Twin paddle CW KEY by EA7HVO

Reuploaded here so I can track my own changes. Design by EA7HVO

The original assembly document is here, below is my take with some changes

BOM

• 4 pcs, MR117ZZ bearings - 7x11x3

• 4 pcs, DIN 467/466 knurled nut, M3

• 4 pcs, DIN 653/464 knurled screw, M3 (thumbscrew)

• 6 pcs M3 nuts

• 2 pcs, M4, 24mm + 2pcs M4 nut

• PCB TRS female jack

• 2 pcs M3x10 screws

• 4 pcs, cylinder magnets, 5x2mm

Assembly

1. print everything. You will need 4 pcs of the cantilevered magnet holder

2. seat the TRS jack and tighten its nut

3. install the magnets in the paddles with cyanoacrylate glue

4. install the magnets on the cantilevers. mind the magnet polarity. I suggest using the same polarity everywhere, so the parts are interchangeable. I found the field interaction between the paddles to be negligible

5. install the wires through the paddles and strip 15-20mm off each

6. pull the wires through, leaving the stripped off part through the hole. 

7. pull the wire through the hole at the end of each paddle

8. install the M3x10 screws, ensuring contact with the wire inside the paddle

   • alternatively, use grub screws instead of the screws, since their sharp tip might be a better contact, and leave the paddles with a bare look

9. install the top (paddle opposite) contact posts. use one knurled screw and one knurled nut on the outside, and a M3 nut on the inside. This nut and part of the screw is the electrical contact point with the paddle

10. install the wire on the contact posts, between the posts' outer side and the knurled nut

    • I used a copper washer here, between the wire and the post, for better contact

    • The author suggest using a metal lug. I skipped on the lug and twisted the wire instead, since I couldn't find tiny lugs that would fit in the hole

11. pull the wire through each hole and route them, through the base to the TRS jack

12. solder the wires to the jack

    • if you want the dah on the left, solder it to the tip of the TRS jack

    • otherwise, the TRS tip goes to the left paddle

13. install the cantilevered magnets. these provide enough force to push the paddles back after a contact. Use the same assy as before: one knurled nut and screw on the outside, one nut on the inside. Unscrew the screws as far as they can go without dropping the nut.

14. install the magnet holder at the end of the the screw, moving it in just a little. Keep the screws as far away as possible, so you can install the paddles next. The layer lines and hole size are good enough for an M3 screw to tap its own thread

15. mount the bearings on the paddles. Use a [swing press](https://avedictionary.com/swing-press/) on its lowest setting.

16. mount the paddles. the magnets go on the outside, the wires on the inside. 

17. route the wires through the center hole and to the TRS jack. leave some slack wire.

    • I suggest an Y connection between the two wires (common ground) and the TRS jack's ground. This way, you only have to solder on wire, and not two, on the delicate connector

18. solder these two wires to ground

19. add the top part, press it down. It should click when the bearings fall in place

20. pull and align everything until the paddles are straight-ish and parallel

21. install the M4 screws, but not completely. keep aligning the top part and screwing a bit more. make sure the paddles are parallel

22. before the final twists, move the cantilevered magnets as close as possible, align the paddles again, and only then permanently screw down the top piece. Repeat this process if disassembling the paddle

23. add weights, pour concrete. I prefer screed.

24. close the bottom and you're done

Adjust to preference. The top screws set the travel, the middle screws set the resistance. 

Other info

The caps come in multiple heights, some tests might be required based on your printer. Or just use the uncovered cap, but your bearings will be exposed to dust.

The 19.5mm base is tall enough to fit eurocent coins, the 20.5 one for US cents.