The dorkbot Edinburgh group meets
every other Tuesday in the Forest Café, a
volunteer-run nonprofit gathering place
near the University of Edinburgh. I had
been attending dorkbot workshops in the
café for a few weeks when one night, I
ventured upstairs to repair some stage
lighting and, surprisingly, found myself
in a church, complete with pulpit, balcony
and, most important, a 16-foot
pipe organ (Figure 1).
It turned out that the building the café
occupies was once the meeting place of the
Edinburgh Congregational Church—
hence the organ. But this wasn’t the instrument’s
original home. Initially installed in
Dublin Castle in Ireland in the late 19th
century by Gray and Davison, the famed
London-based pipe organ builders, the
organ, for reasons unknown, was moved to
Edinburgh in 1900. There it has stayed, in
varying states of repair, ever since.
So after the conversation in the pub,
we leaped into inaction. Over the course
of seven months’ worth of Tuesday
evenings, we pondered, poked, prodded
and prototyped several ways of driving the
organ’s keyboard.
As for the name, we settled on “Project
Waldflöte” for a stop on the organ called
Waldflöte. It means “forest flute” in
German, and since the organ is in the
Forest Café, it seemed poetically apt.
Getting the Mechanics Right
It became obvious very early on in the
development that we could partition the
problem into a mechanical part and an
electronic part. Once we had a solution to
the mechanical problem, we could proceed
with the construction of both parts relatively
independently.
One of the main constraints was
financial—we didn’t have any real money
to spend, just whatever our group of
roughly a half-dozen core people was
willing to throw into the pot. Scouring
the surplus market, we found some solenoids
that looked like they could fit the
bill. We could get a hundred of them for
about a pound each (roughly $1.50), so
we ordered half a dozen to play with on
the organ itself.
PHOTO: MARTIN LING
Figure 1 - The Forest Café pipe organ in Edinburgh, Scotland, was built
by the London firm of Gray and Davison in the late 19th century.
What we found was that the size of the
solenoids was ideal, but the travel of the core
was a bit less than we would need for consistent
triggering of the organ’s white keys.
Although we could drive the black keys
directly with the solenoid core, we would
need some kind of lever for the white ones.
You can see the first prototype of the
solenoid assembly in Figure 2 and a dia-
First Quarter 2009 Xcell Journal 45
gram of how it works in Figure 3. For the
white keys, the top plywood lever is
hinged at the back with a piece of duct
tape, and is pulled down when the solenoid
is energized. When the solenoid is
released, the organ key itself provides the
upward force—there is no need for an
additional spring. For the black keys, a
small pin protruding from the bottom of
XPERIMENT
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