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Date: Tue, 27 Dec 2005 11:32:27 -0500
From: Ernest Christley <echristley@nc.rr.com>
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Alternate alternators
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One of the things Richard and I discussed yesterday was going with the 
RX-8 style of pickup and using the distributor shaft to drive an 
alternate power source.  He rightly noted that the gears probably aren't 
rated to be very strongs, since all they do is drive the distributor and 
oil pumps.  The questions are 1)How much load would a generator add?  
and 2) How much load can the gears take?

I don't have anything for the second question, but I got some numbers 
for the first part using: 
http://www.aeroelectric.com/articles/alternators/UA/Alternators_3.html

Assuming a 20A load at an 800RPM idle as the highest torque a 65% 
efficient generator would be applying:

(14V x 20A)/.65 = 431W needed to drive the generator.  431/746 yields 
.577HP.

(.577HP x 63.024) / 400RPM = .091 in-lb of torque on the gear.

.091in-lb?  I keep thinking that I missed something or miscalculated.  
Couldn't even cheap nylon gears could handle this sort of load?  Is 
there any reason not to trust the distributor drive gears to be able to 
drive an alternate power source?

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