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TRANSCRIPT
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Gear Trains
Image from Simon Fraser University
Image from JTEKT Torsen NA, Inc.
Image from blog of Haja Sherief
Image from HPI Racing
Image from ProQuest
Image from Sandia National Labs
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Image from Fortune, Apr. 30, 2007
MAE 342 – Dynamics of Machines
Variations on Gear Trains
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MAE 342 – Dynamics of Machines 3
Gear Trains
• Gear trains are used to:
Image from HPI Racing
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MAE 342 – Dynamics of Machines 4
Gear Trains
• Naming and labeling:
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MAE 342 – Dynamics of Machines 5
Gear Pairs
• The angle relationship is:
MAE 342 – Dynamics of Machines 6
Gear Pairs
• The “Kinematic Coefficient” is the rate at which a gear rotates with respect to the input
gear:
• The speed ratio is:
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MAE 342 – Dynamics of Machines
Gear Pairs
• Be careful with rotation directions:� For two external gears:
� For external and internal gear pair:
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ω2
ω3
ω3
ω2
N2
N2
N3
N3
ω3
N2 N3
ω2
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Gear Pairs
• The torque ratio is given by:
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Parallel-Axis Gear Trains• Speed ratio calculation
• Idler gears
N2 = 8
N3 = 24 N5 = 24
N4 = 8
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Parallel-Axis Gear Trains• Speed ratio calculation
N2 = 8
N3 = 24 N5 = 24
N4 = 8
• Speed calculation
If ω2 = 120 RPM, ω5 =
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Epicyclic Gear Trains
• Also called:
• Comprised of:
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Epicyclic Gear Trains
• These can be drawn schematically
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Epicyclic Gear Trains• A variety of arrangements are possible
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Epicyclic Gear Trains� 12 possible variations
according to Lévai.
� Bevel Gear Epicyclic Trains
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Epicyclic Gear Trains
• Speed ratio calculation
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Adders and Differentials• Some variations
Automobile differential
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Adders and Differentials
• Chinese mechanism for tracking direction.
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Adders and Differentials
• Limited Slip Differential
• Worm Gear (TORSEN) Differential
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Designing Gear TrainsGiven (typically):
� Overall speed ratio� Input torque� Available space� Location of input and output shafts
Solution:1. Choose gear arrangement (see tables from Gear
Handbook).2. Choose approximate gear ratios for each
reduction.3. Simultaneously choose pitch/number of
teeth/pitch circle radii/center distances.4. “Source” the gears.
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Designing Gear Trains
From Gear Handbook (Editor D.W. Dudley) McGraw Hill
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MAE 342 – Dynamics of Machines 21
Designing Gear Trains
From Gear Handbook (Editor D.W. Dudley) McGraw Hill
MAE 342 – Dynamics of Machines 22
Designing Gear Trains
From Gear Handbook (Editor D.W. Dudley) McGraw Hill