<VV>Mo Mo Fan

[Padgett]

Can ontly think of one way to tell and since I do not have a Corvair yet 
(hoped I would find one over the weekend, didn't) all I have is my shop 
vac.  Blocked the inlet and could hear the motor speed up. Blocked the 
outlet and really could not hear any difference. Unfortunately the low 
range on my clamp-on ac-ammeter is 200 amps which only gives one decimal 
point of resolution but my small shop vac (big one does not have a blower 
connection) read 5.5A(occasionally 5.4A) running open, 5.3A with the intake 
blocked and 5.6A with the outlet blocked (repeatable).

Agree that the more air moved, the more power it takes but that does not 
mean that the system needs to have an output, the air could just be moving 
around in the plenum. If the power is going down when the doors are closed 
then some other effect is taking place which may include reversion around 
the fan (in a gas turbine engine if the first stage goes sonic, you can get 
exhaust reversion through the bypass ducts which will stall the engine. Not 
good on takeoff.)

Yes air has weight but it is also compressible. This means that a given 
volume will weigh more at a higher pressure than a lower. If you block the 
outlet, the internal pressure is going to rise which means the fan is 
moving in a denser medium.

Now obviously empirical data is showing a fan loss drop if the doors are 
shut. To me this means that something more complex is going on than just 
blocking the outlet.

Padgett


>I hope that Padgett would run this test. But to me it's just so obvious 
>that air has weight, and it takes power to move that air. So the more air 
>that is moved, the more power it is going to take. Blocking the damper 
>doors closed reduces or eliminates the air movement, so the power required 
>goes way down.
>Regards,
>Bob Helt