Homebrew Drum Computer (magnetic heads) - test-drb@ccmp.vtda.org

16 Dec 2007

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Subject: Homebrew Drum Computer (magnetic heads)
   From: Robert Nansel <bnansel at bigpond.net.au>
   Date: Mon, 17 Dec 2007 09:31:49 +1030
     To: cctalk at classiccmp.org

I think I might have a whack at making R/W heads using small ferrite  
cores/beads, the kind used in radio work.

My plan is to string several cores up on a straight brass rod with a  
snug fit  to their I.D., then bed the whole lot in wax and remove the  
rod.  Next I'll use an abrasive <mumble 1> to grind a tiny V-notch  
from the inside of the cores, taking care not to break through the  
outer diameter.

After removing the cores from the wax I'll wind <mumble 2> turns of  
<mumble 3> gauge magnet wire on them, fixed in place with super  
glue.  Then I would re-bed them in more wax, this time with the coils  
down and the internal notches up.  The cores would be almost  
completely embedded in the wax to provide strength for the fInal  
step, grinding a flat very slowly from the outside until the sharp  
end of the notch is exposed for each core.  This makes the gap.

I'll remove them from the wax and mount them on <mumble 4> blocks  
with <mumble 5> screw adjustments.

As for the drum part, I think I'll be best off with a disk instead,  
perhaps a 14" washing machine platter and spindle from a 3000RPM  
<mumble 6> Gonkulator.

So, aside from the mumbles, does this sound like a workable plan? 
Ah no.  the gaps have to be narrow less than .001".  that hs been done
two peice ferrite heads (half beads) with oe side of the magnetic circuit
filled with .001" thick brass shim stock.

Or you could pull the heads from a number of old floppies.

The 14" platter is a good source for media.

Allison

...
 -Bobby

> Fri Dec 14 14:22 Gary Oliver go at ao.com said:
>
> I have a reference somewhere for a drum project from the 40s that used
> what would now be simple machine-shop procedures (assuming one had a
> small drill-mill and lathe) to fashion a small drum of a few k-bit
> capacity. I'll try to dig that out and send it along. I was sort of
> planning to do something along this line myself at some point during
> "retirement" (which won't be for a few years, I suspect.) I've  
> acquired
> a few of the components for fabricating the drum and will give it a
> "whirl" some day. I was definitely NOT planning to make a flying head
> device and to keep it simple enough I could fabricate a few heads from
> "first principles." 