Version 0.31 update

I've been working on preparing the design for production this summer, as we've now hit 10 weeks until I leave for Ghana. I've re-packaged the CAD model (Dragon 0.31) and uploaded it, but more importantly, the Google Drive Repository now includes PDF blueprints. This effectively marks the release of the design for public development, and I hope to implement more detailed assembly instructions and imagery as the design continues to evolve.

I've been working on assembling a copy of 0.31, using "basement power tools" level equipment. I'm not entirely satisfied with the system, particularly with the supports for the cam assembly. I'll be redesigning those and releasing a new update (0.32 probably) within the next week or two. However, I have assembled a case and functional front access cover, which exceeded my expectations. By using a sheet steel and end cap design, I've been able to reduce the thickness of sheet steel to 28ga  -- about 0.3mm. This has brought cost down by an order of magnitude, and makes cutting and bending components far easier.

While the incorporation of plywood has eased assembly and reduced the complexity of the model, I feel that there's still improvements to be made. I'm interested in replacing the endcaps with sheet metal angle brackets, perhaps riveted. I'm slightly concerned about accessible screws on the outside of the device, and using rivets would also solve that -- while I've designed the case to be impossible to access without access to the rear or the padlock, I'm concerned about encouraging petty vandalism with exposed Phillips Heads. Rivet guns are cheap and readily available in Accra, I'll want to make sure both options are possible. There's also currently unused scraps created from cutting out the case, I'm interested in reducing material requirements by using those.


I've done some initial hunting for sheet steel and other suppliers in Accra, and the results are promising. While I won't know for sure until I get there, it looks like many materials should be easier to find than I've feared.

Here's some pictures of things and such:

Face of inventory chute (PN001), cut from 23/32 plywood

Inventory chute (PN002), also from 23/32 plywood this time

Drilling the mounting holes in the case. Note shameless product placement.

The case was cut by printing the pdf blueprint at 1:1 scale, rubber cementing it over 28ga sheet steel, and using tin snips to cut along the lines. Pretty painless. All blueprints are also fully dimensioned, allowing traditional layout methods as well, if a printer isn't readily accessible.

Here's the case and inventory chute inside. Note the lock mount, and two hinges. These aren't in 0.31's CAD models or blueprints, but I'll incorporate them in 0.32.

Mostly closed. The 40x150mm slot for the customer to recieve the product hasn't been cut yet, since I'm still adjusting the design of the cam mechanism and the location may change slightly.

Case, in open position, and removed inventory chute. The blueprints are still on the outside of the case, since they look cool and I'm too lazy to remove them. It's also much easier to mark on paper than the steel underneath, and protects the steel from scratching during assembly.