The RPM of "A" is 150 and hobbed with 86...

Question 1 of 270705eccefa3bacbc34ba4d47cd0

The RPM of "A" is 150 and hobbed with 86 teeth. If gears "B", "C", and "D" have 66, 22, and 48 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 between gear teeth and RPM in a simple gear pair (speed ratio = driven teeth ÷ driver teeth) • How a compound gear train works when two gears (B and C) are rigidly mounted on the same shaft and therefore have the same RPM • Carrying ratios step‑by‑step from gear A → gear B → gear C → gear D

💭 Think About

• First, write the formula connecting the RPMs of two meshing gears using their tooth counts. Which gear is the driver and which is the driven in each pair shown? • Look at gears B and C in the illustration: do they appear to share a shaft? If so, what does that tell you about their relative RPMs and how you pass the speed from B to C? • After you find the RPM of gear B (and thus gear C), how do you use that value and the tooth counts of C and D to get the final RPM of gear D?

✅ Before You Answer

• Be sure you’re using the correct ratio direction: driver RPM × driver teeth = driven RPM × driven teeth • Confirm from the illustration that B and C rotate together (same shaft, same RPM) before treating it as a compound gear train • After computing RPM for D, check if the value is reasonable: does each meshing step speed the train up or slow it down based on relative tooth counts?