[PRCo] Re: Drum__Brakes_--_All-Electrics,__etc........

Sat May 26 21:23:03 EDT 2007

Fred Schneider wrote:
.
> There was, by the way, a study written by Transit Research Corporation 
> in 1940 that compared the St. Louis 1500s with spring applied shaft or 
> drum brakes with the air cars and the conclusion was that spring 
> brakes would not work on all of Pittsburgh's grades. They did seem to 
> work satisfactorily on most lines, however.
.
Some of this is detailed on pgs.155-157 of PCC Car That Fought Back, but 
I-F the report is 1940 it can easily be assumed that many modifications 
// improvements were made to the drum brakes by the time the PRCo fleet 
was constructed. The SLPS PCCs, all 300, could be considered 
experimental All-Electrics and the 1500s were The First such cars (body 
construction was Identical to PRCo 1200s, including trolley cowl, except 
for front end.) Here is a quote of some pertinent info from the 
aforementioned (for those who Donut have the book:::::::)
.
"""The only significant problem with the drum brake apparatus was a 
lower braking rate than with the air equipment which doubled the use of 
the track brakes and materially reduced rail life. There was some 
initial fear of increasing the strength of the brake application springs 
for fear that the drums would lock car wheels. It was later discovered 
that the problem was more imagined than real because the coefficient of 
friction between the brake linings and the steel brake drum did not 
increase rapidly just before a complete stop as was the case with steel 
brake shoes rubbing against steel wheels. The solution to the imagined 
problem, however, meant that the brake drums on the St. Louis car would 
not be effective in holding a fully loaded car on a grade steeper than 
4.8%, which was in stark contrast to 16.8% grades with Pittsburgh 
air-brake car."""
.
So the Imagined Problem was not corrected for SLPS but Was adjusted for 
later All-Electrics.
.
The Drum is spinning 7.x times faster than the wheel because of the 
gearing of the motor which helps to smooth the stop. Surface area as 
well as drum configuration (much smaller diameter) may also play a roll 
in smoothing the stop. PRCo Ops of Tens and Elevens were instructed to 
release and reapply the brake Just Before The Stop Was Completed to 
prevent jerking the car. This was presumably not the case for later 
Air-Cars, and the 12s were spring applied brakes anyhoo --- more later 
on 12s.
.
INCLUDED___BELOW__ is a copy of 2-emails dated 2004.03.20 from Boris 
where he calculated that an empty PRCo 17 """should hold the car (empty) 
on 20.6% grade. With 100 passengers on board it would be about 13.8% 
grade.""" This was taken from my files and reformatted for easier 
reading --- Please Check this date in Noah's Ark Ives to verify that I 
haven't fudged anything.
.
Remember that the last SLPS cars - 1700s - were sold to SF. SF did have 
some trouble with the drums but they were modified and worked reasonably 
well on grades here, not unlike in Pgh but much more intense in many 
cases with very heavy street traffic as well.
.
Bob Rathke also told us about a charter for the NMRA convention in 
Pittsburgh in mid to latter 1950s where the organizer (from PTM) went 
directly to Palmer to get a sample car from each and every series as 
well as a 1601-Interurban as well as 17-Interurban. The tour took in the 
40-Mt. Washington and shop crews had banned both 12s and 17s from the 
line becsause of spring applied drums and perception that they wouldn't 
do as well with the added problem of the motormen needing to crawl part 
way under a 12 to release the brakes - dangerous in any condition but 
esp so on hills. Shop had a fit but the cars made it ok and after that 
it wasn't uncommon to see these cars on the 40. This info I-S also in 
Noah's Ark Ives for this list.
.
.
> I can assure you that they did not work well on Fineview because I 
> arranged to take 1707 up there in 1958 and the shaft brakes were 
> inadequate to hold it.
.
And a year later (1959) Rocky Engleman from Baltimore chartered 
PRCo__All_Electric__PCC__Interurban__1709 and we did not experience any 
problems on any hills, Fineview and New Arlington included. Believe the 
pole dewired through the frog entering single track upgrade on New 
Arlington and the car stopped and held just fine. I was sitting in the 
back seat so reset the retriever and replaced the pole by reaching 
through the window!
.
A-N-D__.......-- This Info has been disgusted here before so it IS in 
Noah's Ark Ives for this list!
.
.
> PRC normally rate 1600 air cars on it with boosted air pressure. PAT 
> apparently had some dissatisfaction with 1700s on Old Washington Road 
> (Arlington Avenue) on the tunnel bypass although we know they ran 
> there all the time and that grade was not as steep as roue 8 that had 
> 1700s all the time.
.
Mr. John Swindler informed me that the 1680s were so modified 
specifically for Fineview.
.
.
> On May 22, 2007, at 2:28 PM, Boris Cefer wrote:
>
>> We have a few grades nearly 6 % in Ostrava and our cars have no 
>> problems. I am also an expert on this and I can prove that.
>> By the way, the manufacturer of TATRA T3 car claims that its shaft 
>> brakes are capable to hold a fully loaded car (that means 150 
>> passengers!) on a 8 or 9% grade (I do not have the book by hand and I 
>> am not certain which figure is correct). What does this say?
>>
>> <VBG>
>>
>> B
>>
>>> On May 22, 2007, at 1:00 PM, Boris Cefer wrote:
>>>
>>>> It seems the subject of the jerky operation of 1711 somewhat 
>>>> evaporated...
>>>>
>>>> But there is an interesting chart which I got from Russ Jackson.
>>>>
>>>> Boris

http://lists.dementia.org/files/pittsburgh-railways/Pgh%20Grades.jpg

Subject:
[PRCo] Re: Drum___Brakes
From:
"Boris Cefer" <boris6 at volny.cz>
Date:
Sat, 20 Mar 2004 21:21:48 +0100

To:
<pittsburgh-railways at dementia.org>

These actuators with 160 lbs pull should hold the car (empty) on 20.6% 
grade. With 100 passengers on board it would be about 13.8% grade. I 
think WABCo SE-2 has softer spring adjustment. But I haven't seen 
drawings of particular brakes - and cannot judge.

B

----- Original Message -----
From: "Jim Holland" <PghPCC at pacbell.net>
To: <pittsburgh-railways at dementia.org>
Sent: Saturday, March 20, 2004 8:27 PM
Subject: [PRCo] Re: Drum___Brakes

> > Boris Cefer wrote:
> >
>> > >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
>> > >
>> > > 
> >
> > Absotively Positive -- Solly, Cholly!
>
> >
> > <><><><><><><><><><><><><><><><><><><><>
> >
> > Jim
> >
> > <><><><><><><><><><><><><><><><><><><><>

------------------------------------------------------------------------

Subject:
[PRCo] Re: Drum___Brakes
From:
"Boris Cefer" <boris6 at volny.cz>
Date:
Sat, 20 Mar 2004 20:20:50 +0100

To:
<pittsburgh-railways at dementia.org>

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 and 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
> >
> > <><><><><><><><><><><><><><><><><><><><>