Buttermilk Race Car

This is a toy: rubber band powered car made out of buttermilk paper bottle.

To make the car you need one empty buttermilk paper bottle , four lids from Starbucks oatmeal cups, three paper straw (could be found in craft store), about one foot of ~3 mm solid cupper wire (hardware store), one rubber band 5-7 inches (office supply store). Please pay an attention that rubber bands on the photo are shorter and different of what I actually used for the car.

Mark with compass circle in thew middle of each wheel (diameter should be the same as diameter of paper straw). With sharp knife make eights cut through the center of circle and bend paper sectors in.

On sides of the car body cut four round opening for axes.

Make the hole through the middle of straw with awl. Insert rubber band inside straw. To make that process easy you may attach wires to rubber loop. Apply some glue to small wooden stick and insert it in to the hole. Glue needed to attach stick to paper straw. Stick must be put inside rubber loop but there is no need to glue rubber to wood.

Let the glue dry out and cut the extra part of stick with knife or hawk saw blade. Cut another straw alone, apply glue inside and put it over straw with rubber loop to secure wooden stick in place.

Insert straw with rubber engine into openings and one more straw into another openings. Apply glue to straw ends and put wheels there. Let glue dry out.

With awl make two holes on the bottom and two holes on the top of the car close to rear wall. Shape wire and insert it in holes. Shape wire as shown in the first picture and attach band loops to holders. If band is too long (as in may case) turn it around one or more times. Ideally rubber inside axis should be neither loose nor tight.

Charge the car by rotating drive wheels in the direction opposite to future car movement. Run car on flat and smooth surface (like hardwood floor).

As you can guess using buttermilk bottle is not mandatory. Here you can see the car made ten years ago (under my guidance) by one school student. Different components but the same principle. Feel free to experiment. Just one tip: for car to run longer the size of drive wheels should be big enough (the bigger the better). Size of other wheels is not important.