Knowing what it is like for amateur organ builders in places like
Australia, I sympathise with their need to improvise.

The blower described by Michael Taylor sounds more like a muck blower,
most unsuitable for an organ.  I was given a unit exactly like the one
described with a 1500 rpm motor fitted, with similar results.  Organ
blowers are designed to give a constant pressure, no matter what the
load, by designing the blades with a curve -- not very easy to
recreate.

There is a simple answer to this problem from an unlikely source:
a 'Flymo' type lawn mower has such a fan, and one of these has been
supplying wind for my 96 MIDI organ very well.  With a two-pole [50 Hz
AC induction] motor running at 2600 RPM it gives virtually constant
7 inches water gage pressure, with lots in hand.  My unit was, in fact,
made by another amateur organ builder with a particle board housing,
and I do not think this is particularly critical.  Just round off all
the internal corners to reduce noise; mine has a most acceptable noise
level.  This tip comes from one amateur to another.

Best of luck to all you Aussie organ builders.  I like what you do.

John Smith, UK