Pocket Prototyping
In engineering we frequently have questions to which we’d like practical answers to keep us moving forward. If a simple prototype will do, don’t forget to look in your pocket, your home, your lab, your hobbies, or just down the street.
In your Pocket
“Dad, what did you do to your cell phone?” My daughter's inquisitive eye gravitated to the small colorful bricks scattered across my desk surrounding an unusual contraption; a cell phone embedded in a four-wheeled Lego® cart with camera pointing up, and curious mirrors surrounding the lens. “Our well-drilling customer,” I responded, “needs to inspect their drill-pipe between each use.”
“Drill-pipe? Really? So, what are the little mirrors for?”
“I found them at the craft store. They split up the photograph into several quadrants so that each image frame captures the full circumference inside the pipe.”
“Cool, Dad. Isn’t it dark in the pipe? How will you propel the cart through the pipe?”
I’ll get back to this scene in a moment. First, I love the prototyping journey inside and through the pipeline of possible engineering designs. Often, pinched for time, short on budget and resources, we need ‘fast and simple’ [1] ideas, feedback, validation, and conversation [2] for early progress. High fidelity prototypes are eventually important; but, as a good engineer we must make initial discoveries using resources at hand, or in our pocket, home, lab or town. We need to look around and learn.
An automated robot with wireless capability for real-time imaging and control was the ultimate goal for drill-pipe inspection, but we were just getting started and that old box of Lego bricks in the toy closet was handy, and there was a ready-made imaging device right there in my pocket. As a bonus, the cell-phone had a suite of sweet instruments such as a gyro, accelerometer, proximity and ambient light sensors, and inertial instruments to stimulate the imagination.
In your Home
On another occasion; my wife entered my office and said, “Ken, what are you doing on your desk? And why is your foot on the scanner?”
Indeed, I was standing with my left foot on the desk, bare right foot on the scanner glass, left hand gripping the high back wobbling chair, and right index finger reaching for the ‘Scan Now’ button. Before I could explain, the scanner hummed and the light-bar moved slowly under the glass supporting my foot.
“Well?” she asked.
“If I could just hold steady,” I thought silently, “for a few more seconds…” The scan soon completed and I answered my tolerant companion as the barefoot image appeared on my screen, “We’ve got to find a better way of scanning the foot,” I responded.
“Who does? Why?”
Figure 1: Foot image using flat-bed scanner and image with compressible tubes
Years ago, my BYU Capstone team was chartered to improve foot arch-support digitization and fabrication, reducing orthotic waiting times from weeks to hours. “What technologies could be used to scan the foot,” we asked, “while the foot is weight-bearing?” I couldn’t resist. While the team was doing their research, almost spontaneously, I climbed onto my desk to get the first weight-bearing image of my foot. It wasn’t a pretty picture, (standing on my printer, nor the resulting foot image) but it started the flow of ideas and step-by-step (pun intended), the prototypes progressed. Needing image data that could be more easily analyzed, I then laid rows of household weather-stripping (hollow rubber tubing) on top of the glass, and scanned the image while compressing the strips under my foot. See Figure 1. And on and on using resources at hand until much later a camera-box and resistive pin mold device evolved to capture the shape. See Figure 2. The final product did not use a flat-bed scanner, but the scanner experiments were rousing and revealing, thus uncovering issues and unveiling insights to get to a successful product. (see Engineering Stories, ‘Foot Notes,’ 2013 for the whole story [3])
Figure 2: Pin mold, foot image, and patent illustration of image capturing device [4]
On yet another occasion, “May I help you find something?” The ‘associate’ at the home improvement store asked their usual pitch.
“Yes, thank you. I’m looking for ideas for a science project. I need something that converts rotary motion into linear motion.” Puzzled, he looked at the rough sketch in my hand, raised an eyebrow and walked away saying, “You might try to tool aisle.”
At the time I was performing research on controlled flexible surfaces. [5] I needed a way to induce a bending moment into an elastomeric (e.g. flexible) material to change its shape. Strolling the tool aisle, my eye caught hold on a wood-screw clamp which contains two square-thread rods for adjusting and applying force to woodwork. “Hmm, rotary to linear motion.” I picked one up, rotated the handles back and forth, then wished for a much smaller version for my application. This reminded me of my high-school days and three years of drafting class. “A compass,” I recalled, “has a small precision rotating thread with a knurled knob to adjust the distance (and angle) between compass points. As the angle changes, a curved leaf-spring changes shape slightly. “What if I cut off the spring and bond elastomeric material in its place? I could then make fine adjustments of curvature in the elastomeric material.” (See Figure 3) The results were successful; but more importantly, the thought process is powerful. Using readily available things all around, you can bring early value and keep your team moving forward.
Figure 3: Wood clamp, compass, and modified compass elastomer moment device
And don’t forget your Talents, and Hobbies
As part of the flexible surface project, I needed to assemble a number of servo motors in a confined space. I couldn’t just line up a dozen motors in a row because the motor body size required the motor shafts to be too far apart for my application. I struggled to find a solution. Relaxing one evening playing, “Dust in the Wind” [6] on my guitar, my eyes fixed for a moment on the guitar head stock where six closely spaced guitar strings are controlled (tuned) by six tuning pegs spaced-out roughly in the direction of the strings. “Ah,” I thought as the ‘dust’ cleared, there’s my answer. “The motors don’t need to be in one line.” After a number of sketches and iterations, the configurations in Figure 4 emerged.
On the same project I asked, “Where can I quickly get a dozen accurate and cheap prototyping servo motors?” Using benchmarking techniques [7], I thought, “what industries or products already have similar devices?” Another “Ah!” Radio-controlled (RC) aircraft. A quick trip down the street to the hobby story and I returned with a dozen RC servos for a dozen dollars each. “What a deal.” My project flew on, leaving dusty disruptions in the wind
Figure 4: guitar head and angularly aligned servo assembly for controlling flexible spline
Nearly every day in engineering we have a simple question to which we’d like a reasonable answer to keep us moving forward. If a simple prototype will do, don’t forget to look in your pocket, your room, your lab, your hobbies, or just down the street.
References
[1] John Salmon, The Second Face of Innovation: The Experimenter, The BYU Design Review, Mar 11, 2022, (see discussion about the Experimenter employing testing and prototyping)
[2] Chris Mattson, Why Designers Make Prototypes, The BYU Design Review, Jan 18, 2023
[3] Kenneth R. Hardman, Engineering Stories, Book, 2013, chapter ‘Foot Notes’
[4] Three dimensional variable forming apparatus and methods of use thereof, United States patent US8956145B2, Granted and Publication 2015-02-17
[5] Kenneth Richard Hardman, Concept development for direct numerical to physical surface manipulation, Master of Science Thesis, Department of Mechanical Engineering, Brigham Young University, April 1995
[6] Kansas (band), Dust in the Wind, Point of Know Return album, Kirshner, 1978
[7] Mattson, C. A., and Sorensen, C. D., Product Development: Principles and Tools for Creating Desirable and Transferable Designs, 2020, Springer, Cham. Section 11.2
