[PRCo] Re: Wire crossovers ?

[prcopcc at p-r-co.com]

Robert:
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The frog URL that Boris provided is for a crossing, not a diverge::
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http://lists.dementia.org/files/pittsburgh-railways/Wire%20frog.jpg
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The following URL is for a diverge:
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http://lists.dementia.org/files/pittsburgh-railways/Frog%20Left%20Wheel.jpg
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For both frogs  --  Crossing and Diverge  --  Contact Wires are in place and 
these are bolted on Underneath with tips on each end making for a smooth 
transition  --  frogs can be replaced WithOut disturbing the continuity of 
the overhead.    For a diverge frog there is usually a clamp for holding the 
two wires in place that is then bolted to the top of the frog.
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The diverge frog is placed approximately 1/3rd the distance from the end of 
the track point to the track frog and slightly offset toward the curve / 
diverge.
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Picture Black Velvet for the following Movie:   Standard 50-foot radius Left 
Turn - Diverge Frog wired as listed above.    PCC has 11-foot+ overhang in 
the rear measured from the kingpin.    As the PCC moves into the turn, the 
TrolleyPole Itself Does Not Move as it is on Tangent overhead  --  
TrolleyCar actually turns underneath the Trolley Pole.    Once the last axle 
is into the turn the trolley pole starts to move but it moves back toward 
the center of the car while the car is turning left - diverging movements - 
this helps the pole to select the right wire into the diverge frog.   Too 
much speed will cause the pole to dewire or to follow down the wrong wire 
which then results in a dewirement.
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Spiral Easement turns are Very Tricky to wire the overhead.     These are 
usually right turns and spirals are used so the back end overhang doesn't 
foul the opposing track.    Radius starts at about 350- or 300-feet and 
progresses more sharply every degree or two to allow the two tracks to 
diverge for clearance on the turn.    Turning into this means the TrolleyCar 
is still making its turn and still turning underneath the trolley pole which 
then makes it much more difficult for the trolley pole to follow correctly  
 --  the trolleycar isn't completely into the standard radius  --  either 35- 
or 50-foot radius, or somewhere in between  --  until the back truck reaches 
the track frog or a little beyond~!~!~!     Interurbans heading North on the 
Smithfield bridge and turning right toward Grant After the rebuilding for 
removal of the B&O station is an example of such  --  a little tricky to 
make the turn which would occasionally, but not often, result in a 
dewirement because the pole followed the wrong wire toward Smithfield.    
Many // Most right turns on double track are so constructed with spirals 
unless there isn't room in the streets and then the turn becomes NC - No 
Clearance - and two cars can't pass on this turn~!~!
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Shallow Angle Turnouts are problematic as well  --  Dawn Jcxt on 42, 38, 39 
 - 42 on occasion would follow along the wrong wire and dewire - Wash Jct. 
and a few other places come to mind.    Sometimes the overhead diverge frog 
is placed more than 1/3rd the distance to allow the pole to track properly.
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> Boris wrote:
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> Does this answer your question?
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> Boris

 ----- Original Message -----
From: "ROBERT R ROCKWELL" <w3syt1 at msn.com>
To: "pittsburgh-railways" <pittsburgh-railways at dementia.org>
Sent: Sunday, September 23, 2007 6:48 PM
Subject: [PRCo] Fw: Wire crossovers ? 


> 
> How do these work ?  Roughly I suppose. 
> 
> 
> Robert Rockwell

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Jim Holland 

Studying Pittsburgh Railways Company 

....................From 1930 -- 1950 

Pennsylvania Trolley Museum (PTM) 

http://www.pa-trolley.org/ 

N.M.R.A. 

http://www.nmra.org/