Ten simulations
Gear
Two meshing spur gears. Vary teeth Z₁, Z₂, and input RPM, and watch the inverse relation between speed ratio and torque ratio.
Pulley
Stack 1 to 6 movable pulleys. The number of supporting ropes N divides the pulling force and multiplies the pulling distance.
Lever
Move the fulcrum to switch between 1st-, 2nd-, and 3rd-class levers. The moment-balance F₁·L₁ = F₂·L₂ becomes visible.
Linkage
A four-bar linkage. Change link lengths to switch between crank-rocker, double-crank, and double-rocker — and trace the coupler curve.
Cam
A cycloidal cam profile drives a follower. See the connection between cam shape and the motion of the follower.
Crank
A slider-crank. Change crank radius r and rod length l to see how piston motion deforms with the ratio r/l.
Screw
A power screw. Lead L, torque T, and efficiency η give thrust F = 2π·T·η/L. Smaller leads multiply force.
Hydraulic
Pascal's principle, with two cylinders. The piston-area ratio becomes the force-multiplication ratio.
Belt drive
Two pulleys connected by a belt. The pulley-diameter ratio D₁/D₂ becomes the rotational speed ratio.
Robot arm
A 2-link planar arm. Joint angles at the shoulder and elbow uniquely determine the tip position (x, y) — forward kinematics.
What we focus on
Move it to learn it
Every screen has live animation and parameter sliders. You don't just read formulas — you feel them.
Formula and story
Each screen has an info sheet linking the visualization to the underlying formula and historical context.
Bilingual
UI in Japanese and English. Switchable from system language settings.
Offline-first
Everything runs offline except for the banner ad. Useful in low-connectivity environments.
The "RAKU" series
This is volume 15 of the "RAKU" series.
SUUGAKU (math), BUTURAKU (physics), DENRAKU (electricity), HARAKU (waves), NETURAKU (heat), SEIRAKU (stars), KORAKU (light), RYORAKU (quantum), RYURAKU (fluid), KAKURAKU (probability), KIKARAKU (geometry), KAGAKU (chemistry), KINRAKU (microbes), and NOURAKU (brain) — each app in the series puts a discipline within reach by letting you see and move the underlying ideas.
KIGAKU does the same for the machine elements and mechanisms humanity has built up.
Who it's for
Engineering students
An entry point to machine design, robotics, and mechatronics. Equations land harder when you see them move.
Self-taught engineers
Refresh your intuition for gear ratios, mechanical advantage, and the trade-offs between force and distance.
Science teachers
One-to-two-minute, visual-first demonstrations you can drop into a class.
Family learning
Start from pulleys and levers, end at a robot arm. A shared way to talk about machines at home.