As mentioned in a previous blog I decided to create a pneumatically powered ping pong ball launcher. This ping pong ball launcher had to create kinetic energy from a store of potential energy. The design I went for was a top feed magazine design that could hold up to 15 balls.
This launcher operates using Bernulli’s principle. This means that the fast moving air in the barrel of the launcher will create an area of low pressure in the magazine thus making the launcher self reloading. In fact the area of low pressure creates such a suction force that the launcher can reload while being held upside down.
As discussed in a previous blog my barrel and magazine were constructed out of a heavy pvc tube with an internal diameter of 40mm. This is the closest fit to the ping pong balls diameter of 38mm. Ideally to make the two pipes join I would have used a pre-made 90 degree T piece however there were none available for this gauge of pipe. I therefore decided to cope the pipes together I did this using a combination of an angle grinder and a box knife. This allowed me to achieve a snug fit between the two pipes.
To attach the pipes to one another I used a two part epoxy commonly referred to as plastic welding this gave a smooth strong joint to the two pipes and allowed the balls to move smoothly between the two pipes. Next I capped off the back using the lid of a 20 litre oil drum and a sizeable amount of Tech7 silicon. At the base of this cap I drilled a hole that allowed the nozzle of the air gun to fit in. I taped the trigger of the air gun in the open position. Then using a small metal bar and a some elastic bands I built a trigger mechanism for the launcher this allows me to fire the balls at my own discretion.
I then used some scrap metal and my arc welder to create a stout and sturdy base for the launcher that would allow adjustment of firing angle
To power the device I am filling the tank of a old air compressor to 50psi and the connecting it to the air gun to give a constant flow of high pressure air.
After using my design I would make small modifications to the design to make the device more accurate. Firstly I would try premium ping pong balls as the ones I was using had many imperfection causing unpredictable flight paths. I would also try to use a tighter barrel tube so that the ball had less movement when being propelled. Another aspect I would like to explore would be electronic reloading as I feel this would be a fun addition to the project however with time constraints and other college work this was not possible. Lastly i would like to fit the launcher with a pressure regulator as it was very hard to keep a constant air pressure in the system.
