Description of a Wimshurst machine.

The disks are 30cm diameter and made of 2mm acrylic, these are attached by three screws to turned brass bosses fitted with (ex-hard disk drive) ball bearings. They are driven by round rubber cords from wooden pulleys (60mm diameter) on a brass axle supported on ball bearings in the vertical supports. The axle is turned by a wood and brass crank handle, also on ball bearings. The neutralizer brushes are made from raw carbon fibre which is extremely soft (like human hair) and mounted in holes in the ends of 4.75mm brass rods. The charge collectors are made from the same rod with springy brass wire pushed into holes to form the points. The combs are soldered onto rods which enter the wooden balls. They are fixed to a brass mount glued onto a 12mm glass fibre rod that runs down the centre of the Leyden Jars. The fibreglass rod is slightly shorter than the Leyden jars so when it is screwed to the base, the jars are fixed firmly by compression between the ball and the base. The electrodes push into the wooden ball and over a section of charge collector rod that has been turned down to 3 mm. The handles are of the same fibreglass material as the charge collector support and the large balls (18mm) are from discarded computer mice. The small balls (9mm) are from spray paint cans. All balls have been drilled and tapped to screw onto the end of the electrode. The Leyden jars which double as supports, are of 32mm PVC water pipe, cleaned and polished (looks like porcelein). The wall thickness is 2mm, giving 40kV dielectric strength each. The capacitance has been measured at 77pF each. A removable shorting bar connects them in series.

Julian Phillips
Electronics Technician
University of Canterbury.
30 October 2000