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9 Mothers is a venture-backed defense technology company developing AI-powered counter-drone systems designed to intercept and neutralize Group 1/sUAS threats in real-time. The company builds low-power systems for deployment on vehicles, at bases, and in field conditions, with a focus on immediate operational capability rather than long-term research.
This Senior Mechanical Engineer role focuses on mechanism design and is not tied to a single product. You will solve the hardest mechanical problems across the company's portfolio: feed systems, belt-fed shotgun actions, gimbals, drive trains, gearboxes, linkages, and timing mechanisms. You will be the go-to engineer for complex kinematics and dynamics problems that block product development.
Key responsibilities include:
- Owning mechanism problems from concept through working hardware, including kinematic/dynamic analysis, detailed design, and testing
- Designing for motion under load: cams, linkages, gear trains, springs, ratchets, escapements, and detents
- Prototyping hands-on: machining, 3D printing, fitting, assembling, and instrumenting test articles
- Diagnosing failures through observation, hands-on inspection, and data analysis; partnering with test engineers on high-speed video and instrumented testing
- Recognizing and killing bad ideas early based on real-world constraints (tolerances, contamination, temperature, field conditions)
- Ensuring manufacturability by designing mechanisms that suppliers can build repeatably; producing GD&T drawings
- Collaborating across electrical, firmware, and controls on actuator selection and electromechanical interfaces
- Supporting field testing at ranges and in operational environments
This is a hands-on role requiring comfort with machine tools, bench work, and the willingness to tear down and rebuild machines to understand failure modes. The company values field-ready capability, direct technical decision-making, and rapid iteration.
Requirements:
- 10+ years of mechanical engineering experience with a proven track record of mechanism design on hardware that shipped and performed in the field
- Demonstrated talent for mechanisms: ability to visualize how mechanisms move, identify binding points, and predict wear; capability to sketch linkages or cam profiles that work on first or second attempt
- Fluency in kinematics and dynamics: linkage synthesis, cam design, gear train design, spring and energy storage design, impact and high-rate loading, tolerance and clearance analysis for moving assemblies, and associated analysis tools; multibody simulation experience is a plus, but sound engineering judgment about simulation limitations is required
- Deep practical knowledge of mechanism failure modes: friction and lubrication, wear, fatigue, backlash, fretting, galling, contamination, thermal effects, and material/surface-treatment solutions
- Hands-on prototyping and troubleshooting skills; comfort with mills, lathes, and bench work; history of disassembling and reassembling machines both professionally and personally
- Strong GD&T and drawing skills; ability to produce fully constrained drawings for moving assemblies that suppliers can build to
- Engineering judgment to recognize which clever ideas will fail and the directness to communicate that assessment
- Efficient, low-ego, collaborative approach; ability to build rapport quickly and move work forward without drama
Nice-to-have qualifications:
- Enthusiasm for firearms as mechanical machines; experience designing or working on firearm actions, feed systems, or fire control
- Experience with high-rate, high-shock, or high-cycle mechanisms (firearms, ammunition handling, automotive powertrain, industrial automation, printing/packaging machinery, aerospace actuation)
- Experience with precision gear trains, harmonic drives, or servo-driven gimbal and turret systems
- Experience taking mechanisms from prototype through production, including work with machine shops and contract manufacturers on tolerancing and process capability
- Experience in a venture-backed hardware startup
