--- instrument: Barrel Organ slug: barrel-organ family: woodwind class: hand-cranked mechanical organ with pinned barrel and windchest readiness: L2 V5 build-packet candidate authority: concept_only / pending_measurement --- # Barrel Organ Design ## Design Thesis A barrel organ is a mechanical wind instrument where a crank links three jobs: advance the music program, supply wind, and pace the player's performance. The barrel stores note events as pins or raised features. Followers or trackers read the program and open pallets in a windchest. Wind from bellows and a possible reservoir speaks a pipe rank. This L2 packet deepens the architecture enough for review and mule planning. It does not define barrel diameter, pin pitch, gear ratio, pallet travel, wind pressure, pipe scale, pipe length, tuning, or cut geometry. ## Subsystem Plan ### Program Barrel The barrel program is the mechanical score. The first review should decide whether the study mule uses a fixed barrel, removable barrel, or replaceable pinned strip. Each option remains `pending_measurement` because pin retention, follower wear, indexing, reset-to-start behavior, and timing repeatability have not been tested. Planned evidence: - barrel indexing method chosen and tested; - follower contact material selected from a wear/noise test; - tune-start registration checked without pipework; - pin-retention method reviewed before any drill/CAD/DXF work. ### Crank And Drive Train The crank must coordinate barrel advance and bellows pumping. A future drive table should record crank cadence, lost motion, backlash, and reset behavior, but this packet assigns no ratios or wheel sizes. The first mule should allow the barrel drive and bellows drive to be isolated so timing and wind faults can be diagnosed separately. ### Followers, Trackers, And Pallets The action path is: ```text barrel pin -> follower -> tracker or lever -> pallet -> pipe channel ``` The review target is a small number of channels with visible motion and easy adjustment. Authority remains `pending_measurement` until lift, return force, friction, sealing, and noise are measured. ### Bellows, Reservoir, And Windchest The bellows and optional reservoir must smooth crank pulses before the windchest feeds pipe channels. The L2 packet records the need for a wind mule but does not set pressure, flow, reservoir volume, gasket dimensions, or channel layout. The windchest should be serviceable: pallet faces, gaskets, springs, and tracker attachments need access before tonal work starts. ### Pipe Rank Options The first voice may be flue pipes, reed pipes, or one comparison channel of each. This packet keeps both families open because package size, voicing effort, wind demand, and reliability are not yet measured. No pipe pitch, scale, mouth geometry, reed dimensions, or tuning system is claimed. ### Case And Service Access The case is treated as an inspection frame rather than finished furniture. It must expose the barrel, follower row, tracker path, windchest, and bellows for testing. Handles, enclosure layout, mass, clearances, and access panels remain `pending_measurement`. ## Parametric Intent Future tables should use explicit status fields before numbers appear: - `barrel_program_status` - `barrel_indexing_status` - `pin_retention_status` - `follower_material_status` - `tracker_motion_status` - `pallet_seal_status` - `crank_drive_status` - `bellows_wind_status` - `reservoir_need_status` - `windchest_channel_status` - `pipe_rank_status` - `case_access_status` Numeric fields must be labeled as `estimate_pending_measurement` until they come from a measured mule, reviewed drawing, supplier specification, or validated design table. ## L2 Mule Plan 1. Build or mock the crank-to-barrel motion without pipework. 2. Add a follower/tracker/pallet channel and log repeatability. 3. Add bellows and a simple windchest test channel. 4. Compare a flue-pipe and/or reed-pipe response only after wind steadiness and pallet sealing are understood. 5. Update `visual-output-register.csv`, `bom.csv`, and `cut-list.csv` before any CAD, DXF, or tuning table is introduced. ## Authority Boundary This is an L2 planning packet. It is not a barrel drilling plan, pinned tune layout, pipe-scale chart, wind-pressure design, CAD source, DXF release, or fabrication package. Every artifact remains either `concept_only` or `pending_measurement`.