Trammel of Archimedes facts for kids
A trammel of Archimedes is a cool machine that helps create the shape of an ellipse. An ellipse looks like a stretched circle, like an oval.
This machine has two small parts called shuttles. These shuttles slide back and forth in two straight grooves or channels that are at a right angle to each other (like the corner of a square). A long rod is connected to these shuttles with special turning points called pivots. These pivots are fixed along the rod.
As the shuttles slide along their channels, the rod moves in a special way. Every point on the rod draws out an elliptical path! This movement is called elliptical motion. The size and shape of the ellipse depend on how far apart the pivots are on the rod.
If you look at the points where the pivots are, they actually move in straight lines. These straight lines are like very flat ellipses! Also, the point exactly in the middle of the two pivots moves in a perfect circle. This circle is also a special type of ellipse where both sides are the same length.
What is an Ellipsograph?
An ellipsograph is a special type of trammel of Archimedes. It's designed to draw, cut, or even carve ellipses. Imagine attaching a pencil, a knife, or a small cutting tool to the rod. As the machine moves, it creates a perfect ellipse!
Usually, you can change the distances between the pivots on an ellipsograph. This lets you make ellipses of different sizes and shapes, from long and thin to almost perfectly round.
No one is completely sure when the ellipsograph was invented. Some people think it might go all the way back to ancient Greek thinkers like Proclus or even Archimedes himself!
Fun Toys and Gadgets
Sometimes, wooden versions of the trammel of Archimedes are made as toys or fun gadgets. They are often called Kentucky do-nothings, nothing grinders, do nothing machines, or smoke grinders.
Instead of a pencil or cutter, these toys usually have a handle that you can turn. The sliding parts are often fixed in place. They don't really "do" anything useful, but they are fun to watch because of their interesting motion!
How it Works
- How the Trammel Works
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An animated model showing how the trammel draws an ellipse.
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A diagram of the trammel, showing the rod and sliding parts.
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This image shows the paths (called 'loci') of different points on the rod. The green circle is the path of the midpoint.
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A more complex version of the trammel with three sliding parts.
Imagine the two channels are like the 'X' and 'Y' axes on a graph. One pivot slides along the 'X' axis, and the other slides along the 'Y' axis. As the rod moves, any point on the rod traces out an ellipse.
The trammel of Archimedes is a type of four-bar linkage. This means it's a system of connected parts that move together. It's a special example of a more general type of machine called an "oblique trammel." In some versions, the channels don't even have to be perfectly perpendicular, and the points on the rod can form a triangle, but it will still create an ellipse!
Old Machines
- Examples of Old Devices
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A wooden ellipsograph from around 1900, now kept at the Smithsonian Museum.
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A "Grinder" toy from around 1960.
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An ellipsograph on display at the Musée d'histoire des sciences de la Ville de Genève (Museum of the History of Science in Geneva).
See also
In Spanish: Elipsógrafo para niños
