I therefore propose that we increase the proposed project card size from
2x4
to 4x4 which is a 'happy medium' which Phil suggests below. This also
allows
for Phil - VK6APH BPF board, A Jupiter GPS receiver etc. For 'Dead Bug'
expeimenters like Bill - KD5TFD, he could use a 4x6 full length card and
have 2" sticking out the front for experimenting without a card extender.
It
also allows us to get on with Motherboard design with a maximum vertical
dimension of 96 mm. (case height between lands). I propose the
motherboard
height dimension be the the size of the 96 pin mating connector (3.7").
The
holes in the connector will mate with standoffs for rigidity.
I think a 4x6x4 enclosure would make a cute little radio!
I think that the ability to put the connectors, controls, etc. on the
PCB is a huge benefit for repeatability and reliability of whatever this
group builds.
You might want to consider designing the "motherboard" to accommodate
the card spacing dictated by the slot spacing in this extrusion, then
build a motherboard and at least one board of the proposed dimension,
preferably with one or more PCB-mounted connectors or controls.
Next, measure the extrusion length required based on the stackup,
including the mounting arrangement for the motherboard, to be sure you
get the length of the extrusion exactly right. You don't want it to be
too short, and you don't want a lot of "slop". Consider how the cards
will be retained in the mechanical system design.
Then, order some extrusions cut to the known-accurate length, allowing
for the tolerance of the cutting operation.
I won't mention how many times I've been bitten by not measuring, only
calculating, an enclosure size.
Another thought: the motherboard could be sized such that its PC board
forms the backplate of the enclosure. Downside is exposed connector
tails -- or maybe that is a plus for having exposed test points?