This page documents some miscellaneous engineering projects and reports that I've completed as a student at UW that do not quite fall under "Work" or "Research". Nonetheless, I hope they can convey some of my engineering experience and abilities.

 

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Senior Design Capstone Project - "Wyoming Wheels"

Wyoming Wheels 2.0 prototype

Project Background

Like most ABET accredited programs, the pinnacle of the mechanical engineering curriculum at the University of Wyoming consists of a senior design capstone project. This is an intensive, year long project where mechanical engineering students (usually in groups of 4) identify a problem and propose a unique product or design that they would like to develop as a solution. Then, with only minimal help from engineering faculty, the students must follow all necessary stages of the engineering design process to bring their invention to life (i.e. planning, budgeting, detailed calculations, prototyping, machining, testing, etc.) The final deliverables of the project include a comprehensive report of all aspects of the project as well a presentation at UW's annual Undergraduate Research Day.

At the start of my senior year in the fall of 2017, I formed a team with 3 excellent classmates - Nick Staiano, Matt Jones, and Jacob Porter. The four of us received a special opportunity to continue a project that had been started by a group of seniors the previous year. This was because two of the original group members - James Francis and Nick Reh - had won funding through the UW Fisher Innovation Challenge and were seeking to form a startup company for their product. They decided it would be beneficial to employ the help of another senior design group to design and develop an improved prototype (free labor for them, and a well established project with clear objectives and "corporate sponsors" for us). Thus, our project dubbed "Wyoming Wheels 2.0" was born.

What is Wyoming Wheels?

The traditional design of a wheelchair has, unfortunately, not changed much since it's invention (i.e. the mid-1600's). This design generally gets the job done, but it often lacks key ergonomic considerations. Specifically, many wheelchair users ultimately suffer from severe injuries to their shoulders and wrist since their wheelchairs require these parts of their body to do all the work. Wyoming Wheels is therefore a geared, lever-action, manual wheelchair system designed to mitigate these types of injuries. It allows for wheelchair users with functional upper body strength to instead engage muscles in their core, chest, and arms, rather than relying on more vulnerable muscles in their wrists and shoulders. This also simultaneously allows for wheelchair users to travel faster, farther, and up steeper inclines.

 

The core design consists of vertical levers which allow the user to power the rotation of the wheels. A planetary gear system, coupled with a 3-speed internally geared hub, provides the user with the option to easily shift between various advantageous gearing ratios. Brakes with traditional bicycle controls were also implemented into the handle, ensuring that the user can also safely slow down. This means that the Wyoming Wheels system consists only of the wheels and it's attached gearing, levers, and controls - not the chair itself. Therefore this system could be implemented to any existing wheelchair with universal wheel fittings. 

James Francis demonstrating the original prototype

As previously mentioned, the original proof of concept for this design was originally developed by a group of senior engineering students in the previous year. Their prototype was functional and successfully conveyed the concept of the design. However, it was largely overbuilt and desperately needed to be optimized. One of the major concerns was that the original gearing system was cut out of solid steel, resulting in an extremely heavy system (about 70 pounds in total!) The design's ratcheting system at the planetary gear interface was also extremely noisy. It was also desired to choose more advantageous gearing ratios and to generally make the system less intrusive.

Our group ultimately met all of these goals. An optimized version of the Wyoming Wheels prototype was successfully developed. The overall weight of the prototype was reduced by 40%. The noise of the gearing system was reduced to that of an ordinary bicycle. More productive gearing ratios were implemented. The braking system and overall safety of the chair was improved. A default neutral capability was implemented, allowing the user to seamlessly switch between using the Wyoming Wheels system or reverting back to grabbing the wheels directly.

My Role in the Project

To some degree, my group members and I largely collaborated on all aspects of this project. However, one component of the design that I was largely responsible for was the planetary gear system. The 2.0 version of the Wyoming Wheels system implemented an internally geared 3-speed bicycle hub to address many of the project goals simultaneously (i.e. it includes built-in gearing and braking in a lightweight, compact, low-noise package.) However, a planetary gear system was still necessary for two main reasons. The first was to increase the overall gearing ratio of the system. The gearing ratios of the internal hub were simply too low for this application, but they were effectively multiplied when connected in series with the planetary gears. The second reason was to allow for a way to easily engage and disengage from all gearing to allow for the default manual option. The planetary design accomplishes this by allowing for a two-way pawl attached to the vertical lever to engage and disengage the outer edge of the ring gear, accord to the user's control on the upper handle.

I used SolidWorks to design this gearing system. The figure below shows the design of the planetary gear system. The sprocket of the internally geared bicycle hub replaces the sun gear. Two layers of planet gears are necessary to ensure that the ring gear and sun gear / sprocket rotate in the same direction. The following clip shows this design in SolidWorks, complete with accurate gear mates.

Planetary gear system design

SolidWorks model of the planetary gear system 

The planetary gear system was built using Delrin plastic. Delrin is an acetal polymer used for many gearing applications due to it's self-lubricating abilities and high resistance to wear. It also exhibits a large tensile strength relative to most plastics, and is less than half as dense as aluminum 6061 - a critical property with respect to our weight reduction objective. Traditional low-friction skateboard bearings were used on each planet gear.

All gears were cut-out on an industrial water jet. I learned how to use a lathe in order to machine custom, press-fit pins that were used to attach the planet gears to the planet carrier. I also learned how to use a 3D printer to create custom tabs that were used to mount the ring gear to the carrier. The sun gear was also a custom 3D printed creation, such that it could fit the planetary system and still act as the sprocket for the internal hub.

Front and rear view of the planetary gear system

Final Deliverables

This project resulted in a complete working prototype which was delivered to the original project sponsors. A comprehensive report detailing all aspects of the project was also produced. For more information about this project beyond the limited summary provided on this page, please consider viewing this report. A copy of this report can be found on the online University of Wyoming Repository here: https://repository.uwyo.edu/honors_theses_17-18/40/, or, a direct download can be started by clicking this link:

This project also served as my senior capstone project requirement for the UW Honors Program minor. Therefore I presented this project individually at the 2018 University of Wyoming Undergraduate Research Day. A video of my presentation is embedded below. Jump to 8:50 for a brief demonstration of the wheel.

Wyoming Wheels presentation at Undergraduate Research Day 

 

Automatic Graduation Cap

“Normal people believe that if it ain’t broke, don’t fix it. Engineers believe that if it ain’t broke, it doesn’t have enough features yet.” - Scott Adams

Automatic Graduation Cap

This was a fun little project I put together before my undergraduate commencement ceremony in December 2018. I had attended UW's commencement ceremony during previous semesters and noticed that among the many graduating students that elected to decorate or personalize their mortarboard, engineering students were significantly underrepresented. I deemed this unacceptable and decided to put a bit of an engineering touch on my graduation cap.

I designed and built a system that would automatically advance my tassel from the right side of my cap to the left, signifying my graduated status, just by pressing a button from a small wireless remote. I also threw in a few LEDs and an LCD message board to add a bit of flare and to announce my graduation status in an abundantly clear fashion (I would recommend some pyrotechnics for anyone investing a 2.0 model).

 

An Arduino Uno handled all of the necessary logic. An IR sensor was mounted at the edge of the cap to receive signals from the remote. The brightness of the LCD backlight could be adjusted using a rotating potentiometer. A small servomotor was responsible for advancing the tassel, which was fed through a short length of 1/4" PVC pipe (Lesson #1of Statics: you can't push a rope.) A manual push button was also added on a small secondary breadboard. This allowed for the the tassel to be advanced "manually" (but still in dramatic fashion) in the event that a critical failure of the wireless remote were to occur. The entire system was powered with one 9V battery. The second battery that can be seen mounted on the cap was something between a convenient backup, and a necessary counterweight to keep the cap balanced. 

I worked on this project individually, meaning I wrote all of the code, designed all of the circuits, and built the final product myself. However, the idea itself was not 100% original, as I had taken some inspiration from a number of other "tassel moving machines" that I had seen online. I hope my design can also act as inspiration for anyone else considering a similar project. I've included my Arduino code (i.e. C++) as a .txt file in the link below. Please feel free to contact me if you have any other questions about the wiring or hardware I used.

Finally, the best part of this project is that it worked! The video embedded below shows a brief demo of the cap as well as my flawless execution during the big moment. 

Automatic graduation cap demonstration

 

Compiled Course Work

Naturally, I've worked on many projects during my time as an engineering student at the University of Wyoming. Below is a compilation of several key reports that I've completed, both individually and with groups of my peers. I hope that sharing these examples can further demonstrate my writing skills, graduate-level engineering student experience, and the wide range of coursework that I have completed. 

Click any of the links below to view the corresponding PDF:

© 2020 David J. Tobin