Build a motorized robot, race car, and countdown timer – all that run without any batteries or electrical power! The secret behind these fascinating machines is a power source called a mainspring – a spiral-shaped spring that stores up energy when wound up by hand, and then converts that stored energy back into motion when it discharges.
Related products
$ 13.50 Select options This product has multiple variants. The options may be chosen on the product page
$ 13.50 Select options This product has multiple variants. The options may be chosen on the product page
$ 13.50 Select options This product has multiple variants. The options may be chosen on the product page