The B9 robot’s collar is the accordion-style flexible section connecting the torso to the head assembly. It’s one of the more visually distinctive elements of the robot’s silhouette — the pleated, bellows-like neck that allows the head to rotate and tilt while maintaining the visual connection between body sections.

Getting the collar right is important because it’s visible in almost every shot of the robot and its proportions affect the overall look significantly. Too short and the robot looks squat; too long and it loses the proper silhouette.

Original Prop Reference

The original B9 collar was constructed from a flexible material — the specific construction method varied between seasons, with the collar being rebuilt or modified at various points in production. The accordion pleating was a consistent design element throughout all three seasons, though the exact dimensions and pleat count changed.

Season 2 and Season 3 configuration is more commonly replicated. Reference images from the show and from the B9 Builders Club forums document the approximate pleat count and proportions for each production year.

Key dimensions to establish before building:

  • Inner diameter — must fit over whatever neck/head support structure you’re building
  • Outer diameter — affects the visual proportion relative to the torso
  • Height — the collapsed and extended range of the collar
  • Pleat count — visible in reference images; affects the silhouette

Material Options

Foam-Based Construction

The most common approach for replica collars uses upholstery foam or closed-cell foam:

  1. Cut foam strips to the pleat profile — each pleat is a strip with a specific cross-section that, when assembled, creates the accordion effect
  2. Cover the foam armature with fabric or vinyl stretched over the form
  3. The fabric covering is what’s visible; the foam provides the shape and some structural support

Foam density: Medium-density upholstery foam (2.0–2.5 lb density) holds its shape while remaining flexible enough to allow head rotation. High-density foam is too stiff; low-density foam collapses under its own weight.

Covering material: Black neoprene fabric or thick vinyl are the most accurate matches to the original prop’s appearance. Stretch fabric over each pleat and secure at the inner and outer edges.

Vacuum-Formed Plastic

For a harder, more durable collar:

  1. Sculpt or machine the pleat profile
  2. Vacuum form black ABS or PETG over the form
  3. Assemble individual vacuum-formed pleat sections into the full collar

Vacuum-formed collars are stiffer than foam constructions and hold their shape better over time, but require vacuum forming equipment and more complex assembly.

Cast Silicone or Urethane Rubber

Some builders cast the collar in flexible urethane rubber (Shore A 20–30) or silicone, using a mold taken from a sculpted master. This produces a one-piece flexible collar with excellent detail reproduction.

Advantages: Most accurate surface texture; durable; one-piece construction eliminates assembly seams Disadvantages: Requires a full mold; heavy material; the mold for a collar-sized piece requires significant silicone investment

For builders already set up for mold making and casting (which covers most B9 builders at this stage of the project), cast rubber is worth considering for the collar. The complete mold making guide covers the process.

Structural Considerations

The collar must:

  1. Support the head assembly weight — the head, dome, brain components, and any electronics inside the head all rest on or attach via the collar area. The collar’s internal structure needs to transmit this load to the torso without deforming.

  2. Allow rotation — the head rotates; the collar must accommodate this without binding. A central rigid tube (aluminum pipe or heavy PVC) inside the collar that the head rotates around is the standard approach.

  3. Accommodate wiring — power and signal wiring for any head-mounted electronics (dome lighting, motors) must pass through the collar. Plan a wire chase before finalizing the collar structure.

Typical structural approach:

  • Central aluminum tube (3–4" diameter) as the rotation bearing surface
  • Foam or rubber collar construction around the exterior of the tube
  • Wiring routed through the center of the tube

Fitting and Finishing

The collar is one of the trickier fit challenges on the robot because it bridges the torso (which has a fixed top edge geometry) and the head (which rotates). Test the fit incrementally rather than finishing the collar completely before checking against both sections.

Color: The original collar was black. Flat or matte black is more accurate than gloss. If using fabric, black neoprene is already the right finish; if vacuum forming or casting, finish with matte black paint.

Seam management: Any construction seams should be positioned at the back of the robot where they’re less visible, or hidden within the pleat geometry.

Once the collar is fitted, it connects to the torso construction at the bottom and the brain/dome assembly at the top, completing the robot’s upper body. The construction overview covers how all sections integrate.