Decision 01
Three-lug bayonet
Three lugs at 120° spacing give the interface rotational symmetry. A separate 30° turn locks the attachment and draws it 0.40 mm down onto the seal.
Specified intent · modelled, never built
Industrial · Hair-styling tool
THERMA
A handheld hair-styling tool whose attachment locks with a three-lug bayonet.
Design study2026Independent project
Locked CMF: mineral orange, warm grey, graphite grip, satin aluminium.
01 — The product in 10 secondsTHERMA
Every key dimension a variable. One mineral orange.
- What it is
- A 40 × 36 × 155 mm handle with a detachable 82 mm airflow concentrator.
- Who it is for
- People who style their hair at home and need a compact tool with a clear, secure attachment interface.
- The problem
- An airflow attachment has to lock securely, seal the air path and show at a glance whether it is locked.
- What is different
- Three lugs, a 30° turn and a 0.40 mm draw-down. A side window shows amber until the attachment is locked.
- Lug spacing · three bayonet lugsSpecified intent
- 120°
- Locking rotation · 0.40 mm draw-downModel dimension
- 30°
- Concentrator length, locked after three studiesModel dimension
- 82 mm
- Physical prototypes · performance unsetNot claimed
- 0
02 — The systemObject → system
How it locks.
01 / 07
The object
A 40 × 36 × 155 mm handle and one detachable airflow attachment — the only coloured part.
02 / 07
The attachment comes off
Without it, the collar shows the interface: the Ø28 mm air opening, the seal and three bayonet tracks.
03 / 07
Three lugs, 120° apart
The attachment enters on three lugs spaced 120° apart, so it seats in any of three positions.
04 / 07
A 30° turn locks it
Turn it 30°: each lug runs along its track to the locked position, and the amber signal arcs swing clear of the side windows.
05 / 07
Drawn down onto the seal
The same turn draws the attachment 0.40 mm down: its shoulder meets the Ø30.4 seal, and the helical track squeezes it from 1.52 to 1.27 mm.
06 / 07
Air straight through
The air path runs Ø28 mm through the collar to a 26 × 6 mm outlet slot. A void runs between the shell and the duct wall (2.6 and 2.0 mm nominal); they come no closer than +0.23 mm — geometry only.
07 / 07
The finished object
Every value here is a model dimension or a specified intent. Nothing has been built or tested.
The drawings are traced from the 3D model’s own geometry: model dimensions, not measurements. Switch to Evidence to see their dimensions.
03 — The design challenge
A head that locks, seals and shows it.
The concentrator carries the airflow, so the interface must hold it, seal the Ø28 mm air path and make its lock state readable. The handle was developed in controlled 3D geometry iterations — proportion, bridge, interface, concentrator, CMF — each frozen after a side-by-side comparison, so later decisions never reopened earlier ones.
04 — My contributionIndependent project
What I did.
Self-initiated · no client
- Industrial design and form language
- Bayonet interface architecture
- 3D development · key dimensions as variables
- CMF study and locked direction
- Geometry study of the frozen shell
- Visualisation
05 — Design response5 decisions · reason · evidence
The decisions that shaped it.
Decision 02
A lock you can read
Amber arcs sit behind two 28° side windows while the attachment is unlocked and swing clear when it locks, so the lock state reads at a glance.
Specified intent
Decision 03
Air through the interface
A Ø28 mm air path runs clear through the collar; contact pins (Ø1.5) sit in pockets, their faces 0.95 mm below the top of a 0.5 mm wall.
Specified intent
Decision 04
A fork, not a bolt-on
The bridge emerges from under the collar and joins into one root — a Y-crotch — that never exceeds the collar’s Ø47.
Designed
Decision 05
A geometric thermal break
A void runs between the shell and the duct wall (2.6 and 2.0 mm nominal). At their closest, measured normal to the surfaces, they are +0.23 mm apart. It is geometry only: no thermal performance is claimed.
Designed · geometric only
06 — Form developmentWhat changed, and why
Iterations that explain the final geometry.
Proportion
Before any detail, the first base was re-proportioned: collar depth 15 → 10 mm, front transition 13.5 → 10 mm, control spine 114.5 → 100 mm.
Bridge
Five bridge variants were compared under identical cameras. B1 was short (18 mm penetration, 2 × 9.5 mm legs); B2 long (30 mm), with a central field. The selected B2.2 fork joins its legs into one root under the collar, with a 0.70 mm shadow gap.
Concentrator length
Only the transition length varied. 75 mm compresses the three cones into one dome; 90 mm drifts toward a bottle silhouette; 82 mm keeps the rate changes legible — locked.
Shoulder
Three shoulders on the same 7.5 mm zone — crisp, balanced and soft. The balanced one, a 2.8 mm land and a 3.4 mm eased facet, was selected.
07 — Product architecture & engineeringDesign study
How it is built.
A 3D-developed design study. The interface was frozen after three iterations and checked on the model. Nothing has been built or tested: every value below is a model dimension or a specified intent, never a measurement of a part.
| Item | Value | Level |
|---|---|---|
| Handle envelope | 40 × 36 × 155 mm | Model dimension |
| Collar | Ø47 mm | Model dimension |
| Lug spacing | 120° · three lugs | Specified intent |
| Locking rotation | 30° · 0.40 mm draw-down | Model dimension |
| Seal | Ø30.4 · 1.52 → 1.27 mm (16 % squeeze) | Specified intent |
| Air path | Ø28 → 26.0 × 6.0 mm outlet slot | Model dimension |
| Shell-to-duct clearance | +0.23 mm, normal to the surfaces · geometric only | Measured on model · minimum |
| Shroud wall | 1.55 mm minimum | Model dimension |
Engineering notes the longer story
THERMA is a 40 × 36 × 155 mm handle with a detachable airflow attachment. Every key dimension is a variable, and every stage was frozen only after a side-by-side comparison: five bridge variants led to one fork, three interface iterations to a three-lug bayonet, three concentrator lengths to 82 mm.
Behind the exterior sits a geometry study, revised through several review rounds, of whether the frozen shell can hold a real product: a lateral clamshell split, a lofted cavity and a register of conflicts. Flow, heat, power, noise and safety are not established.
08 — CMFColour · material · finish
Material with a job.
Three CMF directions were compared under one camera and one lighting set, then refined in a micro-study. No pure black, no pure white; the rejected directions are shown below.
- Mineral orange#A6633B
Attachment shell · Roughness 0.42
A mineral orange rather than a safety orange: the attachment is the one coloured part.
- Warm grey#C7C2BA
Handle body
- Graphite#575659
Grip
- Signal amber#E6852E
Lock-signal arcs · Seen only through the side windows
Colour as state: it shows only while the attachment is unlocked.
- Satin aluminium#D1D0CE
Fork and collar · Satin anodised — a finish direction, not a compliance claim
Moved from polished to satin in the refinement study.
09 — The finished object
THERMA
10 — Project status
Design study- Stage
- Design studyOne question taken deep — a mechanism, an interface, a form or a colour system — in CAD or drawings. Not a complete product.
- Role
- Industrial design, 3D model (Rhino), CMF, geometry study
- Project type
- Independent project
- Year
- 2026
- Tools
- Rhino (3D model)
- What exists
- A 3D model, available in Rhino, with a frozen interface, a locked CMF and a geometry study of the frozen shell.
- Physical evidence
- None — no physical prototype.
- Not claimed
- Airflow, heating or temperature rise
- Power, noise, mass or duty cycle
- Safety or compliance
- Manufacture
- Still open
- Attachment 02 not started.
- Performance requirements — flow, temperature rise, power, noise, mass — are unset.
- A 0.35 mm detent is specified but not yet in the model: the entry slot cuts it away.
- Prototype validation required: lug engagement, seal squeeze and the feel of the lock.
- Images
- Renders of the THERMA 3D model, available as a Rhino model (design study); the technical diagrams are drawn from the same model geometry. The six-image art set was rendered from the locked CMF model in a separate, AI-assisted workspace: these are renders of the model, not AI-generated images.
ArchiveDevelopment dossier — the archived 2026 technical sheet, for more depth →
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