Nostalgia & History > 2 MUNI Cable Car Shots, 1975

These were taken November 23, 1975.  Noticed almost nobody is hanging on because there are no tourist crowds.  November to April is a good time to go ride and photograph the San Francisco Cable Cars.

1. Car 8 working its way up Powell Street from Market Street.

2. Car 60 about to enter the intersection of Powell and California Streets.  It is a California Car having open ends at both ends.  The Powell Cars have an open end only at the front end. The Bay Bridge is visible in the distance.

Enjoy,
Marty Bernard



Edited 2 time(s). Last edit at 05/04/15 12:54 by MartyBernard.

---

---

OK Marty--  I'd like to TEST your knowledge of this item you decided to photograph !!!
A cable car in San Francisco has "how many" brake systems in case of various braking requirements.  Can you NAME them, please ??

And let's all give Marty a chance to respond..  Cheers.

KRK

I think, 3(three);a. cable its self
                         b. "regular" brake system (from the Cable's Operator)
                         c. manual, rear from the Conductor's platform.
from a plainsman, wag216

wag216 Wrote:
-------------------------------------------------------
> I think, 3(three);a. cable its self
>                         
> b. "regular" brake system (from the Cable's
> Operator)
>                         
> c. manual, rear from the Conductor's platform.
> from a plainsman, wag216xx

Actually, I think a fourth, kind of an emergency brake. A wedge which when deployed jams into the cable slot  you would get a violent sudden stop, if the wedge stayed with the car.  Better than a run away I guess.

The cable cars are truly timeless. A shot today looks like one taken in the 1960s ... only the cars on the street change :-)

Ken asked me about cable car brake systems. I know of four.

First let me digress.  I worked on renovating a MUNI California Cable Car one winter at Orange Empire Railway museum.  The steps at all four corners were rotting away.  The photo show one of the replacement steps I made being installed.  I'm pretty sure I used oak.  It is the exact measurements of the original step.

I also worked on a Cable Car Trailer.  Early cable cars had a small grip car in which no passengers rode and a trailer which was usually a left over horse car.  The grip car replaced the horses!

Now to Ken's question. 

• The cable could be used as a brake when the car is going down hill, i.e. a car gripping the cable will not go faster than the cable, i.e. 9.5 mph.
• There are brake shoes on the wheels similar to regular railroad cars.  On a railroad car these brakes work by either air pressure on the "back" side of the brake piston or mechanically by winding a chain connected to the brake rods.  On a cable car they are just mechanical.  Both the conductor and gripman can actuate these wheel brakes.
• Then there are track brakes.  A piece of wood is pressed against the track.  The wood smells like pine when it is being heated during braking a moving car, so I assume it is pine.  I don't have a good photo, but looking at the second photo of a car on Powell St. you can just see it between the wheels of the front truck.  Those are the feet of the hanging-on passengers standing on the first step like in Picture 1. Each side of each truck has wooden track brakes for a total of four.  I'm told they need to be changed every few days.
• There is an emergency brake the gripman can use which I don't understand.

OK Ken, turn about is fair play.  How many brake systems does a PCC car have and how do they work?

Marty Bernard



Edited 3 time(s). Last edit at 05/04/15 15:53 by MartyBernard.

---

---

The fourth braking "system" on a cable car is called the "slot blade".  It's activated by the red lever that's usually closer to the front of the car than the grip lever or the service  brake lever.  One Saturday night in 1968, when I was visiting The City, I looked up Powell St. and saw a welding crew at work.  I asked the foreman what was going on, and he said, "Burning a slot blade."  I moved away and left them to their task.  This can be the case when "all else fails" and the gripman has to pull the red lever.  The slot blade will stop the car RIGHT NOW!!, but sometimes cannot be dislodged by having the wrecker truck push the car while a mechanic pushes in on the lever.  The next day I was visiting Central Control, the dispatcher's office which was then in the old Geary St. carbarn building.  I commented, "You had some trouble with the cable cars last night."  And he replied (with some asperity), "We're ALWAYS having trouble with those damn things! They oughta push every one of them into the Bay!"  But it's over 45 years later, and, after a planned outage of two years, they're still going up and down the hills, just as God and Andrew Hallidie would have it.

Another "only in San Francisco" experience was the night I wandered by the cable car barn/power house and saw the splicing crew busily splicing one of the "ropes".  This is a lengthy and painstaking process, because the splice must be the same diameter as the rest of the cable.

Thanks Bob for explaining the emergency brake.  I can claim the reason I didn't understand it is because it was never used while I was riding a car.  I understand now.  It must also damage the slot if the cars is heavy with passengers and moving along.

Marty Bernard



Edited 1 time(s). Last edit at 05/04/15 17:50 by MartyBernard.

As explained in one of the well-known books on Cable Cars...  " When the gripman pulls the red-handled emergency brake, it jams a chunk of steel into the cable slot so tight that a crew of welders has to be called out"  !!

KRK

MartyBernard Wrote:
-------------------------------------------------------
> Ken asked me about cable car brake systems. I know
> of four.
>
> First let me digress.  I worked on renovating a
> MUNI California Cable Car one winter at Orange
> Empire Railway museum.  The steps at all four
> corners were rotting away.  The photo show one of
> the replacement steps I made being installed. 
> I'm pretty sure I used oak.  It is the exact
> measurements of the original step.
>
> I also worked on a Cable Car Trailer.  Early
> cable cars had a small grip car in which no
> passengers rode and a trailer which was usually a
> left over horse car.  The grip car replaced the
> horses!
>
> Now to Ken's question. 
>
>

• The cable could be used as a brake when the car
  > is going down hill, i.e. a car gripping the cable
  > will not go faster than the cable, i.e. 9.5 mph.
  >
• There are brake shoes on the wheels similar to
  > regular railroad cars.  On a railroad car these
  > brakes work by either air pressure on the "back"
  > side of the brake piston or mechanically by
  > winding a chain connected to the brake rods.  On
  > a cable car they are just mechanical.  Both the
  > conductor and gripman can actuate these wheel
  > brakes.
  >
• Then there are track brakes.  A piece of wood
  > is pressed against the track.  The wood smells
  > like pine when it is being heated during braking a
  > moving car, so I assume it is pine.  I don't have
  > a good photo, but looking at the second photo of a
  > car on Powell St. you can just see it between the
  > wheels of the front truck.  Those are the feet of
  > the hanging-on passengers standing on the first
  > step like in Picture 1. Each side of each truck
  > has wooden track brakes for a total of four.  I'm
  > told they need to be changed every few days.
  >
• There is an emergency brake the gripman can use
  > which I don't understand.
  >
  > OK Ken, turn about is fair play.  How many brake
  > systems does a PCC car have and how do they work?
  >
  > Marty Bernard
•  
• A PCC car has FOUR braking systems:       Dynamic Service Braking; Friction;  for Final Stop, Park;   Magnetic
• Dynamic brakes were the service brake on all PCCs; when almost stopped, friction brakes completed the stop and held the car in "park". Dynamic brakes slowed the "Air" cars to 3.0-mph at which point a lock-out relay allowed automatic application of air-applied friction brakes against each of the eight wheels. On All-Electric cars the dynamics were effective to 0.75-mph where the lockout relay then allowed a spring applied friction brake to engage a drum on each of the four motor drive shafts; this completed the stop and held the car in park. Drum brakes were released by an electric solenoid operating from low-voltage battery power; a power failure would prevent the drums from releasing which would prevent power application, a fail-safe feature. Drum brakes were quite popular and greatly reduced maintenance thus some "Air" cars were retrofitted with drums. Four magnetic brakes, one between the wheels on each side of each truck, applied additional braking for emergency stopping where all brakes were generally employed.

As Art Baker said on TV years ago,  "You Asked For It"  !!

KRK

You can easily see the magnetic track brakes between the wheels on the San Francisco PCC car in the photo.

Question.  Where was the power generated by the dynamic brakes dumped?  There are no resistor banks like on a diesel locomotive with dynamics.  Was it dumped back into the wire?  If so, it would be an early version of regerative braking.  I never heard of that.  I certainly think the back EMF would be a problem.

Marty Bernard

---

Look at the small standee windows in the last photo. Must have been a pre war air-electric car. All PCC cars built by St Louis after the war were all electric, as are all present PCC cars in Muni's fleet. And they have large standee windows.

Paul Ramer
Cincinnati, OH

Muni 1132 was one of the cars acquired from St. Louis Public Service in 1957.  It was SLPS 1755, built in 1946 by St. Louis Car Co., and like all other Muni PCCs was all-electric.  Some of the ex-SLPS cars are still in existence; one of them is even running in San Diego, but 1132 was scrapped around 1980.

I'm reasonably sure that the acceleration resistors on a PCC also provide the load for the dynamic braking function.

A few words stolen from the Minnesota Streetcar Museum:

What makes a PCC Car go?
Acceleration
Early research showed that even standing passengers could tolerate high rates of acceleration if it was smooth. The eight acceleration points in the controller on a standard car were not smooth.The accelerator pedal in a PCC car activates a pilot motor which turns a commutator cutting resistance in and out. A total of 136 stages are available providing very smooth acceleration.There are four 55-horsepower motors. 

Braking
The PCC car has three braking systems:

• Dynamic brakes
• Shaft brakes
• Track brakes 

Dynamic braking is the primary braking system and is effective down to about 1 mph at which point the shaft brakes are automatically applied to stop the car. For dynamic braking, the motors become generators and the electricity generated is used to heat the car in the winter or dissipated in the resistor banks. The shaft brakes, which also serve as parking brakes, are applied by springs and released by solenoids, each of which weighs 140 pounds. Magnetic track brakes are also applied if the brake pedal is depressed far enough. 

Dynamic braking utilizes the same pilot motor as acceleration except that there are 272 levels of braking. Braking rates are determined by how far down the brake pedal is depressed. 

If the brake pedal is depressed to the floor, all hell breaks loose. In addition to the dynamic and shaft brakes, the magnetic track brakes are applied, the rails are sanded, a buzzer sounds, and the doors are balanced so that they can be manually opened in case of an accident.
 

I frequently rode the Jones Street cable cars in 1952/3, hopping off as the car turned west on Pine Str on the trip up from Market.
Some time in the '70s, after many years away, I visited Bagdad By The Bay and rode the Powell line to Fishermans Wharf. I was horrified when the crew left the car parked on the downward side of the last hill before the wharf and disapeared around the corner, their shift done. The car was jammed with tourist. I pushed my way through to stand by the levers to make sure nobody messed with them. It must have been 5 minutes before the next crew showed up.
Was there someway the crew could have configured the controls so that the car could not be made to move?
 

riorita, with either the track brakes or the wheel brakes fully set it's not going anywhere.  With them both set, which I assume they did, unless somebody who know how to release the brakes, the car is quite safe.  And I'm sure the car was way below the steepest part of the hill.  Anyhow, I'm confident the crew knew what they were doing so they would not loose their jobs.  They probably do it every day.

Marty Bernard
 

When I visit San Francisco, my wife usually does not come along.  The local boosters may call it "everyone's favorite city" but they haven't asked her yet.  So if someone calls our home when I'm in MuniLand, she may tell the caller, "Bob's not here.  He's up in San Francisco sniffing cable car fumes."  "Cable car fumes"?  Coming down the steeper hills, such as Hyde St. the wooden track brake blocks get hot enough to start smoking, and they can be quite aromatic.  Like wow, man!

Check the post-war PCCs, built by St. Louis Car; Kansas City Public Service cars do not have stand-in windows. Visit the car at Union Station in Kansas City, MO. wag216

Ok Loren--  I say FOUR systems--  you say THREE--  Who is correct ?

KRK

lwilton Wrote:
-------------------------------------------------------
> A few words stolen from the Minnesota Streetcar
> Museum:
>
> What makes a PCC Car go?
> Acceleration
> Early research showed that even standing
> passengers could tolerate high rates of
> acceleration if it was smooth. The eight
> acceleration points in the controller on a
> standard car were not smooth.The accelerator pedal
> in a PCC car activates a pilot motor which turns a
> commutator cutting resistance in and out. A total
> of 136 stages are available providing very smooth
> acceleration.There are four 55-horsepower
> motors. 
>
> Braking
> The PCC car has three braking systems:
>
>

• Dynamic brakes
  >
• Shaft brakes
  >
• Track brakes 
  >
  > Dynamic braking is the primary braking system and
  > is effective down to about 1 mph at which point
  > the shaft brakes are automatically applied to stop
  > the car. For dynamic braking, the motors become
  > generators and the electricity generated is used
  > to heat the car in the winter or dissipated in the
  > resistor banks. The shaft brakes, which also serve
  > as parking brakes, are applied by springs and
  > released by solenoids, each of which weighs 140
  > pounds. Magnetic track brakes are also applied if
  > the brake pedal is depressed far enough. 
  >
  > Dynamic braking utilizes the same pilot motor as
  > acceleration except that there are 272 levels of
  > braking. Braking rates are determined by how far
  > down the brake pedal is depressed. 
  >
  > If the brake pedal is depressed to the floor, all
  > hell breaks loose. In addition to the dynamic and
  > shaft brakes, the magnetic track brakes are
  > applied, the rails are sanded, a buzzer sounds,
  > and the doors are balanced so that they can be
  > manually opened in case of an accident.
  >