Principal Mechanical Engineer

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, Next Era 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

Mainspring is seeking a Principal Mechanical Engineer to serve as a company-level technical authority in a critical mechanical engineering domain for our Linear Generator platform. In this role, you will shape long-term technical direction, define or strongly influence architecture and design principles, guide high-consequence technical decisions, and help the organization solve problems that are novel, ambiguous, and central to long-term product and business success.

This role is intended for engineers who have already demonstrated broad technical leadership across multiple teams, systems, or major program areas and are now ready to create durable company-level technical leverage. A strong candidate should be able to operate with exceptional autonomy, advise senior leadership, anticipate long-term technical and business risks, and create principles, standards, methods, or decision frameworks that improve how Mainspring approaches major classes of engineering problems.

Candidates who primarily shape technical direction across multiple teams or system areas may be better aligned to a Senior Staff Mechanical Engineer role. Principal-level candidates should bring rare technical judgment in a company-critical domain and demonstrate impact that extends beyond individual projects, teams, or near-term program execution

• Lead company-critical technical direction in a mechanical engineering domain with high ambiguity, high consequence, and broad cross-functional impact.
• Define or strongly influence technical architecture, design principles, standards, methods, and long-term product direction that affect product capability, reliability, cost, scalability, manufacturability, serviceability, and business outcomes.
• Solve the organization’s most difficult and unprecedented engineering problems, especially where existing methods, assumptions, or design approaches are insufficient.
• Advise senior leadership on technical decisions with long-term product, customer, operational, financial, or business consequences.
• Define evidence and learning strategies for high-consequence decisions, including the right mix of analysis, testing, modeling, field data, production learning, external expertise, and engineering judgment.
• Create durable organizational leverage through technical frameworks, review practices, architecture decisions, standards, methods, or risk approaches that improve how teams execute engineering work.

• BS, MS, or PhD in Mechanical Engineering or a similar engineering field, with a distinguished track record of solving high-consequence mechanical engineering problems in a company-critical domain.
• Demonstrated ability to shape technical direction across major systems, platforms, product areas, or organizations, not only within a single project or team.
• Exceptional mechanical engineering judgment, including the ability to balance product capability, reliability, cost, scalability, manufacturability, serviceability, safety, customer needs, and business priorities.
• Proven ability to solve novel, ambiguous, cross-functional problems where requirements, ownership, evidence, methods, or tradeoffs are not initially clear.
• Deep experience using analysis, testing, modeling, field learning, production learning, and engineering judgment to guide long‑term technical strategy and high-consequence decisions.
• Strong executive‑level communication and influence skills, including the ability to…