Re: steam bicycle
Steam theory and the basic components of a steam powered system are not all that complicated, but getting it all to work efficiently enough to put it into production is.
It's been nearly a century since a steam powered car was on the market and it was at best marginally successful, limited in convenience, range and speed. Even with all the research going on today you rarely see anything get beyond the experimental stage. There are various web sites dedicated to this very topic with plenty of engineers and such who know a lot more about this than you or I and still, there's nothing in production.
I'm currently building a steam powered bike. My build thread is in the beach cruiser section: "Something new and kinda sorta 100 years old looking". It's not rocket science, but it's fairly involved.