I previously posted that this recent trip to San Francisco was my 20th visit and while I often like to return to places I have been before, it is nice to experience new adventures as well.
On Sunday before the course, we drove down to Monterey and had a great time at the Monterey Bay Aquarium, which I suspect my wife will blog about in the future, on Mindfulmagpie.com. So I will describe another adventure that piqued my interest, me being a scientist.
After an archetypically steep uphill hike from the San Francisco BART stop, we walked in the door to what appeared to be a busy machine shop. I’m not sure what I expected, maybe row after row of old cable cars much like the historical transportation museums I had been to in Europe. I quickly realized that unlike the other museums I had been to, the Cable Car Museum was an actual working museum.
Standing on the promenade overlooking the mechanisms, this is the view you are greeted with. The two large wheels in the foreground are the drivers for the cable with a third wheel in the distance supporting the returning cable. The position of the distant third wheel and the triangular towers supporting the cable are movable to compensate for the up to 100 foot stretching of the cable that can occur during its lifetime before it must be replaced.
At first I was puzzled by why the two big wheels, one being driven by the electric motor, where turning in opposite directions. That is until I saw from the side that the cable makes a figure-8 pattern snaking between the two wheels to maintain maximum contact between the cable and the drive wheels to prevent slippage of the cable.
The names above the cables signify the cable car line being driven, one cable for each of the four lines. The cables are continuously moving to provide a constant 9.5-mile per hour speed to as many as 26 cable cars simultaneously. Which begs the question, if the cable doesn’t stop moving, how do the cable cars stop and start?
This is where this device comes in. If you have ever ridden on one of the cable cars, you may have noticed the driver pulling on this handle.
The grip is what the driver or more correctly, the gripman uses to clamp onto the moving cable to provide propulsion for the car. And depending on how tightly the clamp grabs the cable, can adjust the speed as needed. The small red wheel, pictured here, is what the cable runs along underneath the street, a multitude on each line providing the cable singing tone you might hear when walking across a cable car track. The cable for each line is one continuous steel loop, almost like a giant rubber band, that runs along these wheels and larger transverse mounted wheels to feed the cable around corners and throughout its route.
Whether going up or down the steep hills of San Francisco, it is the grip tightly clamped onto the cable, which provides the uphill propulsion and the downhill resistance to prevent a runaway car.
And when it is necessary for a car to stop, there are two types of brakes applied (along with a third emergency brake). First, there are metal shoe brakes that are pressed against the wheels and second, wooden brakes that are pressed against the track. It is the latter brakes that leads to the burning wood smell you may notice after a stop. Soft wood is used to provide maximum resistance but which must be replaced every two to four days.
The museum provides excellent explanations of the workings of the cable cars and their history, along with working cars, the above being the oldest cable car in the world.
My wife, less interested in the workings of the cable cars, chose to sit out most of my exploration but when I was excitedly explaining everything to her later, she was most surprised by my unsolicited detailed explanation.
Hopefully this brief discourse has struck an interest in you, my reader, to learn more. So the next time you happen to be in San Francisco, rather than just catching a ride on one of the cable cars, visit the museum as well.
After seeing these cars over my whole life, it was fascinating to learn how they actually worked and how the nearly mile-long cable serpentines under the street providing their propulsion.