Static Pressure (educated guess)

[Menschenstimme]

I have no way to measure the actual static pressure within the organ's wind lines without drilling a hole somewhere and I prefer not to do so. Please help me do some educated guesswork.

The factory label on the blower says that it is providing 13-1/2" static pressure. The blower feeds directly into a muffler box and then into a static reservoir and then onward into the organ's wind lines. There are no labels or notes or other indications whether or not the static reservoir is sending 13-1/2" of wind to the organ or a bit less. (The blower has ONE large output.)

There is one high-pressure rank in the organ and that is on 10" WC. Thus, one would presume that the static pressure in the lines must be at least 10" WC. Based on your experience and observations over the years, what would you guess the actual static pressure in the organ's wind lines to be? I have minimal experience with such matters; so if you asked me to guess, I would come up with 12" WC.

Thank you!

[kcbooboo]

I'll put my foot in my mouth (puns intended) and say that if you've got one rank at 10", that's the maximum pressure in the organ. The reservoir ahead of it should regulate down to that. You need a little more coming out of the blower for the reservoir and regulator to work properly under all operating conditions. You might get 12" with no keys pressed but once some air goes into the pipes it will drop a bit.

You could make a simple manometer (or buy an actual WC pressure gauge) with a rubber hose on it that you'd put into a pipe's toe hole (after removing that pipe), then cause the pipe to sound. This will give you the wind pressure at that pipe. No holes need to be drilled; you just need a decent seal in the toe hole.

Bob M.

[Menschenstimme]

Thank you very much, Bob!
I have a wind gauge. Most of the organ is on 3-1/2" to 4-1/2" WC. A few pipes are on 5" and the high-pressure rank is on 10" WC. There is no hole anywhere in the organ where I can access the actual static pressure in the wind trunks.

Thus, your educated guess is that when the builder was deciding what the static pressure should be flowing through the wind trunks, he used the static reservoir to drop the 13-1/2" to 10" to match the highest pressure rank in the organ. By the way; this 10" WC rank has its own small reservoir. This makes me wonder if there should be at least just slightly more than 10" going in to be sure to get 10" out?

Once again - many thanks!

[pictureroll]

What brand of blower is it? In my experience Spencer Orgoblos put out more than nameplate says - ratings are very consertive on an orgoblo.

Cheers from Dallas,Tx ♫♫

[Menschenstimme]

It is a Zephyr from Schantz - less than 10 years old. If my memory is correct, I seem to recall Schantz verbally saying 15" WC. So perhaps the 13-1/2" WC on the nameplate is purposely conservative?

Thank you for responding!

[Terpodion]

Why don't you want to drill a hole? If you are afraid of sawdust getting into the wind system, there really isn't much danger if you do it correctly; usually a 1/2" to 5/8" hole is required to fit the manometer tube. Make sure the wind is on when you drill so the majority of the dust will blow out. I usually just go all the way through but if you are still concerned about dust getting in you can go halfway through with the hose - sized bit and drill the rest of the way with a smaller bit - say, 1/8" to keep the dust to a bare minimum. The manometer doesn't need much of a hole to get enough wind to work. When you are done, just stick a cork in it. Also, even if you get sawdust in the system, it usually just settles to the bottom of the wind lines and stays there. The air in an organ's wind system really doesn't move around as much as people seem to think. Stand inside an Austin Universal Air Chest while the organ is playing and your ears will pop but you'll hardly feel a breeze.

[VaPipeorgantuner]

an easy, non-invasive, way to find out what the static pressure feeding the 10" pressure regulator would be to set your manometer (pressure gauge) up just like you are taking a regular reading at a pipe hole, then while that note is playing - completely compress the lid of the regulator down against the box frame so that it is collapsed (as if the organ were turned off, and the floating top is down against the stops). that will open the regulating mechanism (such as a curtain valve) fully and you will get the static wind reading on your gauge.

Rick in VA

[Menschenstimme]

Thank you for the clever and creative suggestion, Rick!

[fugueist]

Hello All,

I'm wondering why you need to measure the static wind pressure at all. Your pressures for the fluework sound about right, and you are getting ten inches on the trumpet. If you have no wind sag when playing big chords, for example, then you're home-free. Have you tuned the instrument yet? If so, did it tune to the required level (presumably A440)without doing major surgery on the pipes? If you had to resort to cutting pipes down to get the correct pitch, then you need more pressure. You can't do anything to get a higher static pressure, except put in a more powerful blower. So, you have to raise the pressure on the reservoirs. You have three options: add more weight on top of the reservoirs, add springs (of whatever type the instrument is using) to the reservoirs, or a combination of the two. It is likely that you won't have to do this, however. More likely is you will need to steady the wind. Remember, you only need more pressure if the pipes don't easily speak the correct pitch.

If everything seems fine, try this test: hold a chord at the bottom of the keyboard (C major will do) with both hands, all stops on, C and G in the pedal. See if the wind sags. It probably will, but if not, you're really in good shape. That thick texture on full organ would never appear in a composition. Thin it out by playing low C, tenor C,E,G, middle c), with low C in the pedal, still on full organ. Listen for pitch sag. If there is none, or it is minimal, you're good to go.................almost! Now, on full organ, play some repeated chords. If the reservoirs start dancing, you need to steady the wind. You will have to put concussion bellows at various places. I presume you don't want to make these, so tell your supplier your exact problem, and they should be glad to make suggestions. As an alternative, you could put in so-called "schwimmers". Ditto, get them from a supplier.

Cheers,

fugueist