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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 Mechanical Engineer - Frame and Air Spring

Mainspring Energy is seeking a talented Mechanical Engineer to join the team responsible for the design and development of the frame support structure and air spring system for our innovative Linear Generator technology. These systems are critical for maintaining our very tight alignment of subassemblies, withstanding significant structural and thermal loads during operation, and storing potential energy during part of our cycle. This is a challenging, hands‑on role where your creativity, strong engineering fundamentals, and practical skills will directly contribute to making a significant impact on our clean energy solution.

Core Responsibilities

• Design and develop frame and air spring subsystems projects, including conceptualization, detailed design, 3D CAD modeling (Solidworks), engineering analysis (FEA/CFD tools like ANSYS for thermal, structural, and flow), testing, root cause investigation, and comprehensive documentation.
• Focus on challenges specific to our frame structure and air spring systems, such as achieving and maintaining a very tight alignment, design for high load transfer and fatigue durability, design for thermal management and improving system performance.
• Collaborate effectively with cross-functional teams (Controls, Manufacturing, Suppliers) to ensure seamless subsystem integration, performance, and support new product introduction (DFM/DFA, work instructions, tooling/fixtures).
• Plan and execute rigorous verification and validation testing to ensure designs meet demanding requirements (functional, durability, thermal, vibration, acoustic, safety, reliability).
• Support the continuous improvement of engineering processes, tools, standards, and best practices within the team. Provide technical guidance to technicians.
• Stay current on advancements in mechanical engineering relevant to power generation, identifying opportunities to reduce costs, improve performance, and enhance reliability as Mainspring scales its technology.
• Uphold and further Mainspring's mission to create clean, affordable, and reliable power generation that accelerates the world's transition to a sustainable energy future.

Qualifications

• Bachelor's or Master's degree in Mechanical Engineering or similar field.
• 3+ years as a professional mechanical design engineer.
• Delivered products through 1+ full design lifecycles from concept to manufacturing support, preferably involving industrial equipment, power generation, engine systems, or similar demanding applications.
• Self‑starter with a proven ability to deliver functional designs in a rapid development environment and a track record of innovation and continuous improvement.
• Direct experience designing components or systems operating in high‑cycle and high‑load environments.
• Demonstrated engineering fundamentals in structural mechanics and thermal design. Experience with structural analysis (FEA) is essential.
• Direct experience designing systems with bolted joints that carry load.
• Familiarity with design considerations for durability, fatigue, and reliability in demanding applications.
• Proficiency in 3D CAD modeling (Solidworks preferred), engineering drawing creation (GD&T, detailed datum selection), and experience with PDM/PLM or similar CAD version control system.
• Knowledge of mechanical design principles, materials, manufacturing processes (machining, sheet metal, welding, casting, forging), and ability to identify and resolve design for manufacturability issues.
• Hands‑on mechanical prototyping, assembly, and testing skills. Experience with relevant instrumentation (thermocouples, accelerometers, pressure sensors) is a plus.
• Experience applying engineering analysis tools (FEA, tolerance stack ups) to solve design problems and validate concepts. Familiarity with acoustic analysis is beneficial.
• Excellent problem-solving, creative thinking, communication, and collaboration skills for effective cross‑functional teamwork.
• Ability to work independently and manage multiple projects in a fast‑paced environment.
• Passion for clean energy and commitment to creating a more sustainable world.

$119,000 - $140,000 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.