I got Vance's water pump dyno set up in the hangar today.
I very carefully adjusted the position of the motor in the frame
to be certain the axis of the motor coincided with the pivot
axis of the frame. I then static balanced the whole rig by adding weight
to the top of the motor to compensate for the motor mounting flange
on the bottom of the motor and the weight of the frame.

I used a digital fish scale that can read down to one oz.
With the motor off it reads zero. With no water in the system
and the motor running it reads three ounces (.19 pound) due to 
friction in the pump bearings and seals and V belt inefficiency. 
That is a torque of 39 inch ounces (.2 foot pound) at a motor 
RPM of about 3600 RPM. That is .14 HP if my arithmetic is correct. 

BTW at 746 watts per HP that is 104 watts. At 12 volts that would 
be a current draw of about 8.7 amps assuming the DC electric motor 
was 100% efficient. At 80% typical motor efficiency that would be 
about 11 amps. 

I then put some water in the system and the 30 amp 220 volt circuit 
breaker promptly blew and the motor smoked. It worked fine in Vance's 
shop. Just my luck the CC motor decided to take a crap just as I was 
getting ready to take some good data. Vance is coming over to have a look.
If necessary I will buy a new motor.

Paul Lamar
 
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