Bird Weighing Capsules

Parametric OpenSCAD models for capsules to weigh birds during ringing and banding operations. A capsule holds the bird securely while it is placed on a scale, minimizing stress and movement. All parts are designed for FDM 3D printing.

License: CC BY-SA 4.0
Author: Ken Werner

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Overview

The capsule is a tapered cone that narrows toward the bottom, keeping the bird calm and still in a natural head-down posture. It screws onto a threaded base stand that sits on a digital scale. Seven size variants are provided, covering species from the Goldcrest (Regulus regulus, ~5 g) to the Mallard (Anas platyrhynchos, ~1000 g).

Models

Part	Description
Capsule	The main holding cone; seven size variants (can be customized)
Base 1	Cross-shaped stand with a threaded rod; general purpose
Base 2	Rectangular stand that fits a pocket scale tray (76.4 × 65 mm); threaded socket (two variants: stand_thickness=4 and stand_thickness=10)
Connector	Double-ended threaded coupler for joining Base 2 to a capsule

Base 1 and the capsule use a male/female threaded connection (17 mm diameter, 1.5 mm pitch). Base 2 has an internal thread and requires the connector piece.

Size Variants

Variant	Species	Common Name	German Name
1	Lymnocryptes minimus	Jack snipe	Zwergschnepfe
2	Paridae	Tit, Meise
3	Regulus regulus - Sylvia borin	Goldcrest - Garden warbler	Wintergoldhähnchen - Gartengrasmücke
4	Sylvia borin - Coccothraustes coccothraustes	Garden warbler - Hawfinch	Gartengrasmücke - Kernbeißer
5	Coccothraustes coccothraustes - Dendrocopos major - Turdus philomelos - Turdus merula	Hawfinch - Great spotted woodpecker - Song thrush - Common blackbird	Kernbeißer - Buntspecht - Singdrossel - Amsel
6	Picus viridis - Gallinula chloropus	European green woodpecker - Common moorhen	Grünspecht - Teichralle
7	Columba palumbus - Anas platyrhynchos	Common wood pigeon - Mallard	Ringeltaube - Stockente

Requirements

• OpenSCAD (any recent version)
• BOSL2 library - place it in your OpenSCAD library path

Usage

Open bird_weighing_capsules.scad in OpenSCAD. The file renders all variants and base stands side by side in the preview. To export a single part for printing, comment out the parts you do not need and export as STL (F6 to render, then File -> Export -> STL or 3mf).

Key parameters

Parameter	Default	Description
wall_thickness	2 mm	Shell thickness throughout the capsule
show_back_half	false	Cuts the model in half for inspection; set to false before exporting
threaded_rod_d	17 mm	Thread outer diameter (shared across all parts)
threaded_rod_h	stand_thickness	Thread engagement depth (defaults to stand_thickness)
slop	0.15 mm	Clearance added to mating threaded surfaces for print tolerance
border_h	2.6 mm	Wall height for Base 2 (not a global parameter, used in draw_base2())

Customizing capsule dimensions

draw_capsule() accepts explicit inner diameters (id1-id4) and section heights (h1-h3) for each of the three tapered sections. Adjust these values to fit additional species or scale platform sizes.

     |<---------- id4 ---------->|    ^
     |                           |    |
     |                           |    |
     |                           |    h3
     |                           |    |
     |                           |    |
     |                           |    |
      \<--------- id3 --------->/     v
       \                       /      ^
        \                     /       h2
         \<------ id2 ------>/        v
          \                 /         ^
           \               /          |
            \             /           h1
             \           /            |
              \<- id1 ->/             v
                | rod |

Printing Notes

• Print capsules upright (open end up) without supports.
• Base 2 should be printed upside down, then no supports are needed.
• The threaded interfaces also print without supports due to the bevel geometry.
• Adjust slop if threads are too tight or too loose for your printer.
• PETG or ASA is recommended for outdoor use.