Setting aside future problems for the moment, Jin decided to throw himself into the project he wanted to tackle most: building an automobile.
"Jin, what are you up to?"
Just then, Reinhard arrived. Having finished his official duties, he had apparently come by to clear his head.
"Hey. I’m trying to build that automobile I mentioned briefly the other day," Jin explained.
Reinhard’s eyes sparkled with interest. "That sounds wonderful. I'd like to try building one myself."
"Yeah, that might be a good idea."
Jin intended to debut the vehicle in the Shouro Empire first. He figured that if Reinhard could build one as well, it might lessen the perceived "otherworldliness" of the technology.
"So, what kind of machine will it be?"
In response to Reinhard's question, Jin spread out a conceptual diagram sketched on a sheet of wood-paper.
"Oh, wood-paper... I see, I see. A design similar to your carriage, Jin—and of course, no horses. I follow."
Jin had once read in a book about model cars that the very first automobiles were sometimes called "horseless carriages." A horse-less carriage—Jin had adopted this specific aesthetic because it would be easily accepted by the people of this world.
"But knowing you, Jin, I'm sure the internals are anything but simple, right?"
Elsa’s eyebrows twitched slightly at those words.
"Haha, not really. I'll use high-quality materials, but I'll camouflage them and keep the performance within reasonable limits."
Jin laughed, adding that he wouldn't be able to drive it around openly otherwise.
"Well, that’s a relief."
With that settled, Jin and Reinhard set to work.
First came the chassis—the frame that served as the vehicle's foundation. The engine and transmission would be mounted here, with the body eventually sitting on top.
"We'll use a ladder shape for this."
This was known as a ladder frame, a structure well-suited for vehicles navigating rough terrain. More importantly for their current situation, it was relatively easy to manufacture.
Jin prioritized sturdiness and durability over sheer rigidity, choosing chrome molybdenum steel for the frame. It was a special steel known for its rust resistance and tenacity. Another reason for the choice was that a typical engineer would likely be unable to distinguish it from ordinary carbon steel.
Reinhard used the same material provided by Jin. For this project, Jin kept a degree of standardization in mind, deciding on a size that could comfortably accommodate six passengers.
The engine was crafted from the same material.
"This is fascinating."
As expected of a master craftsman, Reinhard managed to construct his first Golem Engine without a hitch, even while receiving a bit of help from Elsa.
The issue was the tires—or rather, the wheels. Since Jin had no intention of introducing tubes or valves yet, a wooden wheel fitted onto an iron rim would be the standard for the time being. Jin hoped to eventually transition to all-rubber tires, then tube tires, and finally tubeless versions.
For this first stage, however, they would use wooden tires. Jin began the process of selecting the right timber.
In Japan, "oak" carries the image of a hard, sturdy wood, but in terms of pure hardness, it isn't at the very top of the scale; persimmon wood is often harder. However, when it came to overall toughness, including elasticity and tenacity, oak was world-class.
Ancient large wooden sleds called "Shura" found in Japanese burial mounds were made of oak and were used to transport massive stones. Incidentally, one theory suggested they were named after the Asura who fought Taishakuten because they were used to move "large stones" (Taishaku).
But that was an aside.
Utilizing the legendary toughness of oak, Jin decided to use the wood for the wheels. He set the diameter at 50 centimeters and the width at 5 centimeters.
"To turn left and right, we use this kind of mechanism."
"It definitely needs a brake."
"For the suspension, we'll use a Golem arm."
Jin finished the automobile while explaining these mechanical concepts to Reinhard and Elsa.
Even for Jin, although he had built specialized vehicles for Hourai Island in the past, he had never built a "passenger car" beyond a model. The classic design, reminiscent of the dawn of the automotive era, suited the project perfectly.
With the assistance of Reiko, Edgar, and five Smiths, two Prototype Model 1 automobiles were completed near dusk. The process took a bit longer than expected because Jin, realizing several features were missing for a vehicle intended for public use, had stopped to add refinements three separate times.
"It's finished."
"Indeed."
Jin and Reinhard had the golems carry the automobiles to the front of the laboratory. Eager to conduct a test drive, they climbed into their respective seats.
As a safety precaution, Reiko sat beside Jin, and Edgar sat beside Reinhard. Even so, since it was a land vehicle, they didn't anticipate any major risks.
"Alright, let's go."
Jin slowly depressed the accelerator.
Though it was called an engine, the Golem Engine had a flat torque curve, meaning its rotational force didn't depend on high RPMs. Furthermore, it didn't require warming up and started smoothly from a standstill. It could even reverse with the flip of a single lever.
The prototype car rolled forward in response to the pressure on the pedal. Having been "convinced" to drive small industrial vehicles like turret trucks at his former job, Jin was able to drive with a fair amount of stability.
"Okay, my turn."
Seeing Jin’s success, Reinhard also stepped on the accelerator—but he pushed a bit too hard. His prototype car tore up the soil as it lurched forward with sudden speed.
"W-Whoa!"
The sudden acceleration pinned him back into his seat, which naturally lessened the pressure of his foot on the pedal. Reinhard managed to regain control just in time.
"Whew, that gave me a fright."
Elsa, watching from the sidelines, was equally startled.
"Rai-nii, be more careful!"
Reinhard waved a hand with a sheepish smile toward his younger cousin, who had called out a warning in an uncharacteristically loud voice.
"Ah, I see. It's dangerous if you aren't used to the response."
Jin considered a solution. Having the accelerator response be too sensitive was its own problem.
"Maybe a fluid clutch...?"
A torque converter would be the logical evolution, used in modern automatic cars. However, Jin didn't know the precise internal structure well enough to build one on the fly. Practical application would require much more prototyping. He decided on a different approach.
"I'll adjust the control."
Jin decided that rather than having the accelerator depression and engine output be directly proportional, he would program the control core to provide low output during the initial depression and then increase it exponentially as the pedal was pushed further.
This was similar to how audio volume knobs worked—using a "logarithmic change" rather than a linear one so that the human ear perceives a smooth transition.
Since this only required a small tweak to the control core, he finished it quickly. It was a temporary fix, but he figured he could find the optimal values through testing later.
"Reinhard, try it now. It should be easier to handle."
"O-Oh."
This time, aided by both the adjustment and his own caution, Reinhard started without any trouble.
Within fifteen minutes, both Jin and Reinhard had become proficient. The operability was roughly on par with a go-kart at an amusement park, so they adapted quickly.
"Elsa, want a turn?"
"Mhm."
Having completed a lap around the grounds, Jin invited Elsa. She climbed in with visible excitement—straight into the driver's seat.
"Wait... do you want to try driving?"
"Yes."
Jin remembered that she had been the pilot during the Golem Boat Race in Port Rock Town, so he yielded the controls to her.
"Thank you."
Elsa already understood the fundamentals: the accelerator for speed, the brake for stopping, and the wheel for steering.
"Just don't push the pedal too hard," Jin cautioned.
With only that one piece of advice, Elsa handled the automobile with remarkable ease.
"She's actually better than I am," Reinhard admitted.
"That's the boat racing experience for you," Jin thought. She likely had an instinctive feel for the nuances of acceleration and deceleration. Generally, jerky operation was the enemy of any machinery, and Elsa seemed to understand that moderation naturally.
"Maybe I should make a smaller car specifically for you, Elsa."
"Really? You'd do that?"
Elsa looked up in surprise, her face breaking into a joyful smile. She truly did seem to enjoy vehicles.
"Yeah. A light car—a four-seater."
Jin decided that if the six-seater they had just finished was the standard car, then a four-seater would be a "light car."
And so, these prototypes became the foundation for the automotive standards that would soon follow.