Principal Mechanical Engineer

About the role

Mainspring Energy seeks a Principal Mechanical Engineer to act as a company-level technical authority within the critical mechanical engineering domain for the Linear Generator platform. In this capacity, the hired individual will shape the long-term technical direction for key mechanical systems and define, or exert strong influence upon, overarching architecture and design principles. The role requires guiding high-consequence technical decisions and assisting the organization in solving problems that are novel, ambiguous, and central to the long-term success of the product and the business. This position is intended for engineers who have already demonstrated broad technical leadership across multiple teams, systems, or major program areas and are now prepared to create durable company-level technical leverage. The successful candidate must operate with exceptional autonomy, advise senior leadership, anticipate long-term technical and business risks, and create the 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, making the Principal-level candidate someone who brings rare technical judgment in a company-critical domain. The impact of this role must extend beyond individual projects, teams, or near-term program execution to influence the foundational mechanical engineering strategy of the company.

Key facts

What you'll do

Investigate and analyze complex mechanical failure modes and system-level interactions within the Linear Generator to identify root causes and define corrective actions.

Define and own the mechanical architecture and system design principles for critical assemblies, ensuring alignment with reliability, manufacturability, and performance objectives.

Lead the development and maintenance of mechanical standards, validation methods, and decision frameworks that guide cross-functional engineering efforts.

Perform deep technical investigations into material behavior, stress states, and dynamic interactions to inform design trade-offs and mitigate high-risk scenarios.

Champion the identification and resolution of cross-functional mechanical dependencies, coordinating with electrical, software, and systems engineering teams.

Evaluate and recommend new mechanical concepts and enabling technologies that could enhance the performance, efficiency, or durability of the product lineup.

Own the mechanical portion of technical documentation, including design rationales, trade studies, and failure mode analyses, to ensure institutional knowledge is captured and accessible.

Guide the mechanical validation and testing strategy, ensuring that test plans rigorously verify performance, durability, and safety requirements.

Mentor mechanical engineers across the organization by providing expert consultation, elevating technical discussions, and promoting best practices in design and analysis.

Partner with operations and supply chain to ensure that mechanical designs are practical to manufacture, assemble, and service in high-volume production environments.

Assess and mitigate long-term mechanical risks related to degradation, wear, and environmental exposure to protect product lifetime and warranty obligations.

Provide executive-level communication of mechanical status, trade-offs, and roadmaps to senior leadership, translating technical complexity into actionable business insights.

Drive the resolution of the most challenging mechanical problems that span multiple programs or require fundamental changes to the architectural approach.

Establish clear technical requirements and acceptance criteria for mechanical components to ensure alignment between design, verification, and field performance.

Requirements

Candidates must hold a Bachelor's degree in Mechanical Engineering or a closely related technical field as a non-negotiable eligibility criterion.

A minimum of 10 years of relevant experience in mechanical engineering roles is required, demonstrating a consistent track record of technical contribution and leadership.

Applicants must possess a proven history of designing, testing, and launching complex mechanical products or systems into demanding operational environments.

Demonstrated experience in leading and influencing technical decisions across multiple teams or programs is essential for success in this role.

The candidate must have deep expertise in mechanical analysis methods, including but not limited to stress analysis, dynamics, and thermal management.

Strong proficiency with CAD, simulation, and analysis tools is a strict requirement to perform the core functions of this position.

The ability to operate autonomously in ambiguous situations and make high-quality decisions with incomplete information is mandatory.

Excellent written and verbal communication skills are required to effectively collaborate with cross-functional stakeholders and leadership.

Nice to have

Experience with energy conversion technologies, fuel systems, or high-efficiency power generation is strongly preferred.

Background in high-volume manufacturing and supply chain constraints is highly desirable.

Experience with standards development, validation, testing, and certification processes is preferred.

Prior experience in a data center, utility, or mission-critical power environment is advantageous.

Practical notes

The work location for this role is in Menlo Park, California, requiring presence in the office during standard working hours.

This position is compensated with a salary, and the specific range is determined based on candidate qualifications and internal equity considerations.

Travel requirements are not specified in the current description, implying the role is primarily focused on onsite collaboration within the defined operational context.

Candidates must meet the stated eligibility requirements without exception, as these form the baseline qualifications for consideration.

The posting will remain open until the role is filled, and early application is encouraged to ensure full consideration.