The RPM of "A" is 150 and hobbed with 94...

Question 1 of 270705eccefa3bacbc34ba4d47cd1

The RPM of "A" is 150 and hobbed with 94 teeth. If gears "B", "C", and "D" have 80, 30, and 46 teeth respectively, the RPM of "D" in the gear train illustration is __________. See illustration MO-0088.

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Question 1 of 27070

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🔍 Key Concepts

• Relationship for meshed gears: (Speed₁ × Teeth₁) = (Speed₂ × Teeth₂) • How a compound gear train works when two gears (B and C) are on the same shaft and therefore have the same RPM • Overall speed ratio in a train is the product of each individual gear-pair ratio (driver vs. driven)

💭 Think About

• From the sketch, which gear is directly driven by gear A, and which gear is on the same shaft as that gear? • If A drives B, and C is rigidly attached to B, how can you express the RPM of D in terms of the RPM of A and the tooth counts of A, B, C, and D? • As teeth count increases from driver to driven, does the driven gear turn faster or slower? Use this to check if your final RPM should be greater or less than 150 RPM.

✅ Before You Answer

• Write the gear equation for each mesh: A–B and C–D separately before combining them. • Be sure you treat B and C as having the same RPM because they are on the same shaft (compound gear). • Before picking an answer, check that your final RPM changes in the correct direction (overall reduction or increase) based on whether the driven gears have more or fewer teeth than their drivers.