The pantographs are either up or down. They spring over centre for up & down.

I measured a handful with pantographs up not under catenary. The height on various locos range from 29mm to 32mm. Most around 30mm.

Don't forget you need enough height for the catenary. My catenary bends up a bit inside the tunnel, soldered to a section of rail at 90° across the tunnel. I only use catenary in the visible areas as it is a pain loading trains under catenary.


I have 36mm from top of rail to under side of bridge. Should be 37mm for masts if there is one under a bridge. I was trying to save every mm in height for spiral.

This modern tunnel is 59mm diameter & 40mm high at the centre above top of rails. Old tunnels 56mm diameter 37mm high. Both a few mm larger inside.

Road tunnel 38mm diameter & 25mm high.

Tunnel portals are bigger than one first realises. You can look up the ISO standards easily these days.





For maintaining 37mm height spirals at 2% gradient the track radius needs to be 295mm. I have my uphill track always on the outside so the downhill track always on the inside is tighter.

Don't go steeper than 2% otherwise you will get frustrated once built.



A bit hard to see rail at 90° to solder catenary to. There are actually 2 rails for the catenary, one each for the inner & out catenary as they were at different distances into the tunnel. Ends of rail bent to lock in place. Just simply the easiest solution & bullet proof.




Do your ballast into the tunnel about 70 to 150mm depending on scenery viewing angle, before installing tunnel portals or you won't reach!

P.S. If you have any questions, please ask (I am an architectural model maker, retired). Get your master plan right before you lay the first piece of foundation, let alone track, will prevent endless stuff-ups. The simplest start is to draw out the layout to the Z scale on butchers paper. You can then place all the RLs (relative levels) for spirals etc. It may sound tedious but it is 1/100 as tedious as rebuilding. I have made a lot of money fixing architects' failure to get their design right. Including a major model for the 2000 Olympic games site in Sydney.

Edited by user 31 July 2023 06:20:27(UTC)  | Reason: Typo: If > It & architects' ( ' )

More information with catenary in this thread: https://www.marklin-user.../t36639-z-scale-catenary

Personally I can't see the point of powering via catenary. You will then need some form of catenary everywhere.

As I already mentioned loading trains under catenary is irritating.

Thirdly, because the track is DC, you will need to think through block sections & dead track in stations etc as power is only being used from one rail. There is probably an issue which direction the loco is pointing as it will only pick up power from one side, (Maybe someone with experience with powered Z catenary can clarify this). So you need to work out which rail will be the common powered rail.

Ah yes, the Biaschina viaducts near the tunnels near Bodio.