Add another level of fun to your trigger time.  Hitting a pressurized plastic bottle using this cap will result in a 150 decibels sonic boom that can be heard up to 2 kilometers away!

Screw this cap design on top of a regular 28mm PET disposable water, or soft drink bottle to compress the air in the bottle with an air pump needle & regular air pump. Similar in functionality to the Umarex Blast Caps.

Any air powered pellet or BB gun, airsoft, etc. or bows. that is capable of propelling a projectile to at least 125 meters per second will cause a wall puncture of a standard plastic bottle when struck. Caps are reusable.

See this video for an example of the explosion effect: Experiment: Homemade Exploding Water Bottles

Printer Settings

• Bottle Cap
  • ABS
  • 50% infill
  • 0.15mm STRUCTURAL
  • No supports
• Valve
  • FLEX (the more flexible & stretchable the better; example: Ninjaflex)
  • 100% infill
  • 0.2mm STRUCTURAL
  • Supports

Assembly

Fit the narrower part of the valve into the bottle cap hole from the bottom.  It will require a bit of effort to fit it through. Make sure it is properly seated so that it is completely through the hole & sitting flush with the top of the bottle cap.  Also, make sure the wider portion of the valve is pushed all the into the bottom of the bottle cap.  If you did it properly, the top & bottom should look like the photos shown below:

Recommended Bottle Pressure

• 50 psi for thin walled water bottles
• 80 psi for 2 liter soft drink bottles

How to Inflate

Use a bicycle tire floor pump or athletic ball hand or foot operated floor pump with a built-in pressure gauge.  Make sure that the pump can accept standard athletic ball inflator needles. 12V pumps that run off vehicle cigarette lighters can also be used as long as they have a pressure gauge.  Motorized garage/shop air compressors are not recommended.  The needle might be a little difficult to insert the first time but it should fit through if your valve material is flexible enough.  When inflating, do not exceed the recommended pressures highlighted above & follow the safety precautions listed below.

Try using a colored liquid or baking powder for additional visual effect when the bottle explodes.

Disclaimers

Misuse of a pressurized container can cause injury of death.  Make sure your read the safety precautions listed below.  By constructing & using this product, you acknowledge and accept all associated risks and responsibilities. The designer holds no responsibility for its use.

Safety Precautions

Pressurized plastic bottles can contain a sizeable amount of power.  Treat it with respect & follow these safety precautions:

• Always use safety glasses & heavy gloves when inflating the bottles;
• Do not hold the bottle or stand over the bottle when inflating; 
• Always use a netted of meshed bag, or similar enclosure when inflating the bottles in case of accidental explosion;
• Always place the bottle on the ground and on its side when inflating;
• Once pressurized, handle all bottles with care;
• It is recommended to keep the pressurized bottle at least 20 meters away from the shooter or any spectator & to always wear safety glasses.

Enjoy Responsibly!