The use of wheels of small diameter rather than wheels of large diameter to drive a set length of belt has the disadvantage of
A. requiring lower belt tensions.
B. requiring a higher shaft speed.
C. increasing belt speed.
D. causing high bending stresses.
The correct answer and explanation is:
The correct answer is B. requiring a higher shaft speed.
Explanation:
In mechanical systems involving belts and pulleys, the diameter of the wheels (pulleys) is directly related to the rotational speed of the shaft and the speed at which the belt moves. When a small diameter wheel is used to drive a belt, the shaft that drives this wheel must rotate at a higher speed compared to a system with larger diameter wheels. This is because the belt travels a fixed distance for each rotation of the pulley, so a smaller pulley must complete more rotations to cover the same length of belt travel.
The relationship between the speed of the wheel and the belt is determined by the circumference of the pulley. The larger the diameter of the pulley, the longer its circumference, and therefore the slower the speed at which the pulley rotates to cover a given length of belt. Conversely, a smaller pulley has a shorter circumference, meaning it must rotate more times to cover the same length of belt.
When the small diameter wheels are used in a system, the shaft speed needs to increase to maintain the required belt speed. This higher shaft speed may lead to increased energy consumption, wear, and tear on components due to the higher rotational forces involved. Moreover, it may require more sophisticated or larger motors to achieve the necessary shaft speed.
On the other hand, larger diameter pulleys can help to achieve the same belt speed at a lower shaft speed, which can reduce the mechanical stress on the system and minimize the need for higher-speed motors. Therefore, the disadvantage of using small diameter wheels is that it leads to the need for a higher shaft speed to maintain the same belt speed.