Lego Mousetrap Car

Step 13 FIN!

Now you need to wind it up, which some people find difficult. First you need to pull the string tight, but don't pull the trap up, just make the string taught. You should have around 3 inches of excess string behind the rear axle. Start wrapping it around the axle. Once you have around a half an inch or so left slide what you have done together. You then need to push the excess string under the taught portion, so that when you wrap it up more it will run over it and hold it there. Once you get that to work, wrap up the car from the wheels so that the string remains taught. Horrah! This wrapping technique allows for the release of the string after the mouse trap has expended its energy.

Oh, and make sure to wrap it the right way, or your car will go backwards...