Building a light but rigid pc case out of plywood.

[f592b]

Hello everyone,
I'm looking to build a portable pc case with built in screen out of 4mm thick baltic birch plywood and I was wondering if it will be rigid enough to hold about 5kg worth of parts in a box with a 40cm x 35cm base and a height of 9cm?

The other alternative is to construct a case with 0.5mm thick aluminium sheet and bond 3mm plywood to it on the outside.

Which one would be better for case rigidity? I would also be interested in alternative materials that you may know of but the total mass of the case has to be under 1.5kg.

Does anyone know the density of birch plywood? I've been using 0.65g/cm3 (~40 lb/ft3) to estimate how much the case will weigh.

I'm from south east London and I was wondering if anyone here could recommend a place where I can get some 4mm baltic birch if that ends up being the plywood I go for.

Advice will be appreciated.
Thanks for reading.

 

[AndyT]

If the joints are good, thin plywood can be very strong. Ikea must have sold thousands of their Knuff magazine holders and similar products. They are made of plywood only about 3 mm thick but are strong enough when stuffed full of heavy glossy magazines.

I don't think they cut the comb joints by hand though. :wink:

http://m.ikea.com/gb/en/catalog/products/art/50187340/

 

[devonwoody]

Welcome to the forum.

Have you taken heat into consideration that the case would be subjected too?

 

[f592b]

To deal with the heat I intend to install 3 120mm fans on the top panel of the case which will push fresh air down towards the cpu and gpu area and out through vent holes on the sides.

What sort of temperatures can plywood stand?

 

[ColeyS1]

To deal with the heat I intend to install 3 120mm fans on the top panel of the case which will push fresh air down towards the cpu and gpu area and out through vent holes on the sides.

What sort of temperatures can plywood stand?

I'd say it stand a lot of temperature before catching fire, it's just how much it will bow with very warm temperature on one side and normal temp the other. I recently stuck a picture onto 6mm birch ply and was surprised how much it bowed by not putting a balancer sheet on the back.

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[Sporky McGuffin]

Dunno about the temperatures, but I'd suggest bringing the cool air in at the bottom - warmer air rises, so let the fans work with that natural effect rather than against it.

 

[JakeS]

Dunno about the temperatures, but I'd suggest bringing the cool air in at the bottom - warmer air rises, so let the fans work with that natural effect rather than against it.

The problem with that from a PC case point of view is that the case tends to stand on something, sometimes a carpet - it's nearly always the case that there's better airflow from the top rather than the bottom, unless you have a vent at the bottom front which a lot of people don't like for aesthetic reasons.
There'll usually be a fan venting the hot air out of the back, which helps a lot - especially since the CPU/GPU will often be more or less in line with that, and those are the hottest bits.

 

[Sporky McGuffin]

The problem with that from a PC case point of view is that the case tends to stand on something, sometimes a carpet

Usually, yes (mine's in a CPU carrier bolted to the underside of the desk top) but he said this is an all-in-one with the screen built in, so I figured it'd sit on a desk rather than on the floor.

 

[f592b]

If I'm keeping the case flat on a desk and there are heavy components in it will it bow?

As I'm trying to keep the height of the case low all the components will be mounted horizontally so any airflow from the bottom will only cool the back of the moherboard and gpu backplate which is no use hence why I went the top down route.

To have an idea of what I'm trying to build, go to a search engine and type 'Overclock Lando pc'. I would just paste a link but as I'm a new forum member I don't think I can.

 

[JakeS]

Usually, yes (mine's in a CPU carrier bolted to the underside of the desk top) but he said this is an all-in-one with the screen built in, so I figured it'd sit on a desk rather than on the floor.

Sure, but unless you build very tall feet for your PC, you're still going to have fairly restricted airflow from the bottom if it's stood on anything at all. The nearest I've ever seen has been the bottom of the front panel, for that reason.

To have an idea of what I'm trying to build, go to a search engine and type 'Overclock Lando pc'.

Lando PC

This does raise the question, though: why not use an Al flight case? They're cheap enough, light and sturdy. Are you specifically after the look of plywood?

 

[Sporky McGuffin]

Sure, but unless you build very tall feet for your PC, you're still going to have fairly restricted airflow from the bottom if it's stood on anything at all. The nearest I've ever seen has been the bottom of the front panel, for that reason.

Ah - I wasn't clear. I didn't mean on the bottom "side" of the case, I just meant having the air intake lower than the exhaust. My tower PC, for example, has the intake at the bottom front, and the exhaust at the top back.

Having seen the arrangement of the PC in question, though, I can see it wouldn't work here. Can we pretend I never said anything?

 

[AndyT]

If you find that your design does sag, you could cut some reinforcing hardwood ribs and glue them on. Have a look inside an acoustic guitar to see what I mean. A guitar is another good example of a lightweight construction which is very strong. There are probably several details of guitar construction that you could borrow.

 

[Shrubby]

Whittens in Peckham have Birch ply, I've even had Finnish Aeroply from them last year
Matt

 

[f592b]

A flight case would make the whole process easier but I haven't come across a case which is around 1.5kg, all have been above 2kg.

I actually did consider having fans on the side of the case but I would have to use 80mm or 90mm fans and I really didn't want to use them.

As for reinforcement, I did think about having 5mm square solid aluminium rods going across the case as support for the bottom but using hardwood is a better idea.

 

[ColeyS1]

Out of curiosity why is there a weight restriction on the case ?


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[Monkey Mark]

I'd consider having the fans pull the warm air out rather than push cool air in. With a baffle of sorts to guide the flow over the heat sinks. Pushing the air in can cause turbulence so some of the warm air will swirl and stay inside. Pulling the warm air out causes a lot less turbulence. Couple that with something to guide the air flow. And I would expect much better performance.

Have you considered using polycarbonate or aluminium composite board?

 

[f592b]

The completed case needs to be about 7kg because it will be taken on planes as carry on. I've estimated the parts to come to about 5kg which does leave 2kg remaining but I added 10% just in case there are things which I haven't accounted for. This leaves 1.5kg for the case though I could probably get away with it being 2kg and having a total mass of 7.5kg

I'm not sure if pulling air out of the top will work (which is the only place I can install 120-140mm fans). The gpu and cpu cooler fans force air down towards their heatsinks and if I'm pulling air out, the case fans and cooler fans will be working against each other.

I'm open to any suggestions, I landed on plywood because I was thinking of using something like purpleheart sheets and it was recommended to use an engineered sheet instead of a natural one.

 

[Monkey Mark]

How about a laptop?

Not meaning to be negative, but something which will clearly be home made would surely get lots of attention going through customs. Especially electronics. They may open to see what's inside, perhaps not as carefully as you might like.

 

[KevM]

I've had our technicians knock up many portable PCs over the years, where constraints - such as add-on cards or operating environment (i.e. wet/dusty/cold/hot - not Windows/Linux!), mounting considerations, ... , have meant a laptop wasn't suitable. I've always specified Peli/Storm cases. Get the ones that take the bezel kits and you've got a good starting point to build from. There's a lot of hardware in the defence & offshore industries that is actually a PC, a display and a handful of I/O cards packaged into a Peli case. We've done all sorts with integral screens, keyboards, etc. Just pay attention to RF/EMI (both transmitted and received) if you're doing any acquisition stuff or working in an electrically noisy/sensitive environment.

If you make it our of plywood the odds are you'll still find you want some kind of carry case for it, do it with a Peli and you've got a case you can use as a raft and still chuck into checked baggage!

 

[f592b]

If it was easy as just buying a laptop I would have totally done that by now but it's not suited for what I do and where I do it. With a desktop I'll have a better cpu, workstation graphics, way better temperatures at load and it also happens to be much cheaper especially because the graphics card was given to me for free.

I'm used to taking a desktop pc with me, I carried it in a small shoebox style case. I've never really had any huge issues apart from the security running it through the scanner more and then asking me what it was. Recently, I was asked to turn it on on two occasions and I had to find a screen which I could hook it up to after which they let me go.

That's when I decided to see if a custom portable case can be built.

Pelican cases are more expensive that what I'm willing to spend but the bigger issue is that at the size that I need they weight over 3kg.