The San Francisco Municipal Railway "MUNI" is one of the last remaining railway companies in the world to operate cable cars. The cars are a major tourist attraction to SF and are as much a part of the city as the wooden W class trams are a part of Melbourne (even thought the short sited privately owned tram companies in Melbourne have seen fit to mothball them). MUNI operate an interesting diversity of equipment across their three railways within the city. MUNI is the left overs of the original SF Key System railways which were ripped up in the 1950's after oil company pressure forced their demise. MUNI is a lot of things and lately have actually begun to focus on customer service and improving their poor public image. In my project work I work closely with MUNI Green LRV yard and I've seen the changes up close. One of the best ways to annoy just about anyone at MUNI is to describe one of their vehicles as a "tram" :). I heartilly recommend the experience of riding on the outside of one of the toast rack cable cars with the close clearances between it and other vehicles it is quite a thrilling ride. Only do it if you have strong arms!
The cable cars operate from a driven (pulled) cable which runs in a trough between the rails. There is a (mostly) tourist operation running from the corner of Powell and Market (the centre of SF's CBD) and Fisherman's Wharf on the marina. This line goes up and down some of the steepest city hills in the world. Only a cable or funicular railway could operate on these hills. The other line runs up and down California street from (near) Embarcadero ferry terminal up to the top of Knob Hill. The cars operate by gripping the cable using a "grip". The car maintains a constant speed up and down hills by holding the cable. The number of cars in the system going in any direction is regulated so as not to overload the cable and winding system. The cars do have brakes which are used when going down hills and when stopping.
The brakes are made of maple and oak wooden blocks and are pressed down onto the tracks using a winding handle. If put on hard enough the brakes can lift the wheel flanges out of the tracks, the cable grip prevents this from happening as it is too big to be drawn out of the cable space and cannot be lifted from the cable except at special locations throughout the system. When stopping the operator releases the cable and coasts to a stop using the brakes sparingly. The cable car is incapable of stopping when going down hill and all traffic signals are arranged so that the cable cars have right of way and do not have to stop except where they can do it safely. Surprisingly there are very few accidents. This shot of a typical bogie shows how it connects to the car, and shows the brakes and cable grip equipment in place. Sorry about the poor picture quality. These 100+ year old bogies still operate under the cars today. The car is driven by a single operator who uses a series of huge levers to grip and release the cable and apply the brakes. The operator is assisted by a conductor who collects fares and manages the rear brakes on hills. The cable car operators are the hardest working people at MUNI - their job is tough and often thankless. Tourists often crowd the driver making his/her job just about impossible as they need a great deal of working room. The drivers are rarely shy of telling people to get out of their space. The driving position is between the seats at the front of the vehicle.
These shots show the cramped driving position where the operator has to work and gives some idea of the controls. From what I could figure out during my ride the large black handle engages the cable in the grip and the smaller red handles control the brakes and lift/release of the cable. The car "drops" the cable before going around corners and coasts until getting around where it again picks up the cable. Note the large hole in the floor which enables the grip mechanism to be lifted into the car when it goes into the car barn or is being transported on non-cable tracks.
As the cars are single ended (always driven from the same end) at each end of the line there is a turn table allowing the car to be turned to face the right way at each end of its trip.
The car rolls down hill (there is no cable at the turn table) onto the turntable where it is braked by the conductor. The car is then manually turned. Along with the hard work of driving the car at each end of the run, the driver and conductor have to manually turn the car by manhandling it around.
While they are not used any more these enclosed dummies used to run on the system pulled behind the cable cars. When the system was strictly public transport it was extremely well patronised before the age of the car and only began to decline to its current state in the 1950's.
This is the car barn and winding house for the cable car network. The large chimney suggests that the plant was once powered by steam. Note the slope of the hill alongside the barn, this hill is mild compared to the hills travelled throughout the network. The building houses all the cars, the winding equipment and a small but well detailed museum.
The system is driven by several huge electric motors which drive 3 metre diameter fly-wheels through a reduction gearbox. The system heavilly relies on the stored power in the spinning fly-wheels as the motors themselves are not strong enough to pull the cable when loaded.
This shot shows a better view of the winding equipment showing the detail of the two large motors and gear boxes. I was unable to determine the horse power of the motors, but they don't look much bigger than a traction motor on a modern tram suggesting they may be in the range of 30 to 50 horse power.
These wheels are mounted on sliding bases which are connected to springs and ropes. The bases move back and forth absorbing the shock of cars gripping and releasing the cable as they do their work throughout the network. The towers both guide the cable and are used during cable inspection. The cables are inspected for wear and damage regularly and are usually repaired in situ. If a cable or long section of cable must be replaced the network has to be shut down, the cable tied then cut, the new cable is spliced in and the winding motor used to pull it through the network while the old cable is pulled along by another motor until the new section of cable is in place. The old cable is then cut and the old and new spliced together. The cable splice is quite an art and when done right leaves almost no evidence for the untrained eye that there is a join at all.
Under the street throughout the network there are these huge pullies which guide the cable around corners and help it change elevation. This set does both. Note how the wheel closest to the camera is slanted changing the elevation of the cable from almost flat to travelling up hill.