How Do Friction Toy Cars Work?
Spring Driven Friction Toys
Friction toys, a class of toys both antique and collectible and modern and disposable, are driven by springs 1. The power needed to drive the toy is gathered in the spring and released in a variety of ways as the spring unwinds.
How The Spring Is Wound
The drive spring of a friction-driven toy car is wound when the back wheels of the car are pushed backwards against a high-friction surface. Carpet, or even a wood floor, can work very well as a friction source, spinning the wheels backward and winding the spring. Glass or a wet surface work less well, failing to provide enough friction to move the wheels. In essence, the wheels and axle of a spring-driven friction toy car are being used in the same way as a winder for an old mechanical clock 2.
No Cogs Needed
While many spring driven toys require a cog or series of cogs to change the direction of the force of the winder or the force of the spring, a simple friction toy car seldom needs any cogs. The axle serves as a spool to wind the spring; the backward friction rotates the axle to wind the spring. When the car is released, the spring unwinds again, spinning the axle forward and propelling the car. This use of a spring lacks elegance and control but is delightfully easy to understand.