Wimshurst machines (fwd)

[Steven Roys <sroys@xxxxxxxx>]

---------- Forwarded message ----------
Date: Thu, 13 Nov 2003 20:37:49 -0200
From: Antonio Carlos M. de Queiroz <acmq@xxxxxxxxxxxxxxxx>
To: High Voltage list <hvlist@xxxxxxxxxx>
Subject: Wimshurst machines

Original poster: Finn Hammer <f-h@xxxx>

(This thread was in the Tesla list)

> Wimshursters:
>
> I have had fine results using FR4 PCB material as disks for Wimhurst machines.
> The prototype vas just plain PCB, home etched in ferrochloride. The next
> batch were professionately made, goldplated sectors and soldermask, both
> for "boy, does that look good" effect.

Good to know that this material has enough insulation.

> Makes it easy to have 48 exactly placed sectors. The neutralizing points
> were small roundheaded screws,

Screws? Wouldn't they scratch the disks? I use brushes as light as I
can.
The current is very small.

> and although they promoted interdisk spark
> formation at the low voltage end of the machine,

Sparking close to the neutralizers always happens. The only way to avoid
it is to mount the sectors inside the disks, accessed through small
buttons, as in the old Wehrsen/Wommelsdorf machines. Maybe you can make
a machine using a multilayer PCB with internal sectors using a standard
professional PCB construction method. It's even possible then to mount
the sectors as two interleaved sets in two plates for greater
insulation:
http://www.coe.ufrj.br/~acmq/wehrsec.jpg
http://www.coe.ufrj.br/~acmq/wermov.jpg
Made the access buttons flush with the disk surface, or they break
the brushes too easily. PC boards seem a good method for this.

> they started up easily,
> and produced as much spark as the acryllic disked machines that they
> replaced. Sectors don`t fall off these disks.

> I also deviced a drive layout with only one long belt, which does not have
> to be crossed at one of the disks. This saves the machine from becoming
> covered vith rubber dust in time.

Don't use rubber belts. You know the effect. Ozone destroys rubber.
A classic method of using a single belt is to pass the belt through
two pulleys at 90 degrees with the pulleys in the disk bosses, one
fixed to an axle and another free to rotate over it:
http://www.coe.ufrj.br/~acmq/rovc1.jpg

> This is getting OT, so if anyone is interested in this belt layout, I`l
> describe it in more detail on the high viltage list where it belongs.

The thread is here now.

Antonio Carlos M. de Queiroz