303A: Gearing Principles Flashcards
A gear tooth can be divided into four distinctive quadrants. Identify the names of each of these quadrants.
Face
Flank
Toe
Heel
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The gear pitch line is used to divide the following gear tooth areas:
Face and flank
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When two gears are in mesh, a gap is formed between the tip of one gear tooth and the root in the opposite gear. This gap is called the:
Clearance. Helps maintain a lubrication film.
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Explain why some angle drive gear sets may need to be timed.
To prolong service life and maintain the distinct wear pattern.
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Gears may operate together as direct drive assemblies. Identify and explain two other types of gear configurations.
Reduction: Speed reduction, torque increase. Gear ratio of >1:1
Overdrive: Speed increase, torque reduction. Gear ratio of <1:1
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If a simple gear set has a gear ratio of 4:1, explain which member is turning at 4 revolutions
- Reduction gear ratio
- Drive member is rotating 4x for each driven member rotation
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Which of the following gear ratios would be a reduction gear ratio?
a) 0.10:1
b) 1.00:1
c) 10.00:1
d) 1.00:2
c) 10.00:1
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When installed between a drive and a driven gear, an idler gear affects speed and torque changes between the two gears. (T/F)
False
It will only change the direction of rotation
Explain the purpose of an idler gear
An Idler gear is used to change the direction of rotation in the output gear.
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Name and explain the tooth design used on two types of external gears
- Straight cut spur gear: Teeth cut inline with the mounting shaft. Inexpensive, no axial loads, low strength
- Single Helical Gear: Teeth cut at angle to the mounting shaft. High strength, less noise, has axial loads.
- Double Helical Gear / Herringbone: Greater strength, opposing axial loads offset each other, expensive to manufacture.
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Identify one common gearset where internal gears may be used
Planetary gear sets
What is another name for a double helical gear?
Herringbone gears
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Straight cut spur gears and helical gears both produce axial thrust loads during operation? (T/F)
False.
Straight cut gears do not produce axial loads.
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Identify the 3 main components of a simple planetary gear set.
- Internal gear / ring gear
- Carrier / Planetary gears
- Sun gear
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When a gear tooth has a larger and narrower end, the larger end is identified as the ____ , the middle as the ______ , and the narrower end is the _____.
Heel, Centre, and Toe
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What does the term path-of-power mean in relation to gearing?
Tracing any power flow such as from the engine flywheel to the drive axles.
Used to determine which gears are in use delivering power.
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When gears are used in mobile equipment, such as a differential crown and pinion, the drive side gear tooth has what shape?
Drive side is convex
Coast side is concave
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What are three identifying gear measurements when viewed from the side?
- Root Circle
- Pitch Circle
- Outside Circle
Each is measured from one side of the gear, through the gear centre, to the opposite side of the gear.
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In order to determine circular gear pitch, what must first be established?
The pitch circle & gear tooth centreline.
Circular gear pitch is the distance between the gear tooth centrelines along the path of the pitch circle.
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What is the purpose of gear backlash?
To allow for expansion during operation and allow for lubrication.
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If gear backlash is incorrect, what may need to be adjusted?
Gear mesh
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Do hunting gear sets have to be timed?
No. Every pinion tooth will come into mesh with every crown gear tooth.
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What are the advantages of straight cut spur gears?
- Inexpensive to manufacture
- No axial thrust loads
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What are disadvantages of straight cut spur gears?
- Low strength
- Noisy
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