[PRCo] All--Electric___Control___Circuits

[Jim Holland]

Good Morning!


> Boris Cefer wrote:


> When electric brake actuators are adjusted at shops
> (heavy maintenance), they use a dynamometer to adjust
> them at 55 kilogram pull.     Don't know exact value in
> lbs required by WABCo specification.

	Too Easy To Overlook.......

		THANK  YOU,  BORIS.......

for the excellent explanations of drum brake operations
with facts and figures.     Gives a wonderful base
for understanding the mechanics behind the operations
and dispels the myths and rumors.




>> From: "Fred Schneider" <fschnei at supernet.com>

>> Regarding variable rate drum brakes:  drums were
>> generally used only in conjunction with extended
>> dynamic brakes in North America,

> I don't know much about GE, but Westinghouse equipped
> PRCo 1700s had their drum brake control circuits
> designed so as to obtain 3 different braking rates.
> Wiring diagram shows it clearly. And we had the same
> arrangement on earlier equipment.

	Are you able to calculate the braking effect and
grades on which the drums would hold the car at these
3-different rates?

	Do you think this would be common with all
WABCo actuators or does it also depend upon the drum
brake itself?

	You mention that Ostrava  *had*  same arrangement
but apparently does not now.     What does Ostrava use
now and why the change?




>> I was not aware that anyone had variable track brakes.
>> you simply don't use them in normal service because they
>> cause excessive rail wear, particularly at stops.
>> A good operator simply doesn't push the pedal more
>> than half way down.     We also don't want the
>> passengers to be alarmed by hearing the emergency buzzer.

	Passengers would not understand the emergency
buzzer  --  it was barely audible for the operator so
it doesn't cause alarm.     In fact, the emergency buzzer
sounded like the passenger buzzer for Air-Cars! :)
Once talked my mother into walking up to 42-wye to board
the car.     When I told her the operator put the 12 into
emergency approaching Biltmore coming downhill she just
shrugged her shoulders, said:  "Oh," quite unenthusiastically,
and went on reading her magazine!

	Believe that a moderate amount of track brake
was pulled in during  *Full--Service*  braking on PRCo cars.
Putting the car in Service-Latch (as it is called on
some properties  --  pressing brake approx half way and
then releasing deadman which locks brake in place)  was
NOT  full-service  --  *Full__Service*  went a little further
on braking and there was a physical barrier where pressure
increased going beyond that point  --  and beyond that
point is emergency.

	With all the hills in Pgh there would be tremendous
wear on drums or brake shoes doing the final stopping and
a moderate amount of help from the track brake would be
in order.




> GE policy?     Why not.     But again - I don't know GE.
> Westinghouse 1700s had 4 (F-O-U-R) rates of
>	 track brake actuating.     Gives sense to you?

	Would you be able to describe operations with
the 4-different levels of track brake?     What part
is used for normal braking?

	Was watching the cars at the Dormont wye (normal
Summer--Time duties) and one 17 had track brake come on
as car made final stop backing up.     Doors were open
(against rules) for backing move and operator had put
brake in Service Latch and removed feet from pedals.
Several seconds later the track brake  *shut-off*  and
started dancing as the springs lifted it off the rail.
No emergency buzzer but operator had probably pushed it
into  Full--Service  to get it into  Service--Latch or
Park! :)




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Jim

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