*In the wind...*

July 2011

**Measure up.**

When I was an apprentice working in Oberlin, Ohio, we had a
particularly bad winter with several heavy storms and countless days of difficult
driving conditions. As part of our
regular work, my mentor Jan Leek and I did a great deal of driving as we
serviced organs throughout northeastern Ohio and western Pennsylvania. Jan owned a full-size Dodge van – perfect for
our work as it was big enough to carry windchests, big crates of organ pipes,
and long enough inside to carry a twelve-foot stepladder with the doors closed
if the top step was rested on the dashboard near the windshield. All those merits aside, it was relatively
light for its size and the length of its wheelbase, and it was a simple terror
to drive in the snow. There can’t have
been another car so anxious to spin around.

Jan started talking about buying a four-wheel-drive vehicle
and one afternoon as we returned from a tuning he turned into a car dealership
and ordered a new Jeep Wagoneer – a large station-wagon shaped model. He wanted it to have a sunroof but since Jeep
didn’t offer one he took the car to a body shop that would install one as an
aftermarket option. As we left the shop,
Jan said to the guy, “I work with measurements all day – be sure it’s
installed square.” It was.

Funny that an exchange like that would stick with me for
more than thirty years, but it’s true – organbuilders work and live with
measurements all day, every day they’re at work. A lifetime of counting millimeters or sixty-fourths-of-an-inch
helps one develop an eye for measurements.
You can tell the difference between nineteen and twenty millimeters at a
glance. A quick look at the head of a
bolt tells you that it’s seven-sixteenths and not a half-inch and you grab the
correct wrench without thinking about it.
Your fingers tell you that the thickness of a board is three-quarters
and not thirteen-sixteenths before your eyes do. And if the sunroof is a quarter-inch out of
square it’ll bug you every time you get in the car.

And with the eye for measuring comes the need for accuracy
as you measure. Say you’re making a
panel for an organ case. It will have
four frame members – top, bottom, and two sides – and a hardwood panel set into
dados (grooves) cut into the inside edges.
The drawing says that the outside dimensions are 1000mm (one meter) by
500mm (nice even numbers that never happen in real life!). The width of the frame members is 75mm. You need to cut the sides to 1000mm as that’s
the overall length of panel. But the top
and bottom pieces will fit

*between*the two sides, so you subtract the combined width of the two sides from the length of the top and bottom and cut them accordingly: 500mm minus 75mm minus 75 mm equals 350mm.
You make a mark on the board at 350mm – but your pencil is
dull and your mark is 2mm wide. Not
paying attention to the condition of the pencil or the actual placement of the
mark, you cut the board on the “near” side of the mark and your piece winds up
4mm too short. The finished panel will
be 496mm wide. Oh well, the gap will
allow for expansion of the wood in the humid summer. But wait!
It’s summer now. In the winter
your panel will shrink to 492mm and the organist will have to stuff a folded
bulletin into the gap to keep the panel from rattling each time he plays low
AAA# of the Pedal Bourdon (unless it’s raining).

You can see than when you mark a measurement on a piece of
wood you have to make a neat clean mark, put it just at the right point
according to your ruler, and remember throughout the process on which side of
the mark you want to make your cut. If
you know your mark is true and the length will be accurate if the saw splits
your pencil mark, then split the pencil mark when you cut!

I’ve had the privilege of restoring several organs built by
E. & G.G. Hook and never stop delighting at the precision of the
hundred-fifty year old pencil marks on the wood. The boys in that shop on Tremont Street in
Boston knew how to sharpen pencils.

Another little tip – use the same ruler throughout the
project. As I write, there’s a clean
steel ruler on my desk that shows inches with fractions on one edge and
millimeters grouped by tens (centimeters) on the other. It’s an English ruler exactly eighteen inches
long, and the millimeter side is fudged to make them fit. The last millimeter is 457, and the first
millimeter is obviously too big. If I
was working in millimeters and alternating between this ruler and another I’d
be getting two versions of my measurements.
While the quarter-millimeter might not matter a lot of the time, it will
matter a lot sometimes. I have several
favorite rulers at my workbench. One is
150mm long (it’s usually in my shirt pocket next to the sharp pencil), another
is 500, another is 1000. I use them for
everything and interchange them with impunity because I know I can trust
them. With all the advances in the
technology of tools I’ve witnessed and enjoyed during my career I’ve never seen
a saw that will cut a piece of wood a little longer. The guy who comes up with that will quickly
be wealthy (along with the guy who invents a magnet that will pick up a brass
screw!).

My wife Wendy is a literary agent with a long list of
clients who have fascinating specialties.
In dinner-table conversations we’ve gone through prize-winning poets,
crime on Mt. Everest, multiple personalities, the migration of puffins, flea
markets, and teen-agers’ brains(!). Her
client Walter Lewin is a retired professor from the Massachusetts Institute of
Technology who is famous for his rollicking lectures in the course Physics
8.01, the most famous introductory physics course in the world. On the first page of the introduction to his
newly published book,

*For the Love of Physics; from the end of the Rainbow to the Edge of Time – A Journey Through the Wonders of Physics,*Lewin addresses his class:
“Now, all important in making
measurements, which is

*always*ignored in*every*college physics book” – he throws his arms wide, fingers spread – “is the uncertainty of measurements… Any measurement that you make without knowledge of the uncertainty is*meaningless.”*
I’m impressed that Professor Lewin thinks that inaccuracy is
such an important part of the study of Physics that it’s just about the first
thing mentioned in his book.

The thickness of my pencil lines, my choice of the ruler,
and the knowledge about where in the line the saw blade should go are
uncertainties of my measuring. If I know
the uncertainties I can limit my margin of error. I do this every time I make a mark on a piece
of wood. And by the way, if you’re
interested at all in questions like “why is the sky blue,” you’ll love Lewin’s
book. And for an added bonus you can
find these lectures on YouTube – type his name into the search box and you’ll
find a whole library. Lewin is a real
showman – part scientist, part eccentric, all great communicator – and his
lectures at once brilliantly informative and riotously humorous.

Now about that panel that will fit into the dados cut in the
frame members. Given the outside
dimensions and the width of the four frame pieces, the size of the panel will
be 850mm x 350mm (if your cutting has been accurate). But don’t forget that you have to make it
oversize so it fits into the dado. 7.5mm
on each side will do it – that allows for seasonal shrinkage without having the
panel fall out of the frame. So to be
safe, cut the dados 10mm deep allowing a little space for expansion, and cut
the panel to 865mm x 365mm – that’s the space defined by the four-sided frame
plus 7.5mm on each side which is 15mm on each axis. Nothing to it.

Now that you’ve all had this little organbuilding lesson,
look at the case of a good-sized organ.
There might be forty or fifty panels.
That’s a lot of opportunity for error and enough room for buzzing panels
to cover every note of the scale.

**§**

For the last several days I’ve been measuring and recording
the scales and dimensions of the pipes of a very large Aeolian-Skinner organ
that the Organ Clearing House is preparing to renovate for installation in a
new home. I’m standing at a workbench
with my most accurate measuring tools while my colleague Joshua Wood roots
through the pipe trays to give me C’s and G’s.
Josh lays the pipes out for me, I measure the inside and outside
diameters, thickness of the metal (which is a derivative of the inside and
outside diameters – if outside diameter is 40mm and the metal is 1mm thick, the
inside diameter is 38mm. I take both
measurements to account for uncertainties.), mouth width, mouth height, toehole
diameter, etc. As I finish each pipe
Josh packs them back into the trays.
With a rank done, we move the tray and find another one. Now you know why I’m thinking about
measurements so much today.

When studying, designing, or making organ pipes we refer to
the mouth-width as a ratio to the circumference, the cut-up as a ratio of the
mouth’s height to width, and the scale as a ratio of the pipe’s diameter to its
length. If I supply diameter and actual
width of the mouth, the voicer can use the Archimedian Constant (commonly know
as π - Pi) to
determine the mouth-width ratio, and so on, and so on.

Here’s where I have to admit that my knowledge of organ
voicing is limited to whatever comes from working generally as an organbuilder
without having any training or experience with voicing. My colleagues who know this art intimately
will run circles around my theories and I welcome their comments. From my inexpert position I’ll try to give
you some insight into why these dimensions are important.

The width of the mouth of an organ pipe means little or
nothing if it’s not related to another dimension. Using the width as a ratio to the
circumference of a pipe gives us a point of a reference. For example, a mouth that’s 40mm wide might
be a wide mouth for a two-foot pipe, but it’s a narrow mouth for a four-foot
pipe. A two-foot Principal pipe with
diameter of 45mm might have a mouth that’s 40mm wide – that’s a mouth-width
roughly 2/7 of the diameter, on the wide side for Principal tone. The formula is: diameter (45) times π (3.1416) divided by
mouth-width (40). In this case, we get
the circumference of 141.372mm. Round it
off to 141, divide by 40 (mouth-width) and you get 3.525 which is about 2/7 of
141. Each time I adapt the number to
keep things simple I’m accepting the inaccuracy of my measurements.

The mouths of Flute pipes are usually narrower (in ratio) than
those of Principals. Yesterday I
measured the pipes of a four-foot Flute which had a pipe with the same 40mm
mouth-width, but the diameter of that pipe was about 55mm. That’s a ratio of a
little less than 1/4. The difference
between a 2/7 mouth and a 1/4 (2/8) mouth tells the voicer a lot about how the
pipe will sound.

And remember, those diameters are a function of the scale, the
ratio of the diameter to the length. My
two example pipes with the same mouth width are very different in pitch. The Principal pipe (45mm in diameter) speaks
middle C of an eight-foot stop while the Flute with the 40mm mouth speaks A#
above middle C of an eight-foot. Now
you’re a voicer.

**§**

You can imagine that the accuracy of all these measurements is
very important to the tone of an organ.
The tonal director creates a chart of dimensions for the pipes of an
organ including all these various dimensions for every pipe, plus the
theoretical length of each pipe, the desired height of the pipe’s foot, etc.,
etc. The pipe maker receives the chart
and starts cutting metal. Let’s go back
to our two-foot Principal pipe. Diameter
is 45mm. Speaking length is 2-feet which
is about 610mm. Let’s say the height of
the foot is 200mm. The pipemaker needs
three pieces of metal – a rectangle that rolls up to become the resonator, a
pie-shaped piece that rolls up into a cone to make the foot, and a circle for
the languid.

For the resonator, multiply the diameter by π: 45 x 3.1416 =
141.37mm (this time I’m rounding it to the hundredth) – that’s the
circumference of the pipe so it’s the width of the pipemaker’s rectangle. Cut the rectangle circumference-wide by speaking-length-long:
141.37 x 610.

For the foot, use the same circumference and the height of the
foot for the dimensions of the piece of pie: 141.37mm x 200.

Roll up the rectangle to make a tube that’s 45mm in diameter by
610 long and solder the seam.

Roll up the piece of pie to make a cone that’s 45mm in diameter at
the top and 200mm long and solder the seam.

Cut a circle that’s 45mm in diameter and solder it to the top of
the cone, then solder the tube to the whole thing. Now you’re a pipe maker – except I didn’t
tell you how to cut the mouth or form the toehole.

But Professor Lewin’s adage reminds us that no pipemaker is ever
going to be able to cut those pieces of metal exactly 141.37mm wide. That’s the number I got from my calculator
after rounding tens-of-thousands of a millimeter down to hundredths. You have to understand the uncertainty of
your measurements to get any work done.

**§**

As I take the measurements of
these thousands of organ pipes, I record them on charts we call scale sheets –
one sheet for each rank. I reflect on
how important it is to the success of the organ to get this information
accurately. I’m using a digital caliper
– a neat tool with a sliding scale that measures either inside or outside
dimensions. The LED readout gives me the
dimensions in whatever form I want – I can choose scales that give
inches-to-the-thousandth, inches-to-the-sixty-fourth, or millimeters-to-the-hundredth. I’m using the millimeter scale, rounding
hundredths of a millimeter up to the nearest tenth. As good as my colleagues are and as
accurately as they might work, they’re not going to discern the difference
between a mouth that’s 45.63mm wide from one that’s 45.6mm.

And as accurately as I try to take
and record these measurements, what I’m measuring is hand made. I might notice that the mouth of a Principal
pipe is 16.6mm high on one end and 16.8mm high on the other. A difference of .2mm can’t change the sound
of the pipe that much – so I’ll record it as 16.7. I know the uncertainties of my
measurements. I adapt each measurement
at least twice (rounding to the nearest tenth and adapting for uneven mouth-height)
in order to ensure its accuracy. Yikes!

**§**

Earlier I mentioned how people who
work with measurements all the time develop a knack for judging them. I’ve been tuning organs for more than
thirty-five years, counting my way up tens of thousands ranks of pipes,
listening to and correcting the pitches, all the time registering the length of
the pipes subconsciously. With all that
history recorded, if I’m in an organ and my co-worker plays a note, I can reach
for the correct pipe by associating the pitch with the length of the pipe.

Π (pi) is a magical
number – that Archimedes ever stumbled on that number as the key to calculating
the dimensions of a circle is one of the great achievements of the human
race. How can it be possibly be true
that πd is the circumference of a circle while πr

^{2 }is the area? Here’s another neat equation. A perfect cone is one whose diameter is equal to its height. The volume of a perfect cone is exactly half that of a sphere with the same diameter. How did we ever figure that one?
There are no craftsmen in any trade who understand π better than
the organ-pipemaker. When you visit a
pipe shop you might see a stack of graduated metal rectangles destined to be
the resonators of a rank of pipes. The
pipemaker knows π as instinctively as I can tell that the first millimeter on
my ruler is too big. Imagine looking at
a tennis ball and guessing its circumference!

**§**

When you’re buying measuring tools you have to pay attention
to accuracy. Choose an accurate ruler by
comparing three or four of them against each other and deciding which one is
most accurate. Choose an accurate level
by comparing three or four of them.
You’ll be surprised how often two levels disagree. Just as mathematics give us the surety of π, so physics gives us
the surety of level. There is only one
true level!

I’ve been showing off all morning about how great I am with
measurements in theory and practice, so I’ll bust it all up with another story
about van windshields. I left the shop
to drive to the lumberyard to pick up a few long boards of clear yellow
pine. They had beautiful rough-cut
boards around thirteen-feet long, eight and ten inches wide, and two inches
thick. Each board was pretty heavy and
as they were only roughly planed it was easy to get splinters from them. I put the first one in the car, resting the
front end on the dashboard right against the windshield. Perfect – the door closed fine, let’s get
another. I slid the second one up on the
first, right through the windshield. Good
eye!

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