high physical density cluster design -structural...

Jim Lux James.P.Lux at jpl.nasa.gov
Tue Mar 6 11:23:37 PST 2001

Rather than the copper pipe and fittings (which isn't very structural, and
will be a pretty significant problem as it gets bigger), you might want to
look at some alternatives:

1) UniStrut (available in aluminum and in galv steel) is much stronger, has
nice 90 degree connectors, etc.  There are a variety of similar products
made from aluminum extrusions of one kind or another with longitudinal slots
that make very nice rigid boxes. You assemble it with captive nuts and
bolts. The best thing about these products is that they are rectangular, not
round, which makes attaching stuff much easier.

2) Speedrail - a brand of cast aluminum fittings that works with aluminum
tubing to make structures, etc. (and hand and safety railings...)   There
are other brands, as well.  There are versions for 2" and 1" tubing, at
least.  The tubing fits into the socket on the fitting, and you tighten set
screws to hold it together.  (Or you can epoxy it....).  For a given $$, the
aluminum tubing will be much stronger and more rigid than the copper tubing.

As far as design guidelines go,  a 0.6 g side load, or so, would be an
appropriate number.  For instance, you should build it strong enough so that
you can (gently) tip it over on it's side and not have it fall apart during
the move.  In even a small earthquake, poorly braced sheet metal racks
loaded with many pounds of equipment just crumple.  Especially on less
expensive racking, a lot of the strength depends on the sides not buckling,
and once it bends even a little bit, it just caves in.

After all, some day, you WILL have to move the rack a bit, even if only a
few feet to let them take up the tile underneath it.

>> >
>> > Problem 1
>> > """""""""
>> > The problem is in the diagram above, the upside down board has another
>> board
>> > .5" above it - are these two boards going to leak RF like mad and
>> interefere
>> > with eachothers' operations? I assume there's not much to do there but
>> put
>> > a layer of grounded (to the cabinet) metal in between.  This will drive
>> the
>> > cabinet construction costs. I'd rather avoid this if possible.
>> >
>> > Our original construction was going to be copper pipe and plexiglass
>> sheeting,
>> > but we're not sure that this will be viable for something that could be
>> rather
>> > tall in our future revisions of our model. Then again, copper pipe can
>> > bolted to our (cement) ceiling and floor for support.
>> >

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