The track circuit triggering issue (CN, Amtrak)

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I yeah, I remember that set. That was one of my favorite joy rides when I was in high school. I'd take the ~5PM out to Norristown and then ride home on an EMU local. Fortunately, my mom liked to serve dinner around 7 PM, so I was able to make it home for dinner. According to the departure board at Reading Terminal, they called it the "King Coal," and it went to Reading and Pottsville. In its heyday, the Reading "King Coal" ran all the way to Shamokin, but was discontinued in 1963 (according to Wikipedia), a little before my time.
Interesting that they ran through to Pottsville. The one time I got to ride that line, shortly before service ended, it was on a Saturday and we had a 2 car RDC set which I think was the set usually used for the Crusader during the week, with the bar counter (closed for this run). We then had to change in Reading for Pottsville which was a single RDC, more than adequate for the few people on the run.
 
There are a lot of inspections, testing and costs associated with keep equipment roadworthy. As much as I'd love to see the old Heritage dining cars used as axle equipment, I recognize manufacturing parts to keep them in compliance with FRA guidelines may not be the best choice. It may be a better choice to use your existing fleet, which you can maintain, even though it is constrained.
With that in mind it sounds like the shunting enhancement device they're testing with the Midwest Charger is really the only option with any promise that could eventually get these Superliners running back where they should be and put this issue in the rear view mirror since CN seems unwilling to even admit there is actually a problem with their infrastructure. Guess we have to hope it works out.
 
It is 40 years since I was employed by British Rail, but we never had any problems with track circuit operations. Basically, the two rails of a train line are "positive" and "negative / neutral" at a low voltage. All that was required was that a wire capable of conducting electricity should be connected between the two rails, to activate a red signal and show the line was "occupied". We had "track circuit clips" as described above, for use as emergency items if required. In day to day operation, any rail vehicle would take the place of the wire, and it's passage would operate the track circuit equipment by shorting/shunting the two lines/rails.
Either the US rail surfaces are dirty or corroded, or the train wheels are, otherwise any metal wheeled vehicle should "short/shunt" without need for excessive weight?
 
It is 40 years since I was employed by British Rail, but we never had any problems with track circuit operations. Basically, the two rails of a train line are "positive" and "negative / neutral" at a low voltage. All that was required was that a wire capable of conducting electricity should be connected between the two rails, to activate a red signal and show the line was "occupied". We had "track circuit clips" as described above, for use as emergency items if required. In day to day operation, any rail vehicle would take the place of the wire, and it's passage would operate the track circuit equipment by shorting/shunting the two lines/rails.
Either the US rail surfaces are dirty or corroded, or the train wheels are, otherwise any metal wheeled vehicle should "short/shunt" without need for excessive weight?
Did you ever have any issues with the lighter weight equipment, the Pacers for example?
 
Did you ever have any issues with the lighter weight equipment, the Pacers for example?
They did have problems which was apparently fixed by using iron flange brake shoes instead of composite ones.

British Railways also invented the Track Circuit Assistor or Actuator (TCA), which induces a high frequency current between the wheel and the rail thus improving the connection between those two for the low frequency or DC track circuit apparently the Physics of which was not then fully understood. This was done many decades back. This is what is currently being fitted on the Chargers to work around the CN track circuit issue in Illinois.

See this discussion about TCA for some more info: How does a TCA work?

Here is a little illustrative video:



Apparently TCAs are used in Australia too as indicated in this very Aussie sounding group:

Track Circuit Assistor - Railway Forum
 
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Did you ever have any issues with the lighter weight equipment, the Pacers for example?
We did not have pacer type dmu's at my depot, Stratford, in East London. I never heard any talk about track circuits not being activated by passage of trains, or single locomotives, but I bow to Jishnu's more correct knowledge as stated above.
 
We did not have pacer type dmu's at my depot, Stratford, in East London. I never heard any talk about track circuits not being activated by passage of trains, or single locomotives, but I bow to Jishnu's more correct knowledge as stated above.
And I'm guessing not too many level crossings in your region either, correct?
 
And I'm guessing not too many level crossings in your region either, correct?
These days they have CCTV remote controlled level crossings with intrusion detection all over the place, including on ECML and WCML 125mph lines. I think the Brits were more concerned about block signals triggered by track circuit being left in the Clear when they
should be displaying Danger.
 
If they only maintained the axle ground brushes better there would not be a problem.
Each axle has a carbon brush grounding it to Car body, maintenance has been shoddy on them.
How does grounding the car to the axle help? My understanding is the crossing detection triggers off of the axle connecting the two rails electrically, and the car body isn't part of that circuit.
 
by connecting each axle to car body it creates a bigger circuit , not effected by leaves, grease or other contaminants. Even the single car RDC use to have detection problems, unless the ground traps to scraper shoes were maintained. creating a full circuit.
and even then the RDC had to restrict speed to 30 mph prepared to stop when approaching Rail Road crossings for example.
 
How does grounding the car to the axle help? My understanding is the crossing detection triggers off of the axle connecting the two rails electrically, and the car body isn't part of that circuit.
Better grounding of the train body and the truck body through brushes provides alternate routes for the detection current. So if a wheel is dirty due to leafs or track grease it causes less of a problem if the other wheel are OK. etc. In effect 4 contact points connecting to 4 contact points provides a more reliable circuit than just one to one.
 

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