Mechanical Power Transmission Flashcards
7 cards from real SACA practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Mechanical Power Transmission flashcards as text
A planetary gear system has a sun gear with 20 teeth, planet gears with 40 teeth, and a ring gear with 100 teeth. If the sun gear is the input and the ring gear is fixed, what is the gear ratio?
Answer: 6:1
With the ring gear fixed and sun gear as input, the ratio is (ring teeth / sun teeth) + 1 = (100/20) + 1 = 6:1.
Which type of coupling is specifically designed to accommodate significant angular misalignment between two shafts?
Answer: Universal joint (U-joint)
Universal joints (U-joints) are designed to transmit torque between shafts at significant angular offsets, commonly used in driveshafts.
In a flat belt drive, increasing the wrap angle of the belt on the pulley primarily affects which performance characteristic?
Answer: Friction-based torque transmission capacity
A greater wrap angle increases the contact arc, allowing more friction force and thus greater torque transmission before slippage occurs.
What is the primary purpose of a backstop (holdback) device in a conveyor drive system?
Answer: To prevent reverse rotation under load
A backstop or holdback prevents the conveyor from running backward under load when the drive is stopped, protecting against uncontrolled reverse movement.
Which gear geometry feature is measured by the 'pressure angle' in gear design?
Answer: The angle between the tooth profile and the pitch circle tangent
Pressure angle defines the angle between the tooth's normal force direction and the tangent to the pitch circle, typically 14.5° or 20° for standard gears.
A V-belt drive system begins slipping under load. Which corrective action would be MOST effective without replacing belts?
Answer: Adjust the center distance to restore proper tension
Restoring proper belt tension by adjusting center distance is the most direct fix for belt slippage caused by insufficient tension.
In power transmission, what does the term 'service factor' account for when selecting components?
Answer: Additional load capacity needed for application-specific shock, vibration, or duty cycle
Service factors multiply the nominal load to account for real-world conditions like shock loads, frequent starts, or continuous heavy duty beyond rated conditions.