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Old 25th June 2020, 03:22
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aussiesteve aussiesteve is offline
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Join Date: Dec 2017
Location: Bathurst
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G'day,
There are various designs employed for the purpose of derailing an errant train movement.
On main lines at crossing loops and refuges, a Catch Point is generally utilized.
This in the form of a switch rail blade which remains open to prevent anything passing and fouling the main line.
A deflection rail just beyond that switch blade ensures that the wheels of an errant movement is directed away from converging with the main running line.
And the switch blade is closed to permit correct movement out of the loop or refuge.
Within yards and sidings, derailers that sit ontop of the rail are generally utilized.
One version dubbed a Scotch Block.
This derailer has a formed groove to lift the wheel and flange above it and aim the wheel outside of the running rail.
The derailer generally pivots over to the side of the rail to permit correct movement during shunting etc.
Rail yards and sidings are rarely flat, in fact a slight gradient was employed at most yards to permit gravitating wagons during shunting movements.
Imagine a run-away cement wagon at the siding that you mentioned.
Without the provision of either a catch point or derailer, that wagon could roll towards the points onto the main line.
Yes, it would still derail as those points would be set for the main line.
But, the wagon would encroach the main line and present a potential collision risk to a train approaching on the main line.
One location on the NSW Blue Mountains which posed a challenge for heavy coal train crews was Lawson.
The coal train dropping down the 1 in 33 grade and directed into the UP refuge to permit a cross with an UP interurban pas job.
This refuge ONLY just long enough to fit a 33 hopper coalie with quad locos.
A catch point just feet beyond the Refuge starter did not provide any misjudgment and overrun.
Yes, the occasional train did overrun the signal and roll through the open catch points.
It would not go far and be jammed up against the cutting wall.
With much of the train still perched on the falling 1 in 33, only a short section of the refuge adjacent the station platform on level ground.
The loco brakes would NOT hold a 3300 tonner stationary, so you had to leave the train brakes applied.
I believe that one of the "incidents" occurred when the crew got off to go to the shops and had only left the train sitting with the loco brakes applied.
Gravity overcoming the loco brakes.
At the Kandos cement works on the Mudgee branch line, the yard was protected by a catch point that was infact the points to the old loco turn table.
The yard on a falling grade towards the main line.
I was working home from Mudgee one time and we were halted at Kandos works to assist with a run-away cement pot recovery.
The errant cement loaded cement pot had rolled out of the yard, through the points and over the old turn table and buried in the mud on the opposite side.
We detached our loco from the train, stabling it on the main line, and then shunted to enter the works yard and then aim towards the turn table.
The turn table was very wonky and booked out of service for yonks.
So, we could not go onto the turn table, but sit on the other side and use a heavy wire hawser attached to the cement pot to drag it back onto the rails.
Apparently, the hand brake on that cement pot was defective and it decided to roll away.
It is far better to derail an errant movement than incur a collision, especially with a passenger train.
Steve.
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