Tiny Bolts has a guide on constructing a DIY High Pressure Air (HPA) engine for airsoft, emphasizing on its compatibility with standard electronics and its ability to function without modifying the gearbox. He explains that while an SLA resin printer is necessary to prevent air leaks, the design is less dependent on expensive regulators than other DIY alternatives.

The assembly requires a specific list of hardware, including M2 screws, O-rings, and a 3V solenoid valve armature. A significant portion of the project involves "winding your own fun" by wrapping enamel copper wire around the solenoid using a drill, aiming for a very specific electrical resistance. It is a process that turns a simple brass component into a functional air valve, provided you don't mind getting a little messy with silicone grease.

To finish the build, the 3D-printed parts must be cleaned, dried, and lightly sanded to ensure they fit within a standard gearbox. Tiny Bolts suggests using tough resin for durability and offers support through a Discord community for those who might run into trouble. It is essentially a science project that ends with a working airsoft gun, assuming your DIY solenoid winding skills are up to the task.