Surjan Singh

Surjan Singh (SS) is a mechanical engineer who most recently worked at Virgin Galactic and is now on sabbatical. We ran across the fantastic post below from his email, An Engineering Self-Study, and reached out to see if he’d be up for running it as a WITI edition. Hope you’ll enjoy it as much as we did. - Noah (NRB)Surjan here. Ever since I helped design and build a Formula SAE car in college, I’ve never really had a firm grasp on stiffness. The conventional wisdom for cars is that the chassis, or frame, of the car has to be extremely stiff torsionally (in twist). Meaning that if a Hulk-version of you lifted up on the front-left wheel arch of your car, the back-left should lift the same amount (rather than sitting floppily on the ground).The usual explanation is that you want a stable, predictable platform to allow the suspension to work as designed. I never understood why it was so compartmentalized. Why did the suspension have to take all the movement and the chassis none? Am I suggesting you go cut the roof and floor out of your car to make it less stiff? Not at all. You’d be messing with a design that has one, coherent approach towards stiffness. What I am suggesting is that there might be a completely different way to approach the design.I did (and still do) think the idea’s a bit out there. But I got some hope in the form of historical context. In Structures: Or Why Things Don’t Fall Down, J.E. Gordon talks about a difference in Eastern and Western approaches to stiffness when talking about Chinese sailing boats:According to our Western, engineering-school, way of thinking there is very little we can do about this [increased force from high winds], for we would rather be seen dead than allow the membrane - whether it be a sail or part of an aeroplane or whatever - to bulge appreciably between its supports…. What we actually do is make the supporting frame-work strong and heavy and expensive and hope that it won’t break - which of course it often does….One elegant and satisfactory way of doing that has been devised by the Chinese, who, after all, have been sailing about the seas in moderate comfort and safety for a good many centuries…. The battens which cross the sails are attached to the masts and, since the whole rig is constructed from flexible materials, as the wind increases, the sail bows out between the battens…without much loss of aerodynamic efficiency.Why is this interesting?Gordon was mostly illustrating a different point, but what stuck in my head was the two different approaches to stiffness. Maybe the need for stiffness is just driven by the dominant engineering culture. But were there other examples?I thought of the contrast between Japanese armor and European plate armor. The Japanese variety was often made up of leather or iron scales whereas the Europeans preferred the larger, unbroken plates. Both developed around the same time and had to deal with similar weapons to start. You can visually see the difference in flexibility.There is the near-mythical Damascus steel, a long-lost metalworking technique that people attempted to recreate for centuries. From Ancient and Medieval India Vol. 2, “The swords of the Sikhs are said to bear bending and crumpling, and yet be fine and sharp as the scimitar of Suliman.” The legend was that you could wrap a Damascus blade around your body and it would spring back to its original shape.And finally, even fashion seemed to provide an example. In the 1800s, Victorian women had to deal with corsets and crinoline, as shown below, to provide structure to a skirt.By comparison, Indian women’s apparel stood out for its freedom of movement and relative lack of structure.So it seems like there could be something to rigidity being a cultural difference rather than a clear step forward for technology. Maybe stiffness dominates because of its historic usefulness in certain areas, like firearms. I don’t much care for the “East” v. “West” part of the argument, since there are counterpoints. It also discounts the Americas and its flexible designs, like the baidarka. What’s interesting to me is that the current, globalized engineering culture seems to have accepted stiffness as an advancement and flexibility as a more backwards approach. I disagree with that wholeheartedly. Keeping an open mind to the “bend but don’t break” philosophy that nature herself favors could open the door to a host of unique, lightweight designs. (SS)Brake Duct of the Day:The F1 season just kicked off, but inter-team dynamics are in full swing. This week the Renault F1 team officially filed a complaint with the sport’s governing body accusing the Racing Point team of illegally copying the brake ducts from Mercedes. At the heart of the complaint is what’s legal to share between teams (gearboxes, suspensions) and what’s not (aerodynamic elements). The accusation, at the highest level, is that Racing Point, who buys their engine from Mercedes along with using their wind tunnel, is running Mercedes‘ championship-winning 2019 car. Intrigue! (NRB)Quick Links: “Life in Hong Kong has always been impossible” (CJN)Wirecutter finds the best instant noodles (NRB)TIL: Thomas Edison pushed for electric chairs to run Westinghouse’s alternating current to convince people it was dangerous. (NRB)Thanks for reading,Noah (NRB) & Colin (CJN) & Surjan (SS) —Why is this interesting? is a daily email from Noah Brier & Colin Nagy (and friends!) about interesting things. If you’ve enjoyed this edition, please consider forwarding it to a friend. If you’re reading it for the first time, consider subscribing (it’s free!).

Why is this interesting? - The Stiffness Edition

Surjan Singh (SS) is a mechanical engineer who most recently worked at Virgin Galactic and is now on sabbatical. He writes at An Engineering Self-Study and previously published the excellent Stiffness Edition. Today’s WITI is a heavily edited version of a piece he published on his newsletter earlier this week. Be sure to check that out if you want to go deeper. - Noah (NRB)Surjan here. By my estimation, a single number cost $1.5 billion on the Space Shuttle. Almost more amazing is what it represents and how it came to be. But for all its importance and intrigue, the number itself has an unassuming name—the factor of safety.Image from NASAThrough engineering school and the start of my career, I didn’t think much of the factor of safety. The textbook definition is straightforward: it’s the breaking force divided by the expected force. So if you were making a chair with a factor of safety of 2, you’d design it to withstand twice your weight. In other words, the factor of safety is how much of the structure’s strength is “kept in reserve to assure its safe performance.”1In day-to-day work as a mechanical engineer, that’s all you need to know. For example, if you’re designing an airplane wing, a loads engineer will tell you how much force the wing should experience and the FAA will tell you to use a factor of safety of 1.5. You can plug and chug and be good at your job.But at some point, the safety factor started annoying me. As the joke goes, an engineer is someone who calculates to five decimal places, then multiplies by two. Why bother with all that detailed engineering work if we’re just going to slap a massive factor on it anyways?Why is this interesting?Safety factors started being formalized in the mid-1800s for bridge building, where factors as high as 6 were used to cover for the massive inconsistencies in the quality of early cast iron.5 So in its earliest definition, the safety factor was only intended to resolve the difference between a theoretical, flawless material and the imperfect reality. But the definition has changed over time and there doesn’t seem to be a lot of clarity on how or why different disciplines apply different factors.And so I started to hunt. I figured aerospace was the best area to explore, because it has the most to gain from weight loss; the factor of safety would be examined critically from every angle.Even under all that scrutiny, its origin remains unclear. In 1900, Wilbur Wright wrote to his father, “I am constructing my machine to sustain about five times my weight and am testing every piece. I think there is no possible chance of its breaking in the air.”9 If Wilbur wasn’t just lying to calm his dad down, the Wright brothers’ factor of safety was 5. By the early 1920s, it was down to 2, though that was not at all standardized.10The first effort at rationalization came from a joint effort by the Army, Navy, and Civil Aeronautics Administration in the early 1930s. And it was from that group that 1.5 emerged as the factor of safety which has carried forward to this day.11 How did they come to their conclusion? The rationalization was that “airplanes were flying up to two-thirds and more of the ultimate load factor and nothing was happening to the structure; therefore, the evolution of thinking towards a lower factor of safety was a natural one.”12Basically, pilots flew over the limit, but nobody died, so the limit changed. To go back to the chair analogy, it’s as if you designed the chair to support 2x your weight, but while making the chair, you gained 50% more weight by eating lots of donut holes. When you, at 1.5x your expected weight, sat on the chair, nothing bad happened, so you felt comfortable reducing your safety factor. In other words, the 1.5 factor was developed empirically. That one word—empirical—helped me understand the confusion around the definition and why it’s stayed the same for so long. You could argue until you’re blue in the face that the factor of safety only covers freak accidents and does not cover the simplifications we make when engineering. But the truth of the matter is that the extra margin is there and, even if you did not intend for it to, it could very well cover simplifications with or without you knowing.The definition of the factor of safety is almost irrelevant. You can see why JE Gordon called it the “factor of ignorance”13 and the Department of Defense has renamed it to the “factor of uncertainty”.14And the only way to reduce the factor of safety is to take on more risk. It’s no different than any other empirical knowledge. Your grandmother warns you not to eat some delicious-looking berries because her grandmother told her that her cousin died after eating the delicious berries. You suspect that your great-grand-cousin died from something else and the berries were a coincidence. You have only have one option to confirm your suspicion—you can eat the berries. Either you learn that they are harmless or you die.Any attempt to reduce the 1.5 factor would be a similar step into the risky unknown. How did we get to 1.4 for spacecraft then? Who decided it was worth the extra risk for the weight savings? Apparently, the reduction to 1.4 was a one-time decision for one vehicle that somehow got absorbed and established as the standard for all spacecraft.16 Maybe to the engineering community, it looked like someone had tasted the forbidden berry and survived. That berry-taster was Boeing’s X-20 Dyna-Soar (what a great name). In fact, the manned portion of the X-20 was designed to the usual 1.5 factor. It was only the separable boosters that were designed to the reduced 1.4 factor. And even then, an additional factor was applied. The combination of factors came from a lab study that was focused on increasing structural efficiency for the particular use case and materials of the booster.17 Over time, the second factor and the context for the decision dropped away and only the 1.4 factor remained.Boeing X-20 Dyna-Soar from WikipediaThis whole thing might seem absurd, but engineering is a human endeavor with just the same quirks as any other. I think of the factor of safety as a modern-day version of the libation or offering. I’d rather keep pouring out the same amount of wine as my ancestors rather than skimping and risking offending the gods. That $1.5 billion pricetag, which seemed absurd when I began writing this, now just looks like the cost of being human. (SS)Quick Links:If you’re at a SaaS company, check out what I am working on over at Variance. It’s a tool to help grow customers (some people are calling it a PLG CRM). If you have questions, drop a line. (NRB)Bones found as Somerton Man exhumation continues in hope of solving decades. If you need a refresher, here’s the excellent California Sunday article on Somerton Man. (NRB)Mining Bitcoin with pencil and paper: 0.67 hashes per day (NRB)Thanks for reading,Noah (NRB) & Colin (CJN) & Surjan (SS)—Why is this interesting? is a daily email from Noah Brier & Colin Nagy (and friends!) about interesting things. If you’ve enjoyed this edition, please consider forwarding it to a friend. If you’re reading it for the first time, consider subscribing (it’s free!).

The Engineering Safety Edition

Surjan Singh (SS) is a mechanical engineer who most recently worked at Virgin Galactic and is now on sabbatical. He writes at An Engineering Self-Study and previously published the excellent Stiffness Edition and Engineering Safety Edition. Recently over at his newsletter, he’s been working hard to build a new kind of facemask for hockey goalies. You should subscribe and follow along with the journey. - Noah (NRB)Surjan here. Last week, Tom Hodges attended a hockey game in Dallas after a long day selling life insurance. Halfway through a hotdog, he got a call, walked out to his car to grab his gear, and, not long after, made his debut as a goalie in the National Hockey League. Tom is an EBUG, or emergency backup goalie—a product of one of the most unique rules in all of professional sports. Why is this interesting?On an NHL team, there are two goalies: a starter and a backup. The backup usually sits on the bench, looking bored, until he’s called into action due to injury or poor performance. But what if both the starter and the backup get injured? You’d think one of the skaters could put on the gear and hop in the net, but goaltending in hockey is highly specialized and the risk for injury is too high. Hence the EBUG: a local non-professional goalie who stays ready to sub in for either team in exchange for a free ticket. It’s a very rare occurrence—only five EBUGs have ever appeared in an NHL game—but when it happens, it’s always a fantastic story. A regular guy getting to live his dream for a night.Tom, for instance, thought his NHL dreams were over at the age of 12 when he lost most of the sight in his left eye after taking a puck off his head in practice. But he kept playing for the love of the game and ended up with, as he said, an “experience of a lifetime.” And just look at the reaction of his teammates for the night, even after a loss.Anaheim Ducks @AnaheimDucksHe battled for us.
We battled for him.
Thank you, Tom Hodges! 

🧡 this team. 

#FlyTogether 3:08 AM ∙ Apr 30, 202210,103Likes892RetweetsSo in 2022, we have the insurance salesman. In 2018, the accountant Scott Foster stopped all seven shots he faced to preserve a win for the Chicago Blackhawks. In 2020, the Zamboni driver David Ayres famously recorded the first-ever win for an EBUG as he denied his hometown Maple Leafs for half a game.Ayres also lost long-suffering Leafs fans the last of their sanity. Easily the best rule in all of sports. (SS)WITI x McKinsey:An ongoing partnership where we highlight interesting McKinsey research, writing, and data.Mind the (generation) gap. Are you part of Gen Z, or interested in what matters to Zs because you work with or manage them? Don’t miss McKinsey’s new weekly newsletter, Mind the Gap. You’ll get curated reads on today’s hot topics, from mental health to inclusion at work, inflation’s effect on young consumers, and beyond. Check it out.–-Thanks for reading,Noah (NRB) & Colin (CJN) & Surjan—Why is this interesting? is a daily email from Noah Brier & Colin Nagy (and friends!) about interesting things. If you’ve enjoyed this edition, please consider forwarding it to a friend. If you’re reading it for the first time, consider subscribing (it’s free!).