Hub reinforcing rings, alignment disks (was Re: KryoFlux and Commodore Disks)

On 14 Apr 2012 at 9:55, Fred Cisin wrote: I suspect that the issue is one of being able to manipulate write current as well as head offset. i.e., a simple saturating write operation isn't what you want. There's an engineering spec for the Dysan 224a on bitsavers. We set up a rig for doing 100 tpi digital alignment floppies by taking a Micropolis 1015 drive, gutting the Molon stepper on the back and using it as the rear bearing for the leadscrew. We coupled the shaft to a 100:1 precision reduction drive to a separate stepper and mounted the whole affair on a 3/4" aluminum plate and placed in an insulated box. It took forever to get from track 0 to track 76, but we were able to generate digital alignment floppies for the field personnel. Early on, we discovered that, while Micropolis' control on track placement was fine, azimuth was all over the place. Those were weeded out in manufacturing--i.e. drives with out-of-whack azimuth were simply returned to Micropolis. --Chuck