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| The portrait of Iis Siti Aisyah, ST. MT. Ph.D. IPM, the mechanical engineering lecturer of UMM, who responds to recent viral news about a bus plunged into a ravine. (Photo: Istimewa) |
A few days ago, a bus plunged into a 15-meter-deep ravine. The incident caught the attention of netizens. The bus, parked initially, slid downhill until it fell without a driver, which eventually went viral. The bus carrying out a group of pilgrims crashed in the Guci tourist area, Tegal Regency, Central Java, on Sunday, May 7, 2023.
The event was suspected to be due to a malfunction of the hand brake of the bus. Without exception, this incident finally garnered the attention of a UMM Mechanical Engineering lecturer, Iis Siti Aisyah, ST. MT. Ph.D. IPM. The woman, known as Iis, says that the bus driver shouldn't have left the bus running albeit its hand brake has been turned on, especially on a road having steep conditions or slopes.
"In a parked state, the car engine should be turned off. Even though there are no rules prohibiting this in Indonesia, leaving a vehicle parked for too long can be hazardous. The vehicle's engine is scorching, and there's always an instruction in the guidebook not to overheat the car. If it takes too long, it can make the vehicle catch fire. Because the car stops, its usual cooling process is unavailable from a flowing air stream. So the engine and exhaust ducts tend to heat up faster," explains the lecturer.
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Furthermore, she says that the hand brake isn't as strong as the main brake, so there's a maximum load weight limit and slope it can handle. If it's not overcome, out-of-the-ordinary events may cause the vehicle to move.
"The hand brake is never fixed. Because it's a mechanical system and is shared by all four wheels. As an illustration, if the hand brake is applied and the vehicle is started, the brakes aren't strong enough to overcome the engine power," says Iis.
The Head of the Mechanical Engineering Department of UMM also adds that a downhill street position naturally improves gravity, especially when it's passed by a vehicle with a fully-loaded passenger capacity. As a result, the load carried out can't be handled by the hand brake. The slope will shift the resultant force compared to a parked vehicle on an even surface. The resulting force due to the vehicle's weight will be perpendicular to the parallel axis of the car.
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"If parking on an inclined surface, the resultant force won't be vertical but forms an angle according to the slope. The greater the slope, the greater the resultant angle. This gives a pull due to the resultant force caused by the vehicle's weight to the front or rear (depending on the positions of the vehicle's slope and the weight point)," said Iis.
Last but not least, the lecturer, hailed from Sukoharjo, Central Java, says that a driver of large vehicles must have special knowledge related to this. Additionally, regulations must be tightened since an accident often occurs due to drivers' negligence and unsuitable vehicle conditions. (imh/zak/wil)
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