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  • Writer's pictureErik Herman

Out of 3D Modeling and Into the Sandbox

Updated: Nov 14, 2022

I've been teaching a course at Cornell for a few years, PHYS 4500, where students spend a semester designing, constructing, and showcasing exhibits as part of the Physics Bus. My main interest when conceiving of the course was the added value to the community of Cornell students creating eye-popping pieces that inspired science interest. The project would also benefit these students by forcing them to grapple with elusive physics phenomena. In their coursework they would typically only experience some of these concepts with words, numbers, pictures, diagrams, as a demonstration or--if they're lucky--as a lab activity. Whatever the case, there is limited time and space for really delving into something. There is also a "service learning" aspect, doing something that makes a difference in the real world, that can be very meaningful.

What I didn't intend and anticipate was the degree to which the Cornell students would find joy and satisfaction immersing themselves in otherwise frustrating physical puzzles, and how much getting in the sandbox forces an important approach to experimenting and creating. Maybe the sandbox approach is even the best approach?

The sandbox is a term I use for diving right in, to whatever is available, to as quickly as possible get the intended effect. The "sand" in the PHYS 4500 sandbox is tubs and crates full of basic materials like cardboard, fabric, plastic, and wood, to materials with purpose like hoses, pipes, springs, wires, lenses, to artifacts with goals like pumps, speakers, motors, lights, to full-on appliances like an electric toothbrush, tape recorder, boom box, or a sewing machine. Student workbenches quickly fill up with crazy rube-goldberg contraptions. Sounds of whirring and buzzing fills the air.

My job is sort of like a librarian. Sometimes students need a very specific item. Having been in physics education for over 20 years it's extremely rare that I don't have that certain wavelength of laser, a peltier cooler, a diffraction grating, a spool of 18 gauge solid copper with no enamel. Sometimes students have a vague idea and my job is to help them find a physical thing that best matches the image they have in their mind. Sometimes what they have in their mind is from everyday experience, like how a rainbow of colors appears on a puddle in a parking lot, and it's all about how to help them re-create that puddle.

Often what students have in their mind is from something they've seen on the internet. This poses an interesting challenge. Things on the internet are either anybody's guess or they come with plans. For anybody's guess stuff we do our best with our interpretation of how they did it. Things with plans, though, have their own challenges. They have lists of materials--specific materials of certain dimensions fastened together with these particular screws. And because our version has to fit on a Physics Bus it will need to be scaled appropriately. But where do we find a tube with those new dimensions? What will it cost? How long will the materials take to get here? Will the effect we're looking for still even get produced at this size? I've seen how this can play out. It can be like building Ikea furniture but ending up, a hundred dollars and a few hours spent, with cabinet that doesn't fit your plates and with doors that fall off.

Like appliances that are designed without product end-of-life in mind, plans often rely on very specific components that are not readily available except as part of the whole. If you don't have a specific widget, you can end up needing to either attempt whittling your own widget, or if not pratical to do so modify the rest of the apparatus enough that the original plans aren't even relevant anymore. You can even find yourself designing things around the widget--forcing someone else's brainchild to be reborn again. And it's difficult to unsee or unthink how that special widget worked so well.

“I pretended I never saw an airplane before and came up with the Gossamer Condor.”

- Paul MacCready

Creating physics exhibits and demonstrations is basically summoning inanimate things to dance with nature. There are some common ways we all dance with nature everyday, catching a ball, riding a bicycle, or even...walking. None of these activities, that the average 12-year-old human can do with ease and confidence, could be explained or described with words, diagrams, formulas, etc. in such a way that we sensibly could--strictly from those words, diagrams, formulas, etc.--(especially in the time of a 2-credit course) bring forth a comparable effect from an apparatus.* The fact is, we take for granted the complex algorithms that we humans do somewhat effortlessly in our minds to successfully, even sometimes gracefully, accomplish these "simple" tasks. It's pretty much impossible to account for how much time, processing power, and exercise (to say nothing of the evolution of the body) we've dedicated to manage these feats of physics. So when we set off to take an unfamiliar phenomenon for a ride, like the vapor trail of a subatomic particle, a standing wave in a metal plate, or the field lines of a magnet, we begin with a lot of catching up to do.

I believe the best strategy is the one nature itself took to get living, moving, thinking beings wandering around on the planet. First we need some primordial soup and then we need to stir it around. Life...and even humans...came forth from different kinds of chunks bumbling around together. At first maybe just trying to survive. Then maybe to have some fun while we're at it? Surely flying must be fun? Do other creatures play? Yep. Dolphins create air-entrained underwater vortices (you can make them too.) Smart people like Laura Schultz even believe--based on research--that the purpose of play (and generally make problems for ourselves) is to learn. What? Kids wanna learn!?!?

So, with nature as our guide, the recipe for bringing something to life and have fun while you're at it, is to start with a pile of junk and start stirring things up!

One excellent example of the sandbox process taking place effectively in a dance with physics is this wonderful historical account of the Gossamer Condor. They were motivated by an idea (and a grand prize that would settle a debt!) they used nature as their guide, used what they had available**, tried, failed, tweaked it. Tried, failed, tweaked it some more. Then they were flying.

What would today's technology look like if the designers spent more time in the sandbox? A friend of mine, a retired (well not actually retired...but in a next phase) engineer, recently needed to tilt the cab of his LS170 NEW HOLLAND skid steer to get to the hose fitting. A special $1500 tool is required by the manufacturer to accomplish the tilt. Instead, he did it with an engine hoist, a comealong and a jack. "Obviously nobody on that engineering team ever worked on their own tractor."

CAD (computer aided design) is a great approach once you are really familiar with the materials and already have an intrinsic feel for what you want those materials to accomplish. It's not a good path to figuring out what cylinder dimensions give rise to a fog tornado. Get in the sandbox.

* It is arguable...but still unlikely...that someone could use Andy Ruina's formulas (video of talk here), turn them into code, upload it into the brain of their robot, and maybe...just maybe...their bicycle rider could compete with a 7-year-old.

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