Question about overhead lines.....

[Gazza]

Ok, on older parts of the network with quad track the overhead is held up by two simple masts with the wire strung on each side (Ta Google):


But on newer installations they go for a portal that spans the whole track (Ta Bob):


In both situations the mast pairs, or the portals are at about 50m intervals, so that rules out the change being to do with permitting longer spans of overhead.

My question is, why don't they use the former...It appears to use significantly less steel.

[Stillwater]

Perhaps something to do with safety?  And, into the future, maybe able to add an extension out one side for another track.

[Golliwog]

I'm thinking safety too. If the poles are all on the outside of the tracks then theres less objects to obstruct your vision of the path ahead. Yes their path is already dictated, but they would need to be able to see things like say a fallen over tree or a person on the tracks. Plus in cases of derailment, less obejcts to hit (for a quad track there would be only two masts either side as opposed to two in the middle, or sometime more depends on the track allignment (sometimes the pairs aren't close enough to share a mast))

[mufreight]

On the Corinda - Darra it would have more to do with the continued operation of trains during the various phases of the opgrade which require the repositioning of the track and as a consequence the overhead, in some locations there would also be restricted space between the running lines which would be a further factor.
Most if not all of the overhead on the recently constructed Richlands extension is on independent masts (I can not think of a single location on that line that I have seen where a portal has been utilised)
As a preliminary to the recent replacement of the crossovers at Indooroopilly, the new crossovers having a different angle and alignment to those that were removed portals were installed there to carry the overhead in place of the original independent masts some of which were then immediately removed to enable the replacement of the crossovers, the overhead was then reconfigured to suit the realigned running with most of the work carried out without interuption to the operation of normal services.

[ghostryder]

Gazza/All.
The wires went up in the late 1970s, the Quad section between Corinda and Roma St were wired up in two stages. The suburban Mains from the outset and the mains in the 1990s. Alterations and adjustments brought on by new track and or new sections being wired up have brought about the need for the portal span.

scott 

[BribieG]

Off topic but to do with overhead lines. I thought the original idea of electrifying the lines as far as Rockhampton was so that everything could be hauled using power generated from QLD coal and not expensive imported diesel, and the electric prime movers could be built right here in QLD.
However I hardly ever see an electric prime mover any more, all seems to be diesel. Last time we went to Cairns on the Sunlander we stopped at Rocky to change from electric prime mover to diesel and I was talking to a QR guy on the platform about this. He says that nowadays they usually just put electric prime movers in the too hard basket and just diesel stuff out of Brisbane by default. Do Pacific National have electrically hauled freight trains and if not why not? Yet to see one.

Smart state??? 

[brad C]

BribieG
The 30 member 3900 series electric locos were delivered for north coast and central line freight and long distance work and were commissioned in 1989.
As servicing was undertaken at Mayne, a number of 39ers were also utilised to haul a few peak hour SX cars in between long distance runs. (What a joy was the run down from Caboolture express bald hills to bowen hills of a morning!!)
One or two of the 39ers came to grief (Beerburrum derailment comes to mind).
Following a decision to ramp up coal haulage, there was a plan to upgrade the 39ers for coal use and a number of overhauled units were re-numbered 355X.
Some still remain as 3900 series today.
They were first withdrawn from Central line workings and I think from late 2005, they were withdrawn totally from north coast line workings.
At the same time the 2800 class have extended their sphere of influence to include the south east corner.

The 3900s are sadly missed on the NCL. They were much cleaner, quieter and had rapid acceleration to the 2800s.
A very retrograde step, but not surprising, given the withdrawal of the 81 class electrics from freight use in NSW at about the same time.
PN have a number of new electrics (71 series) both delivered and on order from Siemens Germany for use on their export coal runs, They are almost identical to QRN's 3800s.

BradC

[somebody]

It's not comparable to compare the electric trains in QLD to NSW.  NSW has to make do with 1500V DC electrification.  The power draw of 4x 86 class locos is enough to put the infrastructure under severe stress, and make it more difficult for passenger trains.  That's why they don't want them.  This problem doesn't apply in QLD to my knowledge, with 25kV AC electrification.

[curator49]

While electric locos appear to be useful on freight services the 3900 Class were the only Queensland units designed to haul freight rather than coal. I believe this was due to their gearing giving more speed (needed on the NCL) but less grunt (needed for coal haulage).

Diesel locomotives these days have much more efficient engines with less pollution than in the past.

Regards
David Mewes

[mufreight]

The justification for the transfer of the 3900 class to coal workings was increasing coal traffic, once there the majority of them were modified by changing the traction motor gearing, increasing their weight and fitting with equipment to allow them to operate as remote units.
With the deliveries of the rebuild/upgraded 3700 class and the new 3800 class of greater tractive effort the 3900 class have now become redundant.
The cost of reconfiguring the 3900 class so that they can be again utilised as general traffic locos is now being used to justify not returning them to general freight duties and it is anticipated that in time they will eventualy become candidates for rebuilds equivelent to the 3700/3800 classes or if following the privatisation if there is not a continuing increase in Queensland coal traffic for QRN requiring more motive power they will become victims of the scrappers oxy torch as the cost of a rebuild/upgrade is marginal against the overseas new build of similar more modern units.
PN only use their electrics on coal traffic.

[skippy]

Another reason is the older generation diesel locos from Townsville needed refuelling at Rockhampton. This meant that is was economical to put an electric loco on for the leg to Brisbane. The new generation diesels can travel from Townsville to Brisbane without refuelling, meaning it is more economical to keep the diesels going the whole way. When diesel prices get over $2 / litre the economics may favour electrics again.

[somebody]

The justification for the transfer of the 3900 class to coal workings was increasing coal traffic, once there the majority of them were modified by changing the traction motor gearing, increasing their weight and fitting with equipment to allow them to operate as remote units.
With the deliveries of the rebuild/upgraded 3700 class and the new 3800 class of greater tractive effort the 3900 class have now become redundant.
The cost of reconfiguring the 3900 class so that they can be again utilised as general traffic locos is now being used to justify not returning them to general freight duties and it is anticipated that in time they will eventualy become candidates for rebuilds equivelent to the 3700/3800 classes or if following the privatisation if there is not a continuing increase in Queensland coal traffic for QRN requiring more motive power they will become victims of the scrappers oxy torch as the cost of a rebuild/upgrade is marginal against the overseas new build of similar more modern units.
PN only use their electrics on coal traffic.

I don't follow this one.  Why can't they keep the 3900s on coal duties then?  Do they have an excess of electric locos geared for heavy coal trains.  If so, isn't there other slow freight such as grain?

[mufreight]

The modified 3900 class are only about 2/3rds the tractive effort of the rebuild 3700 class and the new build 3800 class locos hence only three locos are now required to do what previously required four, it all comes down to operating cost.

[somebody]

Ok, but wouldn't be cheaper to put 4 3900s into service rather than buy 3 new 3800s and parking the 3900s?  That's what I am trying to say.

[mufreight]

Short answer, NO

[somebody]

Well, you lost me there.  You knew that was coming.

[mufreight]

Comes back to operating costs and reliability, the 3900 class are old locos with DC traction motors and are in need of refurbishment, they might provide the basis for rebuilds but that would be into locos similar to the 3700 class upgrades.
Time and their age are against their refurbishment and reconfiguration back into locos for general freight services but the increasing costs of diesel fuel could change thinking there but the scrappers torch seems more likely at this time

[colinw]

My understanding was that not all the 3900s had the coal conversion, and that 11 of the class remain stored in original form.  They are getting a bit long in the tooth now, and due for rebuild.

IMHO it is far more likely that when oil prices rise further we may see a modern AC traction locomotive come into service to replace some of the 2300s.  Possibly something based on a Siemens Eurosprinter.

Another issue with operating the 3900s on the NCL is that they were only fitted with the older Ericsson ATC system, the trackside infrastructure for which has now been decomissioned.  Before they could be driver-only operated on the NCL they would need to have WESTECT ATP commissioned on them.  The ICE sets also had ATC, but have now been converted over to ATP and the remaining ATC trackside equipment between Caboolture & Gympie North decommissioned.