billy cart

Etymology
From +, referring to the former practice of hitching a cart behind a large goat.

Noun

 * 1)  A rudimentary child's cart; a soapbox car.
 * 2) * 1954 December, Rotary Reporter: Brief Items on Club Activities around the World, The Rotarian, |carts%22+-intitle:%22billy%22+-inauthor:%22billy%22&hl=en&ei=vSTmTuzzH6KViAfDrN22BQ&sa=X&oi=book_result&ct=result&redir_esc=y#v=onepage&q=%22billy%20cart|carts%22%20-intitle%3A%22billy%22%20-inauthor%3A%22billy%22&f=false page 38,
 * Whether you call them billy carts or soap-box racers, they're one and the same: homemade, four-wheeled, motorless racers that depend on a downhill course for their speed.In Coffs Harbour, Australia, for example, the Rotary Club recently held its third annual Billy Cart Derby for cars in two divisions: homemade racers and special championship cars.