Wang Xuan was utterly speechless at Zhang Fei's excitement. He could not be bothered to deal with the restless man and merely watched the test results of this horse-drawn Iron Chariot in silence.
The testing grounds were large enough. One lap covered a full twenty kilometers, leaving plenty of time for the vehicle to accelerate. Gradually, the horses ran faster and faster. Judging by the speed, they had already reached around thirty miles per hour.
That speed was already very fast, but it clearly had not reached the limit. The driver at the front, however, had already begun to turn pale. After all, this was the first practical test, and the four carriages were loaded with iron weights to test their performance under various road conditions after being fully loaded. But if the vehicle overturned at this speed... the driver felt he would probably be crushed into a meat pie and die without a complete corpse.
The track ahead was still straight, allowing them to accelerate and test their speed. Farther on, however, there were curves of different angles, inclines, and declines, all intended to test the vehicle's limits. Seeing that they were about to enter the first curve, the driver trembled as he waved his whip to guide the horses while gritting his teeth tightly, terrified that they would overturn.
When rounding a curve, the entire track needed to be tilted at a certain angle. The resultant force of gravity and the supporting force—or, more precisely, the horizontal component of the supporting force—kept the vehicle stable as it turned. If the track were completely level, the rails would have to deform to provide centripetal force. That would be too dangerous, practically equivalent to derailing, so the track had to be tilted slightly.
Phew, they successfully passed the first small