The B9 robot from the 1965 CBS television series Lost in Space is one of the most recognizable robots in science fiction history. Building a full-size replica is an ambitious multi-year project that draws on skills across mold-making, resin casting, metal fabrication, electronics, and finishing. This overview covers the complete build from the ground up — what the robot consists of, how to approach each section, and what skills and materials each phase requires.
About the B9 Robot
The original B9 was built by Bob Stewart for the pilot episode of Lost in Space in 1964–65. The robot was operated by actor Bob May, who wore the mechanical suit and performed all the robot’s movements on set. The voice was provided by Dick Tufeld, later replaced by the same in the series.
The original stands approximately 6 feet tall (depending on which version of the suit — the prop went through several revisions over the three-season run). Key visual characteristics:
- Tread section — Wide ribbed rubber tread base giving the robot a tank-like mobility
- Leg section — Two pillar-like leg tubes connecting the tread to the torso
- Torso — Large barrel-shaped body with chest light panel, various dials and controls, and rotating capability
- Collar — Accordion-style flexible collar connecting torso to the upper body
- Upper body / radar section — Shoulder section with large hinged arms
- Brain/bubble dome — Clear acrylic dome on top with the illuminated brain unit visible inside
- Claws — Large mechanical claw hands at the end of the robot arms
Construction Sequence
The B9 build is best approached section by section, starting from the base and working up. Each section is structurally complete before moving to the next.
1. Tread Section
The tread section is the widest part of the robot and serves as the base. It typically requires:
- A welded steel or aluminum armature/frame
- Fiberglass or foam shell panels shaped and bolted to the frame
- Commercially available or fabricated rubber tread
The tread frame carries the full weight of the operator inside (if building a walk-in version) or the mechanical structure (if building a static display). Structural strength here is critical.
2. Leg Section
The leg tubes connect the tread to the torso. On the original, these were formed aluminum cylinders. For replicas:
- Fiberglass layup over a form — Build a tube form from cardboard and fiberglass over it, then cut away the form. The result is a rigid, lightweight tube.
- Cast urethane over a core — Mold and cast the leg ribbing from urethane resin, bond to a PVC or aluminum pipe structural core.
- Carved foam — Cut and shaped foam panels bonded to the structural core. Lightweight but less durable.
See the dedicated B9 leg section guide for construction details.
3. Torso
The torso is the most complex single section. It contains:
- The main body shell (large curved form requiring significant mold work)
- Chest light panel (multiple colored lights, typically LED now)
- Torso rotation mechanism (the original torso spins — see the torso rotation reference)
- Control details, knobs, and surface appliqués
The torso shell is typically built in two halves (front and back) from fiberglass or cast resin, with an internal armature structure. See the B9 torso construction guide for specifics.
4. Collar
The accordion collar between torso and upper body is a defining visual element of the B9. The original used a flexible rubber accordion form. Replicas use:
- Cast silicone rubber (expensive but accurate)
- Latex over a form
- Flexible urethane rubber
- Vacuum-formed thermoplastic
5. Upper Body and Radar Section
The shoulder section houses the arms and mounts below the radar dish. The large hinged arms (ending in the claw assemblies) are articulated on the original — replicas range from static display arms to fully articulated and motorized versions.
The radar section is a flat disc assembly that sits above the upper body and rotates on the original. Typically cast from rigid urethane or fabricated from aluminum.
6. Brain and Bubble Dome
The brain section — the illuminated unit visible through the clear acrylic dome — is one of the most striking visual elements of the B9. See the B9 brain and bubble dome guide for construction details.
The dome itself is a formed acrylic hemisphere. Standard dome sizes that approximate the B9 are available from plastics suppliers (approximately 14–16 inch diameter).
7. Internal Electronics
The original B9 was entirely mechanical — no electronics in the modern sense. Modern replicas typically include:
- LED lighting throughout (chest panel, brain, eyes, various indicator lights)
- Sound system (classic B9 dialogue and sound effects from the series)
- Servo-driven mechanisms for rotating torso, moving arms, spinning radar
- Arduino or Raspberry Pi controller
- Remote control capability
See the B9 internal electronics guide for a full electronics overview.
Materials Summary
| Section | Primary Material | Structural Core |
|---|---|---|
| Tread | Fiberglass + rubber tread | Welded steel frame |
| Legs | Cast urethane or fiberglass | PVC or aluminum pipe |
| Torso shell | Fiberglass or cast urethane | Internal armature |
| Collar | Flexible urethane or silicone | None (flexible) |
| Upper body | Cast urethane or fiberglass | Armature |
| Brain dome | Acrylic hemisphere | Aluminum mounting ring |
Scale and Display Versions
Full-size walk-in — Built to original specifications with enough interior space for an operator to stand inside. The most ambitious build, requires significant engineering for the structural frame and operator comfort.
Full-size static display — Built to scale but not designed for occupation. Significantly simpler structure. Most hobbyist builds fall in this category.
Half-scale or smaller — Reduces the construction challenge considerably while producing a displayable piece. At half scale, the robot is still over 3 feet tall.
Community Resources
The B9 robot replica community has been active since the 1990s. The B9 Builders Club maintains forums and member galleries where builders share in-progress photos and construction techniques. Patterns, dimensions, and supplier information are shared among members.
For prop builders who want to develop their fabrication skills before tackling a full B9, the Mystic Seer replica and devil head mold project are good stepping stones — they use the same mold-making and casting techniques at a manageable scale.