On Wed, Jul 1, 2015 at 11:05 AM, Ken Phillis Jr kphillisjr@gmail.com wrote:

Looks interesting, and does this include options to use a laptop Hard drive or Laptop CD/DVD Drive?

no - there's no space, and it's not safe to do so (mechanically): i'll explain why.

ordinarily, laptop casework would be made as a "single unit", right? the base for example is a single huge piece, requiring something like 60,000 kg of force to push the plastic through the injection mold, spreading out across an area 35cm x 20cm at a depth of only around 1mm in depth.

throughout that base there are various "struts" which help support the base: strengthening around holes (such as connectors, cd/dvd drives, and so on), and internal dividers for PCBs, as well as random bits that stop the case from warping when it cools. the warping occurs because the extreme pressure results in different stresses across different parts of the plastic, so you get some parts "pulling" and others "pushing" - end result: warping. bunnie huang has a very good article about the process if you're interested:

http://www.bunniestudios.com/blog/?p=4146

so for a huge hole like a CD/DVD, you can put a huge amount of internal "support", you can create a structural "bay" that is anchored to the rest of the casework, compensating for the fact that, on the outside, you've a huge weakness on the outside edge.

however what i am doing is completely different: i don't have a 3D printer that is capable of printing a single block on a 400 x 300mm bed, and even if it was possible to do i still would not do it because that would require about 50 continuous hours of sitting there monitoring the print to make absolutely absolutely 100% absolute without fail absolute certainty that it printed without a fault. any mistake even at time 49 hours 59 minutes, the end result must be thrown away. i'm not tolerating that:

http://motherboard.vice.com/read/how-to-3d-print-a-laptop

so instead i am designing this in a series of parts, each of which is a maximum of 2 metres of 3mm plastic (about 18 grams), and there are around 15 separate parts. each may be printed separately: one error clearly does not result in the entire lot being thrown away.

also, the middle areas, in order to save plastic, i aim to use bamboo or other wooden laminate. these are *not* joined to the rest of the parts (plastic): they are *not* structural: they are merely protective, and the interior parts will be taped down with double-sided sticky tape (in a "sandwich" effect) with the bamboo being top and bottom, and jammed into and surrounded on all 4 edges by plastic.

so - and this is where you get your answer, ken - each part needs to be strong *on its own*. i have interior cross-hatching inside the middle strut (running from front to back) which ensures that the strut does not significantly bend or twist. the 4 front and back parts (left and right) all require interior bracing. i have not arranged any holes in these 4 front and back parts, so they are quite strong.

however, the left and right edges are where the connectors are poking through, and it is here where there is vulnerability to stress. in particular, the EOMA68 connector is quite long - 55mm - and 5.5mm deep. that leaves only 3mm *above* the CPU card and only 2mm *below* the CPU card, for a total depth of 10.5mm in the casework. that left edge is only 12mm wide...

... can you see how that might not be very strong? :)

i can't add any extra support anywhere else, so i am going to have to rely on the PCB itself (1.2mm thick) to provide some structural support, here. down the entire length of the left (and right) edges i have added a 3mm high strut, and underneath the CPU Card i have filled that in to the maximum possible height (which is only 2mm), but i consider this to be marginal, even though it is the best that can be done.

regarding a hard drive bay: yeahhh there just isn't enough space. i had to move the touchpanel / touch-LCD over slightly, due to its internal connectors coming out in ways that were slightly awkward. that reduced the depth of the (only) available interior space - front left corner.

so the only available space for a hard drive is just a tiny bit too small, but it *is* enough for a USB memory stick (or USB WIFI, or USB 3G). i have made space for 2 such USB dongles.

the entire right-hand side is taken up with a battery (10Ah). it's actually a bicycle battery, and as such is far lower cost than anything that's actually "designed" for a laptop. the reason why the battery is not at the back (and removable) is, again, as you can see from the above: strength. mechanically it is too difficult to arrange a strong compartment at the back of the laptop.

hope that explains why it is not really possible in this design to fit a hard drive or a CD/DVD.

the other reason why it is not possible is because there is simply insufficient power. i have had a heck of a job finding a suitable low-cost PMIC that can provide the amount of current required to drive the LCD and the CPU Card *and* 4 USB devices (the LTC 4155) - it can provide up to 4A @ 5V and it isn't hugely expensive.

if there was an internal DVD and an internal HDD, that power requirement would go up to 6A @ 5V (30 watts). now that's starting to get expensive, as well as almost certainly requiring fans (to cool down the PMIC board).

also it would be necessary to start investigating 2-cell or 3-cell PMICs for battery charging, because 6A @ 5V is a hell of a lot (4A is already into 2oz copper) - and that not only starts to get complicated but also gets costly, *and* i would have to abandon the simple single-cell approach *and* start the process of contacting suppliers... *again*.... asking around for different-sized batteries.

so in summary, can you see, ken, how such a simple-sounding question has absolutely massive implications which, in effect, require completely abandoning absolutely everything that i've done in the past 6 months, in effect starting *entirely* from scratch, abandoning all the component sourcing, PCB design work *and* the casework designed so far *and* requiring to research an entirely new mechanical design approach (from scratch) in order to accommodate the innocently-asked-for parts? :)

this is a simple laptop, with a very straightforward design, where the target sale price (even in 1k volumes) i would like to be around the $USD 350 mark. there's plenty of storage space: two Micro-SD cards (one internal in the laptop, one in the CPU Card), on-board NAND flash for OS, and there are 2 internal full-sized USB connectors behind a removable compartment.

l.