engines test 4, sem 2

The INVOLUTE GEAR profile is the most common gear system used today.

gear is largest of the two pinion is the smallest of the two

true, Spur gears have their teeth cut straight across the circumference and are used to connect two parallel shafts.

•Internal Spur Gears, unlike spur gears, have the teeth generated on the I.D. •They are generally stronger and more efficient than the mating pinion gear. •Internal gears provide the designer with the ability to achieve higher contact and drive ratios than standard spur gears at shorter center distances. • They also enable a velocity change without a directional change.

FALSE -only bevel and helical gears experience axial load

• FALSE • The helix cut creates a wider contact area enabling higher strengths and torques to be achieved.

A: Top, the top of the gear tooth, A.K.A Face, Top land B: Root, bottom of gear tooth, a.k.a “flank” C: Heel, the outside-diameter-end of the gear tooth D: Toe. the inside-diameter end of the gear tooth E: Drive. the convex side of the gear tooth F: The concave side of the gear tooth

TRUE; Bevel Gear are used exclusively to transmit rotary motion between intersecting shafts.

True

Planetary gear systems are typically used to reduce the propeller shaft speed on more powerful aircraft engines.

THE SUN GEAR DRIVES THE RING GEAR AND TURNS HIGH RPM AND LOW TORQUE INTO LOW RPM AND HIGH TORQUE. - These planetary gears rotate around a fixed central sun gear.

• Worm gears are used when large gear reductions are needed. • It is common for worm gears to have reductions of 20:1, and even up to 300:1 or greater.

True

If the gears are meshed too high in relation to the teeth, the load will be transmitted to the smallest portion of the tooth, breaking the teeth because of the load area.

The lashes and patterns are generally most critical where directional changes are made because; they’re adjustable by moving the gears inward or outward to obtain the correct relationship.

feeler gauge or dial gauge to measure backlash

True, Worm and Worm Wheel assemblies must be mounted on perpendicular, non-intersecting shafts.

TRUE • These planetary gears rotate around a fixed central sun gear. • In some planetary gear systems, the sun gear is the drive gear and the ring gear is fixed in the nose section of the engine.

divide 146 by 26 = 5.61 5.61 : 1

56 divided by 16 = 3.5 3.5:1

To find the total reduction ratio • multiply all numbers to get the total reduction ratio EXAMPLE: 1 X 5.6 X 1 X 3.5 = 19.6

false, gears are used to gain a mechanical advantage and or to change the direction of movement.

• The worm is self-locking when the helix angle is less than 5°. • Worm and Worm Wheel assemblies must be mounted on perpendicular, non-intersecting shaft

Heel; located at the largest diameter of the bevel gear Toe; located at the smallest diameter

Involute gear, Yes

a rolling type contact with no sliding involved

Pinion, Yes the big gear can be driven by the pinion or be it’s own driver

1. Straight Cut 2. helical 3. bevel 4. spiral bevel 5. worm

straight tooth

Helical gear

Bevel

Spiral Bevel

Worm gear. resembles a screw

1. spur gears 2. gear (crown) and pinion 3. planetary 4. worm and wheel

1. transmitting motion 2. changing speed 3. changing direction

Spur gear set

Planetary Gear system

a fixed Sun gear in the centre allows the planetary gears to spin around it

it is determined by how the teeth of one gear mate with teeth of another gear

the middle area

gauge pins are used to check for dimensionally damage on the gears teeth to see wear

the rotational arc clearance between a pair of mounted gears in any gear set, some amount of backlash (clearance) is necessary to prevent damage brought about by gear tooth interference

Parallel