Lifter on public display (fwd)

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Date: Sun, 14 Nov 2004 00:43:29 +0800
From: Peter Terren <pterren@xxxxxxxxxxxx>
To: High Voltage list <hvlist@xxxxxxxxxx>
Subject: Lifter on public display

I have finally completed and installed my lifter in the Gravity Discovery Centre in Australia. 
Some considerations for public display:
  HV protection is provided by an acrylic surround (the most expensive part at over AUD$1000).
  Interactivity provided by firstly a "Soft landing" rotary control to control the pulse width modulated 24V to the HV supply. Secondly with a "Crash landing" button (red, of course) in which there is a loud spark as the 30kV supply is short-circuited and the lifter drops 18 inches suddenly. The supply doesn't like being shorted so there is a 17K dropping resistor and a 570pF 40kV doorknob that provides the energy for the spark. Kids love this button.  There is also a dangling string with a piece of foil which gets blown around by the airflow.
  Colour is provided by the argon tubes which are the HV supports and alter brightness as the current draw changes. There are three spot lights of red, green and purple to give reflections of the foil of the lifter. These were made from arrays of 8 x 5000 MCD LEDs each.
  Educational information is provided by an accompanying poster or by the tour guides.
  Reliability.  Light toy kite string was used instead of thread at a small weight penalty.  A lot of care was taken with the hot gluing (and 2 spare lifters were made). The impact point at the feet was also reinforced with hot glue. On earlier lifters I needed to put some tape on the HV feed wires to prevent them getting agitated. On this one, I left the enamel coating on the feed wires and the problem was much better so hopefully wire fatigue will be delayed.  Reducing the agitation of the wires to avoid fatigue is done by small pieces of tape on the feed wires and lifter wires.
  RF interference is a potential problem.  There is a multidetector cosmic ray recorder on the other side of a brick wall.  Leaving the enamel on the feed wires seems to have reduced the RF and I also have about 10 turns of inductance on the feedwires wound around the argon tubes. 
  Ozone will be produced and there is a 6 inch gap between the roof of the enclosure and the wall where this will escape. The mildly darkened theater that it is in is large with perhaps a 40 ft ceiling and is air conditioned.  
  Mains safety. I have an external switchbox which has a fuse and a microwave oven mains RF filter.

I know of only one other lifter on public display in a "Robot museum" if I recall.  Does anyone know of any others?

Details on my site
http://tesladownunder.iinet.net.au/Lifters.htm

Peter