I built a device that combines features from a Biefeld-Brown asymmetric capacitor and the Morton van de Graaff device. It is shown in the attached photo.

It consists of a Schedule 40 PCV tube (1" x 1 foot) pushed inside of two concentric, cut-down PVC slip bushings; the assembly was then affixed to an electric burner drip pan with eight #4 panhead wood screws. The internal electrode is a 2' long cylinder of aluminum flashing which can be slid back and forth inside the tube. The assembly is suspended from wires that are spaced apart with PVC tubing and hung from ceiling hooks with pink nylon string.

The turned-out pan is intended to insure asymmetry even if the internal electrode is slid up close to it. The bushings are also intended to add some extra asymmetrical dielectric mass. The white (-) and black (+) insulated wires connect to a 200,000 volt van de Graaff generator (not shown).

The initial "shake-down cruise" showed no unusual effects. There was no detectable horizontal motion of the assembly when charged or discharged with the internal electrode (+) spaced away from the pan (-). There was no detectable Morton effect (a pulse) when the internal electrode was moved close enough to the pan (about 1.5 inches) to cause sparking. The sparks were of medium intensity. 

A separate nylon string was hung perpendicular to the tube and it did move towards and then away (radially) from the tube during charge and discharge cycles. Morton describes an effect like this. However, in this case the effect seemed to be purely ordinary and electrostatic, much like the leaf in an electroscope.