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From: "Charles Davis" <charlesd1@telkomsa.net>
To: "'Rotary motors in aircraft'" <flyrotary@lancaironline.net>
References: <list-4994093@logan.com>
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Subject: RE: [FlyRotary] Re: New impeller design
Date: Wed, 25 May 2011 16:34:10 +0200
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Hi Ernest,

Yea, I have taken a few lawnmowers apart in my time - I am not claiming =
any original thought on that one ;-) ... I seem to recall that =
lawnmowers run at around 3Krpm, I wouldn't like to be too close to one =
of those fly-wheels at 9Krpm !

Ideally, such an arrangement would be 'advance-less', ie set at a fixed =
advance, and be purely a battery-less backup - add steppers, =
micro-controllers and all the mechanical bits rather defeats the object =
of the exercise ... :-)

Another thought - if the 'ignition' magnet was cast in, say, the top (or =
left) half of the impeller, then one could cast many magnets in the =
'bottom' (or right) half, then have a series of coils wound around =
formers which would be your alternator - being excited by the =
full-circle of magnets

I switched to electric lawnmowers long ago - no chance of forgetting to =
buy fuel ... age does this to us ;-)


-----Original Message-----
From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On =
Behalf Of Ernest Christley
Sent: 25 May 2011 04:11 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: New impeller design

Charles Davis wrote:

> If an impeller were to be cast for this air-induction/super-charging=20
> application, and was tied-in to the e-shaft (key-way or similar) would =

> it work to have a suitable magnet cast-in to the periphery of the=20
> impeller, so that two coils could be mounted, 180 degrees apart, to=20
> provide magneto-type spark to one set of plugs  one coil per rotor at=20
> 180* for a 2-rotor, and 120* for a 3-rotor  this sounds, to me, so=20
> simple that I am surprised nobody has done it before  how good would =
it=20
> be to have a completely battery-independent ignition system for=20
> amateur-built aircraft ?  maybe I should shaddup, & return to lurking=20
>=20
>=20

The system you describe has been working perfectly a lot longer than =
I've been alive.  All I can say is, don't let your=20
wife catch you pulling the flywheel off your lawn mower to power your =
airplane 8*)  There is a magnet cast into the=20
flywheel, and the coil is built around a C shaped stack of stamped =
steel.  That flywheel could possibly handle the RPM=20
of the eshaft (but I wouldn't dare bet anything important on it).

I think the only issue you'd have is modifying the advance.  You could =
accept the "good 'nuff" compromise of a static=20
20* to 25* in exchange for the bone dry simplicity.  Possibly driving =
just the trailing plugs as a dead generator=20
backup.  That, combined with a gravity feed system would make your =
engine electrically independent.  Or you could try to=20
design some sort of advance control.  Maybe use a MegaSquirt and write =
some code to control a stepper motor that moves=20
the pickup?

I'm currently trying to use the space between the engine and the gearbox =
mount plate to install a blower and a=20
generator.  I think that is enough multipurposing of a single piece of =
aluminum for now.  However, at some point in the=20
future I may need a new lawn mower.  8*)


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