Mathematics and harmless fun are blended in this virtual trammel app.
Archimedes' trammel is a device for drawing an ellipse. Also known as the do-nothing machine or the nothing grinder, you can buy one made from wood at your local craft fair for a few bucks.
This app is a virtual trammel … you can grind away at nothing electronically. You can change the length of the handle and placement of the sliders and see how the ellipse changes. You can also relate the trammel drawn ellipse to one drawn with two pins and a piece of string (mathematically speaking this relates the major and minor axes to the foci)
You can also investigate the interesting curve you get if you turn the trammel upside down and move the base while keeping the handle stationary.
Finally we provide a super-trammel: a trammel with 3 sliders, which moves, even though at first glance, you’d think it shouldn't. Take a look and see if you can work out why it is able to move.