For a pyramid or such fixtures simply fasten your appliance to bottom or top as serves your purpose best.
Make your work as near perfect as possible, so the half circles never leave the bands, and exercise great care in insulating, for, while neglect does not always result disastrously it is well to be on the safe side.
THE RUBENS DOUBLE-REVOLVING EFFECT.
The idea is novel and simple. The construction of this machine is inexpensive. Go to any machine shop and have them bore out a piece of shafting so that one will fit into the other snugly. The contact plates are made of copper, lined with asbestos, mounted on wooden circles. In fact, the entire machine can be built for $12. There is no limit to designs that can be made for this arrangement. The novelty of two large pieces revolving in opposite directions, apparently from the point of a single shaft, is in itself a worthy attraction in any window. You will observe in photo that there are two pulleys on main shaft, also a countershaft below. One belt is up straight, the other belt is twisted so as to reverse either shaft. The large pulley on the countershaft is the main driver. The belt attached to this pulley leads to your motor or whatever power you wish to employ. This device is safe as well as simple, as you have ample room for cut-outs.
A—Inner shaft, ⁷⁄₁₆ inch diameter.
B—Outer shaft, 1³⁄₁₆ inch diameter.
C—Contact plate.
D—Holder for brushes.