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Track Circuit Assistor

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  #1  
Old 6th April 2022, 08:39
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aussiesteve aussiesteve is offline
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Track Circuit Assistor

Cooee BW,
I am scratching me cranium, having chanced upon a facet of modern day train operations here in NSW.
This being the first time that I have encountered this concept.
Anyhoo, many moons ago, in 1990, there was a rear ender prang in the tunnels on Cowan Bank.
Soot belcher 3801 stalled on the 1 in 40, due to a nefarious wagon handbrake discovered later.
The hystericals set back dropping sand in an attempt to get mobile.
But, in doing so, the signal behind them cleared allowing the following interurban emu to slam into it.
It hit the fan, and henceforth all motive power had to have DEsanding apparatus.
Air blowing behind the wheels to remove the sand deposited in front of the wheels for traction.
It became VERBOTEN to use excessive sand to maintain traction.
The sand deposited on the rail head insulating the wheels from the signal track circuits for automatic signals.
AND, should a loco pump out too much sand, Train Control had to be notified.
The sanding gear isolated, or if unable to do so, the train worked under Block Working to prevent a following train.
OK, this was always a bug bear to me in the ensuing yearly accreditation exam.
HOW much sand can you use to maintain traction ?
I'll use as much sand as necessary to keep the thing moving.
WRONG !
OK, to the latest Train Operating Conditions manual scrounged today.
EMU and DMU units here in NSW do not possess sand.
However, today our DMU units must possess a "Track Circuit Assistor"
QUE Mr Fawlty ?
This dingus apparently slings underneath the DMU between the wheel sets to act as an antenna.
This to increase the rail voltage at the wheels to ensure positive track circuit activity.
Have you heard of, or seen this in use in the UK ?

Diesel Multiple Unit trains (DMU) fitted with Track Circuit Assistors (TCA's)
The following DMU trains are approved to operate under track signalling (block working not required), provided that at least one TCA per train is operational:
Endeavour
Xplorer
Hunter RailCar

When both TCA's on any train are offline, failed, or inoperative, block working requirements as shown in Sydney Trains Network Rules, NSY 512 Manual block working, shall apply when operating over the track circuited lines indicated in Figure 4 in section 2.16.2. In this case, Xplorer and Endeavour are exempt from mandatory block working between Kiama and Bomaderry.

E GADs what will the boffins come up with next.
Steve.


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  #2  
Old 6th April 2022, 19:41
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Beeyar Wunby Beeyar Wunby is offline  
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Yo Steve.

1) I've never seen one, but it did get mentioned on my original rules course in 1999. Here in Blighty, TCA stands for Track Circuit Actuator and they're used mostly on On-Track Machines, which due to their low number of axles have a tendancy to go around in stealth mode sometimes in low adhesion season.
Here's what a railway chat site says....
Quote:
Originally Posted by ukrailforums
The TCA is effectively a single-turn transformer. There is an incomplete loop of copper tube within the bogie and as stated a signal generator circulates a high-frequency current through this. The other "coil" is the circuit formed by the wheels, axles and rails, which therefore carries a current at the same frequency through all four wheel-rail contact patches on that bogie (or whole vehicle in the case of a Pacer).

This high frequency current reduces the impedance of the contact patch at the lower frequencies (DC up to a few hundred hertz) used by track circuits, and therefore makes it more likely the train will be detected. The TCA is not effective if the rail is fully insulated, for example by heavy leaf contamination, but there is a track-mounted device called at TCAID that can be fitted in the worst areas, and detects the much lower induced current caused by a TCA-fitted train.
2) Sand. I think we may have discussed this before. IMHO, when you have to put it down, you have to. If we keep disrupting track circuits then maybe the infrastructure operator might actually start to clean the railhead properly. We've recently had a serious collision due to railhead contamination, and I suspect that a certain organisation is going to get a big botty-kick for not cutting back vegetation and not cleaning the railhead during Covid lockdown (whilst trains were still working, even if their lineside crews weren't).

Cheers, John
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Last edited by Beeyar Wunby; 7th April 2022 at 10:48.
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  #3  
Old 7th April 2022, 08:17
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Howdy BW,
AH OK, your lot call it something slightly different to our lot.
I actually prefer your mob's terminology.
Actuator sounds more affirmative than does Assistor.
But, the purpose is the same, to ensure that a light rail vehicle is detected by track circuits.
You lot have had such a dingus since 1999, HMMMM.
This TOC manual scrounged being issued in december 2021 is the first mention of the dingus here.
Rusty rail is definitely a problem when trains don't percolate frequently.
The first goods train to rattle over a section of track returned to action would act as a rail clean.
Especially at points.
And, you could find yerself being swung over at a number of spots, which does slow progress down.
With all of this multi-operator capitalism here today, time is moolah.
Maybe they don't perform rail cleans with freighters any more here, fearing operator complaints.
PLUS, to get swung over from the dedicated path, the crew need to KNOW where they are going route wise.
Take the wrong turn-out due to a mistake in the computerized train control system, and the crew cop it.
Leaf litter on rails is not a major drama here.
However, our driverless Metro dingus might encounter some situations where traction becomes a problem.
It has sailed through platforms in the past due to not being able to stop.
Our Bathurst Bullet is a two car Endeavour set dmu, and I always ride in the second car.
Though, not since the plague, I ain't been anywhere, let alone cramped up in a dmu.
Discovering that such dingi now must have this TCA, I might hafta ride on the roof.
That way, I could espy any thing rattling up behind it due to becoming "stealth" mode, not operating the circuits.
I would hafta duck me head numerous times to avoid getting snotted by the low bridges and tunnels en route.
But, I would not need to worry about wearing a mask, as you does when cramped up inside the thing.
When I do next attempt to ride the Bullet, I will now hafta take a gander at the underbelly.
To see if I can squiz this TCA dingus dangling under neath.
It has been known for some moons that our vintage CPH class rail motors (tin hares) are a problem with track circuits.
Hence, they have needed to be run as Block Working when ever the hystericals drag them out of the shed.
Now, it appears that the newer, but still now vintage 600 / 700 class dmu sets have been added to the Block Working.
These vintage machines not being provided with a TCA, I presume either due to cost OR lack of space under neath.
E GADs, simple solution, bring back that bloke who rode a horse along ahead of each train waving a red flag.
The only chance of a rear ender then being if the horse suddenly bolts down the track and the train attempts to follow.
Steve.
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Old 7th April 2022, 11:11
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Beeyar Wunby Beeyar Wunby is offline  
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I've found a video of it on Hugetube.

Linky...Track Circuit Assistor

Cheers, John
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Last edited by Beeyar Wunby; 7th April 2022 at 11:37.
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  #5  
Old 7th April 2022, 13:18
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Quote:
Originally Posted by Beeyar Wunby View Post
I've found a video of it on Hugetube.

Linky...Track Circuit Assistor

Cheers, John
Thanks, I'll add it to my watch list, after one about railway air brakes.
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Old 8th April 2022, 08:53
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Ahoy BW,
Yep, that mob Unipart Rail who produced the video clip also published a VERY brief brochure for the TCA.
I had scrounged the brochure, but I was hoping for some more detailed description.
They have an office in suburban smog hollow.
So, no doubt extolled the benefits of such a dingus to our smog hollow cattle commuter rail management.
I wonder if it works under water.
Smog hollow again copping a deluge is flooded in a number of regions once more.
I have not heard if any of the rail network has been submerged again, but many roads have.
No doubt that more landslips will occur causing rail chaos.
Smog hollow commuters offered some freebie rail travel over Easter to assuage angst at the lengthy repair periods.
If this rain continues through Easter, then not much freebie travel will be possible.
I will be headed in the opposite direction at Easter, WEST.
It will hopefully be a tad drier and warmer out there.
Scomo has dropped the 40 cents per litre petrol excise tax in an effort to placate angst at the Putin cost of living.
So, I have filled the car up with go juice.
Petrol down from the $2.19 per litre extreme last week to $1.79 per litre now.
WHO knows when I will get to take a gander at this TCA dingus dangling under our Bathurst Bullet dmu.
Steve.
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Old 9th April 2022, 07:47
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I see everybody in the world complaining about petrol prices, I have just paid AD3 aprox. per litre.
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