Organ Blower RequirementsI am no expert at this, but can relate to this problem as I had to find a suitalble blower for my 97 key Mortier a while back. Maybe my reply will prompt more discussion. A rule of thumb for theatre organs is 10 cfm per rank. This figure may be excessive for fairorgans because they tend to use small scale pipes, are built to conserve wind, and have shorter piping runs. Maybe 7 cfm per rank is a better estimate.
On the US side of Big Pond, two names for blowers with adequate wind supply come to mind that provide inexcess of 9 inches SP and run quiet enough for organ use: Ametek Windjammer and FASCO/Torin. Both appear on eBay regularly and I had the fortune to find a salvage Torin unit at
www.surpluscenter.com that is rated at 1/2 HP 3465 RPM with a 3" outlet. This unit is a multi-stage blower for which a picture can be found (fig 2) at
www.fasco.com/blow5asp. Unfortunately, the data block for this unit on this webpage is too small to read, but I am believe the seller stated it was something like 280 CFM at 27 inches water. One blower just about carries my 29 rank Mortier which requires 10.5 inches water column. I have two of these blower in parallel, with one just about choked close with an adjustable blast gate. Each run on 120 VAC.
I am feeding the output of these unit to a curtain valve which is regulated by the main reservior in the Mortier via mechanical linkage. This curtain valve can be adjusted to maintain pressure to the Mortier just before the trip valve on the main reservior begans to open. Another advantage to this blower is that the wind to the organ does not tend to heat much, thus causing pipes to run out of tune.
