Sections of plastic tube and brass washers are used to keep the spindle in the correct place relative to the longer upright support. The machine self-excites easily, producing enough charge to be clearly observable with an electromer, or produce flashes in a neon lamp touching the disks. The operation of the doubler is observable, with the electromer showing approximately twice the voltage at each turn after the excitation. This picture shows the modification, and here is a photo of the final machine, and a comparison of the output voltages obtained with and without the shields, as measured by a simple electromer. The machine sometimes reverts the polarity, due to charge accumulation at the outer sides of the spark shields.
Sparks are now visible in the contacts when the machine is excited.
Disks made with a more conductive material would probably be an improvement too, and would certainly cause more visible sparking. A picture of the machine , before the varnishing of the parts, and after . The thin insulation of the varnish over the fixed disk frequently makes the electromer ball stick to the disk.