How Do Cable Cars Work?
by Joe Thompson


Where Should I Go from Here? Visit the Map

How billboard I spotted this ask.com billboard while walking down Third Street one day. September 2012. Photo by Joe Thompson.

In The Cable Car in America, George W Hilton identified four essential features of cable car technology:

In this page, I will also describe some other features of cable cars that are not distinct or essential to the technology, but which I find interesting. Use your browser's "Back" button to return.


The Grip

6 grip Car 6's bottom grip, visible in the pit at the Washington Street exit from the car barn. December 2003. Photo by Joe Thompson.

Types of Grips (front view)
GRIPS
Key
A - Bottom Grip
B - Side Grip
C - Top Grip

black line - Shank. A narrow plate that extends from the car through the slot in the street.
blue line - Jaws. The jaws close upon (grip) the cable.
red line - Dies. Soft metal plates that actually touch the cable.
pink circle - Cable. The cable imparts motion to the car.This shows the position of the cable when held in the grip.
black circle - Cable. This shows the position of the cable when in full release (not held in the grip).

The grip can be in three positions:

  1. Full release. The grip is not in contact with the cable. The cable rides a few inches below the grip. In a bottom grip, the jaws are wide open.
  2. Partial release. The grip holds the cable, but the cable runs freely through it, imparting no motion to the car. In a bottom grip, the jaws are partly closed.
  3. Full grip. The jaws of the grip push the dies against the cable, holding it tightly, causing the car to move at the speed of the cable.

Grips were the source of constant patent litigation during the period when cable cars were widespread.

Hallidie and Eppelsheimer's original grip was a bottom grip. With a bottom grip, the cable is picked up and dropped through the bottom of the grip. It is easiest to pick up and drop the cable with a bottom grip. The surviving San Francisco cable car lines use a later bottom grip designed by Eppelsheimer.

The side grip, single jaw or double jaw, was the most popular type of grip during the period when cable car lines were being built. Designers considered side grips to be simpler, and to have less danger of the cable being accidentally torn out of the grip on a steep grade. Conversly, it was harder to drop the cable at a crossing or in an emergency with a side grip. Double jaw side grips had jaws on each side. This was considered useful for complicated duplicate cable systems like the ones in New York City, and for light single-track systems, as in the Second Street Cable Railway in Los Angeles.

Top grips were used by companies that did not want to pay royalties to grip patent-holders, such as the North Chicago Street Railroad. They required deeper conduits than bottom or side grips. They made it almost impossible to drop the cable for a crossing or in an emergency. There were no redeeming qualities.

Hallidie's original grip used a horizonal wheel to open and close the jaws. The majority of cable car lines used levers to operate their grips, because a long lever gives good leverage. Levers, however, took up space in the car that could be used for fare-paying passengers. Some lines used vertical wheels mounted on the front platforms of cars. This used less space. The surviving San Francisco lines use levers.
Bottom grip Eppelsheimer bottom grip on display at Washington and Mason. March 2002. Photo by Joe Thompson.
Bottom grip jaws The jaws of an Eppelsheimer bottom grip on display at Washington and Mason. March 2002. Photo by Joe Thompson.

Cal Cable Grips President JW Harris of the California Street Cable Railroad standing in front of a car, perhaps at Presidio Avenue, with the refined and original versions of the Root single jaw side grip used by the line. Mr Harris started with the company as a manual laborer in 1879 (Source: "Cable Car Days in San Francisco", Edgar M. Kahn, 1944). Aug, 1997 Picture of the Month.

Endres grip The heavy Endres bottom grip used on Hoboken cable cars. Note the cable lifters before and after the grip. (Source: Image courtesy of Rail-Road Extra). January, 2002 Picture of the Month.

Peckham truck The Peckham Motor Truck and Wheel Company displayed this cable car truck at the 1893 Columbian Exposition in Chicago. "Fig. 4 is ... (was) built by the Peckham Company for the Broadway cable railway. It is similar to the standard 6A truck, but equipped with grip attachments." (Source: "The Exhibit of the Peckham Motor Truck and Wheel Company.", The Street Railway Journal, November, 1893).

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The Cable

Broderick and Bascome spool Broderick and Bascome cable spool at Washington and Mason. March 2002. Photo by Joe Thompson.

The cable is an endless wire rope, made of a hemp core wrapped with strands made of groups of small steel wires. The hemp core gives flexibility and the steel strands give strength.

In cable-making terminology, the direction in which the strands are wrapped around the core is called the lay. In a standard lay cable, the strands are wrapped around the core in the opposite direction from that in which the wires are wrapped within each strand. In a standard lay cable, the wires which peak near the surface of the cable tend to fracture and break, which can lead to broken strands, which can jam in the grip and cause a car to run away. In a Lang lay cable, the type currently used in San Francisco, the strands are wrapped around the core in the same direction as that in which the wires are wrapped within each strand. Lang lay cables are less susceptible to broken strands.

Cables were treated with a variety of substances to make starts smoother. San Francisco used pine tar until the system was rebuilt in the 1980's. Now Muni uses a synthetic lubricant. Operators claim that it makes the cable too slippery.

Crossing two cable car lines is a complicated operation. One line's cable has to pass below the other line's. The method of determining which line was able to hold the cable (the superior position) and which had to drop it (the inferior position) and coast across varied from city to city. At all the crossings in San Francisco, superiority was determined by seniority. The first crossing between two lines was at Larkin ( Sutter Street Railway) and Geary (Geary Street Park and Ocean Railway) Streets. The Larkin Street line had the superior position because it was there first. Some cities, such as Kansas City, considered safety in determining superiority.

Powell Street cable car 28, inbound on Powell, crosses the California Street line. Powell Street cars have to drop the cable and coast across the California Street tracks. Inbound cars have to stop at the yellow line and pick up the cable before proceeding down the Powell Street hill. Taken on 19-June-2007. Click arrow button to play video. (Adobe Flash is required. Some browsers will require two clicks to start the video.)

I have found magazine articles describing the way side grip and top grip lines crossed each other.

At the only surviving cable railway crossing, at California ( California Street Cable Railway) and Powell (Ferries and Cliff House Railway) Streets in San Francisco, the California Street line has superiority because it was built in 1878, while the Powell Street line was built in 1886. Because of the dangerous position, with California Street rising to and from the intersection and Powell Street rising in both directions to the intersection, this crossing is controlled by a signal tower. Read Emiliano J Echeverria's article about the tower.
Washburn and Moen wagon Washburn and Moen used this huge wagon, pulled by 56 horses, to deliver this 31,000 foot, 130,000 pound cable to the Market Street Cable Railway's McAllister Street powerhouse. Source: "Transporting Cables in San Francisco", Street Railway Journal, May, 1895. Page 805.

The last cable car line built in San Francisco, the California Street Cable Railway's O'Farrel/Jones/Hyde line had to drop rope 22 times (9 crossings, powerhouse, end of line) on a round trip. This is described in Gelett Burgess' poem "The Ballad of the Hyde Street Grip".

San Francisco's current system uses four cables, each run at 9.5 miles per hour:

  • Powell Street The 9,150 foot Powell Street cable issues from the Washington/Mason powerhouse, down Washington to Powell, down Powell to the terminal sheave at Market, back up Powell to Washington, and blind up Washington to Mason.
  • Mason Street. The 10,150 foot Mason Street cable feeds blind down Washington to Powell, up Powell to Jackson, up Jackson to Mason, Mason to Columbus, Columbus to Taylor, Taylor to the terminal sheave at Bay, back up Taylor to Columbus, Columbus to Mason, Mason to Jackson, Jackson to Powell, down Powell to Washington, blind up Washington to Mason.
  • Hyde Street. The 15,700 foot Hyde Street cable issues blind up Mason to Jackson, up Jackson to Hyde, up Hyde to the terminal sheave off Beach, back down Hyde to Washington, Washington to Mason.
  • California Street. The 21,500 foot California Street cable has too many turns. It issues blind up Mason to Califonia, down California to the terminal sheave at Drumm, back up California to another terminal sheave at Van Ness, back down California to Hyde, down Hyde to a sheave at Jackson (to allow the cars to go back to the barn), back up Hyde to California, down California to Mason, blind down Mason back to Washington.

San Francisco currently uses a cable with a diameter of 1.125 inches (thanks to Manny Manasievici for the measurement).

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The Conduit

roadbed section Example of the massive construction needed for a cable railway roadbed and conduit. This illustration of a New York cable line is from "The Cable Street-Railway" by Philip G. Hubert, Jr, from Scribner's Magazine / Volume 15, Issue 3, March, 1894. No thumbnail.
The conduit is a trench that runs under the street. The cable runs through the conduit on a series of pulleys. Most conduits have an open slot, through which the grip extends to reach the cable. When a conduit is used only to carry the cable, without an open slot, it is called a blind conduit. There is a stretch of blind conduit in San Francisco, from Washington up Mason to California Street.

The trackbed of a cable car line, including the rails and the conduit, is much more complicated than a standard railway trackbed. The rails cannot be supported by cross-ties because a way has to be left open for the slot. Most lines used a metal form called a yoke to support the rails and form the conduit.

Within the conduit, a variety of sheaves and pulleys are used to support the cable. On straight, level track, when the cable is not held in the grip of a passing cable car, the cable runs on a series of vertical carrying pulleys. At each terminus, the cable reverses direction on a large horizontal terminal sheave. At the top of a hill, a heavy crown pulley resists downward pressure. At the bottom of a hill, a depression pulley, usually movable on a bottom grip line, keeps the cable from rising out of the slot.

Yoke Old yoke on display at Washington and Mason. The open part would be at the top. January 2002. Photo by Joe Thompson.

conduit section Example of the inadequate all metal conduit used in Philadelphia. The slot squeezed shut when the ground froze. This illustration is from "The Cable System of Street Railways", from Manufacturer and Builder / Volume 16, Issue 7, July 1884.

Girder Rail Example of early steel girder rail used by the Clay Street Hill Railroad; it was rolled by the Cambria Iron Company of Johnstown, PA in 1877. This illustration is from Street Railroad Roadbed, by Mason D. Pratt and C. A. Alden, Street Railway Publishing Company, New York. Thanks to Randy Hees for providing the illustration.

The first cable car lines, like the Clay Street Hill Railroad, ran in a straight line from terminal to terminal. The only track curves were used to bring cars into and out of the car barn.

The first cable car line to include a curve in its revenue trackage was the Presidio & Ferries Railway, which had to move cars at an oblique angle from Columbus to Union Street. The shallow angle and local geography allowed cars to drop the cable and coast around the corner. This was referred to as a "let go" curve. The Hallidie bottom grip allowed the cars to drop the cable and to pick it up around the corner with ease. A large horizontal sheave allows the cable to change angle from one street to another. Large sheaves are good because they put very little stress on the cable.

Other locations did not allow for the use of a let go curve. In some cases, the curve was too sharp; in other, the curve had a hill climbing towards it in one or both directions. This called for the invention of the "pull curve", which allowed a car to traverse a curve while holding onto the cable. George S Duncan built the first pull curve in Dunedin, New Zealand, for the Roslyn Tramway, which had to carry cars over a climbing curve around Saint Joseph's Cathedral.

The pull curve is complicated because it needs a series of small horizontal sheaves placed close together to keep the cable in position under the slot around the curve. As the car passes through the curve, it pulls the cable up and away from the sheaves. This puts a heavy lateral strain on the thin grip shank; the lateral forces tend to try to pull the cable out of the grip, or to pull the grip over to strike the sheaves. Pull curves generally include a "chafing bar"; the grip slides along the bar, which holds the grip away from the sheaves. In general, calls have to go around a pull curve with the cable tightly held, at full speed. This can be dangerous in heavy traffic, especially at locations like Manhattan's famous Dead Man's Curve.

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The Powerhouse

Driving Wheel Big drums at the Third Avenue and Sixty-fifth Street powerhouse of New York's Third Avenue Railroad. The driver and the street cable are in the foreground. From "The Cable Street-Railway" by Philip G. Hubert, Jr, from Scribner's Magazine / Volume 15, Issue 3, March, 1894.

During the cable car era, powerhouses were generally steam-driven, so they required lots of room for boilers and coal storage. The surviving San Francisco cable lines have been driven by electricity since the 1920's.

Methods of driving the cable varied, but had to addresss certain problems. The cable had to be set in motion without slipping. This was commonly done by wrapping the cable one or more times around a large powered wheel called a driver, and usually one or more times around a small, unpowered wheel called an idler. The cable had to have a constant level of tension. This was dealt with in various ways. The most common method was the one still used in San Francisco, the tension run. After the cable leaves the driver, it runs down a long corridor to a smaller sheave, which is on a movable platform over a long pit. The platform can be moved along the corridor to keep the cable tight when it stretches. To deal with short-term changes in tension caused by cars gripping and ungripping the cable, the sheave can move on the platform, pulled tight by a weight that hangs in the pit.

LA Cable Powerhouse Tension run at the Seventh and Grand powerhouse of the Los Angeles Cable Railway. The closest sheave is on a movable tension carriage. The drivers and idlers are in the background (Source: [group 2:20], William C. Barry Collection of Los Angeles Area Photographs, BANC PIC 1964.056--PIC, The Bancroft Library, University of California, Berkeley.).

Tension Device Tension apparatus using a tower and a weight. This arrangement used less space than a conventional tension run. This was at the Metropolitan Street Railway's powerhouse at Fiftieth Street and Sixth Avenue in New York. From "The Cable Street-Railway" by Philip G. Hubert, Jr, from Scribner's Magazine / Volume 15, Issue 3, March, 1894.

tension_carriages Tension carriages in the powerhouse of the Glasgow District Subway, from "Glasgow District Subway", an October 1898 Cassier's Magazine article. October, 2011 Picture of the Month.

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Turning the Cars

Unless a transit line operates on a loop, like the Tacoma, WA line, its vehicles have to change directions when they reach the ends of the line. The way in which a vehicle changes directions is in part determined by whether the vehicle is single or double-ended. Single-ended cars or trains were most common during the cable railway era, but San Francisco's surviving lines use both types.

Single-ended Powell Street cars use turntables to reverse direction. I took the following series of photos around the Powell and Market turntable in December, 2001.

turn table 1 The Powell/Market turntable. Note the pipe handles which make it easier to turn. The large hatch which covers the terminal sheave is in the lower right corner of the photo.
turn table 2 Car One coasts onto the turntable. Note the grooves in the bricks where cars have run off of the table.
turn table 3 The conductor pulls a wire attached to the lever which releases the turntable so he, the gripman, and a helper can start turning Car One.
turn table 4 The gripman, and the conductor, who is not visible, push Car One off of the Powell/Market turntable. The helper prepares to rotate the turntable back into position for the next car.

When the car is off of the turntable, the gripman will jump on and pull the track brake handle to stop the car over a small depression, which puts the grip in position to pick up the cable. When he pulls the grip lever part way back, the car is in partial release.

The Powell Street turntable was replaced in October-November, 2002.
This video, taken on 24-January-2007, shows car 21 rolling onto the turntable at Powell and Market, being turned, and being pushed off. Click arrow button to play video. (Adobe Flash is required. Some browsers will require two clicks to start the video.) See more videos on my Cable Car Video page.

California Street cars are double-ended. They change directions using a simple cross-over. I took these two photos in January, 2002 at California and Drumm.

crossover Car 55 coasts through the crossover from the inbound to the outbound track.

gypsy The conductor pulls a lever known as a gypsy to raise the cable to the level at which the grip can close on it. The gripman pulls the grip lever back to take the cable.

California Street cable car 56, built in 1913, coasts through the crossover at California and Drumm Streets. Taken on May 21, 2007. (Adobe Flash is required. Some browsers will require two clicks to start the video.) See more videos on my Cable Car Video page.

At Van Ness, the California Street line ends on a grade. Outbound cars run straight up to the terminal. They drop the rope and coast back down through a crossover to the inbound track.

California Street cable car 50, built in 1910, arrives the outer terminal at California and Van Ness. Commuters and tourists swarm aboard. Taken on 20-June-2007. Click arrow button to play video. (Adobe Flash is required. Some browsers will require two clicks to start the video.)

California Street cable car 50, built in 1910, leaves the outer terminal at California and Van Ness. After one last commuter hops on, the car coasts through the crossover and down towards Polk Street, where the gripman will pick up the cable at a dip in the tracks. Taken on 20-June-2007. Click arrow button to play video. (Adobe Flash is required. Some browsers will require two clicks to start the video.)

Lines in some cities used loops to turn single-ended cars. No San Francisco cable car line used a balloon loop like one at the Camden Ferry in Philadelphia, but for a time both the Sacramento/Clay and Washington/Jackson lines ended in loops.

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The Bells

6 bell pull The gripman's bell pull. Taken on Car 6. December 2003. Photo by Joe Thompson.

Hear a Cable Car Bell.

Bells were a common method of signalling within and outside cars throughout the horse, cable, and electric street railway periods.

Current San Francisco cable cars use a large bell operated by the gripman to warn pedestrians and other vehicles, and to communicate with the conductor. The conductor uses a smaller bell for internal communication with the gripman.

Joe Lacey, former cable car conductor, was kind enough to provide some information about current and former bell signals:

According to the Market Street Railway, Motormen's, and Conductors training manual of July 1929 ,

  1. One bell--- Car must stop at the next stopping place.
  2. One bell (car backing)---Car must stop immediately.
  3. Two bells (when car is standing) ---Go ahead.
  4. Three bells----Car must stop immediately.
  5. Four bells ( when car is standing)-----Car must back up slowly,
  6. Four bells ( when car is moving) ----Car must run slowly in order to collect fares.
  7. Five bells (when car is moving)----Display "Take next car " sign. Do not stop for passengers.

On the Cable Cars in my era , and I haven't found my training manual yet, the bells were

  1. One bell , stop at next regular stop.
  2. Two Bells , ok to go.
  3. Three bells, stop immediatly.
  4. Four bells, Back up

The three and four bells were used when backing down a hill, if the car had to stop, this was most often on the Cal line at 5 pm between Stockton and Powell, when a auto stopped in front of the Cable Car on the hill. Then the conductor had to try to move the autos from behind the Cable Car , and the Conductor had control of the car backing down to Stockton Street and stopping with the grip in the depression of the hill in case the gripman dropped the cable. The gripman often gave two bells on the main bell indicating the front end was clear and he had a green signal and wanting two bells from the conductor, the conductor was in charge of the car , and responsible for keeping it on time. There was also a special signal, if there was a rapid succession of bells on the interior bell , from either the conductor or gripman it ment there was something of special interest to look at, eg: girl in mini skirt, extra crazy person etc.

I have a Cable Car bell on my rear deck now, and it is rung when the 49ers make a touchdown.

Jeff Cleveland has determined that cable car bells are currently (1999) manufactured at Gilberto Godoy's United Brass Foundry in San Francisco's Bayview District.

There is an annual Cable Car Bell Ringing Contest held in Union Square, usually on the second Tuesday in July.

The San Francisco Giants had a cable car bell mounted behind the backstop at Candlestick Park. After any inning in which the Giants scored a run, a groundskeeper rang it once for each run. At Pac Bell Park, they installed an entire cable car, retired Powell Street number 4, in August, 2000. The car is numbered 44 to honor Hall of Famer Willie McCovey. One group of four general admission fans gets to sit in the car. One of those fans gets to ring the bell after each inning in which the Giants score a run. Pretty cool. See some photos of car 44.
6 conductor's bell The bell used by the conductor to signal the gripman. Taken on Car 6. December 2003. Photo by Joe Thompson.

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The Brakes

NY Broadway cable car New York Metropolitan Street Railway cable car on Broadway after striking a pedestrian. Note the grip and brakes, which are operated with horizontal wheels. From Leslie's Weekly, 29-Aug-1895 (Source: Still Pictures Branch (NWDNS), National Archives at College Park). Nov, 1998 Picture of the Month.

Brakes are a critical component of any vehicle. Cable cars use braking systems that were once common on many different types of transit vehicles, but have since become rare.

Current San Francisco cable cars have three braking systems:

  • Wheel brakes - The wheel brake is a metal shoe which presses against a wheel. The front wheel brakes are operated by the gripman, using a foot pedal. On a single-ended Powell Street car, the rear wheel brakes are operated by the conductor, using a goose neck lever on the rear platform.
  • Track brakes - The track brakes on both trucks are operated by the gripman, using a lever. The brake itself is a block of wood which is pressed down against the track.
  • Slot brakes - The emergency slot brake is operated by the gripman using a red lever. It jams a steel blade into the slot and brings the car to a sudden, jarring halt.

The cable also serves as a brake, retarding the progress of a car going down a steep hill.
Cal cable wreck 1 Of course, the brakes don't always work. Two views of a wreck at California and Front on 07-May-1926. Car 17 lost the rope at Powell and ran away down the hill and hit car 10 at Sansome. The two cars rolled back to Front. Two people died (Source: [group 2:12a & 12b], Jesse Brown Cook Scrapbooks Documenting San Francisco History and Law Enforcement, ca. 1895-1936, BANC PIC 1996.003--fALB, The Bancroft Library, University of California, Berkeley. ). Thanks to Walter Rice for the facts. Cal cable wreck 2

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The Electrical System

6 batteries The batteries used to power the car's lights, stashed under the port side front bench on a Powell Street car. Taken on Car 6 on 19-December-2003. Photo by Joe Thompson.

A question arose about the electrical system used in current cable cars.

Early cars generally had oil or kerosene lamps for lighting. Current cars use a 12 volt system powered by 6 volt batteries connected in series. Running lights are amber lights on each corner of the front end of a Powell Street car, with a center headlight, and red lights on each corner of the rear. The lights are not very strong.

The batteries are charged every night. Along the storage tracks in the carbarn are cords that can be pulled down from reels and plugged into the charger on each car. A full charge will usually be sufficient for the next full day and night of service, but sometimes the cars don't get a full charge, or the batteries lose their ability to hold a charge as they get older. If the batteries run down on the road, they are replaced by a shop crew in the wrecker, just as the grips are.

For a time, the batteries also powered a windshield wiper on the center front window. The wiper wasn't very effective, so crews would wipe the window with a pouch of Bull Durham tobacco. My grandfather did that on his auto. The wet pouch leaves a film of oil which causes rain to run off smoothly. Some people prefer to use old newspapers.

Thanks to Bob Murphy, Joe Lacey, and and jeff99 for providing information on this topic.

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Last updated 01-November-2012