Ping Pong Ball Launcher.
The most exciting part has come to this blog series… it’s time to build a ping pong ball launcher that will efficiently launch balls into the basket attachment located on top of the Elegoo Tumbller Robot. Welcome back to another exciting blog on the Elegoo Tumbller Self-Balancing Robot Car.
In order to complete the obstacle course and gain the marks for this design modules assignment, I was tasked to design and manufacture a device that can transfer ping pong balls to the robot as shown in the image posted below — note the size constraints in the image….this measures were initially in place but restrictions on the size of the launcher has been relaxed and we were given more creative freedom. The device should use an energy storage device that converts potential energy into kinetic energy when released (the recommended design will use pneumatic force from an inflated balloon). As with the obstacle course build I was on an extremely low budget and had to use materials that I found around the house. We were told that elements for the device can be 3D printed as needed using printers in the Parsons building in our college but I chose to challenge myself and design something with literal waste material that still exhibits a high accuracy. I owned 6 ping pong balls and I wanted to get all six in a row into the basket… challenging? Yes, but I’m up for the task. The height of “x” used was the height of a 330ml bottle of beer (coors light… as taller bottle than others).
Insted of designing a launcher on paper then going out and buying the materials, I simply collected the materials available to me first and starting making prototypes of the launcher I would use for the final product. Some designs went really well and some were simply too powerful even when scaled down. Below you can see three out of the many prototypes I made for this part of the assignment. The one on the left (prototype 1) used a plastic cup with an arrangement of rubber bands which would send a ping pong ball flying into the air. The prototype on the right (prototype 2) was way too powerful and used a combustion reaction to launch the ping pong ball… I tried scaling this prototype down to make it less powerful but to no avail. I played with different chamber sizes and different propellants but this was still a beast!! A cool creation in itself even if it wasn’t used for the assignment. The middle prototype namely prototype 3 was the design closest related to the final launcher and although the prototype wasn’t accurate at all, I knew it had potential if I just got rid of the excess movement and make it out of more robust materials….. the cornflake box wasn’t cutting it.
A closer look at the prototypes and a link to them in action:
Prototype 1 and 2
Prototype 3
Link: https://www.instagram.com/p/CN2zgnogrIX/
Final Design of Launcher:
This was based off the 2nd prototype as previously stated. It was made from a selection of random materials from coke cans and plastic cups to rubber bands, sellotape and rice cakes? Rice cakes you ask… keep reading. So basically the plastic cup had too large of an opening for precision firing so I decided to put a smaller “barrel” inside the plastic cup… this was a cut up coke can. The rice cakes along with the plastic cup provided the structural support necessary to use the flimsy allumium.
Rubber bands were implemented in a similar way to prototype two which can be seen operating in the link previously given. The rubber bands are attached to the top of the plastic red cup via sellotape. The rubber bands are stretched down and wrapped around a wooden dowel….the stretching of rubber bands is providing the potential energy for this launcher to operate. Another aluminium can had its top and bottom cut off and was also cut along the length ways. This was then curled over on itself and secured with sellotape to provide a smaller diameter that could fit inside the coke can located in the red cup. Holes were made in this second aluminium can and the wooden dowel was inserted through these holes with the rubber bands attached , as seen below. The thinking behind this is if you pull back the dowel the inner aluminium in also drawn back and when released the rubber bands pull the inner can back inside the red cup.
The launcher needs to be mounted and have the ability to be launched via one touch ie. without drawing it back and releasing it… this was implemented by attaching the launcher seen above to a stationary wooden box and a system of dowels and wooden clothes pegs were used to keep the launcher in a state where it could be launched instantaneously. The release mechanism for the launcher is the clothes peg located on the pink sticker. This peg was attached via superglue but can still open by pressing down on it, which would in turn launch the launcher.
Still concerned with accuracy I decided to add a longer barrel made from a scrap piece of pvc pipe. Woo!! We finally arrived at my final launcher design. Look at that beautiful pile of functional trash.
Launcher in action:
After having set myself the goal of getting multiple ping pong balls in a row into the basket which was to be located on top of the Tumbller robot… it was time to test and I was beyond happy with the outcome. This launcher is an aiming BEAST and gets the balls in almost everytime.
Check out my instagram video of multiple balls being fired in a row into the basket: https://www.instagram.com/p/CN3KXRZAogy/
It’s a MUST WATCH!!
In the next blog the robot will have to be programmed to complete the obstacle course and catch a ball in the allocated area before exiting the course…. It’s going to be tricky but I am hopeful I can achieve this task.
Peace and Love,
Michael.
