Double single-sided tandem with slip roads - is this even possible?

[Lacathedrale]

I've been reviewing a plan in the July 1874 edition of The Engineer for Holborn Viaduct, and it has a rather bonkers throat, excerpt of which is shown below.

 

I'm not even going to think about the bonkers crossover from P4 to the 'engine pit', but the formation just above that is quite interesting.  The plan was supplied to the magazine 3 months after the station opened, and prepared by W. Mills, the chief civil engineer for the LCDR - so I have no reason to doubt its accuracy, but seems unusable:

 

 

I have drawn out the formation schematically - it appears to be a pair of single sided. tandem turnouts, the inner tandem having slip roads attached to each of the diverging routes:

 

 

 

I have drawn the problematic section of the track plan in templot. The background shape with the plan on has been hidden for clarity, and I have omitted all routes which aren't part of this formation:

 

It's not clear to me at all how this could work - infact, the whole plan  seems unworkable with 2.5 chain radius curves and the aforementioned bonkers engine crossover which cuts through at least two sets of point blades.

 

How would one manage the crossings in this formation? Is there even a way to approach this in templot!?

 

I note that the 1896 OS grid map (so some 22 years later) does NOT show the tandem turnout in this location, the bottom-most route being removed to make it a simple single slip - so realistically this is something I could easily omit - but it is such a significant component of this early plan I find it hard to believe it would be unmodellable.

 

Any thoughts?

 

 

 

[Stephen Freeman]

Borough Market bridge is one I did in Templot P4 and it shares some of the same characteristics (plan only I hasten to add). The main problem will be how do you make it work electrically? Of course if on 3rd rail then it might be a bit easier, even less hassle on R/C.

 

Be prepared for lots of partial templates.

[Lacathedrale]

11 minutes ago, Stephen Freeman said:

Borough Market bridge is one I did in Templot P4 and it shares some of the same characteristics (plan only I hasten to add). The main problem will be how do you make it work electrically? Of course if on 3rd rail then it might be a bit easier, even less hassle on R/C.

 

Be prepared for lots of partial templates.

 

Shares in Tam Valley Frog Juicers

[roythebus]

Anything is possible if you've got the will to make it happen.

[Derekstuart]

2 minutes ago, roythebus said:

Anything is possible if you've got the will to make it happen.

Have you ever tried lighting matches on a bar of soap?

[roythebus]

Yes, it is possible if you set fire to the soap first.  

 

There was a discussion about this particular track plan either on here a while ago or on the Templot Club site. Someone had made the complete plan in Templot; maybe it was the slightly later 1890's track plan. It would be interesting to see it done! I'd have a go using pcb sleepers just for the sake of it to see if it is physically possible. Although the prototype plan looks accurate, it probably isn't.

 

Looking at the engine pit road, it appears to be dual gauge; did the broad gauge go into holborn viaduct at this time? I know it went into Victoria via the West london Line and Clapham Junction, but did it get to Holborn via the Widened Lines? That would add to the fun and make the need for the engine pit.

 

 

Edited October 1, 2020 by roythebus

[Lacathedrale]

I've designed the throat in the 1896 version and may have posted it on the templot site - it's just as bizarre but in different ways. Oh well, looks like this curio is destined for the X-files.

[Kelly]

Certainly looks interesting! IIRC around that time the SER I believe were still running reversed and there were a number of points where they met the other railways and changed between  Left and Right hand running or vice versa.

[AndyID]

On 01/10/2020 at 06:03, Stephen Freeman said:

 The main problem will be how do you make it work electrically?

 

Dead frogs an a few capacitors.