The Gear Design Chronicles: How a Single Computer Sent Me to Ricardo in the UK

Behind the Deceptively Simple Gear: A Grueling Manufacturing Journey

Whether manual or automatic, if you tear open a vehicle's transmission, you will find it packed with tightly meshed, slanted helical gears. To the untrained eye, these interlocking pieces of steel might look simple. Behind them, however, lies a massive, unforgiving manufacturing process forged by the sweat and blood of engineers.

The journey of a single transmission gear is exhausting just to describe:

• Forging: Red-hot steel is relentlessly hammered to make its internal crystalline structure incredibly dense and strong.

• Hobbing & Shaping: The forged blank is placed on a lathe to rough out its shape, and a massive hobbing machine carves out the gear teeth one by one.

• Shaving: Once the teeth are cut, they undergo a high-precision "shaving" process—much like a clean morning shave—to make the tooth profiles perfectly smooth.

• Heat Treatment: Finally, the gear is baked at extreme temperatures to ensure it achieves the necessary hardness so it won't shatter under load.

The "Stone Age" of 20x Scale Drafting and the Legacy of Mr. Holdman

Back in the late 1980s, transmission design boiled down to three core pillars: gear strength design, synchronizer capacity design, and bearing fatigue life design. While casing rigidity and shaft strength were important, they were mere supporting actors compared to these three.

Following a strict order from my manager, I threw myself entirely into gear design. At the time, South Korean automotive companies routinely invited retired engineers from advanced nations to absorb their expertise. Our transmission team at Kia Motors had a distinguished advisor: Mr. Holdman, a retired American engineer who had spent his career at Ford and BorgWarner.

I ransacked the tall filing cabinets next to our office, photocopying every single document bearing the name "Holdman," and stayed up all night reading them. Midway through my study, I hit a staggering bottleneck. To calculate the gear's "Tooth Form Factor (Y-Factor)," we didn't use computer calculations. It had to be derived geometrically—by hand.

I sat at my drafting board and drew the gears at a staggering 20x actual scale. I meticulously plotted involute and cycloid curves using a compass, hand-drawing the exact path the gear cutter would take. I then used a physical ruler on this giant blueprint to schematically calculate the form factor. It was a brutally primitive, "Stone Age" workflow.

"At this rate, it takes a whole week just to calculate one gear... Designing an entire transmission will take a year. This won't work. I have to find another way."

A 1-Minute Miracle Built via BASIC Coding, and the Attack of the "Mosquito Whine"

Right around that time, the IBM 5550—one of the earliest personal computers—began rolling into our lab. The screen was crude, but it featured the BASIC programming language and elementary graphics capabilities.

From that day on, I practically lived at that computer. I converted the hand-drawn drafting trajectories into mathematical formulas and translated the tedious manual calculations into hundreds of lines of BASIC code. After a tearful, year-long battle with the machine, I finally developed an automated, proprietary tool that could perfectly design a gear in just one minute.

But another hurdle instantly appeared: How do I validate the values calculated by this computer? There was no time to hesitate; I had to move forward.

Using this program, I completed the transmission design for the "Rockstar," a rugged, military-inspired jeep that was Asia Motors' (a subsidiary of Kia) ambitious new project. I personally designed the core gears, the main shaft, the main drive gear, the bearings, and the synchronizer rings. With a colleague's help on the casing, our highly anticipated first prototype was finally born.

However, our joy was short-lived. When we installed the prototype and began track testing, a piercing, high-pitched mosquito-like whine echoed through the test vehicle as speed increased. It was the nightmare every automotive engineer dreads: Gear Whining Noise.

"You Speak English. Go to Ricardo in the UK!"

We tried everything to eliminate the noise, but the root cause remained elusive. Ultimately, the problem traced back to the gear tooth profile. Even if the teeth were precisely cut and shaved, the steel subtly warped and distorted under the extreme heat during the final heat treatment phase. Without a high-precision post-heat-treatment grinding process to correct the profile, this distortion—and the resulting noise—was unavoidable with our existing machinery.

As I sat grasping my head in frustration over another sleepless night, a senior engineer walked up and casually dropped a piece of advice:

"Hey, don't kill yourself trying to solve this alone. You speak English well. Take this to a world-class consulting firm and get a proper Design Review!"

It felt like a lightning bolt of clarity. Of course! Why hadn't I thought of that?

That very day, I began contacting the world's leading automotive engineering consultancies: Porsche in Germany, Daimler-Puch in Austria, and Ricardo in the UK. After a rigorous comparative analysis, Ricardo—the world’s foremost authority on engine and powertrain consulting—was selected as our technical partner.

I packed a suitcase to the brim with every single blueprint of the Rockstar transmission that I had designed with my BASIC program. Thirty-eight years ago, a rookie engineer from the industrial city of Changwon, South Korea, set off for Worthing, UK—the very heart of global automotive technology—embarking on a monumental three-month journey.

Oldtimers gathered next door to the hotel I have stayed in Worthing UK