Speaking of Air Brakes on 1600 B-2s and B-3s

[Jim Holland]

Greetings!

Fred Schneider wrote:

> On air cars, this happens in
> the 5 to 9 miles per hour range.  On cars with extended dynamic braking (the
> all-electrics), dynamic braking was extended down to a very slow walk.

	The figures that I have always seen for the air cars is 2.75 mph for
dynamic fade at which point the friction brake takes over; it is 0.75
mph for all-electrics!  Our new Skoda trolley coaches have very
effective dynamics - variable dynamics/regenerative - which bring the
coach almost to a complete stop.  The first 3-inch movement of the brake
pedal is purely dynamic/regenerative - one has to push further than that
to bring in the air.

> All of the earliest air cars used truck mounted
> air cylinders (like those on a highway vehicle) to apply air brake shoes
> against the wheels.  With all-electrics, brake drums were mounted on the
> motors ... drums similar to those on an automobile.  They could either be
> internal expanding (like the auto) or external contracting.  In general,
> springs were used to apply them and electric solenoids were used to release
> the drums.  Some cars built with air after 1940 used air drums (the
> Pittsburgh 1200s) and some cars were rebuilt (most of the Washington DC
> fleet for example).

	All the 12s, 14s, and 15s came with wheel tread brake shoes; some in
each of these classes were retrofitted with drums and had the wheel
tread brake shoes removed.  The 12s were unpopular with motormen because
they had a tendency to roll back upgrade during brake applications. 
Don't know if this was before or after the retrofit but it may have been
that the friction brakes in either case were applied by spring rather
than air and this was not well developed at that early date.

> If a motor lead tore ... you were down to air and track brakes only ... and
> the air (or spring applied brakes) were never intended to stop the car.

	Believe it or not, a Muni shopman who worked on the PCCs claimed that
the PCC car did not have dynamic brakes when the pole left the wire or
the car otherwise lost 600 volts.  That's why I am operating trolley
coaches  --  because of what the shopman said  --  totally bogus (so how
was he repairing the PCCs?!!!
	And this is why I speak out against grandiose claims about the PCC  -- 
one would think a shopman would have credible information so this can be
easily believed and spread as factual information.
	A PCC always has dynamic brakes unless the system fails for some reason
- and that could happen with the pole on a live 600-volt wire.  But that
is not the norm - it is a failure.  But it IS the norm for the PCC to
have dynamic brakes whether or not attached to the overhead!

> I don't know if the MG set alone
> can handle the entire track brake load if the batteries are shot ...
> Holland, help me out on that.  You ran the critters for many a moon.
> Jim:  How could you hold a Muni 1016 class in Mission Park on the grade (not
> in the level car stop)?   And what is the grade there?  Are there any
> steeper ones in SF?

	The grade you list may have been the steepest.  The Baby Tens
(1016-1040, with 1040 as the last PCC built in North America by St.
Louis Car) and the torpedoes (1006-1015, double ended PCCs which were
ordered in 1946 and delivered in 1948) both had internal expanding
drums.  Neither of these cars had a toggle to operate the track brakes. 
I had no trouble at all holding a Baby Ten on a grade and could come off
the brake and hit the power without a rollback as well!
	But the GE torpedoes were something else to stop and keep stopped. 
They also had a bad habit of blowing the main power fuse which shut
everything down and automatically set up the drums.  You had to hope for
the best then!
	I had 1008 one day for special assignment.  It had clearance apparatus
installed to check clearances for the lrvs.  The Boeing people were
onboard and we were going from Geneva to the N-JUDAH for the testing. 
We were going down thru the Twin Peaks tunnel about 20-25 mph, not very
fast, when the main power fuse blew.  The Boeing men were panicky!  I
flagged down the car behind and we were pushed to 11th St and put in the
hole where I sat for 3-hours before someone towed me back to the barn!

> There was a 1940-ish study by Transit Research Corp. comparing air brakes on
> a Pittsburgh 1200 with spring drums on a St. Louis 1500.  A conclusion was
> made that the springs could never possibly hold a car on Pittsburgh's hills.

	Yes, that was very early in the use of springs for applying the drums;
it was far more perfected by the time the post-war all-electrics were
released.

> I can personally guarantee that the spring drums would not hold a Pittsburgh
> 1700 on Henderson Street (21 FINEVIEW) because I staged such a fantrip in
> 1958.  Track brakes were ineffective too.  The car coasted backward until
> the track shoes were canted upward at a 30 degree angle.

	This could have been the fault of this particular car and not
necessarily representative of the fleet.  On page 106 of *PA Trolleys in
Color Vol-3*  Bill Volkmer says:  "The Fineview line . . . represented
the steepest grade of any trolley route in the country.  As such
(12.16%), it was a must for all charter runs, almost without exception. 
There would ALWAYS be a photo stop at the steepest point on the grade,
if for no other reason than to prove that the cars could start on that
steep a grade."  And the photo caption under the photo of a car on the
21-line hills says:  "Car 1708 is showing her abilities on the grade on
an April 26, 1959 outing chartered mainly to tour the West End Lines
that were about to disappear."
	I have been on interurban 17s and 16s up there and we never experienced
any problems (charters on Fineview.)
	It has been said that PRCo didn't operate 17s on Fineview because of
their concern about the drum brakes, but then they had many bans on
equipment throughout the ages.
	The NMRA charter that Bob Rathke mentioned included a PCC from every
class and that trip went up on Mt. Washington.  But operations 
n-e-v-e-r  assigned 12s to the 40 line because of the spring applied
brakes.  But someone who coordinated the charter knew Mr. Palmer
personally and the Boss thought it a good idea so they got around
operations!
	While Fineview may have had the steepest hills, 6% grades were not at
all unusual all over town!  The 40-line had some very steep grades as
did Carrick, 44, 48, and what about the ramp to W. Liberty, the 49 -
even the 8-Perrysville hills leaving town were quite steep!  And what
about McKeesport, Lincoln Place and various other places in the East
End?

James B. Holland
------- -- ---------
        Pittsburgh Railways Company (PRCo), June of 1949 -- June of 1953
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