Bob Holmstrom's Bean Can Clock

The following description was provided by Bob Holmstrom, who decided to test my claim that the EM Controller was so simple you could use it to make a clock out of a can of beans and a ball of twine.

I took a can of Heinz Vegetarian Beans and hung it with fishing line (Spectra Fibre -low stretch - 20 lb test) from a 1-1/2" tube clamped to a vee block attached to a concrete wall. The attachment is accomplished by a disk brake rotor bolted to the concrete wall with a 2x6x6 aluminum block supporting the vee block. The tube sticks out perpendicular from the wall about 18". I fastened the Spectra Fibre to the tube at two locations approximately 1 foot apart with knots over screws on the tube. The Spectra Fibre loops around the can and is held tight against the vertical can by rubber bands at top and bottom. The can was adjusted level by use of a level bubble.

A small permanent magnet was stuck to the bottom of the can and the pendulum was set in motion over the drive coil of Bryan's EM Controller. The MicroSet output was used to adjust the pendulum to about one second by rotating the tube in the vee block -- i.e. winding up the Spectra Fibre. This method of wire support (wrapping/unwrapping from a cylinder) was used by Bessel for his pendulum experiments and found superior to trying to clamp the wire.

The Microset data attached shows the performance of the Bean Can EM Clock over a three day period. The Bean Can Clock is mounted in a unheated basement (only insulated heating ducts pass through). During the period between the two downward spikes (basement door open) we were away from the house. The only disturbances were a refrigerator on the floor above and an ocasional car on the road. After the second spike, activity for the next day was normal - heat on, the lawn was mowed etc. Though the basic rate of the clock was fast, the rate did not vary by more than about 5 seconds per day over the three day period.