Senior Staff Mechanical Engineer - Structures & Alignment

Company Overview Mainspring Energy is revolutionizing power generation with the world’s most flexible and adaptable local power generation technology, the Mainspring Linear Generator. Commercial, industrial, and utility leaders are choosing Mainspring over traditional options like engines, turbines, and fuel cells to quickly and reliably deliver local power for EV charging, commercial facilities, data centers, and grid-scale operations. The Mainspring Linear Generator is fuel flexible, ramps up and down to meet demand, and utilizes a flameless reaction with near-zero NOx emissions. Backed by top-tier investors including Khosla Ventures, Bill Gates, American Electric Power, Lightrock, and General Catalyst, Mainspring designs, manufactures and delivers its products to customers across the U.S. today, and we’re quickly scaling for international expansion. Inspired by our vision of the affordable, reliable, net-zero carbon grid, Mainspring is rapidly expanding within the $816B global electricity equipment market, and we’re hiring the best talent to meet growing customer demand around the globe. We welcome a broad range of backgrounds, experiences, and talents to bring fresh perspectives and ongoing innovation to our customers. We are looking to build relationships with people who share our values: Pragmatic Optimism. Building a new category of world‑class power generation requires the optimism of ambition and creativity, balanced with practicality to solve problems efficiently. The challenges that arise are opportunities for growth. Excellence without Ego. We bring expertise and commitment to creating the best customer experience, from sales to deployment and service, just as we apply deep technical rigor to building and delivering world‑class products. We strive for excellence and behave as leaders with the humility to acknowledge our challenges, both collectively and as individual contributors. Proactive Collaboration. The integration and cross‑disciplinary nature of Mainspring’s business requires intentionally seeking out others who bring different skills, perspectives, and priorities. Our culture of inclusion and respect extends beyond our team to interactions with our partners and customers. Senior Staff Mechanical Engineer – Structures & Alignment Mainspring’s Linear Generator is fundamentally different from a traditional engine. Instead of rotary motion and a crankshaft, our system converts linear oscillation directly into electricity. A low‑temperature, flameless reaction accelerates pistons and its translator shaft wrapped with permanent magnets through stator coils. Air‑spring chambers reverse the motion—generating power with high efficiency and ultra‑low emissions. Critically, the translator shaft and pistons float on precision air bearings, riding on a thin film of pressurized air. This minimizes friction and wear—but it also removes rigid mechanical constraints. The translator must remain precisely aligned within tight tolerances across the full cylinder length while traveling at resonance under dynamic loads. This architecture is elegant—and mechanically unforgiving. Core Responsibilities Lead structural design and alignment strategy for alignment‑critical components Design and validate bolted joints under cyclic and thermal loading Develop GD&T and tolerance stack strategies across subsystem interfaces Own 3D CAD (SolidWorks) and structural FEA (ANSYS or equivalent) Model structural behavior under vibration and thermal gradients Plan and execute durability testing and structured root‑cause investigations Translate test and field data into improved design standards Partner with Electrical, Controls, and Manufacturing teams to ensure scalable robustness Qualifications Degree in Mechanical Engineering or a similar engineering field from an accredited institution. Experience and degree will determine level, but minimum requirements are: BS + 12 years experience or MS + 10 years experience Delivered products as a technical lead through 3+ full design lifecycles from concept to manufacturing support, preferably with product in high vibration environments with large cyclic loading Expertise in bolted joints, thermal impact on structures, design and analysis for severe vibration environments a big plus Fluent in SolidWorks or comparable CAD package. Experience with using PDM or a similar CAD version control system is preferred Hands‑on mechanical prototyping, assembly, testing skills, and experience with mechanical engineering analysis tools (FEA, CFD, thermal analysis, tolerance stack‑ups) Deep understanding and knowledge of mechanical design principles, materials, manufacturing processes (sheet metal, welding, casting), and ability to identify and resolve design for manufacturability issues Excellent problem‑solving, creative thinking, communication, and collaboration skills for effective cross‑functional teamwork Ability to work independently, manage multiple projects in a fast‑paced environment, and demonstrate leadership and mentoring abilities Passion for clean energy and commitment to creating a more sustainable world $170,000 - $209,000 a year This position is onsite at our Menlo Park HQ. The salary will be adjusted to reflect local market conditions based on employee location as well as the experience of the employee. Along with the base salary, Mainspring offers pre‑IPO stock options + benefits. In more traditional words, Mainspring Energy, Inc is an Equal Opportunity Employer. All qualified applicants will receive consideration for employment without regard to race, color, religion, sex, sexual orientation, gender identity, national origin, or protected veteran status and will not be discriminated against on the basis of disability. This compensation and benefits information is based on Mainspring Energy's estimate as of the date of publication and may be modified in the future. We generally do not negotiate on salary once we have made an offer. The level of pay within the range will depend on a variety of job‑related factors that may include location, relevant prior experience and/or education, or particular skills and expertise. New hires joining the company tend to be paid within the starting base pay range noted above, with opportunities to increase pay over time based on development of additional skills, competencies, and company‑specific knowledge. #J-18808-Ljbffr