In this experiment, two l0-inch bicycle wheels are mounted on opposite ends of a rod that is supported at its center in such a way that it can rotate freely through a small angle about a horizontal axis. Extensions of the rod beyond the bicycle wheels enable one to place weights so as to produce a torque cbout this axis. The whole assembly is mounted on a ball bearing in such a way that it can rotate around a vertical axis through the pivot point of the rod. The rims of the bicycle wheels are loaded with a heavy iron plastic putty, commercially known as Devcon A. The wheels are set into motion by hand and the speed of revolution measured with a strobe light. The angular velocity remains essentially constant for a long enough time that the precession rates with various torques can be measured. The experiment is useful in that it very clearly shows the vector nature of angular momentum when the wheels are rotated in opposite directions.