Because chains suck!

grabcad

This concept is for heroes - fathers who fix everything. They're the ones you call when the cart stops working or you have a puncture. Sometimes, they might even hurt their fingers with a hammer while repairing. Additionally, they help with gravel rash on your arm, but that's another heroine's job! With this design, there'll be no greasy chains to worry about as they won't get covered in dirt and debris.