Senior Staff Mechanical Engineer - Structures & Alignment

About Mainspring

Mainspring Energy manufactures and delivers fuel-flexible, low-emissions local power solutions that rapidly add new capacity and deliver reliable, affordable, and sustainable electric power. The company began commercial shipments of its Mainspring Linear Generators in 2020 and today has hundreds of megawatts in advanced development and field operations for leading Fortune 500 companies, data centers, and utilities. Mainspring also partners with global energy leaders including AEP, NextEra Energy Resources, Schneider Electric, and more.

The core values that ground our work, guide our decisions, and connect us together:

• Pragmatic Optimism
• Excellence without Ego
• Proactive Collaboration

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.

Does your experience not meet all of our posted requirements? Studies have shown that some people are less likely to apply to positions unless they meet every listed requirement. At Mainspring, we are committed to building a diverse, inclusive, flexible, and collaborative environment, so if you want to help us transition the world to clean and affordable electricity, and don't meet all posted requirements for a particular role, we'd still love to hear from you. Mainspring can sometimes be flexible enough to shift responsibilities for the right person, or otherwise identify open or upcoming roles that may better fit your professional background.

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.

We may use artificial intelligence (AI) tools to support parts of the hiring process, such as reviewing applications, analyzing resumes, or assessing responses and identifying potential inconsistencies or verification signals in application materials based on available information. These tools assist our recruitment team but do not replace human judgment. Final hiring decisions are ultimately made by humans. If you would like more information about how your data is processed, please contact us.