I wanted to make this Optimus Prime and Bumblebee costume after seeing Youtube video of actual transforming costumes. Although these costumes do not transform a lot of attention went into detail for looks and mobility.
Design to both costumes for mobility, because cardboard boxes are hard to move in, are shoulder section can move up, forearm boxes have shaped cut outs to bend at elbow but hide shape of arm, same for knees to allow to sit. Flaps in front at waist are also made to flip up when seated and back of costume is cut short above waist so believe it or not bathroom breaks are easily achieved while not having to take off costume.
Feet separate boxes with build in shoes, take any old pair, for comfort and traction, cardboard is very slippery on hardwood floors.
Everything is painted cardboard, windows are layered industrial plastic. Everything was held together with hot glue and silver duck tape. When painting duck tape best to cover with layer of masking tape because paint starts to peel off the duct tape after awhile.
Arms and legs are foam padded to hold piece off of and centered on arm or leg. Main body box is kind of split in half and opens in the back held with Velcro to easily get in and out. I hot glued the Velcro directly to cardboard but after a few times of opening some sections, tore off the top layer of cardboard. I would suggest maybe sewing it right on with a possible reinforcement on the other side to prevent this problem.
I worked the shape of the helmets into the cardboard while fitted to our heads so no attachment is needed they fit on snug and comfortable.
Time worked on both costumes was under 2 weeks a few hours after work each day. Cost was about $100 for glue gun and glue and mainly for paint because cardboard absorbs a lot and needed several layers and primer. All other supplies I got for free from work because cardboard is easy to come by.