The headspans' last stand

[McRhu]

I've been following the various MKIII headspan replacement posts with some interest. Speaking as a headspan enthusiast rather than any kind of engineer or expert, I wonder if it wouldn't be possible to use a stiffer material to replace the headspan wires (which I believe are steel or copper) so that excessive movement under windy or high-speed conditions might be nullified. What about tungsten or titanium or ceramic wires? Or wires consisting of contra-rotated strands (ie - each strand twisted either clockwise or anti before weaving into the cable) that exert a stiffening force on each other even when not under tension (as per twisting a piece of fabric for example to make it more rigid) - maybe even 'polarised' thus at molecular level?

In short, I miss the elegance of the iconic British headspan.

 

[Railsigns]

This wouldn't overcome the headspan's biggest drawback: the inability to independently register the wires above each track.

 

[randyrippley]

Tungsten / Titanium - limited availability and cost would be issues
Ceramic - inflexibility would cause fractures

 

[GRALISTAIR]

Ceramics tend to have poor conductivity. There is a reason copper is used for the contact wire.

 

[zwk500]

Ceramics tend to have poor conductivity. There is a reason copper is used for the contact wire.

Wouldn't it be an advantage for the headspan wire itself to be non-conductive?

 

[edwin_m]

To reduce movement probably requires greater tension in the wire - the flexibility of the wire itself is unlikely to make much difference, and less flexible wires may also be more brittle. The supports may not be able to withstand increased tension.

Would having stronger headspans make any difference in a dewirement anyway?

 

[GRALISTAIR]

Wouldn't it be an advantage for the headspan wire itself to be non-conductive?

You can make that case yes and also argue that since they are not in contact with the pan you don’t need the same impact resistance. It is interesting that we have gone away from ceramic insulators and moved to polymeric ones on modern 25kV systems. Ceramics are useful materials but they have their limitations.

Tungsten and titanium would put costs through the roof and are non-starters.

 

[McRhu]

So... the headspan is going the way of the red phone box and the classic Routemaster, and it's back to portals. I suppose one benefit of all that extra steelwork is that should we ever have another war (God forbid) the GWML stuff could be melted down to make a few hundred aircraft carriers and a couple of regiments' worth of Challenger 3s. Oh well - thanks for your observations gentlemen; much appreciated as always.

 

[randyrippley]

So... the headspan is going the way of the red phone box and the classic Routemaster, and it's back to portals. I suppose one benefit of all that extra steelwork is that should we ever have another war (God forbid) the GWML stuff could be melted down to make a few hundred aircraft carriers and a couple of regiments' worth of Challenger 3s. Oh well - thanks for your observations gentlemen; much appreciated as always.

If you're going down that route of argument........a portal is much more resilient to blast damage than a headspan

 

[Bald Rick]

So... the headspan is going the way of the red phone box and the classic Routemaster, and it's back to portals.

It isn‘t. I confidently predict that Headspans will be with us in large quantities until the railways are de-electrified.