Great Western Main Line electrification - ongoing discussion

[whole diary]

[Electric train]

The 9-car sets will have 2 (or three possibly) diesel engines, which should be able to provide enough power to limp along with pants down to the next station...

Twerking all the way   sorry could not resist I am sure you meant Pan

Erm ... simply so I know how to record this correctly in our 'acronyms and abbreviations' pages, should I refer to 'pantographs', 'pants' or 'pans'? 

Pan in the singular and Pans in the plural ................

Some say they are called a Pan because its short for Pantograph and some say its because the look like a frying pan and you certainly do if you touch one and others believe its to do with Peter Pan because 'lectricary is magic.  As an engineer I'll go with the last one 

[4064ReadingAbbey]

Has there been a change of plans for the GW^▸ (Great Western) electrification?

I understood from the published information that the overhead wires would be individually supported and registered so that if one set came down it wouldn't affect the overhead over the other tracks. In other words - Headspans, R.I.P.

However, while walking along Tudor Road in Reading at the end of last week, this is the road that runs parallel to the railway and connects Station Approach to the Caversham Road, I noticed headspans on the start of the curve from Reading Station towards Reading West.

Then I noticed in the photograph published on page 28 of the September Modern Railways that the tall masts shown at South Moreton seem to be undeniably for headspans.

Is Network Rail trying to save money and will reliability suffer? Why have we not been told?

[stuving]

Has there been a change of plans for the GW^▸ (Great Western) electrification?

I understood from the published information that the overhead wires would be individually supported and registered so that if one set came down it wouldn't affect the overhead over the other tracks. In other words - Headspans, R.I.P.

However, while walking along Tudor Road in Reading at the end of last week, this is the road that runs parallel to the railway and connects Station Approach to the Caversham Road, I noticed headspans on the start of the curve from Reading Station towards Reading West.

Then I noticed in the photograph published on page 28 of the September Modern Railways that the tall masts shown at South Moreton seem to be undeniably for headspans.

Is Network Rail trying to save money and will reliability suffer? Why have we not been told?

When you say you "noticed headspans", do you mean with the support cable (not just any old bit of wire) strung between the uprights? Or do you just mean "tall masts"? I though the same of the pairs of tall uprights elsewhere aroung Reading, until they started fitting double crossbars to them.

[Red Squirrel]

Headspans are fine - what could possibly go wrong?

https://www.youtube.com/watch?v=XgCPPeYmyKw

[4064ReadingAbbey]

When you say you "noticed headspans", do you mean with the support cable (not just any old bit of wire) strung between the uprights? Or do you just mean "tall masts"? I though the same of the pairs of tall uprights elsewhere aroung Reading, until they started fitting double crossbars to them.

Looking along Tudor Road to the west one can see masts placed along the edge of the embankment roughly where Reading Main Line West Signal Box stood. From the tops of these masts, and three or four are visible, are what look to be the top wires of headspans forming a catenary across the tracks. It is not possible to see the corresponding mast on the other side of the tracks from Tudor Road. The next time I'm there or at the station I shall have to have another look to see if my suspicions are confirmed.

The photograph in Modern Railways is taken with a telephoto lens and shows 9 very tall masts on the outside of the curve with an HST^▸ (High Speed Train) passing on the Down Main. There appears to be gaps in the spacing as if two or three masts are missing. There are correspondingly tall masts on the inside of the curve but it is not possible to count them as they are obscured by the curve and the trees. I know it is difficult to make accurate judgements on dimensions from such an image, but the masts appear to be about 2 1/2 to 3 times as high as the rear of the HST which is about in line with the last of the masts on the inside of the curve. In any event they look to be higher than the masts shown in your photograph. This might possibly be an isolation or feeder point but there do seem to be a lot of masts for such a feature.

[paul7575]

I found a few photos on the site dedicated to the Old Dalby test track that conveniently show old and new side by side.  The shot below suggests that the UK1 masts are generally stronger and higher, and although it's only a single track cantilever shown, all the hardware seems to be mounted level with or higher than the contact wire, the old type on the left the cantilever is mounted lower, IYSWIM:

http://www.old-dalby.com/images/14-02-03_new%20registration%20arm.jpg

What might also be significant is that the GWML^▸ (Great Western Main Line) is a '25 kV - 0 - 25 kV' autotransformer installation.  The additional catenary(s) that form the second, anti phase 25 kV supply (the autotransformer feeder - ATF) are normally mounted outside and higher than the portals or cantilevers, if starting with a brand new installation they may have decided to place the ATF higher, because they can.   There are also earth conductors strung along the masts, IIRC^▸ (if I recall/remember/read correctly) - perhaps the more space between everything the better.

However I thought the only OHLE visible in the Caversham Rd area was that present over the depot stabling tracks (there since before they opened) - and that is the lightweight style known as 'trolley wire' under headspans that is typically used in depots at low speed, but that isn't indicative of main line policy.

PS - checked today, the only headspans visible from the station are those over the stabling sidings.  As far as I could see from a train leaving platform 2 for Reading West there is still nothing in place over the Westbury lines.

Paul

[TonyK]

All the trains will have diesel back-up. The 9-car sets will have 2 (or three possibly) diesel engines, which should be able to provide enough power to limp along with pants down to the next station, subject to no entanglement of cables. The engines will be used daily, taking the sets into and out of the depot.

If push comes to shove, they will probably be used to keep the lights and aircon on until a loco arrives to rescueone and all.

Twerking all the way   sorry could not resist I am sure you meant Pan

You do it your way, I'll do it mine...

[stuving]

However I thought the only OHLE visible in the Caversham Rd area was that present over the depot stabling tracks (there since before they opened) - and that is the lightweight style known as 'trolley wire' under headspans that is typically used in depots at low speed, but that isn't indicative of main line policy.

PS - checked today, the only headspans visible from the station are those over the stabling sidings.  As far as I could see from a train leaving platform 2 for Reading West there is still nothing in place over the Westbury lines.

Paul

Here's what you see from the end of Tudor Road. It is trolley wire, evidently, so it must be in the depot. But it is impossible to believe that when looking at it - it just looks far too close! Going further along, into the car park before the Queens Arms, separates the supports in the view, but still leaves the distance impossible to judge as you can't see the ground under them.

Looking from the station (which dramatically foreshortens the distances so they look very odd indeed) you can see supports along the viaduct, which is too far west to be seen from those places, but not on the ramp which should be visible. However, the south side of the ramp is not even finished yet. I think you can see in the second picture that supports in the depot (behind the OHLE supports on the relief lines) are the right thing and do come a lot further east - and I think the gantry in the foreground is the one in the other picture.

PS: looking at the full picture, before I cropped it a bit too much, that definitely is the same gantry.

[tom m]

Looks like the electrification in the new depot is all of the headapan type.

[stuving]

Looks like the electrification in the new depot is all of the headapan type.

As paul7755 noted above, it is usual in depots to use this 'trolley wire' system. That means no catenary - just a contact wire with close-spaced headspan supports.

[DidcotPunter]

Yes, in depots where speeds are low, trolley wires supported by headspans are used. This is the case at Reading. Between Reading and Didcot the stanchions which are being erected will support portal cross-members. You can see these awaiting assembly in the NR^» (Network Rail - home page)/Amey/Lundy Projects electrification compound at Moreton Cutting, east of Didcot. There is also an example of a "half portal" erected in the Balfour Beatty site in the former Langley Fuel Sidings just east of Langley station further up the line. Possibly put up for training purposes for the BB team doing the Airport Junction to Maidenhead section.

[Electric train]

Stuving's first photos shows Jacques Galland 25kV Section insulators well I think they are  Jacques Galland they seem to be the preferred manufacture.

It is highly unlikely that headspan construction will be used on any main running lines on new electrification, if the GW^▸ (Great Western) route had their way the 12 miles of headspan between Padd and Airport Jcn would be replaced but that would be to expensive and disruptive

[ray951]

Saw my first mast in the Didcot area today, just by the signalling centre.
Although it is more like a vertical pipe than a mast, does it get narrower as it gets taller?

[John R]

I wonder if what you saw is the pile that is driven into the ground to form the support? Sometimes you can see one that has been left mostly above ground.

[Electric train]

I suspect that it was a steel pile they are about 600 to 750mm in diameter come in 5m lengths often one is driven in and a second or even a third is attached to the top and then that driven in.  They have a number of bosses for bolting each other together of for attaching the OLE^▸ (Overhead Line Equipment, more often "OHLE") structure base plate to.