Thinking "out of the box" when building a PC

DaveW wrote:
Legally in the U.S. a computer has to have a metal case because otherwise it
outputs powerful RF signals which will interfere with your neighbors
electronics, according to the FCC.

There is no requirement for a metal case. If you could pass FCC class
B, you could make it out of cardboard.

A common method of shielding plastic cases is to spray them with
conductive paint.

That said, it is quite difficult to pass FCC with a plastic case, but I
have done it. It was no cheaper that using a steel case, after all the
stuff we had to do in order to get it to pass.

Mxsmanic wrote:
More and more, as I look at prefabricated cases for PCs, I ask myself:
what prevents someone from building a PC with no case? For example,
why couldn't you, say, build some sort of wooden mounting area into a
wall or a desk, then mount all the components to it, so that you have
something that blends into the furniture and/or something with plenty
of open space to ease maintenance and keep the machine cooler?

It would not keep it cooler. A closed case allows forced air to be
drawn in the front and expelled out the rear, with positive pressure in
the case.

Why does everything always have to be in a cramped box? As long as you
respect things like cable lengths, are there other limitations?

It's very common in a lab environment to have things open. But we
usually have to have fans blowing on the system.

Beyond cable lengths, it occurred to me that perhaps rotating parts
like CD and especially disk drives need to rotate in a horizontal
plane in order to have a symmetric load on the bearings.

No.

Another concern might be EMI, but if you had a metal mesh enclosure or
something around the machine that you could close and ground, wouldn't
that stop EMI? Does anyone really have much trouble with EMI, anyway?

Mesh wil solve the EMI problem, not that anyone that's building a
home-made systems worries about it much.

Anyway, what I picture is a sort of vast PC with tons of room between
components, almost like a huge rack in the style of old mainframes
into which you could easily stick your arm if you had to replace
something. Current cases are so cramped that one must pay careful
attention not to break anything when removing or adding parts, and the
air circulation never seems to be anywhere close to ideal.

The full tower cases are fine for this, but they are not that common
anymore because people want cases that fit into their existing
furniture.

I recently made a system for my son with an Antec SX-1040
(http://www.antec.com/us/productDetails.php?ProdID=81046) precisely
because I wanted a case with plenty of space, and good cooling. It has
excellent cooling, using four 80mm fans, in addition to the power
supply cans. I had to add some cooling fans to the desk, otherwise the
heat just built up in the space for the tower, though the fans only
took 5 degrees off the interior temperature, and 3 degrees of the CPU
temp.

The SuperMicro SC762 is even larger
(http://www.supermicro.com/products/c...tower/?chs=760).

But a lot of people are interested in stylish cases, rather than more
functional ones.

Maybe something that fits under a desktop (literally) would work.
You'd have a hinged door on the desktop, and when you lift it up, you
have your PC components all nicely mounted in a roomy enclosure with
plenty of space to maintain or upgrade them, and powerful silent fans

Ooh, I want some of those powerful silent fans!

On 21 Jul 2005 15:39:15 -0700,
wrote:

DaveW wrote:
Legally in the U.S. a computer has to have a metal case because otherwise it
outputs powerful RF signals which will interfere with your neighbors
electronics, according to the FCC.

There is no requirement for a metal case. If you could pass FCC class
B, you could make it out of cardboard.

A common method of shielding plastic cases is to spray them with
conductive paint.

That said, it is quite difficult to pass FCC with a plastic case, but I
have done it. It was no cheaper that using a steel case, after all the
stuff we had to do in order to get it to pass.

Yep, metal paint ain't cheap, it's often done with metal
sheeting attached to the plastic when possible.

kony wrote:

On 21 Jul 2005 15:39:15 -0700,
wrote:


DaveW wrote:

Legally in the U.S. a computer has to have a metal case because otherwise it
outputs powerful RF signals which will interfere with your neighbors
electronics, according to the FCC.

There is no requirement for a metal case. If you could pass FCC class
B, you could make it out of cardboard.

A common method of shielding plastic cases is to spray them with
conductive paint.

That said, it is quite difficult to pass FCC with a plastic case, but I
have done it. It was no cheaper that using a steel case, after all the
stuff we had to do in order to get it to pass.


Yep, metal paint ain't cheap, it's often done with metal
sheeting attached to the plastic when possible.

Yes. I've got an old 486 system made by Compudyne, I think it is, and it's
a plastic case with metal sheets all over the place inside for EMI shielding.

Looks like a case, pun, of 'engineering' gone amok as it's loaded with
'clever ideas' that seem to univerally make things more of a nightmare than
'better'. Not the least of which being that half of it is structurally
plastic, necessitating the myriad of attached metal panels (cost),
resulting in a case that resembles a half cooked flippy floppy hinged
noodle when opened and that prefers any orientation other than properly
aligned when you try to close it.

It 'works', though, and you can tell that an incredible amount of
engineering and design effort went into the thing. It's just that a plain
metal box would have been infintely superior from just about any standpoint.

David Maynard wrote:

Looks like a case, pun, of 'engineering' gone amok as it's loaded with
'clever ideas' that seem to univerally make things more of a nightmare than
'better'. Not the least of which being that half of it is structurally
plastic, necessitating the myriad of attached metal panels (cost),
resulting in a case that resembles a half cooked flippy floppy hinged
noodle when opened and that prefers any orientation other than properly
aligned when you try to close it.

LOL! BTDT.

David Maynard wrote:

Looks like a case, pun, of 'engineering' gone amok as it's loaded with
'clever ideas' that seem to univerally make things more of a nightmare than
'better'. Not the least of which being that half of it is structurally
plastic, necessitating the myriad of attached metal panels (cost),
resulting in a case that resembles a half cooked flippy floppy hinged
noodle when opened and that prefers any orientation other than properly
aligned when you try to close it.

Interesting though. This may seem bizarre, and I kind of like the idea
of an "open air" computer, so not to knock it, but hell, you could put a
computer in just about anything. For instance, nature worshipers could
go au natural, put their hardware in an old dried up tree hole or
something. Prolly take some serious discipline, and violent cleaning to
turn it around, into something half way decent, and hospitible though.
I know. Way off topic. But still..

http://www.hypography.com/article.cfm?id=34241

Study probes ecosystem of tree holes
Web posted Jun 16 2004 @ 02:09 by Tormod Guldvog

If you think your place is a dump, try living in a tree hole: a dark
flooded crevice with years of accumulated decomposing leaves and bugs,
infested with bacteria, other microbes, and crawling with insect larvae.

"It's a war inside a tree hole"A biologist at Washington University in
St. Louis has studied the ecosystem of the tree hole and the impact that
three factors ? predation, resources and disturbance - have on species
diversity.

Jamie Kneitel, Ph.D., Washington University in St. Louis post
doctoral researcher in biology in Arts & Sciences, and Jonathan Chase,
Ph.D.,Washington University assistant professor of biology, found that
tinkering with any of those factors changes the make up of the
community.

Kneitel uses the Richard the III reference - "subtle, sly and bloody,"
Richard III's mother's description of her son as a little boy - when
talking about the ecosystem he studies. A tree hole can be found in
nearly every forest and is an ecosystem surprisingly overlooked by
ecologists.

Created by a lost tree branch or deformed trunk, the tree hole collects
water, which supports an aquatic community that lets an ecologist like
Kneitel address fundamental ecological questions. In this small
ecosystem, bugs and leaves fall into this pool of water and decompose
which provides the energy for hundreds of species, including bacteria,
protozoa, and mosquito larvae. It's a generally thriving community where
these critters battle each other in a mini-survival-of-the-fittest.

To perform his study, Kneitel recreated the tree hole ecosystem in the
laboratory, which allowed him to change the parameters to create
different ecological situations. The most common disturbance for a tree
hole is lack of water. Resources equate to the food supply, and
predation among the three basic organisms - protozoans, rotifers and
mosquito larvae - is rampant, and varies depending on resources and
disturbance.

"Predators, resources, and disturbances are the most common factors that
affect communities, but few studies look at all these factors together"
Kneitel said. "Not surprisingly, predators, resources, and disturbances
all had really strong effects, but the interesting finding was how these
various factors interacted. Community composition was altered by all
treatments, depending on which treatments were present.


Certain species were associated with each of the treatments - those in
predator treatments were those tolerant of predators, those in
disturbance treatments were tolerant of disturbances, and so on."
Kneitel studied between 20 and 25 protozoan species and four rotifers;
protozoans are single-celled organisms, rotifers, multi-celled, yet some
protozoans are bigger than rotifers and will prey upon them. Mosquito
larvae browse and filter-feed and will attack either of the groups of
species.

'It's war inside a tree hole," Kneitel said. "We found that predation
has the strongest effect when there are no disturbances. Disturbance has
the strongest effect when there is little predation. When there is no
disturbance or predation, competition is the primary source of
extinction. A disturbance - a dry tree hole - pretty much kills
everything but certain protozoans that can go dormant and survive the
cycle."

The results will be published in a forthcoming issue of Ecology. The
work was supported by NSF. Kneitel said most studies of this sort look
at two factors, compared with the three he and Chase studied.

"Our results show that if you change any one of the three factors, you
alter the face of the community," Kneitel said. "We found that we had a
group of species that were good competitors, another that is good at
tolerating predators, and yet another that can survive and tolerate
disturbances.

"These traits (niche) differences allow many species to coexist with one
another at different spatial scales. This is true for this community,
but also many other communities work in this way."

Kneitel said the scale of the tree hole system allows him to ask "big
picture" questions of ecosystems that can't be asked on a large scale.

"You can't really ask these types of questions using long-lived
organisms like wolf and deer populations," he said. "It takes years and
years to see the effects of predation and disturbance on population
dynamics. With these communities, you can do an experiment in a month."

The source of this story is Washinton University in St. Louis.

That plastic case is from Palo Alto Design Group, if it's the big
squarish desktop case I'm thinking of. I did the Compudyne
motherboard/case combinations for CompUSA when I was product manager
for the U.S. office of a very large Taiwanese motherboard company,
many years ago.

It involved every CompUSA store becoming a UL certified "factory,"
since the systems were assembled in the store, plus we had to get FCC
class B for them, for every motherboard/case combination, with a worst
case set of add-on cards.

One day I got a call from a CompUSA, stating that a UL inspector was at
the store, and that he found non-UL approved lithium batteries in the
systems. Some braniac in Taiwan had decided to save money by having
"housewives assemble batteries into plastic cases." We had to take back
thousands of these batteries, and sell them to customers that didn't
care about UL.

ToolPackinMama wrote:

David Maynard wrote:


Looks like a case, pun, of 'engineering' gone amok as it's loaded with
'clever ideas' that seem to univerally make things more of a nightmare than
'better'. Not the least of which being that half of it is structurally
plastic, necessitating the myriad of attached metal panels (cost),
resulting in a case that resembles a half cooked flippy floppy hinged
noodle when opened and that prefers any orientation other than properly
aligned when you try to close it.


LOL! BTDT.

Hehe. We all (meaning engineers) have. It's natural to seek the most
complex solution to a trivial problem because, frankly, the easy one isn't
'fun' and doesn't use the latest toys

David Maynard writes:

It 'works', though, and you can tell that an incredible amount of
engineering and design effort went into the thing. It's just that a plain
metal box would have been infintely superior from just about any standpoint.

The accountants probably told the engineers that a plastic case was
mandatory for cost reasons, and then ignored the engineers when they
explained all the additional work that would be required to make the
case compliant.

wrote:

That plastic case is from Palo Alto Design Group, if it's the big
squarish desktop case I'm thinking of. I did the Compudyne
motherboard/case combinations for CompUSA when I was product manager
for the U.S. office of a very large Taiwanese motherboard company,
many years ago.

Could be. It's a tower that looks like, from the upside down arrangement
with 5 1/4 inch bays on the bottom, they intended it to sit on a desk top.

It involved every CompUSA store becoming a UL certified "factory,"
since the systems were assembled in the store, plus we had to get FCC
class B for them, for every motherboard/case combination, with a worst
case set of add-on cards.

That might explain the clamshell idea because, as I looked at it, I got the
definite impression someone had 'easy to assemble' and 'easy to debug' as
an intended goal.

It's well made inside. It's neat, routed and cable tied with a place for
everything, everything is in it's place, and precisely the right length.


One day I got a call from a CompUSA, stating that a UL inspector was at
the store, and that he found non-UL approved lithium batteries in the
systems. Some braniac in Taiwan had decided to save money by having
"housewives assemble batteries into plastic cases." We had to take back
thousands of these batteries, and sell them to customers that didn't
care about UL.

Oh man. I've been through those 'inconsequential change' things too.