It's pretty clear that DaVincni's journals could not have been deciphered nor his inventions built practically in his time but how much later could they have been built and used?
A modified and successful version of his flying machine, the automobile, the tank, etc.
Is it possible for these things to come about by the mid-late 18th century resulting in DaVincian technology emerging in use and popularity by the Napoleonic Wars or even the American Revolution?
If so, what are the effects?