433A Mechanical Drives and Bearings 5

Question 1

What type of gear arrangement is used when shafts are at right angles and do not intersect?

Accepted Answer

Worm and worm gear

Answer

Worm and worm gear sets transmit motion between non-intersecting shafts at right angles. Unlike bevel gears where the shaft axes intersect, worm gear shaft axes are offset.

Question 2

What is the primary cause of spalling on a bearing raceway?

Accepted Answer

Fatigue from cyclic contact stress

Answer

Spalling is the flaking away of surface material from the bearing raceway caused by subsurface fatigue cracks that propagate under repeated cyclic contact stress. It is the normal end-of-life failure mode for properly maintained bearings.

Question 3

When measuring shaft runout for a coupling installation, what instrument is typically used?

Accepted Answer

Dial indicator mounted on a magnetic base

Answer

A dial indicator mounted on a magnetic base is the standard tool for measuring shaft runout. It is positioned against the shaft surface and reads total indicated runout (TIR) as the shaft is rotated one full turn.

Question 4

What advantage does a synchronous belt drive have over a V-belt drive?

Accepted Answer

No speed loss due to slip

Answer

Synchronous (toothed/timing) belts are positive-drive components that engage with toothed pulleys, eliminating the slip that occurs with friction-driven V-belts. This ensures exact speed ratios between driver and driven shafts.

Question 5

What is the purpose of a bearing isolator compared to a traditional lip seal?

Accepted Answer

It is a non-contact labyrinth seal that prevents contamination without wearing

Answer

A bearing isolator is a non-contact labyrinth seal consisting of a rotor and stator that create a tortuous path preventing contamination ingress without the friction and wear associated with traditional lip seals.

Red Seal Millwright 433A Practice Test

Red Seal Millwright 433A Practice Test

433A Mechanical Drives and Bearings 5