SACA Mechanical Power Transmission 2

Question 1

What is 'mechanical advantage' in a gear system and how is it calculated?

Accepted Answer

The ratio of output torque to input torque, equal to the gear ratio — a higher gear ratio produces proportionally more torque at lower speed

Answer

Mechanical advantage in gears equals the gear ratio: output torque = input torque × (N_driven / N_driver), where N is the number of teeth. Doubling the gear ratio doubles output torque while halving output speed, conserving power (minus losses).

Question 2

In belt drive systems, what is the difference between a 'timing belt' and a 'V-belt', and when is each preferred?

Accepted Answer

Timing belts use positive tooth engagement for synchronous, no-slip drive; V-belts rely on friction wedging for torque transfer and allow slip under shock loads

Answer

Timing belts have teeth that mesh with sprocket grooves, providing synchronous (no-slip) power transmission with exact speed ratio — essential for indexing, registration, and cam-synchronized drives. V-belts wedge into pulley grooves using friction — simpler, absorbs shock, but allows slip and requires periodic tension adjustment.

Question 3

What is a 'flexible coupling' used for when connecting a motor shaft to a gearbox or machine?

Accepted Answer

To accommodate minor shaft misalignment and absorb vibration/torsional shock between connected shafts

Answer

Flexible couplings (jaw, disc, oldham, bellows) compensate for angular, parallel, and axial misalignment between coupled shafts while transmitting torque — protecting bearings from misalignment loads and damping vibration/shock between motor and load.

Question 4

What is 'bearing preload' in precision machine tools, and why is it applied to angular contact bearings?

Accepted Answer

Applying a controlled axial compressive force on bearings to eliminate clearance and improve stiffness, accuracy, and load capacity under combined loads

Answer

Preload applies a controlled axial force between two angular contact bearings (facing each other in 'back-to-back' or 'face-to-face' arrangements) to eliminate internal clearance — increasing stiffness, improving running accuracy, and enabling the bearing to handle combined radial and axial loads without deflection.

Question 5

What is a 'torque limiter' (slip clutch) in mechanical power transmission and what does it protect against?

Accepted Answer

A device that disconnects or slips at a preset torque level, protecting connected machinery from damage during jam, impact, or stall conditions

Answer

A torque limiter (mechanical fuse, slip clutch, or shear pin) transmits torque normally below its set point. When torque exceeds the set threshold — due to a jam, collision, or stall — it slips or disengages, preventing damage to the motor, gearbox, or machine structure.

SACA - Smart Automation Certification Alliance Practice Test

SACA - Smart Automation Certification Alliance Practice Test

SACA Mechanical Power Transmission 2