Shugart 800-8 media centering problem

Chuck Guzis cclist at
Sun Aug 16 00:19:34 CDT 2015

On 08/15/2015 09:49 PM, dwight wrote:
> Sorry about the error in which side has the cone and which side has
> the cylinder. I don't have a 800 here in front of me to look at. It
> still doesn't make any difference if the moving arm is a little off.
> The piece that is mounted on the arm is designed to float on the
> spring. It is still the spindle that aligns the disk. The piece on
> the arm would have to be really out of line to cause the disk to not
> seat fully on the spindle.

That's the conclusion I came to--for a way to see how the whole 
mechanism works, see Shugart's patent 3,898,814 illustrations.

I believe that the earlier Micropolis 5.25" floppy drives worked the 
same way.  I recall that when they first came out, they'd mangle the hub 
area of a floppy because the spindle motor often had been turned off by 
the host.  Eventually, the design was modified so that the motor spun up 
as the drive door closed, which solved the problem.

Before that, Dysan had experimented with putting a reinforcing ring on 
their floppies.  By the time high-density drives came out, the problem 
had been solved so there was no need to reinforce the HD floppy hub area.


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