Back to Topic 3.3 — Mechanical systems
3.3.5Design Technology HL4 flashcards

Combining motions

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Card 1 of 43.3.5
3.3.5
Question

Why are mechanisms chained rather than combined into one part?

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All 4 Flashcards — Combining motions

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Card 1concept

Question

Why are mechanisms chained rather than combined into one part?

Answer

Because each mechanism changes one thing. Chaining gives cheap standard parts, faults traceable to one stage, and ratios changeable by swapping a single component.

Card 2concept

Question

What does chaining mechanisms cost?

Answer

Efficiency, free play and wear. Efficiencies multiply: five stages at 95% each deliver about 77% of the input.

Card 3concept

Question

How should a mechanism chain be analysed?

Answer

Write the motion at each junction first, then name the mechanism that converts each pair. One stage at a time: motion in, motion out, reason.

Card 4example

Question

Name the five mechanisms in a sewing machine and what each does.

Answer

Belt — reduces motor speed. Gears — synchronise the two shafts. Crank — rotary into reciprocating for the needle. Cam — times the fabric feed. Linkage — clamps the presser foot.

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