Pipe organs require high volume low pressure compressed air to blow the
pipes. In the organ world this is referred to as "wind", and wind
pressures are measured in inches of water, easily measured with a "U"
shaped open manometer half filled with water. Typical wind pressures
for a church organ are 4-6 inches w.c., and 10-15 inches or more for a
theater organ. For reference, 15" w.c. is about 0.54 psi. By
comparison, automobile tires typically run in the range of 25-35 psi.
provided multi-stage centrifugal blowers built by The Spencer Turbine
Co. in Hartford, CT, to wind their instruments. A typical 2-stage
Spencer organ blower is shown here in cross section showing the
relationship of the two rotating compressor fans
to the stationary interstage scroll or stator.
Air enters the blower at the
center of the barrel end cover and exits through a round discharge
The output from the first stage fan
on the right is
directed by the scroll
the center of the second compressor fan blade where it undergoes
another stage of compression. A photograph of an interstage scroll
(painted brown) appears farther down the page.
installed previously in Dick Simonton's "Bijou" theater on the lower
level of his home in Hollywood, CA, the organ was powered by a 15 hp
2-stage 1800 RPM Spencer blower with a 42" diameter barrel.
the organ's restoration following its relocation to Great Falls, the
blower was also restored as a matter of course. The local motor shop
tested the motor and found the bearings to be in good condition and
replaced the old input wires. The barrel was cleaned inside and out,
and painted to prevent rust.
The flat belt pulley on the motor
was used originally to drive an electric generator to provide keying
voltage for the instrument.
the installation of the restored Wurlitzer progressed, there came a
time when we could see the need for wind to start testing the installed
windchests. Anticipating this need, I had acquired a used rotary
transformer type of phase converter to produce three phase power since
there is only single phase power available at our home. It was a big
bear with more than enough capacity to run the 15 hp blower we wanted
to test and enough reserve to handle a larger blower if that were found
necessary; but the price was right and it was purchased and trucked in.
Curiously, it cost more to ship it in from Texas than
for it. While it had a number of problems that are described in another
, it did allow us to run capacity tests on the 15 hp
the reassembled blower was first started, it was immediately apparent
that it was very noisy, another problem which would have to be
addressed and resolved. We then went on to measure its static pressure
with no wind consumption. This required blocking the blower's discharge
duct which was accomplished with a piece of plywood held down against
the wind pressure by Jane Quinn. Jane worked on the restoration crew
part time for about four years.
The big unanswered question was
what would be the residual wind pressure when the blower was moving
enough air to keep up with many pipes playing all at once. We would
have to wait until most of the organ was installed and made operational
to determine that.
the preliminary tests, we measured 21-1/2 inches w.c. which was
adequate to provide sufficient headroom pressure to properly operate
the tremolos on the 15" Solo Tibias; but the wind pressure dropped
quickly as we let even just a little air out of the blower, simulating
the effect of wind consumption from blowing pipes. Our concern rose
from the fact that Simon Gledhill's respecification of the instrument
added additional sets of pipes including the 16' octave Solo Tibia
Clausa running on 15 inches which would consume lots of wind all by
itself. So the experienced admonitions of Clark Wilson and John Struve
were proved accurate, and the decision was made to pursue a larger
blower for the instrument.
This decision also gave us the
opportunity to find a slow speed blower which would be inherently
quieter while running. Because our blower room is in fairly close
proximity to the listening area, I had a strong preference for a big
Spencer with a larger 50" diameter barrel so I could run it a nominal
1150 RPM to reduce the noise level generated by the blower.
started to explore alternatives and found that 20 or 25 hp blowers are
hard to find, and expensive when one could be located. There aren't
many left from the old days, and new blowers from Spencer, while still
available on special order, are prohibitively expensive. I was told of
one in a defunct theater in New York City, but that it had been
submerged in water for a long time, and there wasn't much left of the
severely rusted steel shell. Three letters to the building owner
brought no response. Perhaps just as well; pulling a blower out of NYC
could be a real hassle.
break came when I learned of a blower long out of service in the
basement storage area of a big old Philadelphia church. It had the 50"
diameter barrel I needed, so I knew it could be modified for my needs.
Jay Bogart and I spent a very long day driving up to Philadelphia,
removing the blower, and returning with the disassembled pieces to
Great Falls. As church organ blowers go, it was a big one, designed to
deliver two pressures using 3 fans driven by a 7-1/2 hp motor. Two of
the fans could be reused in Great Falls, but the third fan was too
narrow and too small in diameter for our purposes. We wanted a 3 stage
blower, needed for quiet slow speed operation, with enough volume
capacity to maintain sufficient wind pressure for the 15" pipework when
most of the organ was playing all at the same time.
make this church blower into what was needed, I would have to find a
larger motor, fit it with a new long shaft to hold three wide fan
blades, make a new barrel long enough to contain the three wide fans,
increase the width of one stator, and make or buy a new third stage fan
sized to provide the needed volume of wind at our target static
pressure of about 21-22" wc.
I started searching the used
equipment dealers on the Internet, and eventually turned up a dealer in
Toledo who claimed to have been the successful bidder on the contents
of the Tool Crib for Bethlehem Steel Corporation at the liquidation
auction following their bankruptcy. Included in that acquisition were
three 25 hp 6-pole, 240 volt three phase motors, 9 years old, never
removed from the manufacturer's original shipping pallets. The best
part was the $325 price, about 10% of the current price for the same
motor, still in current production, if purchased new from Marathon
Electric. Incidentally, here was another case where it cost nearly that
much just to have the 678 pound motor trucked in from Toledo.
a few phone calls I found a machine shop that would make a new long
shaft for the motor and press it in to the original armature. With
their backlog of custom work, it would take several weeks to accomplish
the work involved. Marathon Electric kindly provided me with an
engineering drawing of the original shaft.
In the meantime, I designed the new barrel for the blower. It had to be
long enough to accommodate the 3 wide fan blades and two wide scrolls
between the fans.
new 32" third stage fan was made for us by Bob Otey in Kent, WA. I
removed the hub from the church blower's 1" wide fan to be reused on
the new third stage fan. Since I wanted to reuse the 2 church blower's
fans, I had to determine the required diameter of the new third stage
fan that would give us the needed pressure gain which when added to the
pressure from the first two stages would give us the desired 23" static
wind pressure for the organ. Copies of original Spencer specification
sheets simplified the process, and subsequent testing confirmed the
expected wind pressures.
church blower had three fans separated by two scrolls. Two of the fans
were 4" wide and could be reused. The church blower's second scroll
feeding the third stage fan was only 1" wide, matching that blower's
third stage fan. I was able to increase the width of the scroll to 4"
by simply welding on strips of sheet metal. That turned out to be a
fairly easy job. You can just barely see the original 1" flites to
which the 4" strips of sheet metal were added. Insufficient diameter,
metal gage and strength issues discouraged me from similarly modifying
the original 1" fan removed from the old church blower. Note the
original 7-1/2 hp church blower motor with the long shaft. There is no
outer end bearing on this type of Spencer blower; the three fans
represent an overhung load and must be very carefully dynamically
two end flanges were removed from the old barrel so they could be
reused on the new barrel. The end flanges are 2" x 2" x 3/8" rolled
angle iron. This picture shows the 2 barrel end flanges on the right,
and on the left is the felt gasketed barrel inlet end cover.
is about 54" in diameter and has a felt gasket glued to its outer
diameter. The cover bolts to the rolled angle iron flange welded to
the end of the barrel. Under the flanges in the picture is the dusty
black motor end cover. I found and removed the yellow fiberglass
glued to the inside of the cover, presumably placed there to reduce
noise. I can imagine how it gradually broke apart from the high
velocity wind and turbulent vibration, to find its
way into the wind chests and pipe valves causing them to cipher (stick
local steel fabricator was found who had a 3-roll bender for rolling
sheet metal into cylindrical shapes. This picture shows a 3-roll bender
making a cylindrical tank. It takes a little time to accomplish. The
operator controls the speed and direction of the roll. As the edge of
the metal plate nears the center of the roll, he reverses direction and
forces the third roll a little closer to the two stationary rolls. This
causes the metal to bend at a shorter radius causing the flat sheet of
metal to be gradually rolled into a cylinder.
provided the steel fabricator with my drawing which specified 12 gage
steel for the main barrel and a 20" diameter barrel that would become
the blower's discharge duct.
The new barrel and outlet were
brought back to Great Falls where the original Spencer rolled angle
iron end flanges were slipped over the ends of the new barrel and
welded in place, and then prime
picture shows the dusty church blower with its original 7-1/2 hp motor
removed. The motor end of the blower would be reused with the new
Apart from a lot of cleaning, scraping and painting, the only thing
done to it was to replace the
thick felt motor shaft seal needed to minimize leakage of
pressurized air from around the rotating motor shaft where it enters
picked up the motor with its new long shaft in place and brought it
back to our shop where I made the mounting spacers from rectangular
steel tubing obtained from the bone pile at a nearby steel distributor.
Here is the new barrel, prime painted, and assembled to the
restored original blower's motor end. The feet are all made from wood
and are spaced so as to distribute the weight of the blower. The motor
is suspended by its lifting eye on one of the arms of a hydraulic
automotive lift in our shop.
a final wash before receiving a coat of paint, the new motor was
mounted to the original Spencer blower end and new barrel. It was
beginning to look like a brand new blower.
The blower was assembled with the discharge duct set
at an angle to permit the blower to be installed tight to the wall and
still permit a direct connection to the main wind trunk feeding the
organ. This eliminated the friction and turbulence noise from another
90 degree elbow.
is the business end of the blower, looking down into the discharge
duct. The motor is out of sight on the left. You can see the motor
shaft coming through the felt shaft seal which I relocated to the
outside of the barrel to make for easy replacement without having to
the fans and scrolls from the barrel. The 3rd stage fan has been
located on the motor shaft very close to the bulkhead separating the
2nd and 3rd stages to minimize pressurized air from the 3rd stage fan
chamber from short circuiting past the fan back into the 2nd
The nearly finished blower was
moved from the shop to the outside entrance to the blower room.
Loading the blower on the trailer was easy in the
shop using the hydraulic lift. It was a bit of a hassle for the two of
us to wrestle the thing off the trailer using pipe rollers, a Johnson
Bar, and furniture dollies. Once on the floor of the new blower room,
it was easy to roll the blower in place on two furniture dollies.
we can rest for a few minutes. Among the next projects is the finish
paint for the blower barrel, installing the waffle pattern rubber
vibration isolators under the blower, installing and wiring the
Variable Frequency Drive, and finally making and
installing the flexible connection between the blower outlet and the
main wind trunk which will deliver wind to the pipe chambers. The main
wind trunk out of the blower room is actually a 10 ft. long sound
absorbing duct silencer to control fan noise coming from the discharge
duct of the Spencer blower.
spiral wound steel duct silencer pictured here is similar to the one we
installed in the main wind trunk that delivers wind from the blower to
the two pipe chambers. This significantly attenuates blower outlet
noise that can be carried into the pipe chambers through the wind
ducting system. These round duct silencers are reasonably priced and
take the place of the large carpet lined wood boxes that are often used
for the same purpose when the blower and its associated noise are
located in close proximity to the listening area.
prevent its operation from being heard in the studio listening area,
the blower was placed in its own small room between and just behind the
2 pipe chambers. A sound attenuating acoustical louver was installed in
the air path followed by expended wind from the organ returning to the
blower room. Since much of the noise generated by the blower comes from
its intake opening, this louver provides additional reduction to the
sound to be isolated from the studio listening area. Also, we hung two
solid core wood doors on the same door frame to the blower room to
further isolate blower noise from the listening area in the studio.
Pictured is a typical acoustical louver and section.
is what it looks like today with the VFD and Load Reactor cabinet in
dramatically quieter than the old 42" high speed blower tried earlier,
you can still tell when this machine is running when standing inside
the blower room. Blower operation is inaudible in the studio.
inlet silencer has not been found necessary, although we did make a
filter for the air entering the blower inlet. Air is pulled through a
filter assembly made up of five 4" thick by 24" square high efficiency
paper filters, arranged together to form a cube, capable of passing
4500 cfm of air with only 0.2" w.c. pressure drop.
In actual practice, we run the blower at around 1,000 RPM which
maintains sufficient static pressure while delivering all the wind
volume the organ ever needs.
In the next section, you will see pictures
describing the installation of the restored organ parts and components
in the pipe chambers in the barn.