Mechanical Engineer, Senior

Senior Mechanical Engineer

Location: Onsite — Austin, TX

Employment Type: Direct Hire, Full-Time

About 9 Mothers

The modern battlefield has changed. Cheap, autonomous suicide drones have turned the tactical advantage upside down, and the world is looking for a solution. At 9 Mothers, we aren't just "innovating"—we are building the shield.

Backed by top-tier investors, we develop AI powered machines designed to intercept and neutralize Group 1/sUAS threats in real-time. Our flagship product is a low-power, counter-drone system built for the edge—on vehicles, at bases, or in a soldier's pack.

Why 9 Mothers?

While others build for "awareness" or "long-term research," we build for the immediate survival of those in harm's way. We are a team of hackers, engineers, and mission-driven builders who value field-ready capability over polished slide decks. If you want to see your code or hardware in the field next month—not next year—this is your playground.

Position Summary

We are hiring a Senior Mechanical Engineer who specializes in mechanisms. Everything we build is a machine that has to move fast, hit hard, and keep working: belt-fed and high capacity shotgun actions, feed systems, gimbals, drive trains, and the gearboxes and linkages that tie them together. This role exists because the hardest problems we have are problems of motion, and we need one more person whose talent is seeing how parts move and interact before the parts exist.

This is not a product-owner role and it is not tied to one product. You will go wherever the hardest mechanical problem in the building is that month: a feed path that hangs up under one particular loading, a gear train that is louder than it should be, a latch that has to work at temperature after ten thousand cycles. You will work alongside our existing mechanical engineering team and you will be the person the team brings the ugly kinematics to.

The person we want has a well developed intuition for the ways objects can be made to move, and an equally well developed intuition for the ways objects object to being moved: friction, backlash, inertia, compliance, wear, thermal growth, contamination, and the tolerances that are fine on paper and not fine on a Tuesday afternoon in the dirt. We want clever solutions to complex mechanical problems, and we want the life experience to know when a clever solution is a bad idea. We want the person who hears that something is not quite right in a gearbox before anyone else in the room knows anything is wrong.

This is a hands-on role. You will build your own prototypes, run them on the bench and at the range, take them apart when they break, and figure out why. If your idea of a good weekend involves tearing down and rebuilding a machine to understand it, you will fit in here.

Essential Duties

• Solve the hard mechanism problems. Take on the feed, action, drive, latching, and timing problems that are blocking a product, from first sketch through working hardware. Own the concept, the kinematic and dynamic analysis, the detailed design, and the test.
• Design for motion under load. Cams, linkages, gear trains, springs, ratchets, escapements, detents, and the interfaces between them. Get the forces, timing, and energy budgets right, and make the mechanism tolerant of the real-world conditions it will see.
• Prototype with your own hands. Machine, print, fit, and assemble your own test articles. Instrument them. Cycle them until they break, then explain exactly why.
• Diagnose by ear, by hand, and by data. Find the root cause of a jam, a stall, a noise, a wear pattern, or an intermittent failure, and separate what the hardware is telling you from what the drawing says it should be doing. Partner with our test engineer on high-speed video and instrumented testing when the failure is too fast to see.
• Kill bad ideas early. Bring the judgment to recognize when a concept will not survive contact with tolerances, contamination, temperature, or a soldier, and say so before we spend months finding out.
• Make it manufacturable. Design mechanisms that can be built repeatably with the processes and tolerances we can actually hold, and work with our manufacturing engineer and machine shop to get there. Produce drawings with GD&T that suppliers can build to.
• Work across disciplines. Collaborate with electrical, firmware, and controls on actuator selection, sensing, and the electromechanical interfaces where motion meets control.
• Support testing in the field. Go to the range. Watch the hardware run. Wrench on it when it fails, and bring back the findings that feed the next revision.

Requirements

• 10+ years of mechanical engineering experience with a clear track record of mechanism design on hardware that shipped and worked in the field.
• A demonstrated talent for mechanisms. You can look at a mechanism and see how it moves, where it binds, and what will wear. You can sketch a linkage or a cam profile that does what you want on the first or second try. We will ask you to show us examples of mechanisms you designed and to explain what went wrong with them.
• 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 the analysis tools to back it up. Multibody simulation experience is a plus; sound engineering judgment about when simulation is lying to you is a requirement.
• Deep practical knowledge of how mechanisms fail: friction and lubrication, wear, fatigue, backlash, fretting, galling, contamination, and thermal effects, and the material and surface-treatment choices that address them.
• Hands-on prototyping and troubleshooting skills. You are comfortable on a mill, a lathe, and a bench, and you have a history of taking machines apart and putting them back together, on the job and on your own time.
• Strong GD&T and drawing skills. You produce drawings that fully constrain a moving assembly and that suppliers can build to.
• The judgment to say no. You have seen enough clever ideas fail to know which ones will, and you are direct about it without being difficult.
• Efficient, low-ego, and easy to work with. You build rapport quickly and move work forward without drama.

Nice-to-Have

• An enthusiasm for firearms as mechanical machines. Firearms are among the most refined mechanisms ever built, and people who appreciate that tend to be good at this job. Experience designing or working on firearm actions, feed systems, or fire control is a strong plus.
• Experience with high-rate, high-shock, or high-cycle mechanisms: firearms, ammunition handling, automotive powertrain, industrial automation, printing or packaging machinery, aerospace actuation, or similar.
• Experience with precision gear trains, harmonic drives, or servo-driven gimbal and turret systems.
• Experience taking a mechanism from prototype through production, including working with machine shops and contract manufacturers on tolerancing and process capability.
• Experience in a venture-backed hardware startup.

Benefits

• Meaningful Early Equity: You aren't just an employee; you are a foundational owner. Your contributions directly drive the value of your stake in the company.
• Direct Roadmap Influence: Forget the bureaucracy of big defense. You will have a seat at the table, directly shaping our product and technology trajectory from day one.
• Mission-Critical Work: We don't build for "what if." We build systems the Department of War actively needs to counter immediate, real-world threats.
• The Builder's Playground: Work in a brand-new lab fully optimized for rapid prototyping, equipped with NVIDIA Jetsons, high-end scopes, and 3-D printers.
• 100% Employer-Paid Premiums: We cover 100% of your medical, dental, and vision insurance premiums and cover 50% of healthcare premiums for your dependents.
• Unlimited PTO: We value results, not clock-watching. Take the time you need to stay sharp and recharge.
• Zero Red Tape: You have the autonomy to make technical decisions that would take months of committee approval at a larger firm.
• Austin-Based Culture: Join an onsite team in Austin, TX, where we prioritize high-bandwidth collaboration and rapid field-testing.
• Relocation Assistance: We want the best talent in the room. If you aren't in Austin yet, we'll help you get here, to make your transition to the Silicon Hills seamless.