Staff 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 Mechanical Engineer to own defined-scope mechanical engineering tasks, work streams, or moderate-complexity projects for our Linear Generator platform. In this role, you will design mechanical hardware, support analysis and testing, drive assigned work through validation and release, and work cross-functionally with engineering, manufacturing, quality, supply chain, test, and service teams.

This role is intended for engineers who have developed practical mechanical engineering experience through multiple design, analysis, test, release, or implementation cycles. A strong candidate should be able to independently own defined-scope engineering work, apply sound mechanical fundamentals, identify common risks, communicate clearly, and follow through on deliverables with support available for ambiguity, complex tradeoffs, or higher-risk decisions.

Candidates who are still primarily learning engineering fundamentals, company processes, and task-level execution may be better aligned to an Associate Mechanical Engineer role, while candidates who have already demonstrated independent ownership of significant projects, subsystems, or technical work streams may be better aligned to a Senior Mechanical Engineer role.

• Own defined-scope mechanical engineering tasks, work streams, or moderate-complexity projects with clear objectives and some ambiguity in execution.
• Design moderately complex parts, assemblies, fixtures, or subsystems while considering function, interfaces, manufacturability, serviceability, cost, reliability, and safety.
• Use engineering calculations, tolerance reviews, simulations, experiments, test data, and hands-on troubleshooting to validate designs and guide improvements.
• Develop and execute test plans, interpret results, document findings, and use evidence to support design, validation, and release decisions.
• Track deliverables, manage dependencies within your scope, communicate blockers early, and follow through on design, documentation, validation, and release activities.
• Work cross-functionally with engineering, manufacturing, quality, supply chain, test, reliability, suppliers, and service teams to resolve issues and move projects forward.

• BS or MS in Mechanical Engineering or a similar engineering field, with demonstrated experience contributing to mechanical design work beyond purely academic projects.
• Experience designing, analyzing, testing, and iterating mechanical hardware through multiple project phases or design cycles.
• Ability to independently own defined-scope engineering work with clear deliverables, while seeking guidance for ambiguous, complex, or high-risk decisions.
• Strong mechanical fundamentals, including practical experience with parts, assemblies, fixtures, mechanisms, structures, thermal systems, fluid systems, electromechanical packaging, or other relevant mechanical systems.
• Demonstrated ability to use analysis, testing, data, and engineering judgment to evaluate designs, compare options, and recommend practical next steps.
• Clear communication and execution skills, including the ability to document assumptions, decisions, risks, test results, and project status for technical and cross-functional stakeholders.

• Experience supporting hardware from concept through prototype, validation, release, production, or field use.
• Experience with CAD tools such as Solid Works or similar, including part design, assembly design, drawings, and design documentation.
• Experience with PLM systems, drawing release, engineering change processes, supplier qualification, production support, or field implementation.
• Experience with structured problem-solving, root cause analysis, failure analysis, design of experiments, reliability testing, or risk-based validation planning.
• Experience working with suppliers, contract manufacturers, production teams, quality teams, or field service organizations.
• Experience with energy systems, engines, generators, compressors, pumps, thermal systems, fluid systems, structures, high-cycle fatigue environments, precision alignment systems, or industrial equipment.

$172,000 - $203,000 a year

This position is onsite at our Menlo Park HQ. The salary will be adjusted to reflect local market conditions based on…