3 were designed:
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deltareproduces classic ZX Spectrum+ / Delta-S clone keyboard
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next-likefollows ZX Spectrum Next quite closely, but uses standard third letter row shift of 0.5u instead of Next's non-standard 0.75u. Some other keys were swapped to keep it closer to the Spectrum+ layout.
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13uuses slightly condensed layout, requires only one stabilizer and only one stepped 1.25u key. Additionally it fits my 3d printer plate (256 mm square).
.step files are in keycap models directory, and the source can be found in the onshape CAD:
https://cad.onshape.com/documents/8eec099704dd56ee90a99779/w/f094e603417fd53c8f53642f/e/6200ad26f37156b8d2f7b3c0 (needs free account)
#h_units- 1u key only (horizontal units, supports 1-3u, 4.5u, 6.25u) inside 1u key group - #stab_dist - formula to calculate distance between main key switch mount and stab mounts. Change it to support spacebars different from 4.5u/6.25u.#side_angle(25 deg)#front_angle(35 deg)#rear_angle(5 deg)#key_bend(0.6mm) - amount of key surface bending, mm. 0.01mm is the minimum, also 4.5u automatically uses 0.01mm (flat surface for 3d printing)
All keycap parameters are set after Delta-S keyboard (Kopir / Karon factories), except the slightly bigger base key size. Here it is 18mm, common size for Cherry MX-based key switches, and on the real ZX keyboard it was 17.8 - 0.27mm according to factory blueprints (found an archive with it on the zx-pk.ru forum) - see keycap blueprints directory (all labels there are in Russian).
MX key spacebar stabilizer positions come from https://deskthority.net/wiki/Space_bar_dimensions
Other keycap dimensions are from https://blog.maxkeyboard.com/dwkb/keycap-profile-size-information/
Layout design service used: http://www.keyboard-layout-editor.com/ Plate generation service used: http://builder.swillkb.com/
Files for case parts are in pc-58-case directory. The main design constraint was, again, to fit each piece entirely into my 3d printer volume (cube of 256mm).
For my implementation I chose RPi 2 Zero W as a main board, mainly because of its low price and the fact I already had one. The design is parametric and it can be changed to adopt almost any board. The back cover of the case is a separate piece, so in case of re-printing it would require changing of the bottom piece and the back. The plate and the front keyboard case will remain unchanged. The case design is WIP still, however, I was able to print the plate, keycaps, and assemble it.
The directory pc-58-key has all the files for the layout, keycaps used, plate .dxf file. For the design, the only concerns were to fit into 13u limit, and have dedicated cursor keys (I hope it would help with retro gaming).
It uses the same keycap models as ZX keys, but with other parameters:
#side_angle(20 deg)#front_angle(30 deg)#rear_angle(1 deg)
The keyboard needs 58 key switches (I used yellow gaterons), and 2 stabilizers - 2u and 4.5u (uncommon, but see below about using common 6.25u).
Since I didn't find plate mounted stabilizers for 4.5u space, I had to bend the existing 6.25u stab to the needed dimension. This is a small guiding tool that helps to re-bend stab rod to the size of 4.5u. It requires two M2 screw bolts, 6-10mm long each. The model can be found in auxilliary directory.
