SWR Class 159 short formations

[74A]

Slightly OT I'm on the 1753 from Clapham Junction to Salisbury formed of 8 coaches. Have almost a whole coach to myself !

 

[MCR247]

Why?

Ah. So you couldn't even shut down all but one engine then as the remaining engine wouldn't charge the batteries in the other carriages?

Yes I believe ‘cross feeding’ only became a thing on the later 170 builds - on the oldest ones an engine failure means no power, lights aircon etc. to that coach

 

[Towers]

Yes I believe ‘cross feeding’ only became a thing on the later 170 builds - on the oldest ones an engine failure means no power, lights aircon etc. to that coach

Some 15x/16x have been retrofitted with ‘remote supply’, which does allow cross feeding from an adjacent vehicle in the event of engine failure.

 

[Clarence Yard]

Why?

Ah. So you couldn't even shut down all but one engine then as the remaining engine wouldn't charge the batteries in the other carriages?

Jump as in connecting the low/dead battery to a healthy/live one? Why isn't this possible?
I can see that what I'd call bump starting wouldn't work as the fluid clutch would automatically be engaged while the train speed is higher than the engine speed so the engine would never actually turn. Would this not have been the case for mechanical DMUs too? Bump starting relies on the engine being able to provide a braking force to the train and I thought even mechanical DMU gearboxes had a sort of clutch which automatically cut the engine/wheel connection at throttle notch 0? Otherwise if you accelerate in gear 1 then cut the power and switch to gear 4 to coast as per the operating instructions, the engine would stall?
Maybe I'm overcomplicating it?

Why is shore supply so expensive? The amount of power you need at a location is considerable so you usually have a separate sub to provide it, together with all the appropriate switchgear. Then you have to run those cables underground to the individual control panels at the end of each road. And finally you have to provide the connecting cables and plug to the train, which effectively has to be bus wired to get the benefit.

You can jump across to another unit if you have jump leads. I’ve done it with locos but the cables snake a bit when you power up! But if the unit is outstabled in a remote location, that is a man in a van job.

Class 15x and 16x were built with individual car systems. So the remaining engines wouldn’t be able to charge the batteries. Some units have been retro-fitted with a degree of cross feeding but this tends to be for the passenger facing auxiliaries only, because of the smaller loads involved.

I haven’t ever been involved in bump starting DMU sets but nobody I know seemed to like it, because of the potential damage it does. Much better to jump it or try and start it off a charger. Likewise the old method of trying to start a dead 08 by towing it at very, very low speed and then throw the reverser on the 08 (to turn the T/M into a generator) was pretty dodgy. A lot can go wrong.

 

[computerSaysNo]

Why is shore supply so expensive? The amount of power you need at a location is considerable so you usually have a separate sub to provide it, together with all the appropriate switchgear. Then you have to run those cables underground to the individual control panels at the end of each road. And finally you have to provide the connecting cables and plug to the train, which effectively has to be bus wired to get the benefit.

You can jump across to another unit if you have jump leads. I’ve done it with locos but the cables snake a bit when you power up! But if the unit is outstabled in a remote location, that is a man in a van job.

Class 15x and 16x were built with individual car systems. So the remaining engines wouldn’t be able to charge the batteries. Some units have been retro-fitted with a degree of cross feeding but this tends to be for the passenger facing auxiliaries only, because of the smaller loads involved.

I haven’t ever been involved in bump starting DMU sets but nobody I know seemed to like it, because of the potential damage it does. Much better to jump it or try and start it off a charger. Likewise the old method of trying to start a dead 08 by towing it at very, very low speed and then throw the reverser on the 08 (to turn the T/M into a generator) was pretty dodgy. A lot can go wrong.

Ah, thanks for all that, I hadn't realized the load would be so big that it would require a whole new substation!

 

[Siimo]

Did a return trip between Salisbury and Exeter last week for holiday. Outwards trip was a single 159, which did have a few free seats (contrary to the assertions of two people sitting on bags in the vestibule whinging about standing room only!) but on return we had a 158+159 which then coupled up to another waiting 159 at Salisbury, which I believe makes a normal full-length train. This was Sunday, which was the day before the reduced timetable started, so there must be some capacity to form full length trains. My guess is that this is the reason for introducing the reduced timetable in the first place.

 

[ABDeltic]

Did a return trip between Salisbury and Exeter last week for holiday. Outwards trip was a single 159, which did have a few free seats (contrary to the assertions of two people sitting on bags in the vestibule whinging about standing room only!) but on return we had a 158+159 which then coupled up to another waiting 159 at Salisbury, which I believe makes a normal full-length train. This was Sunday, which was the day before the reduced timetable started, so there must be some capacity to form full length trains. My guess is that this is the reason for introducing the reduced timetable in the first place.

It's never been suggested by SWR that the reduced timetable is due to a shortage of units but it probably helps. Even so there are still a number of short formed trains, particularly in the peaks. What is very frustrating is that there is no pattern to the reduced formations, they vary from day to day.

 

[TEW]

The increased journey times under the temporary timetable table probably negates any reduction in unit requirements from running less services.

 

[RichardAsh1981]

Ah, thanks for all that, I hadn't realized the load would be so big that it would require a whole new substation!

260kW per engine rated power. Say shore supply needs to cover 20% of that for full hotel load (being conservative), you need 26kW per coach. Stable 10 trains of two coaches each and you (in theory) need 520kW of power, which is a small substation. Also historic depot supplies tend to have been designed for lighting only, so very small indeed, so unlikely to have spare capacity.

Whether that level of supply is actually needed most of the time when units are parked seems pretty dubious, because hotel load should be mostly shut down (cleaning equipment uses some, but how many coaches can be actively cleaned at the same time?). The worst case would be trying to fire up the heating/Aircon on all units at once at start of service, which would save more noise and diesel but require a big power supply for use only a short period each day. I wonder what the actual utilisation of existing shore supplies is, and whether the diversity factors used for design need to be reviewed.

We are increasingly seeing 500kVA and 1MVA substations being put in for vehicle rapid charging, and these are typically off the peg package types which should bring some of the costs down.

 

[dgl]

Just keeping the lights on (doesn't necessarily need full lighting, so more to be saved), power for the cleaners and battery charging shouldn't take that much power, less than 5kW one would assume. Especially now most of the lighting is probably LED's
Of course if you also wanted to keep all the control electronics up and the A/C (assuming it's not run directly from the engine) that would naturally use a bit more (especially the A/C).

Would it be correct to assume that units already have a socket for battery charging, it would make sense and if that was used regularly it would at least keep the batteries healthy and not use that much power. Though are the charging connections traction interlocked, you wouldn't want a unit driving off with the wires still attached!

 

[RichardAsh1981]

Though are the charging connections traction interlocked, you wouldn't want a unit driving off with the wires still attached!

Roger Ford thinks first generation units were not, and it happened, but we are probably drifting off topic.

 

[btdrawer]

Still seems to be a problem now despite the reduced timetable presumably freeing up some more units. The rush hour train out of Exeter today is pretty cramped - I'm just glad it's not term time.

Cutting services short at Basingstoke seems most logical at this stage, no?

 

[ABDeltic]

Still seems to be a problem now despite the reduced timetable presumably freeing up some more units. The rush hour train out of Exeter today is pretty cramped - I'm just glad it's not term time.

Cutting services short at Basingstoke seems most logical at this stage, no?

== Doublepost prevention - post automatically merged: 21 Aug 2025 ==

It's been much better this week from Salisbury to Waterloo, but maybe not at the Exeter end due to the two hourly service.

 

[TEW]

Still seems to be a problem now despite the reduced timetable presumably freeing up some more units. The rush hour train out of Exeter today is pretty cramped - I'm just glad it's not term time.

Cutting services short at Basingstoke seems most logical at this stage, no?

I don't think the reduced timetable does free up units, because journey times are extended significantly.

 

[gabrielhj07]

They really do need to stop sending the diesels East of Basingstoke until their reliability is sorted. Strengthen the formations to the West, and direct London passengers onto their choice of 8/10/12 car Desiros.

 

[Anonymous10]

Still seems to be a problem now despite the reduced timetable presumably freeing up some more units. The rush hour train out of Exeter today is pretty cramped - I'm just glad it's not term time.

Cutting services short at Basingstoke seems most logical at this stage, no?

Also a replacement bus on the Salisbury- Southampton service, anyone end to end takes gwr and intermediate stations served by bus. Would gain a extra unit or two.

 

[Kite159]

They really do need to stop sending the diesels East of Basingstoke until their reliability is sorted. Strengthen the formations to the West, and direct London passengers onto their choice of 8/10/12 car Desiros.

Although ideally if they decide to spin the services at Basingstoke they will need to get the XX:35 Weymouth trains to call at Basingstoke (which they should do in my eyes), otherwise you will be left with the 2 stoppers (which nobody will want to take), the semi-fast to/from Portsmouth and the slower Weymouth trains

 

[Nimbus020]

Just a quick question having just seen 159 007 en route west - it has the older SWT red seats - did SWR not complete the light refurb on all its 159s? - many thanks

 

[fgwrich]

Just a quick question having just seen 159 007 en route west - it has the older SWT red seats - did SWR not complete the light refurb on all its 159s? - many thanks

Less a case of not completing it and more a case of when it was last overhauled. The 158s were started first and those that were last painted remained in SWT livery due to the paint warranty, whilst certain others were given the original SWR striped Vinyl. 159007 I believe was one of the first and was therefore subject to the same treatment, before the vinyl was finally dropped for a planer, but smarter, version of the livery where the seats and carpets were also recovered.

 

[gabrielhj07]

Although ideally if they decide to spin the services at Basingstoke they will need to get the XX:35 Weymouth trains to call at Basingstoke (which they should do in my eyes), otherwise you will be left with the 2 stoppers (which nobody will want to take), the semi-fast to/from Portsmouth and the slower Weymouth trains

This would be ideal, much more space on them than a single 159.

 

[ABDeltic]

Just a quick question having just seen 159 007 en route west - it has the older SWT red seats - did SWR not complete the light refurb on all its 159s? - many thanks

159003, 007 and 011 have the old red seats.

 

[Dougal2345]

Just going off at a slight tangent, I had a rare ride on the WoE line on Saturday, three short trips on a different (probably) unit each time.

All had unbelievably loud air conditioning noise in the coaches - not just a roar of air being pushed, but a whine from the fan motors too. In my entire life's experience of train travel, I've never heard anything like it. Any sort of normal conversation would have been impossible.

Have SWR done something to the air-con on these? Dialled it up to 11 for the hot summer and then not bothered turning it down again?

 

[gabrielhj07]

Just going off at a slight tangent, I had a rare ride on the WoE line on Saturday, three short trips on a different (probably) unit each time.

All had unbelievably loud air conditioning noise in the coaches - not just a roar of air being pushed, but a whine from the fan motors too. In my entire life's experience of train travel, I've never heard anything like it. Any sort of normal conversation would have been impossible.

Have SWR done something to the air-con on these? Dialled it up to 11 for the hot summer and then not bothered turning it down again?

Probably just unlucky. I haven’t noticed a pattern between coaches.