Re: Wimshurst machines (fwd)

[Steven Roys <sroys@xxxxxxxx>]

---------- Forwarded message ----------
Date: Fri, 14 Nov 2003 08:38:26 +0100
From: Finn Hammer <f-h@xxxx>
To: High Voltage list <hvlist@xxxxxxxxxx>
Subject: Re: Wimshurst machines (fwd)



High Voltage list wrote:

>>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.

I use very soft and thin wire for the brushes too. But it annoys me if
these wires drag marks around the disk, by touching the disk itself, so
i had holes drilled in the narrow end of the sectors, threaded them, and
put small screws in them, so that the brushes touch them, not the disk.
It is just another way of making the small bump that is often made on
sectors, if they are made from foil, and glued or waxed on to the disks.

I have a picture of one spare disk here, without screws, but with holes.

http://home5.inet.tele.dk/f-hammer/wimshurstdisk.jpg
Battery in the center is a AA for size.
>
>
>>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.

I think that if the disks run true, then it is ok to have the buttons
protrude a bit.
I worry that the marks on the disk could form a conductive path that
would, in time, short out the machine.

snip

>>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

That picture reminds me of how much I have to learn: That is one very
beautifull machine. But I am not able to imagine the drive belt`s path
from the picture and your description. Have you got other pictures? Or
could you spend a few more words? I see that they are using timing belt(s)?

How big is that machine, anyway?

Making pictures of these belt systems is not easy, I am currently trying
to make a 3D rendering of my own system ( based on the work of others)
that shows how it is done. It uses a round polyurethane belt, that I get
on a reel, like magnet wire,  and join by welding the ends together.

>
> The thread is here now.
>
> Antonio Carlos M. de Queiroz
>
Cheers, Finn Hammer