A Lot of Boring Work

Digging tunnels might not seem like the most cutting-edge industry, but the need for rapid and precise boring has become a recent hotbed for innovation. Most of the momentum in the space can be credited to the Boring Company, one of Elon's many "side projects." After joining the CU Hyperloop club at my school, the University of Colorado Boulder, I learned about what goes into creating a tunnel boring machine (TBM). As part of the Boring Company's Not-A-Boring competition, universities and hobbyist groups from around the world design and build a TBM with the goal of digging a tunnel the fastest. For the last competition, the tunnel had to be 30 meters long and half a meter in diameter. 

There are many aspects that go into building the machine that builds the tunnel. Our team was split into subteams such as Excavation, Soil Removal, Tunnel Support, Propulsion, and many others. I joined the team as a freshman and quickly was thrust into the design process. Our club had roughly a year to design, build, and test our machine before the competition. I took interest in the Soil Removal and Tunnel Support areas, becoming the lead for both subteams after one semester. 

When dirt is excavated by the cutting head, it has to be processed and sent to the tunnel entrance. This encompasses the Soil Removal subteam. For this competition cycle, our team decided to take the slurry approach. Water is introduced to a soil chamber directly behind the cutting head and then pumped by a sewage pump to the tunnel entrance. There was a lot of design work that I did in terms of figuring out how to integrate soil mixing and processing mechanisms. One example of this was the agitation rods attached to the back of the cutting head. Although a lot of time and effort went into the soil removal system, most of it was changed for this year's new machine due to clogging issues with the pump and large water requirements for the slurry. 

I believe my most significant contribution to the team came with my idea of implementing a continuous and flexible tunnel support system. In conventional TBMs, heavy concrete pipe sections are slowly placed into the bored dirt to support the weight of the soil. This process not only increases dig time but also is very expensive. Since our club did not have a large budget, I knew the solution had to be cost-effective. After a lot of discussion and brainstorming, I had the idea of using a "dog-tunnel" mechanism. As the TBM progresses, the tunnel support structure unfolds behind it. This allows for continuous and rapid excavation. For the to work, the support structure is held in place at the tunnel entrance by stakes. 

To keep costs low, this support structure was constructed out of heavy-duty poly-tarp and 1/2" steel rings. We made these material choices after conducting a quarter-scale centrifuge test. The test allows for a scale model to be subjected to the appropriate pressures by submerging it in a soil box and then spinning that box in a centrifuge. All the materials are kept consistent in this model, but all dimensions are scaled down by a factor of four. By doing some rough calculations, we estimated the support structure would need to handle 25 kPa of vertical pressure and 12.5 kPa of lateral pressure. To our surprise, the centrifuge test revealed an overall factor of safety of 3 (the model didn't reach failure but the centrifuge couldn't spin any faster with the given load). 

At this point, we also realized that this data was for a fully tensioned support section. Therefore, the tarp and ring segments needed to be stretched before making contact with the soil. This realization lead to the development of a release mechanism that incorporated several linear actuators along with a stepper motor-driven carriage. Essentially, the actuators would hold two rings in place while the carriage stretched them apart by traveling on a leadscrew. 

Unfortunately, financial issues caused our club not to reach an adequate budget. We didn't have funding to fully complete our TBM. But, we decided that it would still be good to conduct some tests at the competition. However, we were proud that our design proposals and technical documents submitted to the Boring Company put us into the "Digging Dozen" - 12 teams out of about 500 submissions that were invited to Las Vegas for the competition. Most teams also ran into funding issues and only one team ended up digging.

The main test we wanted to run was with the tunnel support structure. Essentially replicating digging conditions and putting a portion of the structure into the ground at an appropriate depth to stress-test it. Over the summer of 2021, the manufacturing of the support structure began. It was a back-breaking task. For our 10 meter long test segment, 1/2" steel rods needed to be bent into rings with a 0.5m internal diameter and then sewed into pockets on the tarp sections. With our funding problems, everything was done in-house. However, we were able to finish the segment in time for the competition. 

While in Vegas, I lead the efforts for conducting this stress test. First, a long sloping channel was dug by site staff to place the segment into. I designed a staking mechanism that used rebar, a plywood sheet, and several steel pieces to ensure that the support structure could be fully-tensioned while under soil load. The next issue after situating the segment was data collection. After some team brainstorming, we decided to build a sensor carriage that would be inserted into the support section and slowly pulled out with a pulley system. This system would collect one data set before soil loading and then another after loading. LIDAR and ultrasonic sensors on this carriage would record the distance to the top of the tunnel so that a deformation value could be computed. 

Although very time-consuming, the data from these tests almost perfectly aligned with our earlier centrifuge test. My support structure held up very well against the immense soil pressures and proved to be a good alternative to the conventional rigid segments. However, for this year's competition, there are some vital improvements to be made. For one, the release mechanism needs to be simplified and tested. Additionally, the problem of settlement, soil shifting after subsurface excavation, must be explored. All in all, I think that this experience was extremely valuable. As a team lead, I was honestly very surprised to see my novel, cost-effective design solution work on the first try. There is still a significant amount of work to do before the system is implemented in an actual TBM, but I think it's a pretty good start. See pictures taken throughout the competition cycle below. Click here for a cool centrifuge video. 

ANSYS FEA of Initial Tunnel Support Ring

1/4 Scale Centrifuge Model in Soil Box

Soil Box Mounted in Centrifuge with GoPro for Data Collection

Preliminary Release Mechanism Sketches

1st Iteration of Release Mechanism CAD

Tunnel Support Overview

Competition Tunnel Support Test Overview

Me (camo pants) explaining the Tunnel Support System to Boring Company Engineers

Tensioning and Staking the Tunnel Support Section

LIDAR and Ultrasonic Sensor Carriage System

RC Transmitter CAD Project

 As part of my SolidWorks CAD class, I was instructed to model an item of my choosing for the final project. I chose my drone RC transmitter. After doing some preliminary measurements and sketches, I started to realize how complicated the design actually was. There were a lot of complicated curves, fillets, and ridges in the ergonomic backplate of the controller. Additionally, I wanted the model to have functioning joysticks, so I had to create the appropriate mechanisms. My approach was to simplify everything as much as possible but still retain the key details. I decided not to model the internal electronics because I wanted my model to focus on the mechanical aspects of the design. I took the controller apart so that I could see how each component was manufactured. Furthermore, I needed to see how the joystick mechanics functioned. 

Since I'm an engineering student, I pretty much put this project off until the last week of the semester. During the three to four days that I worked on the model, my sleep schedule was pretty much nocturnal. However, after a lot of hard work and SolidWorks bugs, I finished everything in time. I'm very happy with the final product and it was cool to see the entire assembly come together. See some renders below: 

No-Sweat Biking

After realizing that skateboards are pretty damn dangerous (following my e-board build), I decided to try and make my own e-bike for the lowest amount of money possible. Although an electric skateboard may have a smaller footprint, I think that e-bikes are a lot more practical. For me, I can actually ride a bike around town without getting thrown off when the smallest of pebbles get lodged under the wheel. Additionally, the area behind the rider on a bike can be used for extra storage. 

There are a multitude of electric conversion kits for standalone bikes, but most overcharge for basic components that can be found off the shelf for lower prices. An e-bike is extremely simple. The whole system consists of a motor, battery, motor controller, and other input devices (throttle, brakes). My first decision was about which motor type I wanted to use. In general, the two main motor variants are front/rear hub and center drive. To minimize cost, I decided on a front hub motor. Although not the most powerful, a front hub is the easiest to integrate (no need to modify pedals or gears). After browsing around on eBay, Amazon, sketchy Chinese sites, Craigslist and Facebook Marketplace, I found someone selling a used e-bike kit for a lot lower than market value. The setup included a 36V 350W front hub motor, motor controller, and various accessories such as a twist throttle and e-brakes. In hindsight, I would've liked a slightly more powerful motor, but it still works well for cruising around town (for reference, 72V 1000W motors are essentially the high end of the motor spectrum in terms of power). 

Next, I started thinking of the battery setup. I knew that I needed a pack to suit the motor: supplying a nominal voltage of 36V and an amperage of around 9-10A (350W/36V). From experience building drones and model airplanes, my first choice was a lithium polymer battery. Although widely available, these batteries tend to get expensive when it comes to voltages as high as 36V (most drones run anywhere from 7 to 20ish volts). Also, LiPo batteries tend to wear quickly after many discharge/charge cycles. Because of these factors, I decided to use 18650 (18mm diameter, 65mm long, 0 for circular shape) lithium-ion batteries. These look like larger AA cells and can be found in most older laptops. Even Tesla uses li-ion batteries in their cars (although not 18650s specifically). Depending on the manufacturer, 18650 cells can last a long time and deliver a large capacity in a relatively small package. 

As I soon realized, 18650s aren't the cheapest batteries. That's when I made the decision to harvest old laptop batteries. While this can be dangerous (old cells typically aren't safest), you'd be surprised at how many perfect cells can be recovered. The only real downside with using these recycled batteries is the time it takes to check each cell. I also found it hard to get my hands on old laptop batteries as most people I knew had thrown their computers out (except my grandparents, where I got the majority of cells). After deciding on a battery layout consisting of 50 cells, a 10s5p setup, I began the long process of acquiring the cells. For the pack design, 10s5p means that there are 10 cells in series (3.6V nominal voltage of 18650s x 10 = 36V and 2000mAH capacity x 5 = 10AH - most smartphones are around 2-3AH). To test each cell, I used my drone battery charger to charge and discharge the batteries. I removed any cells that started to overheat during the process and also observed the cell voltages following charging after multiple days to make sure the batteries held their voltage. I also purchased a BMS (battery management system) that would allow me to charge the cells safely and make sure none of them burnt out. Most li-on packs are assembled using nickel strips and a spot welder to make connections. Without a spot welder and a large budget, however, I decided to use a pack assembly kit. The kit was made up of plastic battery holders with screw threads at the terminal ends so that cells could be connected by bridging these threads with nickel strips (and securing them with small bolts). Following a long process of building and checking connections (nearly ruining the whole setup by shorting two cells with a screwdriver), I wrapped the pack in several layers of foam and finished the whole thing off with some gigantic heat shrink tubing. 

Ironically, the bike was the last part of this build that I got. I managed to pick up a decent hybrid for free from a friend that was moving. After testing all the electronics, I started mounting them on the bike. I noticed how the provided e-brakes not only clamped down on the wheels when triggered but also sent a signal to the motor controller to stop the motor. Although the wires running along the frame gave it away, the front hub blended in perfectly. I rode the setup around my neighborhood and got up to 15-20 mph with minimal pedaling. Following some cable management and minor modifications, I started going on longer rides for range testing. I managed to go about 20 miles with not much physical exertion and still had about 25% battery left (voltage in this battery goes from 42V fully charged to 30V completely drained). So far, I've had no major problems with this build and it works perfectly to get around campus (surprisingly, I still have some in-person classes in the age of Zoom). The only real negatives come mostly with the bike itself. The caliper brakes aren't the best (looking to switch to disc later) and the gears don't change very fast. Other than that, the battery is a bit heavy but does provide significant range. 

In the future, I may swap in a more powerful motor, improve the braking situation, add more weatherproofing, and attach a key-start system. Not to mention, the cheap charger I bought doesn't really display charge percentage/rate so it's slightly inconvenient. Also, I had an idea to add a generator to the pedals so I could charge the battery when pedaling (although there might be too much resistance/weight). Overall, this project went a lot better than I expected and I'm genuinely satisfied with the final outcome. See pictures below. 

Motor Controller mounted below the seat

Integrated Motor in Wheel Hub

Fully sealed Custom Battery 

A Smart Garage Door

Instead of acting like a normal person and just placing a spare key outside my house for the times that I get locked out, I decided to make my garage door "smart." By that, I mean integrating it with an Arduino-controlled motor relay hooked up to a server via WiFi. I had an old Arduino Uno sitting around and decided to put it to use. All I needed to link the Arduino and my garage door together was a motor relay. A relay basically acts as a switch that can open and close a circuit when instructed to by a microcontroller or some other device. I discovered a free Internet-of-Things service for these types of projects called Blynk. The service provides pre-written Arduino code and an ecosystem for controlling the whole thing with a smartphone app. After loading up some of the sample code and hooking the relay up, I followed the simple steps for setting up the Blynk app and attempted to test my over-engineered garage door opener. With my phone connected to a network, as soon as I pressed the button in the Blynk app, I could hear the clicking sound of the relay opening and closing. Next, I found an enclosure for the Arduino and relay while also running wires from my garage door motor. After doing some cable-management and putting the wires in their correct locations, I tried opening my garage door from the app. On the first try, the door opened, but as soon as I released the virtual button the door shut immediately. In the Blynk app, I changed the button to a switch, so it could remain open without constant pressure. This change worked and marked the end of this project. I also discovered later that Blynk has its own cloud server, meaning that you don't have to be connected to your home's network to open the garage door. Theoretically, I can open my garage door from across the world, assuming I have some sort of connection. Recently, I also found out (around 2am) that when power is cut to the Arduino, it closes the relay, triggering the garage door to open. That's really the only problem with this project so far. See pictures below. 

Control UX

Relay Connected to Arduino Board

Component Enclosure

Relay Wires Connected to Existing Opener

Laptop Surgery

Oftentimes when a piece of technology breaks, people throw it away or never use it again. I've done this before, especially with old smartphones. While cleaning my room, I found an old laptop that I used in middle school. At the time I used it, around 2015, it was new. It's an Asus Transformer Book T1000 with a detachable keyboard. Perfectly usable today, albeit slightly slow. The screen is cracked in the corner, but the actual LCD panel functions properly. I realized that I had stopped using this laptop because the power button broke. It couldn't be turned on. I decided to take apart the Transformer Book the find the root of the problem. After removing the back plastic cover on the tablet portion, I located the circuit board for the power button. The internal button had snapped off, leaving only a metal contact on the board. With the cover off, I used my screwdriver to short the contact, resulting in the normal boot-up sequence. The power button board simply had a few screws to secure it and a standard ribbon cable to connect it to the motherboard. I searched eBay for a replacement power button board and found one for around $10. Once it arrived, the repair procedure was basic. Everything worked like new. As technology has become more advanced, it has also become less repairable. Companies like Apple have long restricted consumers from taking apart their devices for repair. The idea of planned obsolescence (tech intentionally made to require a replacement) has only spread. The tech industry, with many parallels to the automotive industry, isn't favoring the true enthusiast anymore. For example, if my laptop was a newer MacBook, it would've been a lot harder to find a power button module on eBay. To achieve a sleeker form factor, companies have opted to solder components directly to the motherboard and adopt proprietary designs. This recent trend is not only detrimental to the wallets of consumers in the case of a repair, but also to the environment. The life cycle of technology is decreasing, resulting in more waste. It's probably too late now, but tech companies should begin to support the tinkerer. 

Mousetrap Powered Vehicle Challenge

In a recent project in my physics class, our teacher instructed us to build a mousetrap powered vehicle that can travel at least one meter off of a table. We were only allowed to use basic materials and all the vehicle's power had to come from a mousetrap. The hard part about this project was finding a design. Most high school mousetrap car projects focus on a simpler distance-based challenge, where students build vehicles that can travel for the most distance. There are plenty of these distance designs on the Internet, but not many for the table style challenge. Instead of building a traditional mousetrap car, I wanted to do something different. I felt that a regular car would either break on impact with the ground or have a hard time maintaining momentum after the drop from the table. In my design process, I attempted to come up with the simplest design I could that had the lowest amount of moving parts. In the end, I came up with the idea to attach a mousetrap to the bottom of a ball and basically just launch it off the edge of the table. The potential energy stored in the mousetrap would be used to make the ball jump off the table where it would roll on the ground. I settled on using a ball made of floral foam that I bought at Target. The foam was stiff but easy to cut with a knife. I first began carving out space for the mousetrap to sit in. The difficult part about this process was making sure that the mousetrap was fairly flush with the ball so that the roll wouldn't be affected too much. It took some sanding to get the perfect fit. Next, I used superglue to secure the mousetrap. I tested my contraption at school the next day. It worked pretty well, but on my last test run, the mousetrap fell out of the ball. I decided to add some hot glue along with applying more super glue. Additionally, I applied a lot of duct tape around the circumference of the ball to make sure the mousetrap never popped out again. I did some more testing and my revisions seemed to have been successful. On the actual day of the competition, my ball went about 2.5 meters (measured from the edge of the table to the closest side of the ball). Most people in my class were surprised to see a foam ball brought into class when they had all built traditional mousetrap cars. Click here for photos.

 

A Look Back

Many years ago, when I was around 11 years old, I embarked on my first real DIY project. This was before any drones, 3D printing, or anything else. My cousin, two years older than me, had come to the U.S from India. It was the middle of summer and both of were extremely bored. After seeing a video from the Make Magazine Youtube channel about a compressed air rocket, we decided to try and build it (many other DIY Youtube channels have done this same project since). The design seemed simple enough - a PVC pipe air chamber with a bicycle tire valve using a sprinkler pipe electronic valve controller to release the air pressure and a small projectile. Using the video as a guide, my cousin and I took a trip to our local Home Depot and purchased everything we needed. Our PVC pipes weren't the same size as those in the video, but we figured that the whole thing would be fine. We also found some scrap wood to construct a structure around the PVC components to support the whole thing. Building the frame and installing the valve controller were the easy parts of the project, but adding the bicycle tire valve and actually switching the valve controller on and off were some of the challenges we encountered. I had an old bike tire that I used to get the valve. It took some time to find a proper adhesive to make the tire valve-PVC connection airtight. We settled on using JB Weld to secure the tire valve to the PVC pipe after drilling a hole. Next, we focused on controlling the sprinkler valve. There were no switches or anything else included in the box, so we had to improvise. After searching the garage for some time, we found an old light switch and decided to use it. To power the whole circuit, we used a 9V battery. Wiring the whole setup took a while, as I didn't have a soldering iron (and I didn't know how to solder) and I wasn't too familiar with electronics at the time. After making sure the PVC was airtight and the valve controller functioned correctly, my cousin and I worked on making a projectile. We carved a wooden dowel into a torpedo-like shape and sanded it a bit. Some duct tape was added to the mid-section to make sure that it fit snugly into the top of the PVC launching pipe. To fill the air chamber up, we simply hooked up a bike pump to the tire valve and pumped until the pressure was around 60 psi. Surprisingly, the first time we launched the projectile, everything went as planned. The wooden rocket shot up extremely fast, maybe to around 100-200 feet. This project really motivated me to try others and was essentially my introduction to the DIY space. I actually made a video about this compressed air rocket around the time I built it. Click here to watch it (keep in mind that it was filmed on an iPhone 4 and edited on iMovie by an 11 year old).