Telegraph poles, wires under bridge or over?

[philsandy]

When lineside telegraph poles meet a bridge crossing the railway line, would the wires go over or under the bridge?

I have an arched bridge 17' high on my layout, carrying a road.

[Grovenor]

Could be either depending on circumstances, if the road bridge is over a cutting and the pole route can be run at the top of the cutting sides then the wires would be able to get the required clearance to go over the road reasonably easily. If the bridge has enough room for the pole route clear of structure gauge it can be taken under, if really essential the pole route would be terminated either side and cabled through, this was a last resort as it introduced losses into the communications circuits, especially important if there were any long distance carrier circuits on the route.

Keith

[great central]

I don't know if there is a definitive answer. It may depend on clearance under the bridge. If there's enough room the wires go underneath, however I think some of the ones on the GC go over and there should be ample clearance under their bridges. The ones on the Ely-Norwich line seemed to often go under. There are still odd poles and arms very close to bridges. The GE ones on that line were short poles.

When I started work as a telephone engineer many years ago, we were instructed on the minimum clearances required over different types of road, that may also have some bearing although I've no idea when the limits were introduced. The clearances have since been increased, leading to the silly situation where they had to replace the pole outside our house. The thing is, it's a private road and the approach has very large overhanging trees which the dustbin lorry usually knocks a few bits off every week! Anything bigger would need some serious pruning of the trees to get here! 

[smokebox]

There is a previous question about this topic here which may be helpful.

[corneliuslundie]

If room is limited under the bridge the wires may be supported by insulators attached to the arch of the bridge itself. I have certainly seen this.

[Michael Woolford]

If room is limited under the bridge the wires may be supported by insulators attached to the arch of the bridge itself. I have certainly seen this.

One such example was the bridge at Blunsdon on the old M&SWJR, this bridge still exists today and carries the road over the Swindon & Cricklade Railway. In the two photos below the insulators can be seen still fixed to the wall.

 

Michael

[steve1]

What is the red 'thing' in the first pic please?

 

(apologies for hijacking the thread)

 

steve

[peter220950]

What is the red 'thing' in the first pic please?

 

(apologies for hijacking the thread)

 

steve

 

Plasser and Theurer track machine perhaps?

 

http://madannie.smugmug.com/Trains/Track-Machines-and-On-Track/i-NHp4z4r/A

[steve1]

Think you could be right Peter. Thanks!

 

steve

[Bruciethefish]

Depends on what area you're modelling, SR practice in my area seemed to be to go under whenever there was sufficient clearance. Multiple-arch bridges over cuttings would usually have the wires taken through a side arch on very short poles.