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Date: Tue, 22 Feb 2005 16:45:34 -0700
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
From: Bill Dube <bdube@al.noaa.gov>
Subject: Re: [FlyRotary] Re: 2nd battery Re: Amps required to run
  engine&amp- hours available
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At 05:43 PM 2/22/2005 -0500, you wrote:
>Bill Dube wrote:
>
>>
>>>  The claim that it won't overvoltage is absolutely false.  In the 
>>> bottom of the picture on the right.  That is the regulator.  It works 
>>> by dumping excess energy to ground.
>>
>>
>>         How do you know this?
>
>Because that is how PM generators work.
>Ok. You caught me.  I don't know that is what it is.  But do a google 
>search on motorcycle regulators and you'll find an awful lot of generators 
>and regulator that look exactly like this, along with explanations of how 
>the work and how they break.

         The small size of the regulator lead me to think otherwise, that 
is why I asked. To dissipate 250 watts, the heat sink would have to be 
quite large.

         I suspect that they have a buck converter or some other sort of 
switching regulator in that small box. You can build a cheaper switching 
regulator than you can a shunt regulator these days. The increased 
efficiency of a switching regulator reduces the size of the power silicon 
and the size of the heat sink, thus reducing the overall cost.

         Older motorcycles do indeed use a shunt regulator.

WooHoo!  I just found one that I was looking at earlier.  But my $100 
figure was wrong.  More like...you guessed it...$250.  The $100 was just 
the stator.

>http://www.chopperscycle.com/page/VTS/CTGY/40-173

         I wonder what the dimensions of these are?

         Here are some cheaper ones:

http://www.chopperscycle.com/page/VTS/PROD/40-173/28937