Rudimentary case design questions

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I am wondering what opinions people might have about the following questions. I am reasonably skilled with dismantling and reassembling computers, but not without failures. I have never soldered a computer component, but know pretty much how to solder. I am also reasonably poor, by american standards. I am looking to build a custom computer in the mid to upper g4 range, maybe an intel or dual processor. I have priced used working g4 duals and they are about 300-500 on ebay right now. So I'm considering building my own. My plans are very formative still but I have some questions:

1) About case materials. Is sheet metal ok to use in such applications? seems to me that would be an easy approach to whatever shape piece you wanted and would make adding bezels and holes pretty easy. What about stone aggregrate or thin concrete? It could be molded into any shape and would probably stay pretty cool. I know I could just buy a cheap old 386 case and fill it full of small goodies or whatever, but I want to build my own. which leads me to my next question.

2) Can I use a power supply from a different computer to power on a custom machine, or does it have to come with the case like in those kits? Also do all g4 iMacs use same power supply?

3)Is it probable be able to scavenge all the cables connectors etc. I will need? I have a couple of dead soldiers.

4) As for a display I will probably go with an external monitor. Does this means i will need a motherboard with SVGA ports or can i add one via PCI slots?
Also for the sake of curiosity, is there a way to take an imac display out and adapt it to SVGA or otherwise attach it?

thanks in advance for your input.

brulaheliko

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in reverse order 4: this i

in reverse order

4: this is the holy grail of modding, very hard to do, very expensive. just go with an external monitor on its own card.
3: most likely.
2: yeah sure, as long as you get the pinouts for the power connector of the motherboard you are planning to use, you can use any PSU powerful enough.
1: g5 case is sheet metal, many pc towers are made out of sheet alu, concrete sounds interesting, but heavy maybe.

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heavy is no big deal, its jus

heavy is no big deal, its just gonna sit there. Do you recommend some sort of cooling system?

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Re: Rudimentary case design questions

brulaheliko wrote:

I am reasonably skilled with dismantling and reassembling computers, but not without failures. I have never soldered a computer component, but know pretty much how to solder. I am also reasonably poor, by american standards.

Your skill level and budget is practically identical to mine, then.

Quote:

1) About case materials. Is sheet metal ok to use in such applications?

Absolutely. You can make up a simple sheet metal folding rig with some timber and clamps to make neat folds. Aluminium is more expensive than sheet steel, but it is lighter and easier to work.

You might also want to check out polystyrene craft board - it is used in the iMac fake G5 tower mod, which might be in the case mods section of this site, or else Google it. Or perspex or acrylic for a transparent look. It can also be bent and folded but you need a heat gun or other heating tools to make it flex.

Quote:

2) Can I use a power supply from a different computer to power on a custom machine, or does it have to come with the case like in those kits?

Google "yourmotherboardname atx site:xlr8yourmac.com". If you can get the native power supply, it will be easier, especially with an iMac 'board. Tower conversions are usually reasonably simple.

Quote:

3)Is it probable be able to scavenge all the cables connectors etc. I will need? I have a couple of dead soldiers.

Pretty much, with a few exceptions. The ATX conversion articles at xlr8yourmac will tell you what they are.

4) You can either use a motherboard with onboard VGA (iMac) or one from a tower. All the tower motherboards have AGP video slots as well as PCI, with the exception of some very early G4s and the B&W G3 which used the same PCI-only motherboard, and a different (ZIF) CPU socket. Don't get one of those. CPU upgrades are more expensive.

Probably the best motherboard for your project would be a Digital Audio (DA) G4 tower. It has a 133MHz bus (fastest available for a G4 machine), onboard Firewire and USB, PC-133 SDRAM, four PCI slots (many other models only have 3) and a 2x AGP slot. And the ATX mod is well documented.

They are pretty cheap, especially as the lowest CPU on them is a mere 466MHZ, but they will take up to a dual 2GHz upgrade if you splash out the cash. Try to get a tested and known-good one that the seller is willing to guarantee, and with a CPU to get you started, and/or check out eshop.macsales.com for upgrade CPUs. You can always upgrade later.

If you want a smaller finished case, you could go for an iMac, but you'll pay more, have no expansion slots, and the PS conversion will be trickier.

Forget the iMac LCD, it's a no go.

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Oh also - if you're looking a

Oh also - if you're looking at machines on ebay, CPU speed ending in -00MHz or -50MHz means a 100MHz bus, and ones ending in -33MHz, -66MHz and -67MHz means a 133MHz bus. If you're budgeting for a dual CPU upgrade anyway, you would be better off getting a 466MHz DA for the faster bus and the extra PCI slot than say a dual 500MHz machine.

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Guide to model choices
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This really depends what spee

This really depends what speed processor card you have in the final construct, if you get a dual 1ghz for example you're going to have to put proc fans in it, where as if you get a 350-500mhz you're only going to need exhaust fans to take hot air out the case.
Also depends on whether or not you're going to overclock the card.

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Re: Rudimentary case design questions

brulaheliko wrote:

What about stone aggregrate or thin concrete? It could be molded into any shape and would probably stay pretty cool. I know I could just buy a cheap old 386 case and fill it full of small goodies or whatever, but I want to build my own.

I work with various forms of masonry for my job. Many people use the term "concrete" or "grout" when they really mean other things. In your case it might be best to use a set of terms that would help you find suitable materials for a masonry-based case coating. Stucco/plaster is a common coating. It's generally of two types: hard coat, and an EIFS. Hard coat is the age-old classic of mortar being applied in layers to build up a surface, usually with some sort of re-enforcing material incorporated into the layers, typically steel mesh/lathe, loose fiberglass fibers, old style horse hair, straw, etc. It's usually fairly thick and heavy, on the order of 1/2" to 7/8" of solid material. EIFS (Exterior Insulation and Finish System) is a much newer product that incorporates an insulating foam board backing and a masonry and acrylic coating for water proofing and texturizing. The over all thickness is similar to hard coat, but it is much lighter and has significant insulating properties. The actual coating layers are fairly thin and are a little flexible. An EIFS product sans the foam backing may be best to use for a custom case coating, but it may be difficult to get as they are usually "professional only" products. Brands to research are Dryvit and Parex, and there are/were others but there have been buyouts that I've not kept up on. The Dryvit TAFS may work better, but I've never used it.

Over all, a nice coating of something like the hobby store spray on textures and coating may be easiest. Doing stucco/EIFS installation is not something easy to pickup by an amateur.

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Thanks for the input guys. Jo

Thanks for the input guys. Jon, I actually did mean stone aggrerate or concrete, not stucco. I am talking about mixing gravel sand and cement and pouring slabs for a slip mold or maybe a wooden form etc. But all of that information is still relevant, so thanks again.

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In that case, I'd certainly r

In that case, I'd certainly recommend a mesh re-enforcement in the mold, as concrete doesn't have any flexibility. It also has a certain percentage of shrinkage, which is why stuccoing is done in multiple layers. Most concrete is not made for thin applications such as 2-4" or less. There are concrete surfacing products that are designed to provide a thin coating over a solid base that are different than stucco.
One brand I've used is Tamms, who make a product called Tammspatch (and Tammspatch 2) that can be applied in situations of less than 1", and can be extended to 2"+ by adding pea gravel. Adding some sort of steel or fiber mesh might make it able to bond to the surface of a steel case/framing.

The main issue with using a product like these is that they insulate. There will be little or no heat transfer from the case itself. The material will absorb and hold the heat. Active cooling would be an absolute must.

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Yeah I was thinking of a coup

Yeah I was thinking of a couple of layers of chicken wire and mixin my own so i could make it a little more dense so it would work for a thinner (I was thinking 1/12") wall. I was also thinking of making a partial or full use of this new fibrous cement technology I discovered.
At its basest, fibrous cement, often called papercrete or padobe, is fibers from paper that have been soaked and slurried and mixed with at least cement, although sand gravel and dry earth can also be added. Unfortunately all of these materials are good insulators.
As for cooling, would you recommend air cooling via a fan and vents, what do you guys think is better. vertical or horizontal flow? Or maybe water, saw that one hack, maybe ill go look at that again...

thanks
brulaheliko

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I'd also recommend looking in

I'd also recommend looking into hypertufa, a mix of peat, sand and cement...and sometimes vermiculite depending on the recipe. It's strong and light (compared to concrete at least).
Another link showing how to cast a box shape in hypertufa.

I've been looking for an opportunity to try out some 'papercrete', which looks like it has a lot of potential.

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yeah ive used hypertufa for r

yeah ive used hypertufa for rock gardening and bonsai. Ive had the priveledge of even using real tufa rock at my job in a rare plant nursery focused on rock gardens. The real thing is sooooo light and strong, but roots can go right through it. Funny that you mentioned that, i was thinking of finishing in stone facade maybe, like thre or four inch peices of thin granite, which i have a whole embankment of. ANyway I considered adding a peripheral container to the side to plant a bonsai in. Have to drain it away from the guts but thats about it.

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Take the advice of the first

Take the advice of the first link and don't rush the curing time. There is drying and curing, which are separate things. Curing is the chemical process that gives strength. Masonry and concrete will cure better if they remain wet/damp for a long time. Water is a critical part of the cure, so a dry mix that is left to bake in the sun will have little strength for a long time because it won't have the moisture needed to cure, except what it absorbs via the humidity of the air. Too much water will dilute the mix and make it too soupy, however a very dry mix will not be able to fill in corners and such and will retain air bubbles and pockets. For anyone who's never cast anything, be prepared to do many test casts to find what moisture content is best for your mold thickness and how long a cure time is best before removing the mold and still being able to texture the surface as desired.

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More info from someone with a concrete background

With respect to pouring the concrete into a mold, there does exist some "oil" (OK it is not oil but I don't know what it was) that if added to the concrete it will lower the viscosity for a short amount of time but it will not affect the final strength. I honestly don't know if this is used in the US (I'm from Europe and we used this on a multi-liter scale there) but we called it "float" (exact translation).
Also, in order to cut down on weight, you can add pumice and also small styrofoam spheres. It affects the final strength a little bit but if you are adding reinforcements it should be fine. But I'm not sure that chicken wire is the way to go. I'd pick something less flexible.

IC

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Yep, chicken wire (poultry ne

Yep, chicken wire (poultry netting for the politically correct) is too thin and flexible, thus the use of steel lathe. Stretched steel lathe does have a cup direction, so when installing it it is important to note the horizontal direction of the cups, and also that they are facing "up" so that the concrete, stucco, etc., is pulled back into the center of the mold. ie, the top of the angle in the stretch goes from the top&outside of the lathe to the bottom&inside. Using fiber re-enforced materials with lathe is going to be much more likely to create holes and air bubbles because it will be less likely to flow into the holes.

EDIT: We've used an oil-like additive with regular Type N mortar to be used with an electric drill powered tucking gun. It does make the mortar flow better though the auger, and it doesn't seem to affect the final cure.

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so for the bare minimum, i ne

so for the bare minimum, i need a logic board, w/ all the peripherals;pci, modem, etc. A power supply, and a processor. and cables to connect my drives. What else do I need as far as hardware. (I mean electronic Hardware, I can figure out mounting, etc.

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fans, or whatever system you'

fans, or whatever system you're gonna use to cool it.
If you get an early model G4 then your not going to have temperature sensors onboard to start with. My mdd has them for example, but my Gigabit doesn't. So this means you arent going to be able to tell how hot it is in there unless you put some temperature sensors in.

Also you're probably going to want to get the door of whatever system the board comes from, as the g4's have unique motherboard and processor standoffs that are built into the door. (ie the processor mounts onto these connectors)