How can I design a Foucault Pendulum for my university building?

[hacivat]

TL;DR

How to keep it going?

Hi guys,

I think I have persuaded the administration to install a Foucault pendulum in my university building where a high roof and open spaces are available. The thing is I have to project it with design, cost, etc. Those are domains which I don't have much expertise as a simple physicist. So I am planning to collaborate with architecture dept, etc. But, also I have to find a solution how to keep it going. I am pretty sure Foucault pendulums are not in mass production in the world. So I believe each system is unique in it own way.

So I would like to ask engineers around here about these kind of supporting systems which supplies energy to such systems. I have heard that those 20-30 m long Foucault pendulums are supported by "electromagnets from the top" as is mentioned in the video at the end of the message. But this also bugs me whether if it is going to mess up with its original motion where the oscillation plane rotates. Besides I have no idea what those support system looks like. So any kind of plan or source is appreciated on that...

Thanks in advance...

 

[Baluncore]

But, also I have to find a solution how to keep it going.

I have seen a solution where the bob is driven magnetically from below. The drive coil is mounted in the floor with a vertical axis, below the bob, so it maintains oscillation without influencing the direction. I do not remember if the bob was just iron, or if it had a permanent magnet to react with the drive coil.

The bob position was detected optically as it passed over the coil. I believe the time to cross the optical detector was used to assess the amplitude of the swing, and so to regulate the drive.

 

[Tom.G]

The Griffith Observatory near Los Angeles, California has one. It is a 240 pound Brass or Bronze ball suspended from a bearing that does not rotate with the Earth. If a recall correctly from a long-ago visit, there in not an active drive, the pendulum is manually started each day.

Of the links I've looked at that mentioned the material, all stated Brass. At least one link noted the suspension was a stiff rod, not a cable.

One site mentioned that for accuracy and repeatability, the pendulum is not touched by hand. It is captured with a string, brought to the starting position, and given time to stop swaying.Then the string is then burned through to release it. This eliminates any asymmetric forces that may force an elliptical swing path.

Here is an article by the Smithsonian museum about their pendulum that mentions a magnetic drive. (they also give their phone number in case you want to pick their brain!)
https://www.si.edu/spotlight/foucault-pendulum

Try this search for many links:
https://www.google.com/search?q=griffith+observatory+foucault+pendulum

Sounds like a fun project. Please keep us updated about any progress.

Cheers,
Tom