Re: van de graaff tube (fwd)

[<sroys@xxxxxxxxxxxxxxxxx>]

---------- Forwarded message ----------
Date: Tue, 07 Dec 2004 21:15:37 -0200
From: Antonio Carlos M. de Queiroz <acmdq@xxxxxxxxxx>
To: High Voltage list <hvlist@xxxxxxxxxx>
Cc: hvlist <hvlist@xxxxxxxxxxxxxxxxx>
Subject: Re: van de graaff tube (fwd)

High Voltage list wrote:

> From: Ed Phillips <evp@xxxxxxxxxxx>

>         If pulley driving speed is an option, for any given inner diameter of
> the column there must be an optimum pulley diameter / belt width
> tradeoff.  Widest belt means smallest pulley diameter and maximum shaft
> speed for given belt speed while largest pulley diameter means narrowest
> belt.

The optimum is to have the pulley diameter equal to the belt width.
This assumes constant charge density and fixed rotation speed in the
pulley. Add a small margin at the sides of the belt, and some extra
roller
width.
 
>         Would the teflon block really be OK with any significant belt tension?
> The darn stuff does cold flow.  Wonder how nylon would work?

An attempt to make a bearing with Teflon ended with significant cold
flow.
Nylon doesn't suffer from this problem, but tends to change size with
the ambient humidity. It shrinks in dry weather, and locks the
bearing...
Small ball bearings are quite silent. Specially sealed ones.

Antonio Carlos M. de Queiroz