How they work - what's happening out of sight on the San Francisco Cable cars? 

These cities didn't experiment ... they actually installed and ran cable systems. Read the exhaustively extensive tome "the Cable Car in America" by George Hilton (there's a revised edition). It details the development of the system and covers every city in the US and internationally that had cable traction. It even tells about planned systems that were abandoned when the electric streetcar was developed. It's well worth the purchase price and will leave you appreciating the Victorian-era invention which still runs the exact same way 150 years later.

@@sfmike711 Thanks for that info including the book title. I realize that I mis-spoke with the word "experimented", and have edited my original response. I have a lot of documentation on early streetcars but very little regarding cable-car systems. Interestingly, last year was the 150th anniversary of San Francisco's first line. I was very fortunate to study German with Dr. Alan Rice, who in addition to being a master linguist was one of the top experts in US traction history. I think I learned more about streetcars from him than I did about scientific translation, hah!

I heard SF wanted to eliminate the cable cars completely but yet the cable cars are SF's iconic symbol. Like the Eiffel Tower was only to be a temporary structure but it became iconic symbol for Paris. And the cable cars let you ride on the outside.

@@wrightmf Based on info I’ve seem, both are absolutely correct. The Eiffel Tower was supposed to be torn down a few years after the centennial fair ended but as you say it became a total icon. And SF’s plans to eliminated the last 3 operating cable lines ran into a lot of public opposition, especially b/c of how much tourism they bring. They and the St. Charles streetcar are the only two mobile attractions on the register of National Historic Landmarks!