Water bottle rocket launch latch

thingiverse

This is a release latch for 2-liter water rocket bottles that works seamlessly with standard 21mm (21.3mm/21.5mm/27/32") external diameter waste pipes used as both fill rods and launch rods. The latch glides effortlessly inside the neck of the water bottle, requiring no seal for most 2L bottles but providing a convenient seal to make launching smoother. The hinged parts are attached securely to the hinge plate with M2 x 12mm screws, and you should slide a 21mm x 1mm O-Ring over the pipe and position it in the recess of the hinge plate. To install the latch, gather some 32mm PVC waste pipe couplers from your local DIY store. The internal diameter of these couplers should be 36mm. First, slide them over the launch rod, then attach the hinge plate to the launch rod using a bottle to ensure proper alignment, securing it with glue (superglue/CA works). Once the glue is dry, install the O-ring, screw on the hinge parts, and line up the threads carefully to guarantee correct assembly. Next, slide the 32mm coupler up the tube, which should compress the three threads together, ready to receive the bottle. Screw the bottle onto the threads, pressurize the system, cover your ears, and pull the coupler down to complete the launch.