This influence machine is another variation of the Holtz machine (1865). It can be also considered as a simplified version of the Voss machine (1880). In my version (left), it consists in a rotating disk made of insulating material (acrylic) with an even number of metallic tabs glued to it, exactly as the disks of a Wimshurst machine, that rotates in front of a another, fixed, disk with two insulated metallic plates (inductors) glued to it, covering 90 degrees each. These metallic plates make contact with the tabs on the rotating disk through two brushes at horizontal diametrically opposite positions, and to the machine terminals. A neutralizer wire with brushes, as the ones in a Wimshurst machine, connects opposite tabs in the rotating disk as they leave the influence of the inductor plates.
The machine takes the output directly from the inductor plates, differing in this aspect from the Holtz and Voss machines. In this configuration it is similar to a simple bipolar "doubler" machine as the Belli machine, Lord Kelvin's "replenisher", or a Dirod machine.
A machine with the practically the same structure was described by M. L. Lebiez in L'Électricien, April 1895, pp. 225-227 [p31]. With nice pictures. Front, plan, and schematic (rather poor images).
I used acrylic disks, with metal sectors and inductors made of aluminum foil tightly glued to the disks. The metal connections were made with brass wire 2 and 3 mm thick and aluminum balls. The structure was made of wood and the insulator holding the terminal assemblies of acrylic.
This machine is a little less efficient than a Wimshurst machine, but it self-starts more easily. Its main problem are periodic polarity reversals, due to the fixed inductors. If they are glued in just one side of the fixed disk (the outer side), opposite charge quickly accumulates in the other side of the disk, reducing the electric field and the induction over the rotating disk. At the first spark through the terminals, or just after a speed reduction, the inductors discharge, and the charge in the opposite side of the fixed disk makes the machine start again with the opposite polarity. The process repeats, with a polarity inversion after each spark (specially if Leyden jars are attached to the terminals). This problem can be solved by gluing connected metal plates to both sides of the fixed disk. But then, there is a serious loss of charge by small sparks from the inductors in the inner side of the fixed disk to the rotating disk, that transport by the rotation charge from one inductor to the other. The Voss machine minimizes this problem by separating the output circuit from the inductor plates. The structure of the Wimshurst machine cleverly avoids the problem of charge buildup in the opposite side of the inductors, by changing the polarity of the inductors twice at each turn.
Note that this machine can easily be built with plastic tubes instead of disks, what is difficult with the Wimshurst machine.
Last update: 29 December 2006
Antonio Carlos M. de Queiroz
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