Rendered from docs/DESIGN.md + docs/MEASUREMENT.md in the repository at build time.
Estimates are labelled as such in the source; nothing on this page is a measured result unless it says so.
Measurements
Read this first. Only a few values come from handling the real knob (M1 turns, M2 direction, M6 groove count).
Most others are tape or ruler readings off photos, labelled estimated from photo, not caliper (about ±1-2 mm).
The rest are still old estimates. No caliper measurement has been made yet. The CAD uses these values, so every printed fit is unverified.
12. Measurement checklist + caliper/photo guide#
Guide image: ref/measure_guide.jpg (dimension lines drawn on ref_3).
Use a digital caliper; for long distances a steel ruler. For photos: square-on, ruler held in the same
plane as the part, phone ≥ 30 cm away (less distortion), good light, one photo per measurement.
| ID | Measure | Tool | Value (2026-10-17) / default | Source / confidence | Used in parameter |
|---|---|---|---|---|---|
| M1 | Turns closed → open → closed at the knob (tape flag / pen mark) | eyes | ≈ 1 turn, open at ≈ ½ turn (was 8) | measured 2026-10-17 by turning the knob (pen-mark photo sequence, one direction throughout); approximate | VT_DEFAULT_SPAN_TURNS = 1.0 |
| M2 | Direction seen from below | eyes | CCW end = closed, slats UP (preferred closed / home) → CW ≈ ½ turn = open → CW end = closed, slats DOWN toward the room | measured and confirmed 2026-10-17 (photo series, stated by the owner) | VT_POSITIVE_IS_CW_FROM_BELOW, VT_CLOSE_DIR_DOWN = 0, VT_DIR_INVERT_A/_B |
| M3 | Fluted knob diameter at the top (over the ribs) | caliper | 14.6 mm (was 18) | NOT measured, unverified - scaled from M4 with the old 18/16 taper ratio | knob_d_top |
| M4 | Fluted knob diameter at the tip (over the ribs) | caliper | ≈ 13 mm (was 16); tip is hollow (bore Ø not measured) | estimated from photo, not caliper (end view, ±1 mm) | knob_d_tip |
| M5 | Length of the fluted part | caliper | ≈ 41 mm (was 40) | estimated from photo, not caliper. (Tape reading collar top → tip ≈ 42 mm) | knob_flute_len |
| M6 | Number of ribs/grooves (mark one with a pen, count round) | eyes | 8 grooves (was 12) | counted on the knob 2026-10-17 | knob_ribs |
| M7 | Rib height / flute depth and flute width (caliper depth rod, or photo with ruler) | caliper | 1.0 / ~1.5 mm | old estimate, not measured | rib_depth, spline_w |
| M8 | Smooth collar above the flutes: diameter / length | caliper | 12 / 22 mm | old estimate, not measured. Tape reading 'collar top → tip ≈ 42 mm' vs M5 41 mm suggests a much shorter collar - ambiguous, left unchanged | knob_reference |
| M9 | Tip shape: flat/rounded, edge radius | eyes/photo | r 2 mm | old estimate, not measured | tip_round |
| M10 | Grey rod diameter just below the L-bracket | caliper | ≈ 4-5 mm (4.5 used; was 8) | estimated from photo, not caliper; unverified - needs a caliper | rod_d (knob_reference, collet/sleeve concepts), rod_slot_w |
| M11 | Knob tip → top of hinge barrel (vertical) | ruler | ≈ 81 mm (was ~35). Knob top ≈ 14 mm below the barrel's bottom - no height overlap | estimated from photo, not caliper (tape, ±2 mm) | head/hinge clearance (≈ 33 mm to the pin tip) |
| M12 | Knob axis → frame face (standoff, knob hanging freely) | caliper depth / ruler | ≈ 16 mm (matches the old default); knob back ≈ 8-10 mm from the face | estimated from photo, not caliper (ruler, ±2 mm) | axis_standoff, rod_out |
| M13 | Knob tip → white hook tongue (vertical) | ruler | no hook visible below the knob (was ~60 mm) | photos 2026-10-17: only lift cords + end weight below the knob | tail_len (tail_hook obsolete) |
| M14/M15 | White hook tongue width / thickness / angle | caliper | n/a - no hook (old 9 / 3 mm kept in the obsolete tail_hook) | photos 2026-10-17 | hook_tongue_w/_t |
| M16 | White L-bracket foot size + screw head | caliper | 12 x 14 mm | old estimate, not measured | mount_noholes_clip |
| M17 | Knob axis → hinge barrel inner edge (horizontal, wall-side) and hinge barrel Ø / protrusion | caliper | ≈ 21 mm (was 12-13) / barrel ≈ 14 mm wide in the photo (rod left edge → inner 24 mm, → outer 38 mm); protrusion not measured | estimated from photo, not caliper | collision check, assembly_preview |
| M18 | Knob axis → glass-side edge of the frame face | ruler | ~31 mm | old estimate, not measured | body offset to glass side |
| M19 | Frame face width | ruler | ~41-50 mm | old estimate, not measured | envelope |
| M20 | Lift cord position relative to the knob axis; cord diameter | caliper | hinge side of the rod, ≈ 19-22 mm out from the frame face; sideways offset 12-14 mm and Ø ~1.2 mm still old estimates | depth: estimated from photo, not caliper; sideways/Ø: old estimate, not measured | cord gap, hood clearance |
| M21 | Does the knob swing freely? How far can it be pushed sideways without strain? | hand | - | old estimate, not measured | standoff tolerance |
| M22 | Running torque, both directions; force near the stops (section 8) | luggage scale | 0.01-0.03 N·m | old estimate, not measured | currents, clutch |
| M23 | Left sash: where is its control (left edge / mullion)? same knob? | eyes/photo | mirrored | old estimate, not measured | cable plan |
| M24 | Cable path lengths: outlet → box → head A → head B | tape measure | ~1.5 m + 3 m | old estimate, not measured | BOM |
| M25 | Your 28BYJ-48: can Ø, height, shaft length, flats, wire-box size | caliper | 28/19/~9/3 mm | old estimate, not measured | housing_slim motor params |
| M26 | Rod guide clip (anchor for the clip rail): screwed plate (one screw) + horizontal forked tab; rod ferrule in the fork slot, ferrules just above and below the tab | ruler (photo) | plate ≈ 9 mm wide; tab wings ≈ 11-14 mm (12 nominal, hood grips 11-14); height ≈ 19 mm; tab tip ≈ 19-20 mm out from the face (20 used); clip top ≈ 92 mm above the knob tip. Spread: clip bottom → knob top ≈ 41 mm implies ≈ 10 mm higher; earlier tape (44-47 cm vs tip 56.5 cm) ≈ 20 mm higher | estimated from photo, not caliper (ruler, ±2 mm). Tab thickness, tab height on the plate and ferrule Ø not measured | clip_top_above_tip, clip_h, clip_w(_min/_max), clip_plate_w, clip_proj, rod_slot_w |
Unassigned photo reading (2026-10-17): "knob left edge to the wood/white-casing edge ≈ 34 mm" - which edge and side this is relative to M18/M19 is not clear, so it is not used yet. All "estimated from photo" values are tape-in-photo readings (about ±2 mm); confirm with a caliper before final prints.
Torque test (M22) — the luggage-scale method#
- Wrap thin strong thread 3–4 turns around the fluted knob; hook on a luggage scale (or a bag on a kitchen scale).
- Pull tangentially, slowly, mid-travel; note the steady force; T = F × 9.81 × r (r ≈ 9 mm).
- Repeat both directions; stop before any hard increase near the stops.
- Record both numbers in this file (or the PR that updates the parameters):
IRUN≈ running torque margin, clutch squeeze ≈ 1.5–2× running torque.
Original checklist with the first defaults (docs/MEASUREMENT.md, older than DESIGN.md §12)
This table still lists the pre-2026-10-17 default guesses (for example 12 ribs and an 18 mm knob). The current values are in the table above.
The default parameters in hardware/cad/*.scad come from photo estimates (knob diameter assumed 18 mm). Measure your own window first, update the parameters at the top of each .scad, then rebuild with tools/build_cad.sh. Annotated photo: ref/measure_guide.jpg; mechanism labels: ref/annotated_ref3.jpg. Full walkthrough: DESIGN.md §12.
| ID | Measure | Tool | Default (est.) | Feeds |
|---|---|---|---|---|
| M1 | Knob turns, closed-up → closed-down (tape flag) | eyes | 8 | VT_DEFAULT_SPAN_TURNS |
| M2 | Closing direction seen from below | eyes | CW = down | VT_CLOSE_DIR_DOWN |
| M3 | Knob diameter over the ribs, top | caliper | 18 mm | knob_d_top |
| M4 | Knob diameter over the ribs, tip | caliper | 16 mm | knob_d_tip |
| M5 | Fluted part length | caliper | 40 mm | knob_flute_len |
| M6 | Rib count (mark one, count around) | eyes | 12 | knob_ribs |
| M7 | Flute depth / width | caliper | 1.0 / ~1.5 mm | rib_depth, spline_w |
| M8 | Smooth collar above flutes: Ø / length | caliper | 12 / 22 mm | knob_reference.scad |
| M9 | Tip shape (flat/rounded, edge radius) | photo | r 2 mm | tip_round |
| M10 | Grey flex-shaft diameter | caliper | 8 mm | collet/sleeve concepts |
| M11 | Knob tip → hinge-barrel top (vertical) | ruler | ~35 mm | head length check |
| M12 | Knob axis → frame face | ruler | 16 mm | axis_standoff |
| M13 | Knob tip → white hook tongue | ruler | ~60 mm | tail_len |
| M14/15 | Hook tongue width / thickness | caliper | 9 / 3 mm | hook_tongue_w/_t |
| M16 | L-bracket foot + screw head | caliper | 12 × 14 mm | mount_noholes_clip.scad |
| M17 | Axis → hinge inner edge (wall side) + barrel Ø | caliper | 12–13 / Ø9 | collision check |
| M18 | Axis → glass-side frame edge | ruler | ~31 mm | body offset |
| M19 | Frame-face width | ruler | ~41–50 mm | envelope |
| M20 | Lift-cord offset / Ø | caliper | 12–14 / ~1.2 mm | cord gap |
| M21 | Knob swings freely sideways? | hand | free | standoff tolerance |
| M22 | Running torque both ways + force near stops (see DESIGN §8: the luggage-scale method) | scale | 0.01–0.03 N·m | currents, clutch squeeze |
| M23 | Other sash: where is its control? | eyes/photo | mirrored | cable plan |
| M24 | Cable lengths (box → head A, head rail → head B) | tape | ~1.5 + 3 m | BOM |
| M25 | Motor can Ø / height / shaft | caliper | 28 / 19 / ~9 mm | housing_slim.scad |