[PRCo] Re: Drum___Brakes

[Boris Cefer]

Excellent. Would be better to have a WABCo drawing and specification, but I
can look at this data.
Are you absolutely sure you don't have WABCo?

Boris

----- Original Message -----
From: "Jim Holland" <PghPCC at pacbell.net>
To: "- 1714 PRCo__WP__JTC -" <pittsburgh-railways at dementia.org>
Sent: Saturday, March 20, 2004 8:11 PM
Subject: [PRCo] Drum___Brakes


> ----- Original Message -----
> From: "Boris Cefer" <boris6 at volny.cz>
> To: <pittsburgh-railways at dementia.org>
> Sent: Friday, 12 March, 2004 3:16 AM
> Subject: [PRCo] Re: Fineview___PCCs
>
>
>  > Wasn't the problem of all-electrics in lack of drum brake adjustment?
> Maybe
>  > no. The soft adjustment of standard all-electric drum brake would
provide
>  > very long stopping distance on steeper downgrade and the shoes would
> suffer
>  > heavy wear.
>
>  > Maintenance specification we use here for drum brake says that each
> car must
>  > be tested by removing of drum brake fuse and pressing power pedal to
> reach
>  > starting current of 290 Amps - drum brakes must hold the car (on dead
> level
>  > track). 290 Amps cause approximately the same traction effort as 9.5 %
>  > downgrade. Sometimes we experience drums which are sufficient to hold
the
>  > car at 350 Amps, which would be about 11.5 % downgrade, but this is
> with new
>  > brake shoes and freshly adjusted brake. I think there is no
considerable
>  > difference between WAB brake and our CKD product, as for the braking
>  > capability.
>
>  > But if you find any drawing and cpecification for WAB drum brake and
>  > actuator at Arden (that would need some work - consign it to limbo),
> I can
>  > easily made a calculation and answer the question of maximum grade
which
>  > allows drum brake operation.
>
> Found a *Clark__Equipment__Company* drawing (#703619,) Full Scale, dated
> 1949.09.19 and titled:
> """Motor Mounted - Electric Actuated Drive Shaft Brake For All-Electric
> Car"""
> Some Very Interesting information is printed on the face of the drawing
> concerning braking pressures with GE Actuator L-6735653 and I quote this
> exactly, line for line:::::::
> +++++++++++++++++++++++++++++++++++++
> 103% Braking with 160# Pull By Solenoid Actuator
> Car Weight = 36,000#
> 36,000 ÷ 4 = 9000# Load Per Axle
> Wheel To Rail ƒ = .2
> 9000# X .2 = 1800# Tan. Force At Rail
> 1800# X 12.5 = 22,500# Torque At Wheel
> 22,500 X 6/43 = 3140# Torque At Drum (TRC Specifications)
> Drum Radius = 5.5"
> 3140 ÷ 5.5" = 570# Tan. Force On Drum
> ƒ For Lining To Drum = .316
> [Therefore] 570 ÷ .316 = 1800# Press On 2 Shoes = 100% Braking
> 1800 ÷ 2 = 900# Press Per Shoe
> Lever Ratio On Shoe 8.5 To 18.125
> 900 X 8.5 ÷ 18.125 = 422# Pull On Rod
> 422# + 30# Spring = 452# Req'd. Total Pull "A"
> Bell Crank Ratio = 5.625 To 1.9375
> 452 X 1.9375 ÷ 5.625 = 156# Pull Req'd By
> Solenoid Actuator For 100% Braking
> 160# Pull Available With Actuator Gives 103% Braking
> +++++++++++++++++++++++++++++++++++++
> It actually seems that the above *Full__Scale* Drawing is reduced in
> size because I also have Clark Drawing #702455 titled:::::::
> """Motor Mounted - Air Applied Spring Released Propeller Shaft Brake 80%
> Braking with 60 Lbs Air""" ---- and this drawing is also Full__Scale but
> considerably larger than the other Full__Scale Drawing!
>
>  >>> From: "Fred Schneider" fschnei at supernet.com
> <mailto: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.
>  >> Jim Holland wrote:
>
>  >> Are you able to calculate the braking effect and
>  >> grades on which the drums would hold the car at these
>  >> 3-different rates?
>
>  > I forgot to mention. Each rate (on all-electric) is for one
> particular brake
>  > pedal position; in parked position (pedal half way) the drum
> solenoids have
>  > no power which means the maximum braking effort.
>  > I think if you find drawings with some important parameters, I can
> calculate
>  > it. I hope.
>
>  >> Do you think this would be common with all
>  >> WABCo actuators or does it also depend upon the drum
>  >> brake itself?
>
>  > I don't know details of other actuators. But if the principle of it
> is that
>  > braking effect is reached simply mechanical way by means of a spring
and
>  > releasing is done by a magnetic coil which acts directly against the
> spring,
>  > then the actuator can provide particular range of braking effect. But
>  > remember that NOT all coils, magnetical cores, main springs and pasive
>  > friction between moving parts in mechanism are identical on each
> actuator an
>  > d if you give the same lower voltage to all four actuators on a car,
the
>  > braking effort of each particular brake will slightly differ. And the
>  > difference between particular brakes increases with drum shoe wear.
>
>
>
>
> <><><><><><><><><><><><><><><><><><><><>
>
> Jim
>
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>
>
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