Version 0.1 – Working Draft
This glossary is an open-source working document intended to develop a common language for helmet design. It draws from automotive design terminology while establishing helmet-specific vocabulary. As helmet design evolves with new technologies, materials, and safety requirements, this glossary aims to grow and adapt through community input and practical application. This document is primarily centered around design, although it may be expanded to include material and marketing terms separated by legends.
The current draft bridges automotive and helmet design vocabularies, recognizing their shared foundation in industrial design, aerodynamics, and safety engineering. Terms have been collected from working designers, engineers, and technical documentation. Some definitions are provisional and may be refined through use and discussion.
Contributors are encouraged to suggest additions, modifications, or clarifications based on their expertise and experience in helmet design and manufacturing. Each term is tagged with a functional category to aid in organization, though some terms may span multiple categories as their usage evolves.
Illustrations will be added for clarity. Please leave any comments on this post on LinkedIn.
Category Legend
- AE: Aerodynamic Elements
- DE: Design Elements
- DP: Design Process
- SE: Structural Elements
- TE: Technical Elements
- TS: Testing & Standards
Airdam: A foil or aerodynamic device. [AE]
Arc bones: Primary raised lines that radiate longitudinally across the shell surface, providing structural reinforcement while defining major design elements. [SE]
Arc streaks: Subtle surface lines that follow the helmet’s curvature, primarily decorative but suggesting motion and flow. [DE]
Attitude: When a helmet has a noticeable demeanor and is said to be aggressive, playful, intimidating, etc. Can also describe the helmet’s overall relationship to wearer. [DE]
Axes: In locating points on a helmet body, designers use conventional 3-axis reference lines. X (front to back), Y (side to side), Z (top to bottom). Key reference points include nose bridge, ear openings, and occipital base. [TE]
Backlights/Exhaust Vents: Rear ventilation openings designed for air outflow. [AE]
Badge engineering: The practice of applying different nameplates to helmets with identical or very similar shells. ODM. [DP]
Bakeoff: A showdown between design proposals, usually held in the form of a show with clay models from rival studios or designers. [DP]
Blocking: Preliminary arrangement of major design elements and proportions. [DP]
Bone line: A hard, raised longitudinal peak in a shell. Usually along the side of a helmet shell more massive than a character line. [DE]
Bowl: A partial or full surface, affixed to the underside of a helmet EPS, forming the interior base structure. [SE]
Brow: A raised or protruding area above or around an arch, like a headvent or an ear cove. [SE]
Bugback: A rear of a helmet that curves downward without interruption, like a VW Beetle. Typical skateboard helmet, rounded back. [DE]
Burntab: The descending tab of the helmet in front of the earcove. Sideburns. The hard point mounting location for the helmet straps. [SE]
Buttresses: Cross-supporting structural elements bridging between remaining shell sections around vent slices, preventing material spread during impact and maintaining shell integrity. [SE]
Centerline: A hypothetical line drawn longitudinally through the center of a developing helmet body, also known as the X axis. [TE]
Chamfer: The juncture of two angled or beveled flat surfaces. [DE]
Character line: A raised or indented, creased or peaked line on a smooth surface that adds stronger-than-normal interest to the helmet’s aesthetics. [DE]
Cheat: To exaggerate a design feature in a sketch or model in order to improve the helmet’s appearance or proportions. [DP]
Coved: Recessed. [DE]
Crease battans: Flexible design lines that help define transitional surfaces between major helmet sections. [DE]
Crown: A domed area. Also a subtle rise or convexity in a surface to make it look straight or flat instead of sunken. [DE]
Cutline: The line around an openable body panel. [TE]
Dash: The lines defined by the various testing standards that define where structural parts of the helmet should lie. [TS]
Daylight opening (DLO): The perimeter of any helmet window. [DE]
Deck: The upper surface of the rear of the helmet. [SE]
Dome: The upper portion of the helmet shell that forms the primary protective structure over the crown of the head. [SE]
Earcove: Curved arch opening in half shell helmet for ears. [SE]
Elevation: As seen in front, rear or side views. A side elevation, for example, is a side view. [TE]
Envelope body: A helmet body whose sides have no visual or actual side-surface interruptions or breaks. [DE]
EyeMood: In the analogy of the two front vents to the eyes on a face, the shape and the character of the vents conveyed. [DE]
Facelift: Design changes that make a familiar style or ornament look fresh and different. [DP]
Fast: A word used to describe the angle or tilt of a windshield or backlight. The “faster” the angle, the more nearly horizontal it is. [DE]
Fastback: A body shape in which the roof slopes downward at the rear and blends into the deck with no notch or visual break. [DE]
Fillet: A concave, transitional surface that fills, mates or blends two intersecting surfaces. Similar to Chamfer but rounded. [DE]
Flow chines: Sharp-edged longitudinal lines that cut through the surface geometry, typically serving both aerodynamic and aesthetic purposes. [AE]
Forehead Vent: Primary front-facing ventilation intake, typically positioned above the brow line. [AE]
Gesture: When a helmet has implied motion in its styling lines and shapes. [DE]
Goggle Window: The shape under the brim of a helmet that matches the shape of the goggle. [DE]
Hard points: Specific locations of points that have to be adhered to when designing surfaces, including chin strap mounts. [TE]
Headliner/headlining: The inner trim lining of a helmet. [SE]
Helmond: A raw shape that a helmet would be cut from, a word that combines helmet and almond. [DP]
Highlight: Light that bounces noticeably off a peak or line or convex surface. [DE]
Impact Zone: Specifically designed areas of the helmet that are engineered to absorb and distribute crash forces. [SE]
Line drawing: An outline sketch without shading or color. [DP]
Lip molding: Ornamental bright trim that outlines and visually reinforces a helmet perimeter cut. [DE]
Louver: A slit or narrow opening to let air, light or water in or out. [AE]
Mockup: A representation, usually of the final shape of a styled or engineered body. Can be 3D printed, made of foam, Clay, fiberglass, metal or any combination. [DP]
Monocoque/Monoblock: A type of body construction in which the skins are stressed to form part of the supporting structure. [SE]
Mule: A prototype helmet, usually built with new cosmetics over an existing foam and headform basis. [DP]
Muscular: When a design mimics human and animal forms. The designs surfaces are handled in a way that has muscle-like definition. [DE]
Noble: When a helmet overall aesthetic and proportions commands attention, suggest financial success and social distinction. [DE]
Notchback: A helmet style in which a relatively upright backlight joins a more horizontal rear deck, the join forming a notch. [DE]
Occipital Coverage: The extent and shape of protection provided to the lower rear of the skull. [SE]
One-off: A one-of-a-kind helmet, body style or body type. [DP]
Onion: Describing the layers of surfaces that are cut into and revealed for aesthetics. Also the stack of surfaces on the interior of a helmet that describe headform, padding, foam protection surfaces, etc. [SE]
Organic: When surfaces are made to blend together seamlessly. Forms that appear to have grown biologically. [DE]
Overcrown: To raise above the surrounding crowned surface. [DE]
Overhang: The amount of helmet shell structure, as seen in side view ahead of the forehead and behind the earcove centerline. [SE]
Package (the): A drawing or series of specifications that tell where a helmet’s “hard points” must be. [TE]
Peak: A sharp ridge stamped into a body surface, usually directed upward. [DE]
Pillar: An upright/latitudinal bridge between two ribs or body sections. [SE]
Plan view: As seen from the top. [TE]
Platform: The engineering basis for a helmet, including head form specifications, testing standard requirements, foam density requirements, and molding technology constraints. [TE]
Profile Line: The characteristic side view outline that defines the helmet’s primary shape and attitude. [DE]
Prototype: A realistic, full sized three dimensional representation of an entire helmet, usually made of CNC foam, abs or a combination. [DP]
Proveout model: A model made to confirm that a drawing or numerical model appears as expected. [DP]
Quarter panel: That part of a helmet bodyside comprising the rear panel from the earcove opening backwards. [SE]
Quarter tab: Hard point for mounting the chin straps, the corner behind the ear cove, also called dogknee. [SE]
Rake: Angle of “attack” at front of helmet, the steeper the angle the more “rake”. [DE]
Raw Shell: The finished but unmounted and unpainted shell, ready for graphics and final assembly. [SE]
Rendering: A drawing or illustration that includes shading and detail. [DP]
Retention System: The complete system of straps, adjusters, and buckles that secure the helmet to the head. [SE]
Rifling: Spiral or wrapped surface patterns that flow around the helmet shell, typically serving aesthetic purposes. [DE]
Scoop: An open-fronted area of the body designed to let in air. [AE]
Section: Representation of a body or part of a body as if it were cut and viewed at 90 degrees. [TE]
Shell: The outer protective layer of the helmet, typically made of composite materials or high-grade plastics. [SE]
Sightlines: Theoretical lines from the wearer’s eyes to objects inside the helmet and also beyond or outside the helmet. [TE]
Speed streaks: Surface patterns that represent trails of water swept back by the rush of wind at speed. [DE]
Spline: A gently curved or arched surface. Also refers to a long metal or wooden strip used to form a curve or arch. [DE]
Spoiler: An upward lift of the surfaces at the rear of a helmet, simulating aerodynamic downward force. [AE]
Stack Height: The measured distance from the wearer’s head to the outer surface of the shell. [SE]
Sweeten: In design, to smooth and improve the aesthetic flow of a surface or line. [DP]
Tape drawing: Full-sized “drawings” of side and end helmet-body elevations made with long, thin strips of flexible adhesive tape. [DP]
Template: A hard, cut-out representation of a body surface at a certain section. [DP]
Tension: A purposefully imperfect design feature. A conflicting set of themes combined to generate interest and controversy. [DE]
Testing Lines: Defined boundaries established by safety certification standards that determine minimum coverage areas and impact protection zones. [TS]
Theme: A loose design idea, usually in sketch or model form, that captures the essence of a project goal. [DP]
Tumblehome: The inward tilt or angle of the roof from the beltline up as seen in front or rear view. [DE]
Turn-under: The inward curvature of a helmet body below roughly beltline as seen in front or rear view. [DE]
Vent: An opening for air passage. [AE]
Vent slices: Wedge-shaped voids cut through the shell and liner for ventilation, typically angled for aerodynamic efficiency and water management. [SE]
Ventilation Matrix: The planned arrangement of intake and exhaust vents designed to optimize airflow through the helmet. [AE]
Windsplit: A raised crease that runs longitudinally along a body surface. A windsplit is lower than a fin. [AE]
Working drawings: The mechanical drawings used to complete the body engineering drafts. [DP]
Zero line (horizontal): A locating line at the bottom of the testing lines as seen in side view. Also called “datum line.” [TE]
Zero line (vertical): A locating line at the center of the midpoint point of the headform or established at the front of the helmet. [TE]
Zero point: A point that serves to locate all other parts and surfaces of the body. The zero point is often at the very center of the front of the helmet. [TE]