ignition reference

[Kalle Pihlajasaari]

Hi Tom &c.

> >> My experience is that one is more likely to build a robust, high 
> >> quality timing disk with six or eight accurately spaced notches or 
> >> vanes than one with 360 or 256 notches and I do have access to 
> >> numerically controlled equipment.
> 
> >I would never have even tried to make such a disk (unless sending
> >it out to be laser cut, quite cheap these days :-)
> 
> Has any thought been given to making the disk from a PCB??  The artwork
> would be relatively simple using AutoCAD or such.  I can't see how
> to do it right now -- maybe plate the copper with iron so a hall
> sensor would work with it.  Long ago I used a similar approach
> to make optical encoders: encapsulated a film negative artwork in
> a lexan disk.

You could photo etch a copper or iron disk.  It would probably be
quite easy to do as well.

We were going to make soft copper head gaskets for high compression
conversions for older off-beat engines that there are no kits for
by using sign writing vinyl which can be cut to 0.25 mm accuracy
without any trouble.  We have a set of vinyl masks which would
be about right for a chainsaw but have not had time to try out the 
setup.  With copper it is easier, you take some ferric chloride
and sulphuric acid and then REVERSE electroplate the  holes into the 
sheet with the vinyl mask protecting the gasket.  Making a iron
rotor with 36 - 1 holes or blades for a hall interrupter should be 
almost as easy.  I would tin or zinc plate the iron afterwards to
prevent corrosion.

The laser people would not cut copper for us as the IR LASER beam is
reflected and the cutting is not fast and the reflected beam probably
causes the cutters some concern.

Cheers.
-- 
Kalle Pihlajasaari     kalle at data.co.za
Interface Products     Box 15775, Doornfontein, 2028, South Africa
+27 (11) 402-7750      Fax: +27 (11) 402-7751