Hi Meredith,
Most disks were aluminum, but some of the disks were ceramic/glass, 
especially in the smaller diameters like the 2.5 inch portable drives.
Find some of those and you'd have very hard disks.  The problem is that 
although the surface are polished to very good figures,
the edges were not, so I'm not sure what the final result would be.  But 
starting with those disks, then polishing them could yield
some very good hard edges.
Regards,
Charles Patton

meredith lamb wrote:
> Hi Charles & Chris,
>
> 2 cents....
>
> A possible partial solution for the 3-4" diameter....use old computer 3" hard
> (actually ~3.1" or so) drives for the upright rolling "ends", with
> holding spacers inbetween; and then mount your mass and use the
> spacers for the screws adjustments.  They are light, tough, and have
> precision diameters and have a nickel plated all over....and they can be also
> be cut in two if really necessary.
>
> Meredith
>
> On 2/19/08, ChrisAtUpw@.......  wrote:
>   
>> In a message dated 2008/02/19, charles.r.patton@........ writes:
>>
>>     
>>> One possibility would be to find a flat piece of standard window pane,
>>> mount it, and provide tension screws to physically pressure it into the
>>>       
>> desired
>>     
>>> curve.  After all it
>>> is only 0.001" in 1".  I think glass would bend that much.
>>>       
>> Hi Charles,
>>
>>        Much less than that. You specified a curve of 1000 ft, presumably the
>> radius.
>>        If your strip is 6" long
>>        Center deflection = (0.25)^2 / 2000 x 12 inches = 0.000375"
>>
>>        Regards,
>>
>>        Chris Chapman
>>
>>     
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