<VV>Mo Fan

[JVHRoberts at aol.com]

Most vacuum cleaners use series wound universal AC/DC motors. As such, the  
current should drop quite a bit when the motor is unloaded by blocking the 
flow. 
The tach test MAY work on a Corvair, but the engine is rather powerful  
compared to the HP requirement of the fan, and you may not see anything happen  
when the doors are blocked. 
 
In a message dated 7/16/2005 2:00:50 PM Eastern Standard Time,  
jb30343 at navix.net writes:

An amp  meter probably isn't the best way to test this.  I would expect
the  total power consumption to stay about the same.  The motor  is
producing less torque at higher RPM's, more or less the same HP.   The
power consumption might even go up a little if the vacuum cleaner  was
designed for maximum efficiency at maximum suck.

A better test  for the Corvair blower would be to idle at a typical
driving RPM, say 2500  RPM with the damper doors open.  Block the air
outlets and check the  tach.  --J.B.