RK05 packs

[Paul Koning]

> On Sep 7, 2016, at 2:51 AM, Pontus Pihlgren <pontus at Update.UU.SE> wrote:
> 
> On Wed, Sep 07, 2016 at 01:58:24AM -0400, Ethan Dicks wrote:
>> On Tue, Sep 6, 2016 at 12:11 PM, Marc Howard <cramcram at gmail.com> wrote:
>>> It seems to me that one possible solution would be to whip up a PLL in a
>>> CPLD or FPGA to generate 12 sector timing from a 16 sector pack or vice
>>> versa.
>> 
>> This is one of the recurring conversations here - 12-sector packs are
>> abundant compared to 16-sector packs, and the only difference is the
>> slits in the hub and the consequent formatting on the matching
>> controller...
>> 
>> -ethan
> 
> I do recall discussion of manufacturing new hubs but not the outcome. I 
> imagine that someone with access to a lathe and mill would be able to 
> make new hubs with good enough tolerances.
> 
> Is there some caveat to doing this (besides finding someone with a lathe 
> and mill?)

As one who has a (quite old) lathe and some limited skills in using it, I'd offer some.

You can't make something without having accurate specs -- engineering drawings or equivalent.  The sector mark ring isn't too terribly criticall, but the hub mating surfaces for the spindle are.  One question would be what the required tolerances are, and what the required surface finish is.  Depending on those, the job may be straightforward for a basement machine shop like mine, or they may require more than average skill and/or a high end CNC machine.  If the finish or tolerance requirements are sufficiently tight, the job might require grinding, which raises the difficulty to a whole new level.

The other question is the disassembly of the pack and the installation of the new hub.  How is that done?  What are the concentricity requirements for the platter?  Is there a mating surface (exterior cylinder surface on the hub) or are platter and hub aligned in some fixture and then clamped to hold the platter in position?  Clearly the pack would be reformatted, so a small amount of runout would be ok, but it would have to be small enough that the vibration is controlled.

	paul