Lee Valley Tools

Maxwell's Top 05K96.01
A top very similar to this one was designed by a British professor over 100 years ago as a device to demonstrate gyroscopic principles to physics students. Specifically, Professor Maxwell wanted to be able to show, as convincingly as possible, that a gyroscope will always react at 90 degrees to an applied force.

A child's top is a form of gyroscope. You will find that lateral pressure on the stem of a spinning top will cause the top to slip off to one side rather than tilt. With Maxwell's Top however, because the bottom of the stem is trapped in a cup, pressure against the upper stem causes the top to tilt, not in line with the pressure, but at 90 degrees to it.

As a simple demonstration of the principle, put the top in the frame with the bottom of the stem in the cup and the upper tip of the stem trapped in the innermost loop of the spiral. Bring the top up to whatever speed you can get by rotating the upper stem between your thumb and forefinger. The stem will begin to trace the spiral, but, using the included hex key, back off the setscrew, immediately lift the tracer spiral out of the way and retighten the setscrew. The top should be spinning, but otherwise remain stationary. If you then touch the side of the stem with a pencil, the stem will trace down one side of the pencil and back up the other. This is the simplest demonstration of the principle.

Using the Tracer Spiral
For a much more dramatic demonstration of the principle, you can have the upper stem of the top follow the tracer spiral until it runs out of energy.

Once again, with the bottom of the stem trapped in the cup and the top of the stem in the innermost loop of the tracer spiral, slip the cord through the hole of the stem and turn the top by hand until you have a dozen or more turns of cord on the stem. Now, while supporting the top of the C-frame, pull the cord to give the top some rotational speed. Do not pull too hard; just apply a constant force. The cord will automatically release from the hole at the end of the pull, whereupon the tip of the stem will immediately begin to trace the spiral and will do so as long as energy permits. This is the dramatic demonstration of gyroscopic principles that Professor Maxwell wanted.

Tracer

Making Your Own Tracer Shapes
Using appropriately sized copper wire or coat hanger wire, you can make other patterns for the top to trace. Such a pattern might be your initial, or a logo, or some shape uniquely inspirational to you. The pattern should be no more than 2" in major dimension, so that the upper stem always remains in contact with the tracer.

Routine Maintenance
The top will spin longer if you reduce the friction between the stem and the cup. A very tiny amount of wax in the cup or a very tiny amount of oil (for example, the amount you might transfer on the tip of a toothpick) is all you need.

Disclaimer: All demonstrations are posted for the convenience and benefit of faculty and staff in the Department of Physics at Simon Fraser University and are not intended for outside use. The author(s) assume no responsibility or liability for the use of information contained on this site. Warnings and precautionary measures listed on this site assume normal operation of equipment and are not inclusive. Demonstrations may pose a significant hazard and can, in some instances, result in death; reasonable safety precautions must be taken. Demonstrations should be performed by qualified individuals only.

Prepared by Jeff Rudd, 1999
Revised by Laura Schmidt, May 2007