III
Frameless motors & integrated actuators
Humanoids need dozens of compact high-torque-density actuators; the merchant motor bench is thin and the leaders are vertically integrating.
Humanoids are an actuator-count problem before they are an AI problem. A single bipedal robot needs roughly 28–40 powered joints, and each joint wants a compact, high-torque-density rotary actuator — typically a frameless (rotor-and-stator-only, no housing or bearings) motor married to a strain-wave or planetary reducer, a position sensor, and an integrated drive. Actuators are the single largest line in the bill of materials: one teardown estimate puts them at ~56% of total Optimus BOM cost. The physical constraint is real — torque density, thermal rise, and joint weight are the binding limits — and the merchant bench that can supply qualified, automotive-grade frameless motors at scale is thin.
Who owns it
The Western merchant motor leader is Regal Rexnord, whose Kollmorgen unit builds the TBM2G frameless torque-motor family — the same architecture that underpins HEBI Robotics' H-Series actuator (10x the torque of its prior line, zero-backlash via strain-wave gearing) and RobCo's modular robot joints. Allient, via Allied Motion, calls itself the global leader in frameless torque motors and has published a humanoid motor-selection playbook. Moog supplies integrated smart actuators with deep force-control heritage. But the true chokepoint sits upstream in the reducer: the strain-wave gear that lets a small motor deliver joint-level torque. That market is a Japanese near-monopoly — Harmonic Drive Systems (the category's namesake) and Nidec, whose Drive Technology unit makes FLEXWAVE strain-wave and KINEX cycloidal reducers.
What breaks it
Two forces compress the merchant thesis. First, vertical integration: Tesla designs Optimus actuators in-house, and the rotor/stator/reducer stack is engineered internally — which removes the largest single buyer of merchant frameless motors from the Western order book. Second, China. Tesla's actuator manufacturing did not stay in-house so much as move offshore: Sanhua is the Tier-1 actuator-assembly supplier, Tuopu the rotary-actuator supplier, and Green Harmonic a primary harmonic-reducer source, with Green Harmonic already holding >60% of China's harmonic-reducer market (>35% globally), priced at roughly 40–60% of the Japanese incumbent. The Japanese reducer monopoly is real but contested on price, and the rare-earth magnet input is a separate Chinese chokepoint — Musk flagged the NdFeB magnet constraint on the Q1 2025 call, with each robot needing ~3.5kg of magnet largely sourced from China.
What forces the reprice
The re-rating trigger is the transition from "design win" language to recurring, disclosed revenue. Regal Rexnord is the only listed name here with a specific humanoid figure — though it is an analyst estimate, not company-disclosed: JPMorgan flagged >$30M of annual humanoid-related business already secured against a ~$200M robotics pipeline (Feb 2026). Watch for (a) the first humanoid maker to standardize on a merchant frameless platform at production volume, (b) Tesla's V3 Optimus production ramp (targeted summer 2026 per Musk), which sets whether the merchant or the in-house/China path wins, and (c) any Japanese reducer maker disclosing a named humanoid program at scale.
Be honest about size and earliness
This is a narrative-rich, revenue-poor chokepoint today. Outside Regal Rexnord's ~$30M, none of these names disclose a humanoid-specific revenue line — Allient and Moog have positioning, whitepapers, and components, but Allient's disclosed robotics pull is in surgical robotics, not humanoids, and Moog's named robot work is the research-grade IIT HyQ quadruped. The reducer monopolists trade on OTC as foreign ordinaries with thin US liquidity. The honest framing: humanoid demand is a call option on these industrial cash-flow businesses, not yet a P&L driver — and the option's strike is being lowered every quarter by Chinese cost-down and Tesla in-housing. Size positions to the industrial base case, not the humanoid TAM headline. This is education on supply-chain structure, not investment advice.
Who owns the choke
Allient Inc.
Allied Motion (an Allient company) positions itself as the global leader in frameless torque motor solutions and published an April 2026 whitepaper on motor selection for humanoid robotics. Q1 CY2026 revenue was $138.9M with a $251M backlog; disclosed robotics demand is in surgical robotics rather than a named humanoid program.
- Bull
- Allied Motion's frameless-torque-motor leadership and humanoid motor-selection whitepaper position Allient to supply the thin merchant motor bench as programs standardize.
- Bear
- Q1 robotics demand is disclosed in surgical robotics, not a named humanoid program, so humanoid exposure is positioning rather than booked backlog.
Harmonic Drive Systems Inc.
Harmonic Drive Systems is the world's leading manufacturer of strain-wave (harmonic) reducers, the compact zero-backlash gear in humanoid joints; Tesla Optimus uses 14 harmonic-gear rotary actuators. Humanoid-related orders were ~1.3B yen in Q2 and ~2.5B yen guided for FY3/26, with a 10B yen mid-term target by FY3/27 on improving U.S. prototype-order visibility. TTM revenue ~$375M; OTC ticker HSYDF maps to TSE:6324 (corrected from the HSDEF hint).
- Bull
- Harmonic Drive is the world's leading strain-wave reducer maker (14 in each Optimus), guiding humanoid orders toward a 10B-yen FY3/27 target on improving US visibility.
- Bear
- Humanoid is low-single-digits of ~$375M revenue, the stock carries a ~380x P/E, the OTC line is punishingly thin, and Chinese Green Harmonic undercuts on price.
Moog Inc.
Moog designs integrated smart actuators with electric, hydraulic and hybrid actuation and force-control heritage suited to humanoid legs, arms and exoskeletons. Its named robotics collaboration is the IIT HyQ bio-inspired quadruped; it discloses no humanoid-specific revenue line.
- Bull
- Moog's integrated smart actuators with deep electric/hydraulic force-control heritage suit humanoid legs, arms and exoskeletons, positioning it on the thin merchant actuator bench.
- Bear
- Its only named robotics collaboration is the research-grade IIT HyQ quadruped, and it discloses no humanoid-specific revenue line.
Nidec Corporation (ADR)
Nidec Drive Technology manufactures FLEXWAVE strain-wave and KINEX cycloidal precision reducers for robotics, demoed at RoboBusiness 2025; Nidec also supplies precision motors and has Tesla EV-supplier heritage. NJDCY is the OTC ADR of Tokyo-listed Nidec Corp (6594), a Kyoto motor maker.
- Bull
- Nidec makes FLEXWAVE strain-wave and KINEX cycloidal reducers plus precision motors and carries Tesla EV-supplier heritage, giving it merchant exposure across the actuator stack.
- Bear
- Humanoid presence is demos and product launches with no disclosed design win, and NJDCY is the thin OTC ADR of a diversified Kyoto motor conglomerate.
Regal Rexnord Corporation
Kollmorgen's TBM2G frameless torque motors power the HEBI Robotics H-Series actuator (10x torque vs prior line, zero-backlash via strain-wave gearing) and RobCo's modular robot joints. JPMorgan flagged >$30M of annual humanoid-related business already secured against a ~$200M robotics pipeline in February 2026.
- Bull
- Regal Rexnord's Kollmorgen TBM2G frameless motors power HEBI and RobCo joints, and it is the only listed name with a specific humanoid figure — >$30M secured against a ~$200M pipeline.
- Bear
- The >$30M is a JPMorgan analyst estimate, not company-disclosed, and Tesla in-housing plus Chinese cost-down keep lowering the merchant motor option's strike.
Tesla, Inc.
Tesla designs Optimus actuators in-house — removing the largest single buyer from the merchant frameless-motor order book — while outsourcing manufacturing to Chinese suppliers (Sanhua Tier-1 actuator assembly, Tuopu rotary actuators, Green Harmonic reducers). V3 Optimus production is targeted for summer 2026, with actuators ~56% of BOM cost.
- Bull
- Tesla designs Optimus actuators in-house with V3 production targeted for summer 2026, making it the highest-volume Western humanoid program and the bar suppliers price against.
- Bear
- It outsources manufacturing to Chinese suppliers, faces an unproven ramp, and humanoid mapping spans only actuators and sensing within a vast auto business.
Catalyst calendar
- 2026-07-22Tesla Q2 2026 earningsmediumOptimus V3 production-ramp commentary sets whether in-house/China actuators or merchant frameless motors capture the humanoid joint supply, directly bounding the merchant motor TAM.
- 2026-08-11Harmonic Drive Systems quarterly earnings (TSE 6324)mediumAs the strain-wave reducer near-monopolist, Harmonic Drive's order and reducer-volume commentary is the cleanest read on whether humanoid demand is reaching the reducer chokepoint.
- 2026-10-19RoboBusiness 2026, Santa Clara (Oct 19-21)lowPrimary venue where reducer and frameless-motor suppliers (Nidec Drive Technology demoed in 2025) unveil humanoid-targeted actuator parts and any design wins that would move the chokepoint from positioning to revenue.
- 2026-12-01Humanoids Summit Silicon Valley (Dec 1-2)lowConcentrated forum for humanoid OEMs to announce production-volume actuator platform standardization — the trigger that would re-rate any merchant frameless-motor supplier from option to revenue.