This and a $99 Minitar WAP is my first go at a solution.
The tubing down each side of the back of the laptop sports (so far) two tee pieces, one protruding forwards to support the laptop, and one protruding towards the centre to hold a cross-piece for extra rigidity.
The blue line across the body just below the screen is a piece of Cat5 cable, and the pipes run up the sides of the back rather than making a 45deg turn just to add some lateral stability by clamping the laptop body to the pipework at the edges. The pipes are just jammed into the fittings at this stage; when I’m sure that all is well I’ll add some end caps and lay about with the glue.
What have I learned so far?
15mm PVC water pipe is rigid enough for the job. I worried before trying this out, having seem some pretty flimsy shade-houses and the like built from the stuff, but over runs of a foot or so it’s quite reassuringly steady.
I elected to try 15mm despite my reservations because I worried that the tubing might be thick enough to inconvenience the user. As it turns out, 20mm would have also done fine, and would have been considerably stiffer again. If I ever redo this from scratch, it will be in 20mm pipe.
Even though the laptop’s weight is screenwards of the upright, it’s not screenwards enough. The laptop risks going base-over-apex if someone bounces on the bed (what, you don’t have kids?) and typing into it doesn’t feel very secure (although the actual pecking of keys goes smoothly). I’ll turn the right-angle “kangaroo feet” into tee pieces and add about 25cm of tubing to fix that.
If I can find some 45-degree “tee” peices I might even run a stiffening brace from the “heels” to the uprights. It’s not really needed for stiffness but it might help the bottom joint last longer.
I worried about the below-the-keyboard supports being too intrusive, but in practice they’re not. I’m considering adding an L-shaped foot to each to massively reduce the risk of the laptop slipping forwards off these.
I’ll run another cross-piece between two Ls at the top of the uprights, which will improve the somewhat marginal lateral stiffness as well as making it look a bit less like a backpack frame.
The laptop needs to be mounted surprisingly low. A laptop without so much vacant real estate between the user and the keyboard would not have this problem. If I had a little money to spare, I’d be eyeing off something like the MSI S270. At 1.9kg, this would be easy to support on one piece of pipe, which would not be too hard to rig up to allow it to be rotated out of the way.
I still lack a good mechanism for clamping the top of the laptop body to the frame. An occy strap might do, but it feels a bit, well, analogue to me. Suggestions welcome. Simple, easy to use, robust and cheap are (as always) the design goals.