[PRCo] Re: Track Switch Relay PCCs

[Jim Holland]

Fred Schneider wrote:
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>
> The traditional way of throwing a track switch (except for Toronto's 
> necessary or necessity-action scheme) was power to throw it in one 
> direction and coast to flip the tongue in the opposite direction.
>
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Did TTC have an overhead contactor?     Is this understanding correct  
--  coast the contactor to keep the point in position; toggle // power 
through the contactor to change the position of the point.     In other 
words, coasting keeps the point in the same position but it is Necessary 
To Take Action to change the position of the point.
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>
>    Unless the switch was on private right-of-way, the switch contactor 
> had to be mounted in the trolley wire in close proximity to the switch 
> so that no other car following you could throw it when you were 
> already on the switch, and so that you (the motorman) could see it 
> throw without having automobiles or trucks or anything else on top the 
> switch.
>
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There can certainly be an exception to every rule but even on prw the 
overhead contactor is located as it is in the street  --  TrolleyCars 
under slow order at points to make sure they flip properly.     Can;t 
think of any exceptions to that but one or two might exist.     Remember 
Wash Jct in PCC days  --  contactor was little more than a car length away.
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>
> That means the contactor is mounted in the trolley wire perhaps 50 to 
> 55 feet back of the switch point, allowing five to ten feet to stop 
> the car if it didn't properly throw. If you mount it 55 feet back, 
> then a motorman on a sweeper or a single truck car is 25 feet away 
> from the point when it throws and there is a good chance pedestrians 
> may block his view too.
>
>
> So you don't want a whole lot of room to spare. On the conventional 
> cars you are pulling up to the switch usually with one point of power 
> and brakes applied. The car is completely under control. If it fails 
> to throw you can actually kill power and blead off the brakes in ten 
> feet, make a nice smooth stop, open the doors, get out and hand throw 
> the switch.
>
>
> But a PCC car doesn't work that way. You cannot come up to the 
> contactor with one foot on the power and one on the brake. Brake 
> preempts power. If you push down the brake pedal, the motoring relays 
> automatically open under the car and kill power and the braking relays 
> close. Even on the St. Louis Public Service 2-pedal cars (some of 
> which later ran unaltered in San Francisco), you could not brake and 
> power simultaneously. You needed to fully release the brakes before 
> the cars would take power. The solution was to install a separate 
> resistor on the cars ... measured about the size of a computer 
> keyboard and weighed about two or three times as much ... mounted 
> under car. When you toggled the Track Switch relay it fed 600 volts 
> through that resistor, essentially a larger electric toaster. It 
> simply used current to make heat. They were simply of sufficient 
> capacity to trigger the average track switch circuitry when you went 
> through the overhead contactor. So you could coast through, push the 
> dash switch, and get the same affect as an older car powering through 
> with the brakes on.
>
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As I have already mentioned, The SLPS cars didn't have such a 
resistor.     The Track Switch Toggle activated the Drum Brakes  I~F  
and  Only  I~F  a point or two of power was applied  (if more power was 
applied the drums would not apply nor would the drums apply without 
power)  --  this retarded forward motion of the car and drew far more 
power thru the contactor than was necessary.       The SF 1101s are 
ex-SLPS cars and I tried this a couple times Just To Say I Did It  --  
but our normal operation had us using the magnetic track brake while 
powering up to set the point for diverge.
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1016--1040 had the resistor but in the 1970s we were instructed that 
this usually didn't work  --  these cars did not have track brake toggle 
so we had to hit the power to set the point and then the brake to stop  
--  Absolutely No Problem.     The torps  (1006--1015)  which were about 
5-feet longer with very sluggish brakes worked like the other Tens  --  
hit the power to set the point and then hit the brake.     Did this for 
Many Years WithOut Problem.       We Were instructed to use Power for 
Diverge.
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A couple Baby Tens had working track toggles and I tried it a couple 
times, against just to say I Did It, but it made me antsy since all the 
others had failed and I thought this one could fail too  --  I knew and 
trusted the Power Apply method and preferred using that with SF.     If 
I had reliable equipment with toggle working then I would do that.
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I did this with my models  --  spring return toggle sent power to one of 
the coils on Twin Coil Switch Machine depending upon which position it 
was in  --  trolley pole completed circuit when it brushed against a 
contactor  --  Really Enjoyed using this  --  had crude foot pedals to 
which was wired a transistorized throttle which gave programmed 
acceleration depending upon how far down the pedal was pushed with 
brakes working similarly  --  definitely not the on // off of regular 
power packs.
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http://tinyurl.com/qqm5e
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http://tinyurl.com/l7wy6
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Now I have the Real Foot Pedals from an All-Electric which some day will 
be hooked up to run models again  --  HopeFully~!~!~!~!
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^~^~^~^~^~^~^~^~^~^
Jim  Holland
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Studying Pittsburgh Railways Company
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....................From 1930 -- 1950
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Pennsylvania  Trolley  Museum  (PTM)
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http://www.pa-trolley.org/
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N.M.R.A.
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http://www.nmra.org/