Petter usually is turned through two or
three full cycles before it hits and when it does it throws the hand crank
(which looks like a disembowling hook) free of the gov weights cover where
it engages.  For the Crossley, it has a half-compression cam and a retard
lever on the mag.  It also has VERY heavy electric flywheels.  That one is
usually turned through 4 or 5 cycles before it fires reliably or before I
poop out.  That beast is a lot to turn over fast!!  When it hits, its a
little "softer" than the Petter and the crank comes off the crankshaft
very smoothly.

The inertia of the moving flywheels is enough to prevent a kick-back.

Hope that helps.

See ya,  Arnie

Arnie Fero
Pittsburgh, PA
fero_ah at city-net.com


On Fri, 11 Mar 2005, Andy Glines wrote:

> >I've got three engines with rotary high tension mags.  The Crossley and
> >the Petter do not have an impulse, and my two cylinder Novo Roller does.
> >
> I certainly didn't mean to speak as though I were an authority on the
> subject.  I was only drawing from my own, albeit limited, experience.
> Arnie, do you have to do anything special when starting the engines sans
> impulse?  Like was already stated impulse on a mag is an aid for
> safer/easier starting.