Gear and belt drives
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Flip to reveal answersHow do you design a gear train to a required ratio?
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All 4 Flashcards — Gear and belt drives
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Question
How do you design a gear train to a required ratio?
Answer
Input speed ÷ required output gives the overall ratio; split it into stages of about 5:1 or less; choose tooth counts that multiply to it; then check direction and physical size.
Question
Why split a large ratio into stages?
Answer
A single 30:1 pair needs a gear thirty times the driver's diameter. Two stages of 5.5:1 multiply to the same ratio inside a hand-sized housing.
Question
How do you keep the output turning the same way as the input?
Answer
Use an even number of external meshes, or add an idler. The idler restores the direction and leaves the ratio unchanged.
Question
Why avoid an exact whole-number gear ratio?
Answer
The same pair of teeth then meet on every revolution, so any imperfection wears a pattern into that pair. A ratio like 5.5:1 spreads the contact.
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Topic 7.3 hub
Mechanical systems applied
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