What are compound gears?
Two gear stages in a row multiply their ratios. If one gear pair makes things 3 times slower, and a second pair on the next axle makes it 3 times slower again, the total is 3 × 3 = 9 times slower — and about 9 times stronger. That is how tiny motors lift heavy things.
Try Compound Counting Bench for freeComplete MightyCog booklet collection: 82 PDF booklets for $12.99. Instructions only; individual booklets remain free.
Explore the printable packTry it yourself
Count how many turns of the crank make the last gear turn once.
Build it: 2 builds that teach compound gears
- 🔬 Compound Counting Bench: Two five-to-one stages multiply: count 25 input turns for one output turn. (level 2 of 5, about 20 minutes, 7 steps)
- 🏁 Three-Speed Car: Two little gearboxes in a row make a big one: crawl, cruise or fly! (level 4 of 5, about 60 minutes, 20 steps)
In the classroom
- M3 Gearboxes: How Cars Go (Engineers, Advanced)
Common engineering questions
How can I try compound gears at home?
Count how many turns of the crank make the last gear turn once.
Which builds teach compound gears?
2 MightyCog builds teach it: Compound Counting Bench and Three-Speed Car. Start with Compound Counting Bench: 7 steps, about 20 minutes.