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The drum is the rotating frame inside one character module. It holds all 64 cards in a fixed order. The motor turns the drum forward while the pawl lets the cards fall one at a time.
| Property | V2 Final value |
|---|---|
| Card positions | 64 |
| Drum diameter | 85 mm |
| Space between the inner faces | 51 mm |
| Complete outside width | 55.3 mm |
| Card-pivot circle radius | 40 mm |
The 51 mm inside space is the 50 mm card body plus 1 mm total side clearance. Two 2.15 mm drum sides make the complete drum 55.3 mm wide.
flowchart LR
A[Module receives position 0-63] --> B[Motor turns forward]
B --> C[Cards pass the pawl]
C --> D[Requested card pair is visible]
D --> E[Motor stops and releases]
The controller never sends a character to a module. It sends a number from 0 to 63. The installed card order decides which character that number shows.
- Editable drum geometry is in the CadQuery mechanical model.
- STEP, STL, DXF, SVG, and a machine-readable manifest are in
V2/Hardware/Final/mechanical/generated. - The full dimensional match is in the physical variants contract.
Caution
Generated geometry is not proof of a working mechanism. Check card fall, motor direction, shaft fit, pawl position, and clearances on one module.