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Date: Sat, 06 Nov 2004 14:33:06 -0500
From: Ernest Christley <echristley@nc.rr.com>
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: PM alternator/generator with EWP
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Per the discussion of breaking belts...

Belts are needed for two things, the alternator and the water pump.  But 
if we replace the water pump can we get rid of the belt?

Has anyone considered replacing the crank angle sensor with a PM 
alternator/generator?

The things are relative simple (a can of coiled wire with some magnets 
on a spinning shaft in the middle), but what effect would a spinning 
magnet have on the hall effect sensor that drives the ignition system?

I've been looking at this a while.  It looks like a hole could be tapped 
and threaded into the top of the crank angle sensor shaft.  A generator 
with a threaded shaft would be screwed into that, properly oriented 
threads insuring that the generator shaft will never come unscrewed, and 
some straps on the housing to keep it from spinning.

A 35A generator, is < 500W would only need a few ft.oz. of retaining 
force at 6000RPM.

The front pulley could be replaced with the same sort of installation.

Another consideraton.  Alternators have a heavy shell, bearings and 
mounting because there is a substantial side loads and vibrations 
derived from the belt.  A gear driven generator can be much lighter, 
with just a sheet metal can for a housing.

I've got a number for an electrical engineer who is going to help me 
work out the feasability and sizing for this application, but I'd like 
the thoughts of anyone on the list.


-- 
http://www.ernest.isa-geek.org/
"This is by far the hardest lesson about freedom. It goes against
instinct, and morality, to just sit back and watch people make
mistakes. We want to help them, which means control them and their
decisions, but in doing so we actually hurt them (and ourselves)."