Suzie

I am just going by experience. Most modellers who use analogue DC tend to consider a layout longer than 3' excessive, and having any motive power more than one steam tank loco on a layout beyond the pail. There are of course exceptions...

You can get 3-position double pole ON-ON-ON type toggle switches which can be wired to create a pulse each time the switch passes through the central position. This is the best hope you have of achieving what you desire.

Correct. Power routing is one of those things that was used in the olden days when analogue control was used on layouts with more than one loco. It is a niche requirement nowadays.

Yes

I think that the Unifrog can be used in any way you like. It can be used out of the box as dead frog. It can be rewired to use the switch rails to power route as Insulfrog. It can be rewired as Electrofrog. Or it can be used as intended as live frog just by adding a frog switch. If you have a problem, then one of the above solutions will cure it. There is nothing you can do with the old Insulfrog and Electrofrog that you can't do with a Unifrog, but there are some things you can do with Unifrog that would take a lot of surgery on an Insulfrog or Electrofrog. I just don't see any unsurmountable problem.

It probably does not like the shorting on the Insulfrogs. When you lay the Insulfrogs, link the frog rails and wire them as Electrofrogs, that way you will eliminate the shorting and things should be better. It is much easier to do this when laying the track.

The treads would have to be pretty wide to be a problem, the sort of wheels which would be unsuitable for code 100 track.

Wikipedia has a good page for this:- https://en.wikipedia.org/wiki/French_railway_signalling But to answer your specific points two reds will be found on an absolute signal protecting a junction and means stop and do not pass, whereas a single red may be permissive depending on the specific signal type such as a block signal. The purple is equivalent to two reds and is used in a similar way to the way a ground signal would be used here to protect the exit from a yard (purple equivalent to two horizontal reds, white equivalent to two inclined whites).

ahh, 360114 - the first 360 I saw, still had the plastic on the seats running with 360104.

You can mount a PL10E motor on a PL9 base below the baseboard, and link that to a PL12 on top of the baseboard if you don't want to mount the PL10 on top. As long as the extension arm is free to move and straight the length makes little difference.

Patrick, I think it might be easier to do it this way. It sort of depends on how small your opto-isolator is compared to a couple of 1N4148 diodes. Activating the green wire will turn off the rear lights, and using separate resistors will allow red lights at both ends for when you are parked (if this is a feature of your loco, and available on your decoder). Circuit will draw 12mA or thereabouts per LED whether turned on or not, but that probably will not eat too much in to the power budget. If using a single resistor as in the original diagram you don't even need the diodes with most decoders.

Well, it might need a bit of fettling... ... perhaps there could be some blowing from the other end? Perhaps lose the other cab?

Perhaps like this one in a later livery, smaller fuel tank being as the load will be shared between the two locos.

I think that early experience with the 40s should have inspired a project to produce some single cab 40s that would be used in pairs where more than 2000 HP was required. It might have inspired a HST type arrangement made from a pair of these 40s and a rake of Mk1s in the 1950s. Now that would have left its mark given how long Mk1s and 40s remained in service, probably only being displaced on the Highland main line with the cascading of the more modern HSTs. I guess they would have had a 1C0-C0 wheel arrangement being a bit shorter without the cab and nose at the back.

You can use a PL12 with the extension bar going under the track. For difficult situations make a longer extension bar, or use two! This is handy when you want to avoid framing under the point as well.

Those redundant DC portals look just like the 1940s Great Eastern ones that are now being replaced due to being end of life. I suspect they will have to go soon whether they get used or not.

You can buy an adapter from Signalist to motorise Ratio semaphores with servos which fits through the baseboard and allows the Ratio signal to just drop in to the hole for easy removal with no linkages to make. https://www.coastaldcc.co.uk/products/harman/ratio-signal-motorising-kit

It looks good, but is probably too late in to the space that Arduino has already taken. It will be interesting to see if Betamax beats VHS in this race!

Nothing else required, just the AC LEDs and resistors shown in the diagram.

I understand it that if you want to do DC power switching you will have to both cut some links and make some new ones.

The track plan looks a lot more complicated than it is. There were basically two loops, a 'Union Pacific' and a 'Rio Grande' with two trains running on each loop. It certainly looked impressive and very busy.

You get four indications. Both lights on meaning the point is in a 'mid' position, and both lights off meaning there is no power to the track. This can be handy for quick fault finding.

The Hornby one should not need the link wire.

What is a 'pc' switch? The diagram is correct as long as you don't use a Peco passing contact switch - the wiring for a Peco switch is sightly different.

Quite big then.