I reinstalled the 6" pulley and set up the flow system to pump through

my

evaporator cores plumbed in parallel.  Pictures are attached.

I borrowed a optical digital tach to measure the actual pump rpm,

however

this created an unusual opportunity.  It works by counting pulses, and

the

flourescent lights give a reading of 3600 rpm due to the 60 cycle

current.

Therefore to measure the rpm, I had to run it in total darkness with a
flashlight illuminating the pulley.  I used two strips of foil on the

pulley

to reflect light pulses back to the tach.  The pump rpm with a 6" pulley

on

the 3450 rpm motor was 5160 RPM.

I then plumbed my evaporator cores in parallel as shown in "Parallel

cores"

photo.  These were hooked to the pump outlet, and full flow tests were
performed.

Motor RPM = 3450
Pump RPM = 5160
Pressure generated at no flow = ~20 psi
Pressure generated at full flow, no evaporator cores in line = 2.5 psi
Pressure with cores in place = 8 psi
Time to fill 5.8 gallons = 14-15 seconds (flowing through rads) = 23-25
gallons per minute.
Current on ammeter = 13 amps = 1560 watts

2.1 HP in ? Are you sure you have that amp meter set right?

Interestingly, the current on the motor with no load (i.e. only spinning
itself) was ~10 amps, which I don't understand. Can someone who knows

more

about motors help expain that?

Bill Schertz
KIS Cruiser #4045

Induction motors are notoriously inefficient at minimum load.  They only
achieve their rated efficiency (which varies widely) at full load.  Current
readings will probably not be much of an indication of actual HP.
Tracy Crook
tcrook@rotaryaviation.com
www.rotaryaviation.com

 
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