Knex Transformer Cannon By 18efroese in LivingLEGO & K'NEX60611Save PDFFavoriteIntroduction: Knex Transformer CannonBy 18efroeseFollow More by the author: About: Mechanical Engineering. Inactive? More About 18efroese » This cannon clips onto Optimus prime and bumblebee. If you have any questions or recommendations just comment! Step 1: Build Now you just pull back and fire!