The Foucault Pendulum in the Thij-College, Oldenzaal, NL Latest change 2017-12-17
The Pendulum in the Thij-College has some interesting details .
See the PDF of the document I got from the Technical Assistent. This is a
partial translation from the original
document in Dutch
interesting thing is the way the wire is suspended:
The threaded rod to which the wire is attached has a hole whicht widens
in a few steps. The aim of the make was to let the wire bend over an
extended trajectory and ot only at the point of mounting. Because the
dimensions are there I made a new drawing to scale with an extra
construct in which the radial dimensions are exaggerated a factor of
10. Then Iaid the wire against the edges and constructed perpendicular
lines on the midpoints of the segments, curious to see if they would
cross through 1 point. The did'nt. But the fact that the
pendulum effectively becomes shorter while swinging out helps
suppressing the precession of the ellips. It makes the period time less
dependent of the amplitude, and that is just the mechanism which
produces the ellipse-precession. If the period of the short
ellipse-axis equals the period of the long axis ther would be no
And yes, overcompensation is a possibility.
This method also works a bit as the Charron ring, the movement of the
short axis encounters more friction than the long axis moevement.
A full analysis of these conditions goes beyond my possibilities. I'd
suggest to simulate it using a finite elements method, based on the
movement equations of the pendulum.
On the left side the hole is drawn, To the right the hole is
exaggerated a factor of 10 for the width only, and the wire (light
blue) is laid against the edges.
The purple lines ar mid-orthogonal to these segments and do not cross
in 1 point. However the crosspoints do come closer with larger
Some photos I took during my visit at november 15, 2017. Click for
Seen from above
The Topmount with the tube. The electrical connections are just visible.
The board with the control electronics normally sits below the
From left to right: Terminals, Power supply 24 Volts, PLC, Solid-state
switch, leds en buttons, Terminals for the electro-magnet.
The 12 Volt powersupply is not on the photo.