itti at cco.caltech.edu
Mon Aug 28 23:22:32 EDT 2000
I have built many similar machines using plexiglass as a base, and a good
drill press from the student machine shop. Typically, you make a template
using a sheet of metal from home depot, and then mass-drill all your
actual boards, by clamping the template onto a stack of boards (number
will depend on plexiglass thickness; start with just one, as trying to do
too many can be disastrous). Remember rule No. 1 with the drill press: "it
brakes for nobody," so be sure to never hold your work yourself, but have
it clamped to the workplan instead and keep your hands clear ;-)
For the M.B. mounts, you can buy motherboard standoffs at good PC part
stores (the kind of guys who specialize in connectors and adapters).
there are two problems, though:
1) cooling. Recent motherboards will work much better if you have some air
flow; you seem to suggest that having many holes in the sheet of metal
will do the trick, but keep in mind that the motherboard does not have
such holes, so that will kill any vertical air flow in your rack. In my
experience, 2 fans pushing air into the front of the box and 2 pulling
out at the back gives infinite uptime (i.e., for me, never reboot unless
city power failure).
If some of your chips run hot, I recommend gluing heatsinks on them with
heat-conducting epoxy glue (use very little, otherwise it will flow over
the pins of the chips as you press the heatsink into place; not a problem
if your glue is not current-conductive, but looks messy).
2) sliding only the motherboard will be impractical because it will have
lots of cabling connected to it -> you should slide the whole assembly
out; that way, you just have to disconnect power and ether (if your cables
are short) before sliding out.
just my 2 cents...
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