Ethan's Clock Project Page

Objectives

One of the most important demonstrations of the engineering design process included in the COSMOS Cluster 2 Curriculum is the design, fabrication, and mathematical predictions of a pendulum clock powered by an escapement wheel turned by a weight spooled to the axle. The design of the pendulum is created using Fusion 360, before the files are imported into AutoCAD and analyzed in WM2D (Working Model 2D). The base of the pendulum is created through the machining of over a dozen parts together into an equally robust and elegant base for the pendulum to attach to. Lastly, mathematical and kinematic analyzes were made in an attempt to predict and simulate components such as the center of gravity, inertial force of the pendulum, and the period of the pendulum.

Through the challenging, yet education process of completing the clock project at the ending of the first week of COSMOS Cluster 2, students are able to master critical engineering skills in a variety of disciplines. This includes a comprehensive understanding of the fabrication process, as well as the use of equipment such as the drill press, the arbor press, and the handheld drill, among others. This provides valuable experience in the workings of a true machine shop, while allowing for students to learn, explore, and fail safely. In addition to the physical machining of parts, members develop a strong command of Fusion 360, as well as AutoCAD though the design and creation of the pendulum. Through the process of working on the aforementioned programs, students are given the opportunity to design a pendulum and express individual creativity through engineering design. The final aspect of the Cluster 2 Clock Project includes the calculation and simulation of the properties of the pendulum, which are compared with the properties of the manufactured pendulum. This is done to educate members on the kinematic principles that govern the movement of pendulums, and provide a strong mathematical basis for the movement of the pendulum.

LazerCam Hyperlapse.mp4

Hyperlapse of the LazerCam cutting and scoring process for the ship pendulum piece. Notice the deep lines etched into the acrylic board, which are cutting, rather than scoring lines used for detailing the item. As a result, the board was reduced to a pile of acrylic scrap and the end of the process, and a new pendulum was needed.

Failed attempt to drill the holes of the correct diameter and location into the escapement wheel. While the central hole, which would connect with the short shaft was able to attach and was in the correct location, the drilling of the hole to the right would likely result in the acrylic escapement wheel cracking at center.

Exported Fusion360 file of the ship pendulum with etching lines highlighted. Notice the large number of lines that would need to be traced and edited in AudoCAD, as well as the overlap on the railings by the bridge and above the bow deck of the ship.

Working Pendulum IV.avi

Early attempt at exporting a successful pendulum swing simulation for upload onto the google site. As a result of a cause still unknown, the video was made entirely unusable due to an error in uploading, despite the sucessfull export of 2 previous test videos.

Project Challenges

Notwithstanding the deep exposure and practical experience gained from the swift pace of the Clock Project, errors or varying severity in almost every engineering discipline were also committed as a consequence of the rapidity of the program. The following have been documented to illustrate the challenges and solutions encountered throughout the week in the pursuit completing the clock project.

Machining and Physical Fabrication

Errors concerning the alignment of the prick punch when preparing to drill a hole to fit the upright piece would result in a prick that was slightly skewed above the hole of the upright. This was compounded with the use of the center punch, with the final drilling revealing the error in location of the holes. In order to remedy the misalignment of the holes, which were originally drilled with an 8-32 drill bit, a 10-32 drill bit was then used to widen the existing pair of holes, allowing for the screw to fit through them without risking damage or a crooked it. While the solution creates space between sections of the screw and the plate, the tension from the attachment of the screw to the plate will hold the fabricated piece together.

In addition to the errors in the construction of the pendulum, the switching of layers in the LazerCam machine, as outlined in the challenges section, resulted in the scoring on the escapement wheel simply becoming etching. As a result, an attempt was instead made to manually bore the 0.25" and 0.079" holes by hand. As illustrated in the image on the left, these holes would not have functions on the pendulum due to their gross misalignment, and a new escapement wheel was made on the LazerCam.

Fusion 360 and AutoCAD Software

In the design of the Pendulum shape and etching in Fusion 360, a boat was chosen to the similarities between the rocking motion of the waves and that of an oceangoing vessel. While aesthetically pleasing, the extreme amount of detail on the pendulum resulted in a technically challenging design process. The hundreds of lines used to create the appearance of the bow of a ship on a 2D surface resulted in dozens of cases of overlapping lines, disconnected sections of CAD, and predicted lazering issues in AudoCad. The latter proved the most difficult to overcome, and many cutting lines were discovered to run through the structure of the ship, which required large amounts of time and effort to be directed into cleaning up the lines and ensuring new overlapping.

Analysis and Pendulum Simulations

Despite the use of only straight lines in the creation of the design in hopes of alleviating the issue, the design of the ship failed to correctly load into WM2D. Connection issues concerning the overlap of lines resulted in the software not accepting the imported file. In order to address the inability to correctly upload the file into the program, the outline of the ship was retraced and simulated. While the outline closely followed that of the one created in Fusion 360, the absence of the smaller holes, and more fine details of the design resulted in a skewed analysis from the WM2D software.

Outcomes

Give a summary of the most important outcomes, This may include a picture of your design and a summary of your analysis. A side-by-side comparison of a movie of your Working Model 2D simulation and your actual clock would be good to include here.

Working Video.avi

Working Model 2D

tty.mp4

Physical Pendulum Clock

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