[PRCo] Re: Bent Pole

[Edward H. Lybarger]

Interesting...I was not aware that the retrievers on 1700-1724 had been
replaced through the years.  But then again, I was not paying attention to
things like that in that era.  1711 at PTM is equipped with a retriever, as
are PST cars, and we teach the device separately since it can endanger one's
fingers if one is careless.

Ed

-----Original Message-----
From: pittsburgh-railways-bounce at lists.dementia.org
[mailto:pittsburgh-railways-bounce at lists.dementia.org] On Behalf Of Phillip
Clark Campbell
Sent: Saturday, March 28, 2009 6:38 PM
To: pittsburgh-railways at dementia.org
Subject: [PRCo] Re: Bent Pole


> ----- Original Message ----

> From: BobDietrich <bob.dietrich1 at verizon.net>
> To: pittsburgh-railways at dementia.org
> Sent: Friday, March 27, 2009 3:32:37 PM
> Subject: [PRCo] Re: Bent Pole
> 
> Here is a dumb guess!  The spring tension on trolley poles often 
> causes the poles to bow.  Could it be that this is simply bowing of 
> the pole, it would bow more in the center than toward the ends.  Or 
> could it be weakened there from so much bowing and appears to be starting
to bend?
> 
> OR could the retriever yanked it down so hard a couple of times that it
bent?
> 


Mr.Dietrich;

This is not a dumb guess is it;  this is information I intended to include
before.
The tension of the springs and the resistance of the overhead causes a
natural 'bow' in the pole which amplifies with time.  Simply for the sake of
discussion let's call it a 'convex bow.'  Your description is very good.

Let's use deductive reasoning to apply the above to backing maneuvers.  
The pole wants to stand on end but the overhead resists;  this could force a
kink in the pole like 1702 supplied by Mr. Josephson:
http://lists.dementia.org/files/pittsburgh-railways/pat1702.jpg
The pole may not dewire in such cases.

We associate backing with the 42-Dormont.  Most every yard had much backing
maneuvers didn't they.  In South Hills after the rush hour the cars pulled
onto tracks 3-6 facing south;  shopmen wyed them south of the buildings,
brought them to the ladder track, then backed them onto tracks 1-6 facing
north.  In the summer overhead is soft allowing the pole to rise more
against the overhead in backing maneuvers increasing the risk of kinking the
poles.  This would be quite prevalent on tangent wire at spans;  PRC contact
wire is light.

In addition to South Hills, Craft was primarily backup maneuvers to spot
cars properly; so was Keating as was Glenwood and Ingram.

In the photo supplied by Mr.Josephson, 1702 has a trolley 'catcher,'  not a
'retriever.'
We tend to use these terms interchangeably don't we but they are distinctly
different machines.  A 'catcher' has a spring simply to keep the rope taut;
a crescent lever on the back of the rope spindle is activated by centrifugal
force to engage teeth around the perimeter which stops the rope from moving
out and stops the upward movement of the pole.  A 'retriever' has all this
but also has an additional spring to pull the pole down which is activated
when the crescent lever deploys.  The PRC interurbans, both conventional and
PCC cars, used 'retrievers;'  city cars used 'catchers.'
1716 was the first to lose its 'retriever' in 1958;  as 'retrievers' failed
they were replaced with 'catchers.'  1721 is the last car to use a
'retriever' into the latter 1960s.

A sudden and instantaneous stopping of the upward movement of the pole could
cause the pole to develop a 'convex kink' ala 1702 equipped with a
'catcher.'  Even more damage to the pole, and car, is possible if a
retriever pulls the pole to the roof; this is not common, but possible.

>> ----- Original Message ----
>> From: Bill Robb <bill937ca at yahoo.ca>
>> 
>> Trolley poles get bent when cars dewire at high speed and the pole 
>> strikes any bracket arms in the poles path before the car comes to a
stop.

Relative to the photo of 1702, bracket arms do not exist but the pole would
strike span wires on dewirement.  Let's use deductive reasoning again.  The
pole dewires, moves upward  (remember, while tubular, the pole - the whole
pole - is a mass in motion,)  and strikes a span.  The part of the pole
between the span and the wheel - mass in motion - continues an upward
movement with a potential 'concave kink' as a result.  The the 'most likely
kink' as a result of dewirement, failed catcher or one without time to
activate, then striking a span is in the opposite direction of that on 1702.

>> I remember seeing a picture (perhaps in Trains) of a Niagara St. 
>> Catharines and Toronto interurban that dewired and bent the pole out of
shape.
>> Bill

Pg.375 of Interurban Era by William Middleton in the chapter entitled:
'Wrecks and other mishaps.'  The photo is by Middleton himself.  On pg.342
is another photo of the very same car, 620, by Middleton;  'presumably' both
pictures were taken on the same day as Middleton chased the car with his
auto.

There were extenuating circumstances to this dewirement weren't there:
In the photo on pg.342 please note the distinctly bowed/arced trolley rope.
It is revealed that a high cross wind was present when the pole dewired,
this from the photo caption pg.375.

We need to do a little more deductive reasoning don't we.  Trolleycars are
'generally'
11' to 14' high;  contact wire is 18' to 20' above the rail.  That leaves a
4' to 9' gap between trolley base and contact wire.  How much further does a
dewired pole travel before the 'retriever' activates?  A couple feet which
leaves a gap of 6' to 11'.  The 'retriever' is designed to prevent pulling
the pole to the roof.  It would seem that the maximum retrieval would be 6'
or less;  remember that this is a wound spring which unwinds and loses
strength in the process.

Now let's apply this to 620 - bowed trolley rope, strong crosswind.  Pole
dewires; it must move considerably before straightening the bowed rope or
before causing enough centrifugal force at the 'retriever' for activation.
This means much more rope needs to be retrieved to pull the pole clear of
the overhead and the pole probably hit the bracket arms before this
happened;  after all the car was moving quite fast.

There are limitations to 'retrievers.'  The pneumatic 'retrievers' on
Pacific Electric brought the pole down to the roof but they had to rise to a
pre determined level first;  if there are many cross spans then the rise is
canceled and the pole can be damaged.  Not every dewirement causes damage.

Here is a 'bent pole:'
http://lists.dementia.org/files/pittsburgh-railways/1776_36-SHJ_BentTP_197xx
xxx.jpg

Dewirements on PRC were unusual;  don't know about Pat.

Kinks in poles similar to 1702 most likely due to time, weakness, backing
maneuvers and stress on pole from overhead resistance when backing.  A
simple dewirement where the catcher activates and suddenly stops the pole
movement is another 'possibility.'


Phil



>> > ----- Original Message ----
>> > From: Ken and Tracie
>> > To: pittsburgh-railways at dementia.org
>> > Sent: Wednesday, March 25, 2009 9:18:38 PM
>> > Subject: [PRCo] Bent Pole
>> > 
>> > I have a couple dozen shots of Pittsburgh cars with bent poles.
>> > Here's a shot of car 1702 with one. I wonder what happened?
>> > Not likely to for an interurban using the Dormont wye.
>> > Perhaps back-poling in the shop or yards?
>> > K.