Because chains suck!

grabcad

Here is a concept for the Dads. No I change that. The Heroes. The go to guy when the cart doesn't go any more the go to guy when the tyre has a puncture. And depending on how angry he is when he smashes his finger with a hammer while fixing it, because we all know hammers fix everything. the go to guy when you have gravel rash all up your arm, probably not on that one thats the heroines job. But with this design at least there will be no chain to oil. No chain to get full of grime, mud, sticks.