data stored in moving rust, was Re: Remembering RAMAC

[Bjørn Vermo]

On 27 May, 2005, at 10:29, Eric Smith wrote:

> Tom wrote:
>> certainly, IBM did not invent the disk drive. They may have
>> commercialized it first, but I doubt that even.
>
> I'd be very interested to hear of any working magnetic disk drive,
> commerical or otherwise, predating the IBM RAMAC.
>
>> Hand-wave -- it was obvious.
>
> In hindsight it looks obvious.  I'm not convinced that it was
> obvious 50 years ago.
>
The least obvious part of it was how to make a system where the head 
did not scrape away the coating.
Poulsen had shown how to record to a fast-moving wire. His telegraphone 
had severe head wear. Agfa had shown how to use a paper tape coated 
with iron oxide to be able to work at lower head to tape speeds and get 
less head wear, and the tape backing was subsequently improved to 
acetate film.

How to make this work when the magnetic coating was on a rigid surface 
was far from obvious. Magnetic drum assemblies were extremely tricky to 
adjust. There was a reason why they used fixed heads - the principle of 
moving along the drum axis had been known since Edison made the 
phonograph. The rason why drum storage used fixed heads was that nobody 
had figured out how to make flying heads yet, so they needed a very 
rigid assembly where you could use screws to make micrometer 
adjustments.

-- 
-bv