Rhywbeth Fel Pwll Glo or Something Like a Colliery

To switch to the separate rails, you'll need some sort of point.

 

If you made the point swap the outer rail instead, you would still need just the 3 rails on the cassette.

Not sure what you mean Stu, the spacing is not the same either side of the "centre" rail, so with a 3 rail setup the cassettes could not be turned round?

Something like this might work, another "half K" fixed crossing controlled by check rails

 

No, nor do I. It's too early and I didn't think it through properly. 

Statfold Barn (near Tamworth) have a dual gauge out-and-back line with a reversing loop where the Shared rail swaps sides half way round the loop. My photo of the track at the swap-over position disappeared in a computer crash!

It's a popular outfit, there must be other RMwebbers who have photographed this track feature.??

 

It would be possible to copy the side-to-side swap at the middle of your cassette length. 

Edited October 4, 2019 by DonB

Not something I'd considered before, hmmm

 

I'd have to make a few more complicated cassettes though ......

I've just looked at their web site. It is vastly  more "commercial" than my last visit, probably 5 or 6 years ago. It no longer seems to be a Multi-gauge system, so the swap over mid  loop will no longer exist.

It was, as I recall, a uni-directional loop, the swap being done without point-work, controlled by check rails. Whether such an arrangement would work on a reversable cassette , my tiny brain won't tell me!!