How does a crank and slider turn spinning into pushing?
A turning crank pushes a rod back and forth. A crank is an arm on a spinning axle. A rod joins it to a slider, so round-and-round becomes in-and-out. Car engines work backwards: exploding fuel pushes pistons, and the crank turns that into spinning.
Try Crank Orbit Bench for freeComplete MightyCog booklet collection: 82 PDF booklets for $12.99. Instructions only; individual booklets remain free.
Explore the printable packTry it yourself
Turn the crank slowly — where is the piston fastest? Where does it stop?
Build it: 3 builds that teach crank & slider
- 📐 Crank Orbit Bench: Trace a crank pin’s circle and compare its one-axis travel at equal angle steps. (level 2 of 5, about 15 minutes, 10 steps)
- 🔥 Twin-Piston Engine: See inside a car engine: two pistons race up and down in turns! (level 3 of 5, about 40 minutes, 22 steps)
- 🕷️ Klann Walking Spider: A robot that WALKS instead of rolling — beams and pins turn a spinning crank into steps. (level 4 of 5, about 60 minutes, 17 steps)
In the classroom
- M5 Machines That Seem Alive (Engineers, Advanced)
- M7 Fluid Power (Engineers, Advanced)
Common engineering questions
How can I try crank & slider at home?
Turn the crank slowly — where is the piston fastest? Where does it stop?
Which builds teach crank & slider?
3 MightyCog builds teach it: Crank Orbit Bench, Twin-Piston Engine and Klann Walking Spider. Start with Crank Orbit Bench: 10 steps, about 15 minutes.