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Discussion in 'Traction & Rolling Stock' started by MK Tom, 23 Dec 2018.
Yes this is caused by the ice/frost.
Partly that, but mostly because there were a number of OLE and pantograph failures with the front pan up that caused it to become detached, bump along the top of the train, and disable the rear pan (down). Thus leaving a train with no pans, and thus stranded without power, even when the OLE is re-energised.
By using the rear pan, any such incident only takes out the rear pan. Then when the OLE can be reenergised, the train can move under its own power using the front pan.
Have a look for photos of Class 91s - there's often a distinctive swoop of black dust on the sides, particularly noticeable on the Virgin livery.
Yep there is a dust which is from the carbon strip on the pan head, which is in contact with the contact wire.
Here is a good shot of the two-car Class 309 post-refurbishment (and now a four-car). In this form the vehicle was a DMBSO but as built it was a DMBSK seating 48 second in six compartments plus a toilet immediately behind the first passenger door (the half-width window in the picture). After refurbishment as well as the compartments being opened out the toilet was removed to seat 52. You can just make out the higher secondary roof guttering for the toilet water tank overflow to direct any overflow water away from the passenger door where it could overwhelm the normal rain guttering.
Not to go too off topic in my own thread but I'm curious how these conversions to 4-car were done. I don't imagine there were a load of half sets or spare trailers sitting around. Were some driving cars or regular loco-hauled coaches converted to trailers?
Still not really clear on why 304s/710s etc have the pantograph carriage backwards. Someone made the point that 710s can be expanded to 5-car and still keep the pan car central, and the 4-car 332s had the pantograph car this way round as well I believe, but as far as I can see that's still true if the pantograph car is the other way round and you just add the fifth trailer in on the other side.
The extra vehicles were converted from loco-hauled Mark 1s, both to extend the 2-car sets to 4-car and to replace the catering vehicles that were in some of the 4-car sets.
I've noticed in some countries, especially Japan many Emus seem to have pantographs, almost every other carriage.... Is there some fundamental technology difference that mandates this? Always seems really odd
Its historical, rather than using auto transformers they started off using booster transformers, however when the power demands grew (and especielly with introduction of Shinkansen) they had a lot of trouble with wild voltage fluctuations and discharges so they switched to the European AT system. So the Shinkansen started off with 8 carriages each having their own pantograph but switched in the early 80’s to 2 pantographs being raised and having a bus between the carriages. To maintain compatability with wires and good electrical contact the two remaining pantographs exert the same upward force on the wires as the 8 originally did, 54 N.
To get around the bridging issue they have changeover sections, these are short sections of neutral which can be energised from either side, when it detects a train approaching it will switch the neutral section to being fed from the opposite side until the train has passed through with an air gap to prevent bridging back into the section the train has come from.
I noticed this on the Boston Subway blue line too and was curious about it.
With the pendos .The original intention was always to run the rear pan, there were some issues, which resulted in the sets running front pan for a while. Can't now remember exactly what it was, but there were definitely some Neutral section issues and the APC magnets, either causing pan trouble or bridging neutral sections. We were supposedly allowed to ride through Neutrals with power still applied to leave the speedset in (a form of cruise control). IIRC it was around the time of the introduction of the 9 car sets/ start of Tilt enabled working when we were on the front pan for some time before we eventually went back to running rear pan.
A 10-car formation of class 309s, arriving at Colchester in August 1964; the twin-set is at the front:
When refurbished and converted to 4-car sets, using a class 123 trailer as an intermediate vehicle was considered, but I can't remember if this was actually carried through.
Not a very good photo, but this shows the pantograph on the driving vehicle of a class 307, post-conversion from DC to AC:
Japan uses 1500V DC on a lot of its lines, so that might be part of it.
Not quite- an original (0 Series) Shinkansen was 12 carriages with 6 pantographs, and all varient formations ran with that ratio throught their service life. The 100 series were then built at first with 5 pantographs in a 13 car set (later lengthened to 16), then 6 in a 16 car set (these were reduced to 3 pantographs in the 90s), and the later examples of the series were simply built with three pantographs for the 16 car set.
The 200 Series (slightly older than the 100 Series) seems to be even more complex in terms of builds/pantograph cars, but still seems to have 4 pantographs on 10 car sets on retirement in 2013.
And none of that is to do with DC- the Shinkansen network is 25kV AC 50Hz.
I was just thinking of the commuter trains; I thought the Shinkansen was a fairly standard railway.
One 123 DMU trailer buffet was used late 60's early 70's to replace a damaged griddle car
I was in Utrecht a few years back and saw the then City Night Line train depart hauled by a 1600 loco. To depart, both panto's were up, but once it was on the move, one dropped. I guessed, just to get enough watts from the 1500 dc system the NS uses with all the hotel power a CNL needed (and it was about 10 coaches).
I also remember reading that the APT was built with the power cars in the middle as the OHLE north of weaver junction has been done on the cheap and could not cope with two pantos up at speed.
I think the coaches that extended the 2-car 309/1s were ex-LHCS, and they came with B4 bogies rather than the 309's native modified Commonwealth type.
Yes I remember it clearly. ISTR that it had loose chairs rather than the 2+1 (rather comfy) seating of the original 616? - that rings a bell.
Speaking of Class 304s and 710s, the 4-car Class 332 on Heathrow Express also had a pantograph end adjacent to the driving car.
The same also happened to the LO Class 378 when they were four-car units before being extended to five-car in 2015.
Yes sorry 8/16 which I misread as 8/8. Long article on their power issues and why they made the switch after several accidents here:
It’s more that the OLE anywhere (pre GW electrification) can’t cope with 2 pantographs up above 100mph. And the problem is worse the further apart the pantographs are.
That's an interesting fact when you consider one of the arguments for OLE over third rail is that rail cannot be effectively used above 100mph.
One of the lesser arguments, and it’s not just about contact but also power draw.
It’s really about inadequate infrastructure in this country.
Having seen a four loco “Re20/20” (Re6/6+Re4/4+Re6/6+Re4/4) in Switzerland last year, all pan up and if they so wished a power rating of 25MW (33,500hp), it did rather reinforce just how poor this country is at electrification.
Umm, HS1 copes quite well with 2 pans up at 125 mph+ (Javelins) & 180 mph E-Stars.
The OHLE (Standard French Hi-Speed) seems to be quite simple, with closer mast spacing than elsewhere in the UK, but simple catenary.
Other way round - the closer the spacing the worse it is. IEPs are subject to speed restrictions when running in multiple with the pans up at any configuration other than the extremity of the pair of sets.
Double heading of electric locos is (or is supposed to be) limited to 80mph max as well.
If there was a need to run very high power traction to haul heavy trains through a mountain area, and we had all energy from hydro projects, it would be easy to provide the infrastructurenecessary for them to operate.
And the tension is quite high which means that standing waves are of lower amplitude and of shorter wavelength. Simple catenary haas been the standard in the UK since the '60s. The lines converted from 1500VDC, e.g. GEML, had compound catenary OLE as it was thought to dampen pantograph oscillations, which at the time of introduction were much heavier diamond pattern types. The additional wire in compound also helped to reduce voltage losses. The last compound wiring was removed a few years ago when the GEML OLE was refurbished with F&F parts, similar to those used on the GWML.
Here is a picture of Ilford station, probably in the '90s when 25kV had been in use for over 30 years. Note the compound catenary:
and here is a more recent picture showing the updated OLE with the F&F registration parts installed somewhere near BOW by the looks of it:
Despite this picture showing the transition from one length of catenary to the next giving eight sets for four tracks, each catenary is of simple type and has a minimal HV footprint.
It was an extreme - and rather impressive - example. But we can’t even run a pair of Class 90s through hilly areas (Shap and Beattock) when we need to without isolating traction motors as the infrastructure can’t take the power draw. It’s pathetic.
350s can run in multiple at 110mph on the WCML I think, though I'm not sure if they can do so north of Weaver Junction (towards Preston and Glasgow) on the less robust OLE installed in the 70s.
The APT-P had a single-arm but heavy pantograph. I think one of the twists and turns in its subsequent development was the decision that with the much lighter Brecknell Willis high speed pantograph, it would be possible to have one at each end of the train.
The WCML between London, Liverpool and Manchester was electrified with compound catenary too, possibly excepting some lower-speed sections. The fast lines were upgraded to simple catenary in the WCML modernisation but I think some remains. For example, from the RAIB report into electric shock at Sutton Weaver in 2014: