Re: wimshurst (fwd)

[Steven Roys <sroys@xxxxxxxx>]

---------- Forwarded message ----------
Date: Tue, 29 Jul 2003 20:28:07 -0500
From: Ralph Zekelman <hyperion@xxxxxxxxxxxxxx>
To: High Voltage list <hvlist@xxxxxxxxxx>
Subject: Re: wimshurst (fwd)

Antonio, thanks for reminding me of the 30 cm disc size for the
old William Welch Wimshurst generator. William Welch (now VWR)
was a Chicago supply house and maker of scientific equipment.

On page 244 of the 1990 Central Scientifics catalog is a Wimshurst with 31
cm plates. The price is $479. The description does not state the material
used for the plates but the large photo shows a lot of Lucite parts,
including the housing for the two Leyden jars. The specs call for 12 cm
sparks and a short circuit
current of 30 uA. I would suppose that the use of Lucite rods and
fittings improves the corona control of the older William Welch
model of the 1930s and 1940s era.

snip--snip

>>>>Still limited by sparking across
the disks, but without the sectors making bridges, <<<<

A not too bright experiment we did with the Welch Wimhurst was to hold a
piece of
thin glass between the discharge balls. With the balls touching the glass on
opposite sides, we had a high dielectric capacitor in parallel with the
Leyden jars and cranking
away on the generator built up a voltage high enuff to arc around the edge
of the glass at least twenty inches. QUESTION: Why didn't the generator arc
between the discs?

Ralph Zekelman