Senior 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.

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

• Pragmatic Optimism
• Excellence without Ego
• Proactive Collaboration

Mainspring is seeking a Senior Mechanical Engineer to own significant mechanical engineering projects, subsystems, or technical work streams for our Linear Generator platform. In this role, you will develop robust mechanical designs, drive projects through the full design cycle, and work cross-functionally to validate and release hardware into production or field use.

This role is intended for engineers who have already demonstrated independent ownership of meaningful mechanical design work through multiple design, test, release, or implementation cycles. A strong candidate should be able to own a significant subsystem or project area with limited day-to-day guidance, make sound technical tradeoffs, identify risks early, and drive cross-functional execution.

Candidates who are still primarily building independence on bounded tasks or single work streams may be better aligned to a Mechanical Engineer role, while candidates who regularly improve technical decision quality across multiple projects or teams may be better aligned to a Staff Mechanical Engineer role.

• Own significant mechanical projects, subsystems, or technical work streams from requirements and concept development through validation, release, and implementation.
• Develop and release robust mechanical designs for complex parts, assemblies, fixtures, subsystems, or processes, balancing performance, reliability, cost, manufacturability, serviceability, safety, schedule, and system integration.
• Build and drive project plans, requirements, validation strategies, schedules, risk assessments, and release plans within an agreed scope.
• Use engineering analysis, test planning, experimental data, tolerance reviews, simulations, and hands-on troubleshooting to make design decisions and validate performance.
• Identify and mitigate technical, schedule, validation, manufacturing, quality, supplier, and service risks before they become major issues.
• Lead cross-functional technical discussions, design reviews, risk reviews, and project decisions with engineering, manufacturing, quality, reliability, test, supply chain, suppliers, and service stakeholders.

• BS or MS in Mechanical Engineering or a similar engineering field, with demonstrated experience owning mechanical design work beyond task-level execution.
• Repeated experience designing, testing, iterating, and releasing mechanical hardware across multiple design cycles, not only supporting isolated tasks or one phase of development.
• Ability to independently own a significant subsystem, project, or technical workstream with moderate ambiguity, cross-functional dependencies, and meaningful program impact.
• Strong mechanical design fundamentals, including practical experience with complex 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 make design tradeoffs, validate performance, and resolve technical problems.
• Strong communication and project execution skills, including the ability to define scope, manage dependencies, elevate risks with recommendations, and align technical and non-technical stakeholders.

• Experience taking hardware from early concept through production release, manufacturing implementation, or field support.
• Experience with PLM systems, drawing release, engineering change processes, supplier qualification, production ramp, or field implementation.
• Experience with reliability testing, accelerated life testing, failure analysis, design of experiments, structured root-cause analysis, or risk-based validation planning.
• Experience working directly with suppliers, contract manufacturers, production teams, quality teams, or field service organizations to resolve hardware issues.
• Experience designing hardware for energy systems, engines, generators, compressors, pumps, thermal systems, fluid systems, structures, high-cycle fatigue environments, precision alignment systems, or industrial equipment.
• Experience contributing to design reviews, risk reviews, troubleshooting efforts, or technical decisions outside their immediate project area.

• $140,000 - $165,000 a year
• This…