Mechanical Comprehension: Gears and Cogs Flashcards

If Gear A turns clockwise and is meshed directly with Gear B, which way will Gear B turn?

Answer: Counter-clockwise

When two external gears are meshed directly, they always rotate in opposite directions. Therefore, if Gear A turns clockwise, Gear B must turn counter-clockwise.

A driver gear has 10 teeth and the driven gear has 40 teeth. What is the gear ratio?

Answer: 4:1

The gear ratio is calculated as the number of teeth on the driven gear divided by the number of teeth on the driver gear. In this case, it is 40 / 10 = 4. This is expressed as a ratio of 4:1.

If a small gear drives a large gear, what is the effect on the output speed and torque of the large gear?

Answer: Speed decreases, torque increases

When a small gear (high speed, low torque) drives a large gear, the large gear will rotate more slowly but with greater torque. This setup is used to decrease speed and increase turning force.

In a gear train, Gear A (driver) turns clockwise. It meshes with Gear B, which in turn meshes with Gear C. What direction does Gear C turn?

Answer: Clockwise

Gear A (clockwise) turns Gear B (counter-clockwise). Gear B (counter-clockwise) then turns Gear C (clockwise). Gear B is an 'idler' gear, and its effect is to make the final gear (C) turn in the same direction as the first gear (A).

A driver gear with 50 teeth rotates at 100 RPM. It drives a gear with 25 teeth. What is the rotational speed of the smaller gear?

Answer: 200 RPM

The speeds are inversely proportional to the number of teeth. The ratio is 50:25 or 2:1. This means the smaller gear will turn twice as fast as the larger gear. Speed of small gear = 100 RPM * (50 / 25) = 100 * 2 = 200 RPM.

What is the primary purpose of a rack and pinion gear system?

Answer: To convert rotational motion to linear motion

A rack and pinion system is used to convert rotational motion into linear motion, or vice versa. The pinion is a circular gear that engages with the teeth on the rack, which is a linear gear bar. This mechanism is commonly found in vehicle steering systems.

Two gears are meshed. Gear A has 60 teeth and Gear B has 20 teeth. For every one full rotation of Gear A, how many rotations does Gear B complete?

Answer: Three

The gear ratio is 60:20, which simplifies to 3:1. This means that for every one rotation of the larger gear (A), the smaller gear (B) must complete three rotations to make all 60 teeth of gear A pass by.