Machine Design - Study Mode
[#431] A V-belt designated as B 4430 LP has
Correct Answer
(B) 4430 mm as nominal pitch length
[#432] When the bearing is subjected to large fluctuations of load and heavy impacts, the bearing characteristic number should be _________ the bearing modulus.
Correct Answer
(C) 15 times
[#433] When the shaft rotates in anticlockwise direction at slow speed in a bearing, it will
Correct Answer
(D) Move towards left of the bearing making metal to metal contact
Explanation
Solution: Concept: In a journal bearing, the shaft is supported on a thin film of lubricant which separates the metal surfaces during rotation. Slow speed condition: At slow speeds, the hydrodynamic pressure in the lubricant film is insufficient to fully separate the shaft from the bearing surface. Effect of rotation direction: When the shaft rotates in an anticlockwise direction at slow speed, the load causes the shaft to shift within the bearing clearance. Due to the rotation and load combination, the shaft moves towards the left side of the bearing. Metal-to-metal contact: In this condition, the lubricant film cannot maintain full separation, resulting in metal to metal contact between the shaft and the bearing surface on the left side. Conclusion: At slow speed in anticlockwise rotation, the shaft moves towards the left of the bearing, causing direct metal-to-metal contact.
[#434] When the shaft rotates in anticlockwise direction at high speed in a bearing, it will
Correct Answer
(C) Move towards right of the bearing making no metal to metal contact
[#435] The objective of idler pulley in belt drive is to
Correct Answer
(D) All the above objectives