Re: Mini VDG? (fwd)

[Steven Roys <sroys@xxxxxxxx>]

---------- Forwarded message ----------
Date: Mon, 22 Mar 2004 09:07:35 -0300
From: Antonio Carlos M. de Queiroz <acmq@xxxxxxxxxxxxxxxx>
To: High Voltage list <hvlist@xxxxxxxxxx>
Subject: Re: Mini VDG? (fwd)

High Voltage list wrote:

> From: David Speck <dave@xxxxxxxxxxxxxxxx>

> That is a cute VDG, but not the one that I had.  Mine had a 3" round
> plastic terminal with heavy nickel or chrome plating on it, a dark blue
> cylindrical column with "corona rings" molded into it, and a maroon -
> brown base which held the crank assembly.  I still remember getting
> airplane cement on my fingers in the process of winding coarse wool yarn
> around one of the pulleys.  The collector electrode was a simple strip
> of brass that sat very close to the belt.

The Renwal VDG?
http://www.coe.ufrj.br/~acmq/renwal1.jpg
http://www.coe.ufrj.br/~acmq/renwal2.jpg
These machines appear sometimes in ebay, where I found these pictures
some time ago.

> The weakness of the design was the 1:20 step up arrangement of the crank
> action.  The crank knob was mounted on a flat 3" cylindrical disc with
> gear teeth on the inside circumference.  IIRC, the plastic shaft on the
> 1/2" driven pinion gear wore through and broke fairly quickly, but not
> before I was able to do some nice demonstrations for my grade school
> classmates.  Aaaah, the good old days!

Probably not difficult to replace with something more solid. In my
old little machine, the upper roller melted its bearings, that were
simple holes in the plastic support.

Antonio Carlos M. de Queiroz