Senior Staff Mechanical Engineer - Structures & Alignment

Mainspring's Linear Generator is fundamentally different from a traditional engine.

Instead of rotary motion and a crankshaft, our system converts linear oscillation directly into electricity. A low-temperature, flameless reaction accelerates pistons and its translator shaft wrapped with permanent magnets through stator coils. Air-spring chambers reverse the motion - generating power with high efficiency and ultra-low emissions.

Critically, the translator shaft and pistons float on precision air bearings, riding on a thin film of pressurized air. This minimizes friction and wear - but it also removes rigid mechanical constraints. The translator must remain precisely aligned within tight tolerances across the full cylinder length while traveling at resonance under dynamic loads.

This architecture is elegant - and mechanically unforgiving.

Core Responsibilities

• Lead structural design and alignment strategy for alignment-critical components
• Design and validate bolted joints under cyclic and thermal loading
• Develop GD&T and tolerance stack strategies across subsystem interfaces
• Own 3D CAD (SolidWorks) and structural FEA (ANSYS or equivalent)
• Model structural behavior under vibration and thermal gradients
• Plan and execute durability testing and structured root cause investigations
• Translate test and field data into improved design standards
• Partner with Electrical, Controls, and Manufacturing teams to ensure scalable robustness

Qualifications

• Degree in Mechanical Engineering or a similar engineering field from an accredited institution. Experience and degree will determine level, but minimum requirements are: BS + 12 years experience or MS + 10 years experience
• Delivered products as a technical lead through 3+ full design lifecycles from concept to manufacturing support, preferably with product in high vibration environments with large cyclic loading
• Expertise in bolted joints, thermal impact on structures, design and analysis for severe vibration environments a big plus
• Fluent in SolidWorks or comparable CAD package. Experience with using PDM or a similar CAD version control system is preferred
• Hands-on mechanical prototyping, assembly, testing skills, and experience with mechanical engineering analysis tools (FEA, CFD, thermal analysis, tolerance stack-ups)
• Deep understanding and knowledge of mechanical design principles, materials, manufacturing processes (sheet metal, welding, casting), and ability to identify and resolve design for manufacturability issues
• Excellent problem-solving, creative thinking, communication, and collaboration skills for effective cross-functional teamwork
• Ability to work independently, manage multiple projects in a fast-paced environment, and demonstrate leadership and mentoring abilities
• Passion for clean energy and commitment to creating a more sustainable world

$170,000 - $209,000 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.

Does your experience not meet all of our posted requirements? Studies have shown that some people are less likely to apply to positions unless they meet every listed requirement. At Mainspring, we are committed to building a diverse, inclusive, flexible, and collaborative environment, so if you want to help us transition the world to clean and affordable electricity, and don't meet all posted requirements for a particular role, we'd still love to hear from you. Mainspring can sometimes be flexible enough to shift responsibilities for the right person, or otherwise identify open or upcoming roles that may better fit your professional background.