Gear Terms & Materials

Question 1

Steel Gear

Answer 1

Most commonly used material. Has high strength and low cost. Includes iron, carbon, and other elements. Provides maximum strength when heated.

Question 2

Cast Iron Gear

Answer 2

Consists of iron and carbon. Is brittle. Can be cast into shapes.

Question 3

Bronze Gear

Answer 3

Consists of copper and tin. Can withstand high loads.

Question 4

Plastic Gear

Answer 4

Reduces noise. Brittle and weak under high heat conditions.

Question 5

Helical Gears

Answer 5

Have teeth that are cut at an angle. Allow contact of the gear tooth starting at the tip and rolling down the tooth. Are quiet and strong. Are used in forward gear ranges.

Question 6

Bevel Gears

Answer 6

Typically mount at 90%. Have teeth that are spur-type or helical-type. Have more tooth contact. Are used to change the rotation direction.

Question 7

Worm Gear

Answer 7

Have teeth that look like a screw. Used for large gear reduction.

Question 8

Spur Gear

Answer 8

Have the simplest gear design. Has straight cut teeth. Allow for one tooth in contact at a time. Can be noisy. Hold oil to reduce wear.

Question 9

Gear Ratios

Answer 9

You can calculate gear ratios by dividing the number of teeth on the driven gear by the number of teeth on the driving gear.

(Ex. If the driving gear has 12 teeth and the driven gear has 24 , the gear ratio is 24 divided by 12, this results in a gear ratio of 2 to 1)

Question 10

What happens when the driving gear is smaller than the driven gear?

Answer 10

Torque increases and speed decreases. The driving gear turns faster than the driven gear. The driven gear has more torque and less output speed.

Question 11

Gear Train

Answer 11

A set or system of gears. Transfers torque. Produces multiple gear ratios.

Question 12

Black Lash

Answer 12

Is the clearance or gap between the teeth. Is necessary to avoid wear. Ensures proper lubrications. Compensates for manufacturing tolerance.

Question 13

Toe

Answer 13

Narrow part of the gear tooth that’s located on the inside diameter of the gear.

Question 14

Coast Side

Answer 14

Concave, curves in, and exerts pressure on the gear during braking.

Question 15

Face

Answer 15

The area on the tooth above the pitch line.

Question 16

Flank

Answer 16

Area on the tooth below the pitch line.

Question 17

Pitch Line

Answer 17

An imaginary line near the center of the tooth that runs from the heel to the toe.

Question 18

Drive side

Answer 18

Is convex, curves out. The side where pressure is exerted during forward motion.

Question 19

Heel

Answer 19

The wider part of the gear tooth that’s located on the outside diameter.

Question 20

Root

Answer 20

Bottom

Question 21

Crown

Answer 21

Top

Question 22

Contracting fatigue

Answer 22

Due to repeated stress, causing the metal to flake away from the surface of the gear tooth. Over time the metal detaches from the tooth surface and forms pits with sharp warps.

Question 23

Bending fatigue

Answer 23

Slow and progressive failure caused by repeated loading. Starts with a small crack that runs from the length of the gear tooth in the area where most stress occurs. Weakens the metal leading to failure that causes the tooth to crumble.