Inter Unit Gangways

[Domh245]

This is something I've noticed mostly on newer units, but is also around on older units (eg 455s, 150s). The front of the inter unit gangway often seems to be made in 2 parts, sometimes the difference isn't noticeable, but then again, on some units it is very noticeable. I've also noticed that one of the halves of the front bit seems to wear a lot more quickly than the other, usually on the drivers side. Can anyone say why this is? I'm guessing that one is the positive pole of a magnet, and one the negative, so that they remain attached when coupled, but that doesn't explain the weathering.

This picture is a good example of the 2 things I'm talking about:

 

[swt_passenger]

They aren't magnetic as far as I know, just held together by spring pressure. AIUI one half is a friction material, and the other isn't. The reason they are 50/50 about the centre line is just so that all gangway faces are exactly the same and it then doesn't matter which way round they are connected.

I guess once they originally realised that they only need one friction face and one painted metal, (when paired up) rather than two complete friction faces, it saves 50% of the cost of the material - which is probably significant across hundreds of units...

 

[Peter Mugridge]

...which in turn means you have the friction material rubbing on the painted side on the opposite unit, hence the uneven weathering.

 

[Domh245]

Ah, that makes sense, thanks for the info. What sort of friction material would they use, I can only think of silicon carbide which is more if an adhesive, but I'd guess the material they use is similar. Also, I'm guessing that there would be some sort of group standard about this, or is it just that manufacturers only use the 1 supplier (dellner?) In the days of the sprinters, would the commonality in gangway be specified in the design tender (thinking about the 155s/156s) or just used by the manufacturer knowing that interoperability will get them orders.

 

[bronzeonion]

Well on MK1/2 coaches and I assume on modern trains they are literally just a sort of hard plastic.