Operating Puzzle

[whole diary]

[eightf48544]

Something to keep you amused it comes from my favourite railway see previous post.

You have a single line with a station with a loop equipped with R^ckfallweiche (or hydraulic self resetting points as per the Highland lines) at either end.

You have two up trains  and one down train.

How does the second up train overtake the first up train and both up trains pass the down train?

Hint it requires only one manual point change and I have the video.

[TerminalJunkie]

                   ----------
                 /     C      \
----U2----U1----                ---------DW----
     A     B     \     D      /     E    F
                   ----------

Do you need a manual points change?

• U1 moves B to C
• U1 moves C to E
• U1 moves E to D; U2 moves A to C
• U1 moves D to B
• DW moves F to D
• U2 moves C to F and away
• U1 moves B to C
• DW moves D to A and away
• U1 moves C to F and away

[eightf48544]

Good try termianl junkie but its simpler in practice, you are right that U1 is the only train that has to reverse.

Remember you can manually change one point. Contrary to normal running in the country C is up loop D is down loop. Points are  trailable and return to normal   ABC, FED.

Your way works without needing the manual point change.

[Chris from Nailsea]

QED

... but you've lost me! 

[TerminalJunkie]

                   ----------
                 /     C      \
----U2----U1----                ---------DW----
     A     B     \     D      /     E    F
                   ----------

OK, allowing a manual points change:

• Set points to allow B to D
• U1 moves B to D
• U2 moves A to C
• U1 moves D to B
• DW moves F to D
• U2 moves C to F and away
• U1 moves B to C
• DW moves D to A and away
• U1 moves C to F and away

. 

Contrary to normal running in the country C is up loop D is down loop.

Yes, but I was using Dalmally in my example

[Chris from Nailsea]

Mornington Crescent!   

[TerminalJunkie]

Mornington Crescent!   

Mornington Crescent! 

Repetition

[Chris from Nailsea]

Fair comment, TerminalJunkie - I'd forgotten that one! 

[eightf48544]

Spot on terminal junkie. U1 uses the down loop after a manual point change.

It's actually Schierkeon the line to the Brocken.

It seems to be a timetabled move when a special from Wernigerode to the Brocken is run.

U1 is the special usually Mallet hauled, U2 is the next service train to the Brocken and folows the special. DW is a return service train.

To allow U2 to keep to its booked times it overtakes the special at Schierke.

Even more remarkable is that the line to the summit is a complete spiral. It's quite something to be on U2 and look up the mountain to see U1 coming round the spiral at a higher level 100 metres above your train. Although U2 is something like 5kms behind by rail.

The Harz system shows what can be done with a railway combining as it does steam hauled tourist trains all year round, enthusiasts specials including photo stops, a community rail service for the locals with railcars particualrly for school children, an extension of the Nordhausen tram system to serve the North Western suburbs and a heavy freight railway.

It can be done Portishead! Trams to Bristol centre, railcars to BTM^▸ (Bristol Temple Meads (strictly, it should be BRI)) with a plume of steam for some services plus the freight. They can all run on the same rails.