Ping Pong Launcher Final Version
Hi everyone and welcome back to the blog! This week I will present to you the final version of my ping pong ball launcher. I have made two previous posts in relation to this launcher showing my design principles and prototypes so if you haven’t already I would highly suggest you check them out first. This version of the launcher will be used in the obstacle course and later down the line I will hope to implement it into a Rube Goldberg Machine assignment.
As you saw from the videos in the last launcher blog, my design was very capable and could land a ping pong ball in a 120x80mm basket. So what improvements were made to the prototype you may ask? Well I missed out on one final rule in my previous design which only allowed for the energy source to be triggered once and only once, instead of my design where I had to trigger the springs after each shot. Therefore I redesigned my launcher from a spring propelled device to a pneumatic propelled device. To do this I took inspiration from a paintball gun which also uses pneumatics.
As can be seen from the picture above the paintball marker has a compressed air cylinder at the rear and a reloading device on the top. I tried to incorporate these design cues into my prototype. Therefore instead of springs and a moving cylinder at the rear of my firing tube I used an air propulsion device, which comes in the form of a household hair dryer. I attached it to the rear of my launcher using tape to create an air-tight seal. Just take a look at the final design below!
I did encounter a major problem when I switched from using springs to pneumatics, namely the automatic reloading design from previous prototypes didn’t work anymore at first. This was because as the air was being pushed in from the rear of the tube, it was coming out from the top of the T-piece and the front of the tube. Obviously as the air was being forced out of the T-piece it would push balls out with it. To combat this I decided to make a container for the ping pong balls on top of the T-piece which would be closed off and not subject to atmospheric pressure. Therefore the only low pressure zone would be at the front of the firing tube and the ping pong balls would in fact get sucked into the firing chamber with this design. Now that the first prototype design is complete lets test it out!
— Update 13/04/21 —
So I know that I previously said that the design above was the final one however I missed out on a pretty significant fact that my propelling device must use potential energy. Seeing as my hair dryer was pulling electricity from the mains this was not good news, despite that I got some very helpful info on ways to convert this setup to be rule-compliant from my professor. I swiftly got my hands on a electrical potential energy supply, or more commonly known as a battery. The only problem now was that the hair dryer was adapted for AC use whereas we all know that a battery provides DC electricity. To combat this I decided to take the hair dryer apart, bypass the transformer inside and connect the battery directly to the fan.
As the hair dryer was taken apart I realised this was an incredibly simple machine consisting of just a fan and a resistive heating element, which were turned on by a switch. I had to break existing solders on the positive and negative terminal of the fan and then I attached my own wires with the correct terminals. (I know red and black are supposed to be used but student budget eh)
I then proceeded to assemble the hair dryer together again, without the heating element this time. I considered attaching the fan directly to the launcher without the body of the hair dryer however there were two advantages to using the assembled body again. The first one was the fact that the fan diameter was larger than the firing tubes diameter in the launcher, therefore making an airtight seal would be more challenging. Whereas the front of the hair dryer has a smaller diameter than the firing tube which means it can easily be inserted to fit. Secondly the body protects the ping pong balls from rolling back in the firing tube and hitting the fan.
The electricity would not constantly be on but would have to be turned on. This was a safety concern as I couldn’t just hold a bare wire to the end of a battery terminal. To make this design safe to use with a live car battery I had to incorporate a switch. I decided to use the switch that was already in use on this hair dryer. To add some finishing touches I made a switch panel out of cardboard so that the switch would be easily accessible. Now that all components were assembled and safe to use I attached the hair dryer back onto the firing tube and just look at the final (I promise this is final final) design! Not only that of course we had to test it out as well.
Now please excuse my messy room and of course the accuracy will be fine tuned to land all/most balls in the basket. For now I hope you enjoyed the conclusion of my launcher and are looking forward to seeing it in action in the future. If you like the type of content on my blog please consider following me for similar posts every week!
