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

Here's a more in-depth look at the workings of San Francisco's unique cable cars. What goes on below the slot - how does the cable stay in tension and how does the grip work?


This is a closer look at the technology developed in the 1870s and 1880s which keeps them moving for the delight of tourists from all over the world.

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[johnnyzweig]

The Depression Pulley was driving me nuts for years! How can you grip the cable from above and not bump into the pulley that's holding the cable down when it goes through a concave depression? Finally I have my answer. Thanks a ton!

[RandyKng]

About 30 years ago, on my first visit to San Fran, I was enamored by the whole system, so I spent a day riding, chatting with the brakeman and the gripman and visiting the Cable Car Museum where the power sources are. Absolutely fascinating, I really hope they keep it all going.

[sgt.gunslinger]

So basically its like a chairlift mechanism, just not as automatic. Cool video

[dbdrdbag]

Very detailed and clear explanation of how the cable cars work! Thank you!

[feynthefallen]

It's nice to learn something you always wanted to know, but never knew you wanted to know.

[jossdeiboss]

This is the first time I get full information on how these cable cars work. Great video!

[MichaelMossmanNZ]

Greetings from New Zealand ... this entire setup seems extremely complex, not to mention the maintenance required. The "dyes" only last 2 days, & the cables themselves, between 75 and 250 days! Must cost a fortune =)

[kevinc-]

I highly recommend visit the cable car museum in San Francisco, and you can see the equipment running, and the tension pulleys move back and forth as the cables stretch and shrink as cars accelerate and decelerate, as the cable also slows the cable cars going downhill which balance the cable cars going uphill so the motors are surprisingly small. They also have equipment on display.

[oslro]

How do they replace the cable when that time comes around?

[seanmcgee]

Great content answered several of my long thought of questions THANX!

[rewolff]

Thanks for the nice explanation. Learned a lot.
Keeping the cable under "the same tension" as much as possible will also help in the longlevity of the cable. Less metalfatigue!
Of course the tension can never be completely constant, as the cable cars use a force in the direction of the cable to propel themselves.
This principle of keeping the cable tension constant is fully used in the cable cars (in the mountains) that "ride" on one cable and get pulled by a second smaller cable.

[vinceturner]

Thanks, great explanation of the inner workings.

[JayKarpwick]

Some historical trivia: Several US cities including NYC installed cable-car systems at the end of the 19th C. They wanted an alternative to stringing overhead wires, but found out that moving cables underground were far more trouble-prone and expensive. Most systems were gone by the early 1920s. Even SF eliminated all but 3 lines, keeping only those for steep hills along with their value as tourist attractions.

[ChuckLynch-uwjf]

I lived there for 10 years and whenever my public transit options suggested a cable car I was thrilled. Even locals think it's fun!

[MildMisanthropeMaybeMassive]

Cable Cars and their headquarters/museum smell really nice.

[carsten]

Fascinating, thanks for the explanation.

[djtonio]

Nice video! I'm very surprised about the cable lifespan, of 75 to 250 days, it seems very short, are you sure of that?

[Kivetonandrew]

I saw another video of how this system works a good while back. Very informative and went in to much more detail than this one. Using 3D computer graphics, moving models of how everything works in great detail answered many of my questions. Also, this video dues not explain how the California Street Line has priority owed the other lines at intersections. The other lines have to drop the cable and coast across the intersection.
I'm from the UK but I visited San Francisco a few years ago. Rode all the cable car routes and visited the museum. An amazing system and much steeper than I imagined.

[neilbain]

The Glasgow Subway was later, 1896; the gripper and cable mechanism had certainly evolved. It could be directly operated from the cab. There were two circular lines, one in each direction. It was entirely underground and cars were lifted off the tracks by a crane over a pit in Broomloan Depot. The subway was electrified by 1935. The crane, pit - and all the cars, by then about 80 years old, lasted till modernisation in 1977.
Edinburgh ran entirely on cable cars after horse trams, from 1888, not going all electric till 1923. The network was extensive. Car termini ended in a set of Y points to single track in the middle of the road where the cable changed direction and the grip could pick up the cable on the return and pull the tram through the points in the appropriate direction. There was a city boundary with Leith at Pilrig Street with a terminus where people had to get off and walk a few feet onto a Leith electric tram. When the new tramway was laid to Leith in 2023, a pit with two huge pulley wheels was unearthed (there's a youtube video on their discovery). The wheels were on fixed bearings, unpowered and had a centre ridge. They were offset from each other. They've now been erected as a sculpture on the pavement nearby. I've no idea how they worked.

[marcadiadd]

I share the same questions asked by others and here’s another:

If the system requires a person lifting the cable up to begin, then how does the car let go and then re-grip the cable around a curve or at an intersection without someone there to lift the cable?