Hardman Studio Wurlitzer Theater Organ
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.

Spencer Organ Blower Cross Section Wurlitzer 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 duct. The output from the first stage fan on the right is directed by the scroll to 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.

15 hp Spencer Organ Blower Hardman StudioWhen 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.

During 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.

30 hp Rotary Phase ConverterAs 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 I paid for it. While it had a number of problems that are described in another story, it did allow us to run capacity tests on the 15 hp blower.

Pressure Testing organ blowerWhen 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.

During 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.

I 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.

My 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.

To 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.

New Blower Motor for Hardman Studio WurlitzerAfter 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 3rd Stage Fan made by Bob Otey for Hardman Studio WurlitzerA 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.

Spencer organ blower scroll Hardman Studio WurlitzerThe 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 balanced.

The 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.

The 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 material 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 open).

3 roll sheet metal benderA 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.


New Blower Barrel for Hardman Studio WurlitzerI 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 painted.



Spencer organ blower, motor removedThe 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 longer barrel.

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 the barrel.



Bblower motor with new long shaft for Hardman Studio WurlitzerI 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.


Hardman Studio Spencer organ blower during assemblyAfter 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.

Spencer organ blower outletThis 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 remove 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 stage fan chamber.

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.





Now 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.

Duct silencer for organ blowerThe 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.

Cross section of Louver Silencer To 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. Acoustic Louver cross section

Rebuilt 25 hp Spencer organ blower Hardman Studio WurlitzerThis is what it looks like today with the VFD and Load Reactor cabinet in place.

While 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.

An 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.
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