These model sheets are from various projects and ideas.
The Racer was an idea that came from a drawing theme started over on Atomic Cardboard. The characters are from a futuristic racing team that ride flying rocket bikes. The two human characters are the pilots and the robot is their mechanic. The robotic mechanic was also featured in a Spanish book called “Book of Characters”.
Francis was a character that was also created for an Atomic Cardboard theme. It was for a series on steam punk pirates. You can find more drawings and concepts at the Atomic Cardboard blog.
The character sheet for Tobi was a redesign of character originally created by George Bough. You can find the original concept and more work by George on his Deviant Art page