Pulse Tube Cryocooler - Part 2 (-75C)

Part 1: This is the second part of my video series on attempting to build a Pulse Tube cryocooler. I managed to make significant progress by removing the linear motor and using a conventional rotary motor with a large gear reduction ratio and a flywheel to produce the larger forces needed for higher compression ratios. For pistons, I used pneumatic actuators. I evaluated a 25mm bore and a 40mm bore piston, both with a 50mm stroke. Pneumatic actuators have more friction than conventional pistons due to their rubber lip seals, but theoretically have zero blowby, so they hold pressure, which makes them more effective for low frequency applications. Here are some specifications for the cooler: Pipe diameter: 18mm Regenerator Length: 30mm Regenerator Material: Fine steel wool Pulse Tube Length: 100mm Flow resistance source: 1/8 NPT needle valve Inertance Tube Length: 10’ (~3m) Inertance Tube Diameter: Buffer