Mechanical Drives and Bearings Flashcards

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

Answer: Worm and worm gear

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.

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

Answer: Fatigue from cyclic contact stress

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.

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

Answer: Dial indicator mounted on a magnetic base

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.

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

Answer: No speed loss due to slip

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.

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

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

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.

In a gear reducer, what does the service factor account for?

Answer: The type of driven equipment and operating conditions such as shock loading

The service factor is a multiplier applied to the calculated load to account for the severity of the application, including shock loads, type of prime mover, hours of operation, and nature of the driven equipment.