My son is in 8th grade and wanted to end middle school with the best Halloween Costume. I was little worried on how I could pull this off. I first printed out pictures of the cartoon, original and new versions of Optimus Prime. We then began to search for certain box shapes. One wide enough for the chest/body, long for the legs and square and long for arms.
Supplies that were bought were duct tape in red, blue and silver. Spray paint in the same colors. Glue sticks and colored foam sheets for decoration. Four dollar store flash lights, and ordered auto-bot decal on line. I saved every shoe box, paper towel roll I had. Cut and pasted card board for the head, body and legs. We began with the head. We used an old baseball helmet and built it from there. The next step was the chest/body. All a matter of bending and shaping the card board. I have old window frames I used for the truck windows, I used old house vent filters for the radiator in chest and legs.
The legs were the hardest part. I found long boxes I cut flaps of, except for the one on top and the two on bottom sides. I cut length wise down the leg in back and put a piece of Velcro down so he can get on and out. I used shoe boxes for the feet part. I again got pieces of card board and just built the shape. Then fit the legs onto the shoe boxes (feet) and built the feet. The arms were long boxes I had found and for the silver elbows I used the Styrofoam packing blocks and duct-taped them silver. After all pieces were built, I duct-taped the edges of each piece their color. Then spray painted. I used old toy truck tires we had around the house for the wheels on legs , arms and back.
The pipes are made out of paper towel rolls, spray painted silver and painted to look like pipes on a truck. This whole project was done body part by body part to fit and flow as he walked.