ABSTRACT
New inventions often have to wait for appropriate materials to come about before they become a practical reality. Leonardo da Vinci’s sketch showing the principles of helicopter flight remained a sketch for over 400 years until high strength steels, titanium and forged aluminium became a reality both for the airframe and the engine to drive it. Steam power did not really take a hold until iron could be reliably cast without the brittleness that limited working pressures to a few pounds per square inch and precision of manufacture improved to produce a close fit of piston to cylinder (itself partly a function of materials).
