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

• hacivat
In summary, the speaker has convinced the administration to install a Foucault pendulum in their university building and is seeking advice on designing and implementing the support system. They plan to collaborate with the architecture department and are considering using electromagnets from the top to keep the pendulum oscillating. The speaker has also seen a solution where the bob is driven magnetically from below and is seeking resources and plans for this approach. The Griffith Observatory has a similar pendulum that is manually started each day and uses a string to eliminate any asymmetric forces. The speaker provides a link to an article by the Smithsonian museum and suggests searching for more information on the Griffith Observatory's pendulum. They express excitement for the project and ask for updates on any progress
hacivat
TL;DR Summary
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...

hacivat said:
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.

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:

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

Cheers,
Tom

## 1. How does a Foucault Pendulum work?

A Foucault Pendulum is a device that demonstrates the rotation of the Earth. It consists of a heavy weight suspended from a long wire or cable. As the pendulum swings, the Earth rotates underneath it, causing the pendulum's swing direction to appear to change. This is due to the Coriolis effect, which is caused by the Earth's rotation.

## 2. What materials do I need to build a Foucault Pendulum?

You will need a heavy weight (such as a metal ball or cylinder), a long wire or cable, a sturdy support structure (such as a tall ceiling or beam), and a way to suspend the weight from the wire (such as a clamp or hook). You may also want to use a motor or electromagnet to keep the pendulum swinging.

## 3. How long should the wire be for a Foucault Pendulum?

The length of the wire or cable will depend on the latitude of your location. For example, at the equator, the pendulum will complete one full rotation in 24 hours, so the wire should be approximately 41 meters long. At higher latitudes, the wire will need to be longer to compensate for the slower rotation of the Earth.

## 4. What is the best location for a Foucault Pendulum in a university building?

The best location for a Foucault Pendulum is in a large, open space with minimal air currents. This will allow the pendulum to swing freely without interference. A tall ceiling or beam is also necessary to provide enough height for the pendulum to swing.

## 5. How can I ensure the accuracy of my Foucault Pendulum?

To ensure the accuracy of your Foucault Pendulum, it is important to minimize any external factors that could affect its swing, such as air currents, vibrations, or temperature changes. You may also want to periodically adjust the pendulum's height and direction to compensate for any changes in the Earth's rotation. Additionally, using a motor or electromagnet to keep the pendulum swinging can help maintain its accuracy over time.

• Classical Physics
Replies
10
Views
1K
• DIY Projects
Replies
53
Views
7K
• Mechanical Engineering
Replies
11
Views
2K
• Materials and Chemical Engineering
Replies
1
Views
959
• Mechanical Engineering
Replies
2
Views
1K
• Mechanical Engineering
Replies
17
Views
2K
Replies
2
Views
965
• Mechanical Engineering
Replies
22
Views
2K
• Electrical Engineering
Replies
55
Views
3K
• Mechanical Engineering
Replies
1
Views
2K