So I am starting a WALL-E project with my kids. I like robots, they like WALL-E, its a fit :-)
I am using square steel tubing, wheel chair motors, 2 Deep Cycle batteries, and so on. I need to find motor control boards still. I'm guessing when all is said and done he will weigh around 400lbs, a lot of the weight coming from the batteries.
If it isn’t too late in your design process, you should look for a “Jazzy” wheelchair by Pride Mobility and use those motors. They are smaller & lighter than traditional wheelchair motors but will still move a 300lb person while drawing less than 6 amps. Lighter motors, smaller batteries, and cheaper speed controller mean less weight and longer run time.