Bob:
In response so some of Chuck’s, Juan’s and other’s
suggestion, I have updated the 125x180 module to incorporate integrally
machined support posts and revised the cover attachment to the connector plate.
While making this change permanently attaches the posts to the baseplate, it
also means that there is no flexibility in omitting any posts.
For Chuck’s information the nomenclature of the module
is the PCB size, as it has been for seven years. There may possibly be PCBs that
would be 75mm larger, totaling to be a 200x180mm PCB, but I certainly would not
expect anything larger than that. Also note that the depth of the cavity below
the posts is 6.35mm, save for in the very center where there is an attachment for
the connector plate that is located 0.75mm below the PCB for a space in the center
that is 10mm wide by 6mm deep from the connector plate. I was loathe to locate
such a piece here but felt the need for a third attachment for the connector
plate.
For Juan, the use of socket heat cap screws is not out of
the question, I just did not replace them in this assembly at this time.
For John, I will have to create a revised footprint of the baseplate
interface to the bottom of the PCB, which obviously is not quite as limited as
just some 0.250inch cylindrical posts. I kept the basic pad of that same general
size, but the machining aspects of things get in the way of keeping it quite to
the same exact area of spots.
Bob Davis and I discussed extensively the issue of being
able to remove the cover while the module is mounted in the spacecraft. To
achieve a relief in the issue of the cover dictating the shape of the
baseplate, instead of the converse, this feature had to be sacrificed. I well remember
the discussions of earlier this century, but the issues that Juan raised seemed
to overpower the need to remove the cover while still in the spacecraft. To
accommodate the side-mounted screws the sides of the module were “pulled
in” by 3mm on each side, with the finished module now being 141mm plus
2x0.5mm for the cover (=142mm) and plus screw heads, instead of the former
147mm overall. (Now don’t get bent all out of shape on that fuzzy math.
No comments thereof will be accepted.) The module mounting pitch is 150mm
leaving 8mm between adjacent modules for two sets of screw heads.
One type of module will, however, have to retain its removable
cover feature, however, and that for the power modules as the heat sink screws
must be accessed in order to mount the module into the spacecraft. What this
design is to look like has not been redetermined at this point.