Degree of tolerance for masts/gantries carrying wires?

[Howardh]

http://www.railway-technical.com/_Media/ole-at-old-dalby-labels-prc_med_hr.png

Thinking unless the photograph is distorted, the mast on the right appears to be out of vertical by a couple of degrees.

Considering wind, expansion due to heat, ground giving way slightly etc, where masts are standing alone and they carry wires over the tracks, what is the degree of tolerance (ie if 90 degrees is perfect) before rectification is necessary? Being a total layman on these issues, if the line falls (or rises) I would expect a pantograph to cope up to a certain amount.

Anyone help? Thanks!

 

[GRALISTAIR]

https://en.wikipedia.org/wiki/Corro...le:Corroding_Steel_Electrification_Gantry.jpg

WCML Crow Hall Bridge Newsham Hall Lane 4 miles north of Preston. Way off plumb

 

[Howardh]

https://en.wikipedia.org/wiki/Corro...le:Corroding_Steel_Electrification_Gantry.jpg

WCML Crow Hall Bridge Newsham Hall Lane 4 miles north of Preston. Way off plumb

Thanks
If it (or any structure) lifts the wire that would be only for a short distance and the pentograph would pick it up again shortly if there was no contact for a few dozen yards? That assumes (a) there's no contact at some point and (b) the train is actually moving!

 

[GRALISTAIR]

IMHO - when something like that goes way off plumb, the repair to me is obvious - or should be. Convert it with a bracing crosspiece - that is make it a portal not a headspan. I do make the point though, although I have done materials engineering, I am NOT a structural engineer. So I maybe way off beat. Garry Keenor could opine of course.

 

[pdeaves]

As I understand it, in principle, masts do not have to be vertical, but it makes the structural forces, etc., easier to calculate/manage. The various bits and pieces hanging off it and holding the contact wire are adjustable to put the wire in the correct position. That is of course of little use if a mast suddenly leans after being set up.

 

[Howardh]

As I understand it, in principle, masts do not have to be vertical, but it makes the structural forces, etc., easier to calculate/manage. The various bits and pieces hanging off it and holding the contact wire are adjustable to put the wire in the correct position. That is of course of little use if a mast suddenly leans after being set up.

That was the question I was attempting to ask - seems then that is masts lean they simply adjust the rest; until such a time where it's just leaning too much I suppose!

 

[GRALISTAIR]

As I understand it, in principle, masts do not have to be vertical, but it makes the structural forces, etc., easier to calculate/manage. The various bits and pieces hanging off it and holding the contact wire are adjustable to put the wire in the correct position. That is of course of little use if a mast suddenly leans after being set up.

That is I assume a key reason that when Chat Moss was being electrified they used TGBUs for the masts aka Thundering Great Big 'Uns

 

[Howardh]

That is I assume a key reason that when Chat Moss was being electrified they used TGBUs for the masts aka Thundering Great Big 'Uns

BiB; sorry to be thick, but what are those initials?

 

[furnessvale]

https://en.wikipedia.org/wiki/Corro...le:Corroding_Steel_Electrification_Gantry.jpg

WCML Crow Hall Bridge Newsham Hall Lane 4 miles north of Preston. Way off plumb

Is that a fair example? That is a headspan mast and would probably be installed with a measure of tilt to allow for the pull of the headspan wires.

 

[swt_passenger]

BiB; sorry to be thick, but what are those initials?

They’re the initials of the four words at the end of the sentence...

 

[GRALISTAIR]

BiB; sorry to be thick, but what are those initials?

That is I assume a key reason that when Chat Moss was being electrified they used TGBUs for the masts aka Thundering Great Big 'Uns

There were numerous discussions in the Liverpool Manchester electrification scheme and then they were raised again by me in the Blackpool Manchester thread. The phrase was coined by @LDECRexile with contributions for coining the phrase by @PDG1949 and also I believe @LNW-GW Joint - the URL below should take you there with one or two photographic example. The term is of course not technical and peoples definitions may vary. My definition is any base that has about 4 cubic meters of concrete to support a mast.

Blackpool - Manchester Electrification

 

[GRALISTAIR]

Is that a fair example? That is a headspan mast and would probably be installed with a measure of tilt to allow for the pull of the headspan wires.

Probably not

 

[Howardh]

They’re the initials of the four words at the end of the sentence...

Oh...I thought they may be specific terms for the equipment!

 

[Ploughman]

It was common practice on old Tram / Trolley bus routes for the Masts to lean backwards countering the weight of the wiring.
Is this practice also in use on the railway?

This can still be seen on roads around various cities, such as Liverpool and Bradford, where the original masts are still in use as Lamp standards.

 

[edwin_m]

This may be of interest: https://assets.publishing.service.g.../file/410743/130520_R062013_Littleport_V2.pdf

At 07:19 hrs on Thursday 5 January 2012, the pantograph assembly fell from the roof of a passenger train, breaking two windows on its way to the ground. ... One passenger received treatment for minor cuts at the site, and two others suffered minor shock but did not require medical treatment. There was extensive damage to the overhead line equipment and minor damage to the train body.

The pantograph head lost contact because the overhead line was deflected from its intended position due to a combination of long term movements of the overhead line support mast foundations and the force of the wind at the time of the accident.

The RAIB concluded that maintenance of the overhead line had not been carried out in accordance with Network Rail standards, meaning that the overhead line had not been adjusted to allow for long term foundation movements.