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In the late 1960s, the Mercedes C111 was introduced as one of the most advanced sports car prototypes of its time. A sleek, futuristic vehicle with gullwing doors and a powerful Wankel engine, it captured the imaginations of car enthusiasts around the world. Among those dreamers was a 16-year-old boy from Neustadt named Theo Helmle. That fascination, born in 1969, would drive him to spend decades recreating his version of the C111. He called it the HE111, a personal tribute to both the Mercedes prototype and his own ingenuity.
The Birth of a Dream
For Theo Helmle, the C111 was more than just a car; it was an obsession. As a teenager, he stood mesmerized in front of the bright yellow Mercedes at a car show. The C111, with its revolutionary Wankel rotary engine producing 350 hp, fiberglass body, and distinctive gullwing doors, embodied all the innovation of the late 1960s automotive industry. Yet, Mercedes-Benz never put the C111 into production due to technical challenges with the Wankel engine, leaving Helmle and others disappointed.
“I just had to have it,” Helmle recalls, reflecting on his younger self’s passion. But instead of giving up on the unattainable, Helmle made a decision that would shape his life: if he couldn’t buy it, he would build it.
Reimagining the C111: The HE111 Is Born
Helmle’s journey to create the HE111 began in earnest in 1981. A mechanical engineer by trade, Helmle used his expertise and industry connections to craft his dream car. However, the process was anything but simple. He lacked any detailed plans or molds for the C111, which meant he had to construct the vehicle almost entirely from scratch.
Helmle turned to plaster molds, casting the parts himself, and even designed the entire chassis. His professional experience proved invaluable as he navigated the technical challenges. Over the course of six years, in between work and personal commitments, Helmle spent 4,000 hours working on his dream car. “The HE111 became a completely new car,” he explained, featuring a tubular space frame, mid-engine configuration, fiberglass body, and custom-made gullwing doors.
From Wankel to Renault: Finding the Right Engine
One of the major deviations from the original C111 was the engine. Helmle’s original vision was to equip the car with a Wankel rotary engine, just like the prototype that had captivated him decades earlier. However, sourcing an affordable Wankel engine proved nearly impossible. The Wankel Institute quoted him a staggering €100,000 for the engine, far beyond his budget.
Determined not to let this setback stop him, Helmle opted for a more accessible, yet still powerful alternative. He installed a 3.3-liter turbocharged engine from a Renault Alpine A610, a French sports car, which produced 270 horsepower. This substitution maintained the spirit of performance, even if it wasn’t a rotary engine.
Craftsmanship and Innovation
While the HE111 remains a close visual replica of the C111, Helmle’s creation includes several innovations of its own. One of the key modifications was the use of carbon fiber-reinforced plastic (CFRP) for the gullwing doors. Unlike the original fiberglass doors of the C111, these lighter, stronger doors improved the car’s stability in the event of a side impact while reducing its overall weight. At 1,100 kilograms, the HE111 is around 140 kilograms lighter than the C111, helping it achieve a top speed of 250 km/h.
Although capable of such high speeds, Helmle has no intention of pushing his creation to its limits. Instead, he prefers to showcase the HE111 at classic car meetings and events, where it can be admired in a more controlled environment.
A Labor of Love and Legacy
Despite its frequent appearances at classic car shows, the HE111 spends most of its time in Helmle’s garage, meticulously maintained but seldom driven. For Helmle, the car is far more than a mode of transportation—it is a deeply personal project and a testament to his passion, dedication, and craftsmanship. “You can’t just leave a car like that standing there,” he notes, recounting times when curious onlookers crowded around his vehicle, once even damaging the lock while attempting to open the door.
Helmle’s attachment to the HE111 runs deep. Even though it took years of hard work and occasional frustrations, he is adamant that he will never part with the car. “I compare myself a little to Reinhold Messner,” Helmle says, referencing the legendary mountaineer’s arduous journeys. “I wanted to turn back several times halfway there, but when you finally manage it after unspeakable effort, it is simply an indescribable feeling.”
Looking to the Future: The Wankel Dream Lives On
Helmle’s interest in automotive engineering hasn’t waned. Even at 71 years old, he remains passionate about the potential of the Wankel engine. Currently, he is developing a Wankel diesel engine with direct injection and compression ignition, which he believes holds great promise for the future. The engine, designed for hybrid cars, is compact and lightweight, making it an ideal companion to an electric motor. Helmle’s vision is to test the prototype in the coming year.
Though Helmle’s personal Wankel dream has not yet been fully realized, his HE111 is a remarkable symbol of perseverance, skill, and ingenuity. By building his own car from scratch, Helmle didn’t just recreate a piece of automotive history—he built his own legacy.
