Here are a few relevant links to things written/posted about on this site.
Neat Old Toys: http://www.neatoldtoys.com/
Bit of Tonka history: http://www.fundinguniverse.com/company-histories/tonka-corporation-history/
Tonka Corporation – more detailed history: https://www.pgpedia.com/t/tonka-corporation
Flywheels – good detailed summary: https://www.explainthatstuff.com/flywheels.html
Friction motors: https://en.wikipedia.org/wiki/Friction_motor
Gears – good summary: https://www.explainthatstuff.com/gears.html