In a quick experiment, John Rhodes gathered this data on the air
flow through a bleed:

>  I fabricated a bleed from .007" brass shim stock soldered to
>  the end of a short (1-inch) length of 1/4-inch copper tubing,
>  then I _carefully_ drilled a hole with a #75 drill (.021-inch
>  diameter nominal).  The hole appears to have minimal burr, is
>  quite round, and is not more than .001" oversize.  All of these
>  dimensions will be verified later with an optical
>  comparator and microscope.  I was careful not to thicken the
>  brass stock with the solder, but this too must be verified
>  later.  (I'll peel off the shim stock from the tubing to
>  examine both sides of the bleed.)
>
>  Then I measured the time required to displace approximately
>  280 milliliters of water with 5, 10, 20, 30 inches-of-water
>  differential-pressure across the bleed.  Results:
>
>  differential  time
>  (inches H2O)  (sec)
>
>     5           42
>    10           30
>    20           20
>    30           16
>
>  These numbers are crude, because I was supplying the pressure
>  by blowing on the hose. (Try sustaining 50 inches for 15 seconds;
>  you'll turn bright red!)

Has anyone performed this type of experiment?  Anyone have some
similar data for comparison?

-- Robbie Rhodes