Senior Design Project: Multi-Sport Ball Launcher
As part of the locomotion sub-team of New York University’s Tandon School of Engineering Robotic Design Team, the goal every season is to design and construct the manner in which the robot will traverse the environment. One of ideas proposed for the 2021-2022 season was a screw tank, and I wanted to understand the feasibility of this design approach.
Given the nature of the design and the manufacturing constraints of a school engineering team, I assumed certain materials and manufacturing methods that I incorporated into my analysis. Since this design would be operating in a mixture of sand and rocks, I decided to assume a material of hardened steel since it has the least abrasion to sand (according to this resource: https://nvlpubs.nist.gov/nistpubs/jres/5/jresv5n3p553_A2b.pdf). Additionally, I concluded that the most cost-effective and simplest solution for this design, was to use sheets of hardened steel to construct the screw cylinders and its threads by wielding them together.
After graphing the equation for necessary torque with respect to the angle of the thread, and with conservative constraints (I set the maximum diameter of each screw to total 0.5 meters, the largest allowable width of the robot), the lowest torque required to overcome the weight of the robot was found to be at a thread angle of approximately 73.6 degrees, to be 0.94 ft-lbs.
Overall, there was an increasing trend of smaller required torques for higher thread angles. This was expected because the smaller the thread angle, the lower the pitch (the distance between thread tips), which means that the number of threads on the screw will increase, putting less force and stress on each individual thread.
However, because the number of threads on the screw has increased, the screw must rotate more, to go travel the same distance as a screw with less threads. As a result, a motor with a relatively high RPM would be required for this configuration. More interesting however, was if the diameter of the screw decreases, then the required torque will also decrease, but the output torque will be larger than a screw with a larger diameter because of its higher mechanical advantage.
Unfortunately, at an all-team meeting this design proposal was discontinued in favor of redesigning the traditional locomotion wheels, given the familiarity of its cost-effectiveness and manufacturability, and its ease of integration with the other subsystems.
The Turner’s Cube is a machinist exercise to learn how to mill using a CNC machine. The Turner’s Cube is essentially an illusion of a cube within a cube. I thought it was an interesting piece of metal to learn how to make, and I also wanted to familiarize myself with the practicalities of a CNC machine.
The process first started in the CAD software SolidWorks, to initially design and configure the dimensions of a typical Turner’s Cube. The cube overall was 2 inches in length, width, and height. The holes needed to be cut at varying depths, so starting from the surface of the stock material they were, from the shallowest to the deepest, respectively: 1/3 in, 2/3 in, and 1 in. The diameters of each hole varied as well, so similarly, starting at the top of the stock, from largest to smallest, those dimensions were: 1.6 in, 0.8 in, and 0.3 in.
Then, the CAM feature of Fusion360 was used to export a file written in gcode, a language that the CNC machine will need to actually mill the Turner’s Cube from aluminum, the most practical metal to machine as it is relatively “softer” than other metals.
All that was left was to actually mill the aluminum stock until it was the finished cube you see below.
Although, Christopher Nolan’s Inception first premiered slightly over 11 years ago, the movie’s premise and atmosphere are still so incredibly refreshing to watch. Anyone who has seen this film knows that its mood is a perpetually toilsome attempt to organize what is reality and what is not. Central to this idea is the “totem”, a failsafe method to prove if one is in a dream or not. The main character, Cobb, uses his totem the most throughout the movie: a spinning metal top. If it bizarrely continues to spin indefinitely, then it means that one is in a dream but if it wobbles and falls, it means that one is in reality.
After searching the internet far and wide, I was unable to find much on any specific dimensions for the top publicly available without actually buying it and measuring it myself. As a result, I had to rely on various images from the film and actual replicas to gauge the dimensions by eye and the dimensions from online retailers.
With the complied images above, I decided to sketch the profile of the top by hand and to set the principal dimensions.
After sketching the top, I constructed it using the CAD software SolidWorks according to the proposed dimensions and then sent the file to be 3D printed out of clear resin so I could see if the dimensions were sufficient enough before being made out of metal.
Since the beginning of last spring I’ve found myself spending a lot of my newfound free time messing around with the different puzzles and games collecting dust in some forgotten corner of my house. I especially enjoyed playing with my old Rubik’s cube, one that I never bothered to actually solve since I was 13. Slowly, over time, it became a pleasant obsession of mine, a relaxing portion of the day I indulged in between class calls and at the end of lecture.
It inspired me to create my own version of a modernized Rubik’s cube that could serve equally as a decorative ornament and more challenging puzzle.
To turn a plastic toy into a double-functioning modern ornament, I determined that I needed to choose a set materials that would be most likely found in any contemporary office or home setting: wood and metal.
I decided on an entirely metal cube because its texture differed the most from plastic and would be highlighted the greatest against most traditionally wooden furniture.
Initially, I considered using different metals to simulate the traditional cube colors, but that also would have been relatively costly and time consuming. As a result, I decided to go with aluminum because it is the most cost effective material and is “softer” than most other metals, making it easier to manufacture and fabricate. I then thought about spray painting the metal or anodizing it, but both techniques felt it would detract from the experience of the cube, so I went with something else.
I decided to instead, engrave the metal faces of the cube and initially considered engraving different designs on each cublet, but finally settled on a engraving each face of the cube with an eight word phrase from authors/musicians/people, whose books/talks/music I read/listened to during my time in school thus far.
These were those decided phrases and some of their paraphrased versions:
Go all the way, otherwise, don’t even start.Charles Bukowski
Empty your mind, be formless. Shapeless. Like water.Bruce Lee
Don’t gain the world and lose your soul…Bob Marley
What stands in the way, becomes the way.Marcus Aurelius
Have the courage…to engage in unconventional living.Alex Supertramp
Your life is what your thoughts make it.Confucius
Through a combination of online resources (https://homes.luddy.indiana.edu/stsher/files/Rubiks_Cube.pdf, http://lulabs.net/machining/ss-cube/) and my own measurements, I was able to design each component within SolidWorks and then prototype it from PLA material on an Ultimaker 3D printer.