H2O model train figure 8 track, How?

[Geek-9pm]

This is way off topic. It is a logic problem. Or maybe a hardware thing.
When I was a kid I had a Lionel O gauge with three trails.It was a figure 8.

At that time I learned that only the three rail mode train would have a figure 8 track layout.  The H2O standard is two rail and you can not have a figure 8. It would short out the power supply if you tried. But that was a longtime ago.



I have tried to find the answer in Google search,but I just do not know how to express the concept. I am sure somebody somewhere has done it with relays and sensors. You have to set up some kind of automatic switching that will separate the sections of track and swap the polarity when the engine comes near the  place where you want to change the polarity.

I was hoping to see how then did it and how many relays they had to use and if it works smoothly. Does anybody understand what I mean?   

[BC_Programmer]

One track passing over another as in your image I would not expect to present a difficulty. It is only if the two tracks actually pass through one another. For that, It seems to me the simplest solution would be to simply not have the square section where the tracks actually pass conduct electricity at all for one route. have the conductor itself instead go underneath the track surface and back up on the other side.

This would work particularly well with engines that accept power from both their front and back wheels. Then even when passing over the non-powered segment, the engine will still be able to run. With a single pair of wheels Inertia may be enough to bring it over as well.

[Geek-9pm]

Thanks, BC .
You are right, I just could not visualize how it works.
I am gonna takes some color pencils and draw the figure 8 again and again 'till I can see it in my mind. This has bothered me for years.

Is there a branch of mathematics that deals with this kind of thing?

[Salmon Trout]

You can see the insulating sections in this photo. In England, we call this a 'diamond crossing'.

As for the polarity on a figure-of-eight layout, draw the layout with the 2 rails, and label one + (positive) and one negative (-). Now follow either one around with your finger and you will see it joins up with itself. What is the outer rail in one loop is the inner rail in the other. Here, I did it for you....

[Salmon Trout]

Is there a branch of mathematics that deals with this kind of thing?

Topology, maybe?

[Salmon Trout]

Of course, real model-rail buffs will tell you that most toy type model trains are hopelessly unrealistic when it comes to starting and stopping. A real train weighs hundreds of tons and takes a while to get going (and also to stop!). Toy trains weigh not much, and are wildly overpowered, so as soon as you put the power on, they rush away from a stand, and when you turn the power off, they stop at once. Not realistic. You can get model locos with flywheels in the drive to add a bit of inertia, and these days, you can simulate that with the digital control systems. Either way, a model train should coast over the small gaps at a crossing or switch.

Here is my namesake, No. 60041 'Salmon Trout', in OO Gauge.



And a cheaper version



See the flywheels and clutch?

[Geek-9pm]

From dictation.
Thank you both for your help. For years I had thought that figure 8 was impossible with the H2O scale because it has only two rails. Now I can see that I was wrong and I don't know why I got that idea when I was a youngster that the figure 8 only work with the three rail Lionel oh track.
So now that I have that resolved, I can sleep easier at night and not be confused by my lack of understanding of what can be done with model train scale H2O.
And Salmon Trout, thank you so much for the illustrations in the photos of your engines. That was a clever idea about putting off like we'll inside of the engine to make it more realistic.
Unless anybody else as something to add to this, I am satisfied with the answers provided.