X-Mozilla-Keys:                                                                                 
I tried out the airflow sensor and it worked great.
With 9 volts it was putting out about a 3 volt peak
to peak pulse. The $60 BK VOM Hertz counter worked great.

 I then made the mistake of taking it
apart and cutting off the steel armature and copper 
windings to reduce the drag. Wrong! For some reason 
that brushless motor design needs those parts for the 
pulse generator to work. I suppose I could have
cut some of the rubber permanent magnet away instead.
Hind sight.

Don't bother with this modification. If you have airspeeds
of less than 20 MPH in your duct or on the back side of your
rad you are in big trouble anyway.

I went back to Fry's and found another type with the three
wires that was cheaper. $11.99. It is probably a brush
type motor but who cares. It rotates quite fast if you 
blow on it. It is also smaller than the first one I found
at two inches square and 25/64ths thick. It too has a ball
bearings. The curved side of the blades goes towards
the source of the air flow.

The model number is PL50D12M
The outside of the box there was a sticker on it
with these numbers.
PLU# 2562611
PA-K6B-02B

I will hold it outside the car window tomorrow and see how
fast one has to go before it start rotating.

Paul Lamar
 
The Aircraft Rotary Engine Newsletter.              Powered by Linux.

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