Limitations of British OLE

[HSTEd]

How do you take down old electrification structures these days? Simply turn an oxy acetylene torch on them at the base and then take out the foundation whenever it is convenient or is there some more finessed method?

 

[ole man]

You got it right first time, in fact i did the Cement sidings at Bletchley, though these days you look more like a astronaut with all the gear on.
Lead this lead that.....

 

[LNW-GW Joint]

I was interested to see recently that the old MS&L-route OLE through Woodhead had been completely removed through Sheffield, and you would not know the route had ever been electrified.
But on the other side of the Pennines there are still lots of redundant posts, around Guide Bridge in particular.
An ugly wasteland if you ask me, with loads of scrap steelwork just ripe for the picking.

At Edge Hill they wired far too much trackage for the West Coast electrification, and eventually dewired east towards Olive Mount, leaving the posts.
At least they might be able to reuse these in the new electrification project.
There are still miles of wired sidings at Edge Hill which must have been redundant a long time.

Finally, the Heathrow Express route out of Paddington is mostly headspan wiring, though it only has to cope with 100mph Desiros at the moment.
Will it cope with 125mph IEPs?
Be interesting to see what design they use west of Airport Jn.

 

[ole man]

If you walk the Trans- Pennine route from Hadfield towards Penistone you can still see some old OHLE structures that weren't burned right to the ground.
As for re-using Old stuctures these would have to be stress tested and be in a good enough condition, my opinion is that they will be replaced with new ones, as they might not suit the design.

Onto HeX Route the present OHLE will stay up but will be subject to a major upgrade, as said before can't see Headspans being used again, so going west i think it will be 4/6 track portals.
Though you never do know??

 

[HSTEd]

If one was going to take the route of having the gantry assemblies ready above the current wiring and then lowering them into place after the previous wire has been removed and immediately before the wiring train arrived to put new equipment up, would you be able to change one tension length over a night while retaining the normal service?

Ie. would you be able to splice the two kinds of track together every night as the new equipment advances one tension length at a time?

 

[swtandgw]

Finally, the Heathrow Express route out of Paddington is mostly headspan wiring, though it only has to cope with 100mph Desiros at the moment.
Will it cope with 125mph IEPs?
Be interesting to see what design they use west of Airport Jn.

I probably expect so, because if I'm right, they are of the same BB MK3 design as the ones used on parts of the WCML, ECML and the MML from St Pancras to Bedford. As for beyond the airport junction, it might either be a continuity of the existing design, or a completely new design based on modular portal spans.

 

[Old Timer]

Something like that, although I now realise that is only a two track line.

The wire running from the Structure to the top of the portal boom is a brace wire. Its purpose is to support the boom from bending under the weight of the OHL. In the UK we install pre-curved booms, which straighten out as the full weight of the SPS (Small Parts Steel) is taken.

A slightly similar arrangement could be found on the MK2 Equipment used on the Wemyss Bay/Gourock line, where the Cantiler top arm was actually a wire stay.

The arrangement from which the registration arms (now known as steady arms) are supported in the picture is called a "Parrot's Perch". These were included as part of the Mk 1 design but have not been replicated into Mk2, Mk3 or UK1 that I am aware of.

With regards to cutting Structures the older ones bear a lead based paint whereas more recent ones (typically Mk3 onwards) have a galvanised coating. Both need special disposal. The staff involved with the older Structures have to be medically monitored for Lead and work under those Regulations. The vapours given off are also harmful and the working area is therefore an exclusion zone.

With regards to the GW, depending on the 10-foot distance, I would anticipate STCs on the outer lines and BTBCs (Back to Back Cantilevers) on the inners.

Obviously it depends on the clearances.

 

[LNW-GW Joint]

Did we learn anything from the HS1 OLE installation, which I assume was a French design (Alstom?).
I know Network Rail didn't install it, but as that is the most recent big UK installation and seems to work well, wouldn't it be a good idea to start from there on the GW scheme?
I can understand NR using older UK techniques on the smaller NW scheme.

 

[Old Timer]

HS1 is not a system designed for the UK market. It is what is known as a constant height system, which means that the Catenary system is standard throughout the route. This sort of equipment can be thrown up by relatively unskilled staff fairly quickly.

In the UK our loading and structure gauge means that of necessity UK Equipment has to be able to cope with varying changes in height and gradient in order to replicate the track geometry which is more complex than in Europe generally.

 

[apk55]

HS1 is not a system designed for the UK market. It is what is known as a constant height system, which means that the Catenary system is standard throughout the route. This sort of equipment can be thrown up by relatively unskilled staff fairly quickly.

In the UK our loading and structure gauge means that of necessity UK Equipment has to be able to cope with varying changes in height and gradient in order to replicate the track geometry which is more complex than in Europe generally.

Do not forget that a normal electric railway has to cope with two extremes
1/ Low bridges and tunnels where the wire is at the minimum hight. In the UK normal train hight is 3.15M so the wire hight has to be that plus about half a meter electrical clearance ie 3.65M. In some cases (particularity on closed systems such as Manchester Metro-link) lower stock may be used so that an even lower wire hight may be used in places.

2/ Level crossings where it has to be well clear of the roof of lorries and buses. EEC regulations limit them to 4.3M but it is normal to design structures for 4.8M to allow for tolerances and bounce. Add another half meter for electrical clearance and the wire hight must be at least 5.3M

Therefore a pantograph has to cope with a wire hight variation of around 5.3 - 3.65 = 1.65M. On a dedicated high speed line there is no level crossings so the wire can be kept at a constant hight all the way.

 

[Old Timer]

These are the correct Contact Wire Height dimensions based on a 4.04m nominal kinematic loading gauge.

Open Route Nominal Clearance

• Mark 1 4.88m
• Mark 3A 4.72m

“Normal Clearance” (close tolerances)

• 4.240m min.

Overbridges & “Reduced Clearance”

• 4.190m min.

Tunnels “Special Reduced Clearance”

• 4.165m min.

Level Crossing
Minimum – unless otherwise authorised by the Department for Transport

• 5.60m

Maximum

• 5.94m

The pan variation is therefore between 4.165 and 5.94 subject to an allowance for uplift which has to be calculated releative to whether it is mid-section or not, and the actual height above 4.7m. Normal permissible uplift in mid-section is 350mm.

 

[HSTEd]

Ive seen pictures of waterering equipment for steam engines on wired tracks on the Woodhead line, how high were the clereances for that equipment to allow the wire to clear the watering boom?

 

[Old Timer]

Ive seen pictures of waterering equipment for steam engines on wired tracks on the Woodhead line, how high were the clereances for that equipment to allow the wire to clear the watering boom?

I am sorry but I really couldn't comment. Remember that this route was 1500 DC so the clearances would be vastly different from today's equipment.

You may find the following 30 minute film about the original GE Electrification Scheme to be of interest.
Construction of the GE Electrification

 

[nlogax]

Just found a fantastic scan of an old 1972 public pamphlet describing the GN electrification works.

http://www.railwaysarchive.co.uk/documents/BRE_GNElectric1973.pdf

Fun things to spot;

- 313s designs (as we know them) weren't quite finalised at the time of publication, so the modified PEP with pantograph car (Class 920) featured on the publication.

- The 'Reducing Costs' section on page 17 summarises the introduction of both headspans and the 'few feeder stations located further apart'.

 

[HSTEd]

That video really shows what a different world it was, things built and designed in britain, no safety precautions of note and apparently everything done properly the first time.

 

[Old Timer]

That video really shows what a different world it was, things built and designed in britain, no safety precautions of note and apparently everything done properly the first time.

The Midland Suburban Electrification scheme was constructed in much the same way, as you may have seen from my pictures in an earlier topic. It is only in the last 15 or so years that there have been major changes, some like to removel of the wiring trains, for the worse.