Building a light but rigid pc case out of plywood.

[MMUK]

If weight is a major consideration, what would be the feasibility of fitting a laptop screen? They are much lighter.

 

[f592b]

A 17.3" laptop screen is what I've planned to fit into the case but I can't seem to find a rough estimate on what these panels weigh.

 

[MMUK]

A 17.3" laptop screen is what I've planned to fit into the case but I can't seem to find a rough estimate on what these panels weigh.

If it helps, I had a replacement screen for my old Vaio, a 19", which weighed about 300 grams.

 

[WibbleWobble]

Not sure if you would have access to one, but the comb joints could be cut in 4mm ply using a Laser Cutter. I have made a number of such boxes using Inkscape and clever plugin that makes the tabbed boxes, the plugin I have used is called Tabbed Box Maker.

 

[f592b]

I had a rough weight of 500g for the screen so I guess that I can keep it that.

I've come up with a design that will allow me to use 1cm to 1.25cm plywood:
http://i.imgur.com/pXlEv0g.jpg?1

The top part shows how the base will look, it's 40cm x 35cm, has a 2cm thick border around and the bits sticking out (2cm wide by length of component) are where the parts (some which weigh 2kg) will be mounted. The bottom part shows how the sides will look. It'll have 2cm borders with a large opening in the middle which will be covered by a dust filter. At the moment I can use 1cm thick plywood but if I make the border and the sticking out parts of the base 1cm wide instead of 2cm I can increase the thickness of the whole case to 1.25cm but is there a big difference in rigidity between the two thicknesses?

I was thinking of getting the base made out of a single piece and attaching the 4 corners to it but If I glued and bolted the component supporting parts to the walls of the case, would they break under the strain?

 

[Sporky McGuffin]

Ply typically comes in multiples of 3mm thickness, so you're looking at either 9mm or 12mm. I built an ugly but functional printer trolley from 12mm ply and it's massively overbuilt - nary a creak if I sit on the thing and it's very, very heavy. I reckon even 9mm might be excessive for your application especially given the weight limit.

 

[Benchwayze]

If i was making a case, I would use 2mm aluminium sheet, with aluminium angle all around the joints, I'd have socking great nuts and bolts (Brass probably) to hold it together, and I'd get out the camouflage paint, so it looks really functional, and purposeful. Then I'd feel I was making a job of it, making it worth the doing, and novel-ish. (No doubt, someone has done this already!)

But I do agree with Andy on the strength of plywood, so I'd say go for it.

HTH

John

 

[Eric The Viking]

It sounds like this is for gaming -- am I correct?

On fans, move the air in at the lowest practical point, up and out of the highest one. You can get radial fans for PC applications, which move much more air for a given fan volume than the common radial ones, but are noisy and consume a lot of power (relatively speaking).

Don't worry about the CPU fans as such, but don't either be afraid to use baffles of some sort inside to arrange the airflow to be best over the hottest parts. Most DC fans can be reversed - it might be worth experimenting, as the CPU might be better cooled by air coming in at the sides then up and away, assuming the heatsink's thermal profile is hottest in the centre. Do some experiments to see which works best. You can buy cheap thermocouple thermometers on eBay, for consistent measurements.

You can disassemble the power supply to save weight, BUT there are two issues: safety (higher than mains voltages inside, at currents that can kill you), and RFI (emissions) - they operate as quite effective long wave transmitters, and their metal cases screen them. Regarding PSU cooling, I'd put it last in the airflow. The PSU components are more robust than the CPU and they run hot - no point pulling warmed air over the most sensitive component (the CPU).

I've made display cases for trade shows in the past, requiring fans, PSUs, etc. Don't underestimate the problems of shock and vibration - what seems like a strong and secure mounting arrangement can break in transit, especially if you're travelling a lot. You have to allow for an airline taking it from you and putting it in the hold, even if you don't want that.

It's also fatally easy to put hand luggage down heavily when tired (I often travel with heavy and expensive camera gear, so I know this!).

If you're using this anywhere other than a desert island, people will expect you to have given some thought to RFI emissions. That usually means pasting cooking foil to the inside of the case, and making sure there are no narrow gaps, etc., that will allow radio emissions to escape. You might use the aluminium foil tape that air conditioning contractors and insulation companies use. I've used it with success on 'wall wart' power supplies in the past.

The tape's sticky surface acts as an insulator on that side. I puncture it in places so that the puncture edges make a connection between overlapping layers, either with a short knife cut or just a drawing pin or similar. Check everything intended to screen is connected together, and to earth, with a test meter - you need as low a resistance as you can. You can't solder aluminium, but screws holding down washers and solder tags work well (do a couple of bonding points close together if you expect it to flex a lot or vibrate).

With modern bus speeds, the clock pulse "wavelengths" are really quite short, and holes tend to act as waveguides more than they used to - a Faraday cage now needs very small mesh to work properly! Also use ferrite rings and beads on any wires going to the outside world (google for the correct way to wind wire on ferrites for this purpose - it matters!). This is for blocking common-mode RF transmission (in both directions!). The PSU usually has a blocking choke on its board at the mains input, but you may need to put chokes (ferrite rings) on other wiring, to audio connectors, USB and network sockets, etc.

Hope that helps in some aspects,

E.

PS: I'm sure my camera bag has been close to allowable weight limits for carry-on many times. I've not yet been asked to weigh it in, but I know it depends on the carrier.

 

[woodenstx]

Ohh interesting project... I'm meaning to make a case for a non moving machine in MDF, with one air intake and one outlet. this will mean I can pressurise the case with filtered air, thus keeping the dust out and lots of cool air in.
I planned to use 18mm MDf since that's what I have spare from a job last time, overkill, but "free" :lol:

 

[Droogs]

If you are really worried about heat, then why not use a water cooling system?. Can I asked what your intended use for the systems is, will it be a portable gaming rig or do you just want a ruggedized and portable desktop? I ask as I've just started a business making wooden laptops, desktops and games console, with the addition of boulle maquetry and inlays of metal and semi precious stones. Currently in the process of sorting out the new workshop. But would be happy to chat about what you're looking to do in depth if you like.

If you could give us an idea of the spec and kit you are thinking of using them maybe can work out a design for you (no charge), just like the idea of the challenge. I do think that a water cooled system would be better for you as it would also be a lot quieter, with less chance of dust/dirt/grit ingestion into the system as you would only need a much smaller exhaust sysfan with say a side vent with a sliding cover for when in transit.

rgds
droogs

 

[f592b]

If i was making a case, I would use 2mm aluminium sheet, with aluminium angle all around the joints, I'd have socking great nuts and bolts (Brass probably) to hold it together, and I'd get out the camouflage paint, so it looks really functional, and purposeful. Then I'd feel I was making a job of it, making it worth the doing, and novel-ish. (No doubt, someone has done this already!)
But I do agree with Andy on the strength of plywood, so I'd say go for it.

HTH

John

I've been shifting between using aluminium and plywood and even some designs which use a combination of both such as a plywood base with aluminium walls.

It sounds like this is for gaming -- am I correct?

On fans, move the air in at the lowest practical point, up and out of the highest one...

It's a quadro gpu which I use for work mostly but I do game on it sometimes.
I plan to do a lot of airflow testing to see what gives the best temperatures. I sometimes have to work in really hot places so good airflow and temperatures are important to me.

I don't think I'm willing to modify the psu, it's already a really good gold rated unit and in all my designs the psu fan has it's own opening in the case.

Once the case is built I'll actually put it in a foam lined fabric case just to add a bit more safety from the inevitable bumps that it'll acquire. It's better than nothing.

I never even thought about RFI, so thank you for all the advice regarding that.

I've only been asked to weigh my hand luggage once but I've noticed that the more a person seems to struggle with hand luggage the higher the chance of them being asked to keep it on the scale.

Ohh interesting project... I'm meaning to make a case for a non moving machine in MDF, with one air intake and one outlet. this will mean I can pressurise the case with filtered air, thus keeping the dust out and lots of cool air in.
I planned to use 18mm MDf since that's what I have spare from a job last time, overkill, but "free" :lol:

I always like to have positive pressure high airflow with dust filtered fans, it keeps the temperatures down and dust out.

If you are really worried about heat, then why not use a water cooling system?...

I don't won't to water-cool because I have to take it through airport security and I don't want them to tell me to throw away my closed loop cpu cooler or having to remove it and store it in the luggage. I also don't want to custom water-cool the cpu and gpu because I would have to drain it and fill it (plus leak test it) every time I flew.

The computer doesn't need to be ruggedized, I just need it to be portable (with a screen) and have a total weight of less than 7.5kg which gives you about 2kg for the case.
This is a rough scale drawing of most of the components: http://i.imgur.com/OON6c4W.jpg?1

The screen will be on a hinge so it'll basically look like a super thick laptop. The only main component that isn't there in the drawing is the driver board for the monitor.

 

[Benchwayze]

I'm using Tufnol for a new guard for my Sedgwick planer. It crossed my mind you could use sheet Tufnol of 3mm thickness. It comes in various shades of mucky brown though!
Other makes of sheet plastic are available!

 

[Eric The Viking]

I forgot to mention: you might find an alternative shape power supply helpful.

The ones on my two HP 'Microservers' are long and thin (about 300W, IIRC), and in the past I've bought from a company called Skynet, whose PSUs were very reliable (the company I worked for then bought them by the thousand). Different shapes can be had, if that helps, but you do need to know how much current for each rail.

 

[Droogs]

for RF Interference, coating the interier with bacofoil and earthing will suffice

 

[f592b]

I looked into using a 1u psu and while there are two good options I would prefer to deal with an atx psu for two reasons. First, it'll be easier to transfer to a normal itx case just in case this project doesn't work out. Secondly, with the type of psu you suggested I could have brought down the height of the case base to ~60mm but it would have compromised the cooling ability of the case. The current plan has a height of 90mm but I get to use a far better cpu cooler as well as multiple fans.

Since JakeS mentioned it a couple of days ago I've been giving more thought towards using a flight case and I think it might be possible to build in this. When weights are quoted they usually include the foam and for my project all of it will be removed plus I will also cut out pieces from the sides and attach mesh which will also reduce the weight. I'm looking to buy a case for some experimentation.

 

[masopa]

I've built a few PCs and you really need to pull cool air in from the bottom and push cold air out through the top. It doesn't have to be dead bottom and dead top, but you won't have the space to fight convection currents if you're building in a conventional full tower or smaller. If it's a mini tower or less then just forget it unless you optimise the airflow. And that's using metal as a case - wood obviously won't conduct the heat away so you need extra heat dissipation with the airflow - basically hot air stuck in the case will slowly cook everything if you're using wood and don't have sufficient air moving through.

I'm assuming here you're going to be using a higher power CPU (Haswell or similar) and a proper graphics card. If you're using low power CPU (e.g. mobile) and onboard graphics then you have a bit more latitude.

The suggestion of watercooling is a very good one, although you'll need to vent your radiator well.