GWR IET's with at least one engine turned off.

[irish_rail]

I do wonder if, in the end, the engines will have to be derated.

There is an emerging theme with these units, whether it be the GUs, potentially the wrong grade of aluminium used in key components (or the welding thereof), durability of the seats, durability of the toilet equipment, the wheelsets not lasting to overhaul and so on. They are not exactly trouble free.

Some kind of new build for the Wofe route then on the cards? They are slow enough as it is through Devon and Cornwall. If derated, they would be having to extend journey times. That won't go down well.

 

[Clarence Yard]

Which is why we are still running the engines at the higher rating and will do for the foreseeable future.

 

[themiller]

I don’t suppose that this could be yet another example of Government interference in a project for political purposes going wrong when it should have been left to people who know about the matter in hand! Think Euston (HS2) platforms, Boris’s bridge to Ireland (or tunnel), etc.

 

[Master29]

I don’t suppose that this could be yet another example of Government interference in a project for political purposes going wrong when it should have been left to people who know about the matter in hand! Think Euston (HS2) platforms, Boris’s bridge to Ireland (or tunnel), etc.

Er yes. Exactly that.

 

[irish_rail]

Right, I don't confess to know much about the engines (as drivers we are basically told they are there and when they don't work, thats about it). But what strikes me , is the acceleration is very quick up to 40 mph and then trails off. Would it be kinder to the engines if they were slower to 40mph (ie like HSTs) then acceleration improved as they hit the mid speed range. This may be more appropriate to an intercity train (whereas the first 40mph is more relevant to commuter stock). As I said, my knowledge of engines is poor to put it mildly, but is there any chance that changing the acceleration like this (ie slower to start but quicker from 50mph say) help in doing less damage? It would certainly make for a smoother ride (a personal bugbear is when a driver just whacks it straight to full power causing that nasty jerk pulling away and potentially causing people finding a seat to lose balance! ) Can someone with knowledge of engines explain if this would likely help or not???

 

[2192]

It’s very normal - today 20 units in the GWR fleet have at least one GU out. All because of faults - engines are not isolated for loading reasons.

What's a GU?

 

[43096]

What's a GU?

Generator unit. DfT don't like the words "diesel engine" so GU is a euphemism used in its place.

 

[themiller]

What's a GU?

Generating Unit. Basically the engine and alternator.

 

[Clarence Yard]

Right, I don't confess to know much about the engines (as drivers we are basically told they are there and when they don't work, thats about it). But what strikes me , is the acceleration is very quick up to 40 mph and then trails off. Would it be kinder to the engines if they were slower to 40mph (ie like HSTs) then acceleration improved as they hit the mid speed range. This may be more appropriate to an intercity train (whereas the first 40mph is more relevant to commuter stock). As I said, my knowledge of engines is poor to put it mildly, but is there any chance that changing the acceleration like this (ie slower to start but quicker from 50mph say) help in doing less damage? It would certainly make for a smoother ride (a personal bugbear is when a driver just whacks it straight to full power causing that nasty jerk pulling away and potentially causing people finding a seat to lose balance! ) Can someone with knowledge of engines explain if this would likely help or not???

Unfortunately it isn’t possible as they have a different maximum power curve to an HST so on diesel the acceleration will trail off in the mid range, irrespective of any electronic intervention. That is one reason why the engines have to be worked hard (as a % of max output) for longish periods.

 

[Irascible]

Which is why we are still running the engines at the higher rating and will do for the foreseeable future.

If they're derated but you can keep all GUs operational, that's surely a better scenario than present...

 

[Clarence Yard]

I wouldn’t guarantee that would be the case.

 

[800301]

If they're derated but you can keep all GUs operational, that's surely a better scenario than present...

Surely a train working to how it was designed shouldn’t be too much to ask for without having to compromise. There seem to be many short comings with these trains yet they are still being ordered across the UK, Paint, Diesel Performance, Seat comfort, ride quality, structural cracks are just a few issues of a train that should have been the future and been built properly with a lot more over engineering than that seemed to happen

 

[Railperf]

If they're derated but you can keep all GUs operational, that's surely a better scenario than present...

They are not 100% reliable at the lower power setting either. Services will require slower timings between stations on higher speed sections of diesel running.
Seems like a serious upgrade or redesign of the GU needed in the long term to address these issues - unless the failure rate is within contract specification?

 

[Sporty60]

This is a really interesting topic for customers like myself.
Thank you to all participants.
Such an informative forum!

 

[irish_rail]

Unfortunately it isn’t possible as they have a different maximum power curve to an HST so on diesel the acceleration will trail off in the mid range, irrespective of any electronic intervention. That is one reason why the engines have to be worked hard (as a % of max output) for longish periods.

Thankyou for clarifying that. Frustrating really, you'd think in this day and age that if there was a will there would be a way.

 

[Chuffing Heck]

I could never understand why on diesel they only run at 100 and 125 on electric, I would have thought they should operate at the same speed.
We were sold the assumption that new trains would be rated for 150 especially as passengers have paying higher prices under the assertion that new trains would be faster when they are just the same if not slower than HST’s and more uncomfortable, and surprise surprise we are not seeing a price reduction now those trains are now operational!

 

[gingertom]

I'm wondering if the GUs proposed for the EMR's 810s would be suitable. In that they have a bit more horsepower- 984 instead of 940.

 

[Railperf]

I'm wondering if the GUs proposed for the EMR's 810s would be suitable. In that they have a bit more horsepower- 984 instead of 940.

You would hope it is a more advanced version of the engines used on Class 80x. The difference is that EMR class 810's will have 4 GU's, but how often will this even more powerful version of the 800 series trains be running with a GU out?
EDIT: To put the matter into perspective, the ideal scenario would be to have more engines running at a lower power level. But hey, we have that exact scenario with Classes 180/185/220/221/222 all having a 750bhp diesel engine under each vehicle - but these are not immune to having an engine out. But losing one of five 750bhp engines is less of a performance loss than losing one of three 940bhp engines. So let's face it - electrification of more track miles and reducing diesel running would be the best scenario.

 

[Fidelis]

I could never understand why on diesel they only run at 100 and 125 on electric, I would have thought they should operate at the same speed.
We were sold the assumption that new trains would be rated for 150 especially as passengers have paying higher prices under the assertion that new trains would be faster when they are just the same if not slower than HST’s and more uncomfortable, and surprise surprise we are not seeing a price reduction now those trains are now operational!

Other than HS1 the UK line speeds are not 150mph. The vast majority of GWR unelectrified routes, where diesel is used, the line speeds are lower than 100mph often varying between 60mph and 90mph making 125mph an unnecessary cost.
Cannot recall ticket prices being raised with the promise of faster IET trains but perhaps a general declaration of newer and faster trains.

 

[Master29]

Cannot recall ticket prices being raised with the promise of faster IET trains but perhaps a general declaration of newer and faster train

Which in itself would, by Joe public in general be construed as meaning faster times surely. The rail industry would clearly know this so a little false advertising perhaps?

 

[3RDGEN]

Which in itself would, by Joe public in general be construed as meaning faster times surely. The rail industry would clearly know this so a little false advertising perhaps?

In 2013 typical journey times,

London - Swansea was 3hrs now 2hr 45.

London - Cardiff was 2hrs now 1hr 50.

London - Bristol was 1hr 45 now 1hr 35.

Times vary but in general electrification and the new fleet has cut journey times and capacity increased too.

 

[Railperf]

Right, I don't confess to know much about the engines (as drivers we are basically told they are there and when they don't work, thats about it). But what strikes me , is the acceleration is very quick up to 40 mph and then trails off. Would it be kinder to the engines if they were slower to 40mph (ie like HSTs) then acceleration improved as they hit the mid speed range. This may be more appropriate to an intercity train (whereas the first 40mph is more relevant to commuter stock). As I said, my knowledge of engines is poor to put it mildly, but is there any chance that changing the acceleration like this (ie slower to start but quicker from 50mph say) help in doing less damage? It would certainly make for a smoother ride (a personal bugbear is when a driver just whacks it straight to full power causing that nasty jerk pulling away and potentially causing people finding a seat to lose balance! ) Can someone with knowledge of engines explain if this would likely help or not???

what I recall from past conversations is that the acceleration curve has been tuned to provide this initial burst of acceleration - good for exiting platforms and allowing faster platform reoccupation - but then in the mid-range the power load has had to be detuned to improve reliability - reducing the torque levels which were causing power surges - which can damage the GU. The gentler torque curve is designed to avoid this. The net result is slower than hoped for acceleration. The initial faster pull away from rest is offset by the slower acceleration from 40 to 100mph - with a net result that 0-100mph and 0 to 5 miles are similar to a 2+8 HST.

 

[irish_rail]

what I recall from past conversations is that the acceleration curve has been tuned to provide this initial burst of acceleration - good for exiting platforms and allowing faster platform reoccupation - but then in the mid-range the power load has had to be detuned to improve reliability - reducing the torque levels which were causing power surges - which can damage the GU. The gentler torque curve is designed to avoid this. The net result is slower than hoped for acceleration. The initial faster pull away from rest is offset by the slower acceleration from 40 to 100mph - with a net result that 0-100mph and 0 to 5 miles are similar to a 2+8 HST.

Also the "quick to clear the platform" thing isn't necessary (or desirable) on the Wofe route. A slower initial acceleration whilst passengers are finding their seat and stowing luggage, followed by a decent burst of power once upto 40ish would be better. I get that on commuter stuff round London clearing the platform quickly is more important, but not for the West route.

== Doublepost prevention - post automatically merged: 25 Jun 2023 ==

In 2013 typical journey times,

London - Swansea was 3hrs now 2hr 45.

London - Cardiff was 2hrs now 1hr 50.

London - Bristol was 1hr 45 now 1hr 35.

Times vary but in general electrification and the new fleet has cut journey times and capacity increased too.

What about routes to Penzance????.....

 

[hexagon789]

I could never understand why on diesel they only run at 100 and 125 on electric, I would have thought they should operate at the same speed.
We were sold the assumption that new trains would be rated for 150 especially as passengers have paying higher prices under the assertion that new trains would be faster when they are just the same if not slower than HST’s and more uncomfortable, and surprise surprise we are not seeing a price reduction now those trains are now operational!

LNER and TPE sets run at speeds up to 125mph on diesel on Sundays between Newcastle/Edinburgh; GWR sets run at 110mph on diesel every day.

 

[Snow1964]

The engines are swapped out individually for overhaul on a regular basis and sometimes Hitachi can be awaiting an engine back from East Grinstead so the unit runs around with one locked out of use, out of hours.

So is it simply that not enough spares were purchased.

Cannot expect to play catch-up for 27+ years, unable to swap because not enough repaired spares available to do the swaps.

Surely the decision to abandon wiring to Bristol had consequences, one of which is need more diesel units to cover them using hours quicker.

 

[boiledbeans2]

what I recall from past conversations is that the acceleration curve has been tuned to provide this initial burst of acceleration - good for exiting platforms and allowing faster platform reoccupation - but then in the mid-range the power load has had to be detuned to improve reliability - reducing the torque levels which were causing power surges - which can damage the GU. The gentler torque curve is designed to avoid this. The net result is slower than hoped for acceleration. The initial faster pull away from rest is offset by the slower acceleration from 40 to 100mph - with a net result that 0-100mph and 0 to 5 miles are similar to a 2+8 HST.

I'm not sure this is correct. I'm not familiar with the specific train setup, but I'm familar with motors in general.

From what I understand, the GUs only generate electricity to power the motors. Therefore the torque output of a GU is not so critical on its own, but the power output is more important.

The high acceleration at low speeds is because modern motors (post 1980s, power electronics controlled) give maximum torque from standstill until maximum power is reached, after which it operates at maximum power, and torque (and therefore acceleration) decreases.

My suspicion is that maximum power under diesel is lower than under wires, because the power output of the GUs are limited. Therefore, you will feel an acceleration (motor torque) drop off at 40mph under diesel. Under wires, the drop off would be at higher speeds.

 

[D6975]

Once IETs get past the Exe estuary, most of the line to Penzance is 60mph or lower. There are a few sections above 60, but these are mostly in/around stations where they stop anyway. There's a section along the sea wall that's 70, but the almost permanent TSRs effectively take that out. Once in Cornwall, the last time I did Plymouth-Penzance (in a HST), we never went above 62mph according to my satnav app on the phone.

 

[irish_rail]

Once IETs get past the Exe estuary, most of the line to Penzance is 60mph or lower. There are a few sections above 60, but these are mostly in/around stations where they stop anyway. There's a section along the sea wall that's 70, but the almost permanent TSRs effectively take that out. Once in Cornwall, the last time I did Plymouth-Penzance (in a HST), we never went above 62mph according to my satnav app on the phone.

There's a decent 75mph section from St Erth to Marazion. Although, yes most of Cornwall is in or around 60mph.

 

[ac6000cw]

My suspicion is that maximum power under diesel is lower than under wires, because the power output of the GUs are limited. Therefore, you will feel an acceleration (motor torque) drop off at 40mph under diesel. Under wires, the drop off would be at higher speeds.

This PDF from Rail Engineer has power on electric and diesel listed for 800/801/802 - https://www.railengineer.co.uk/wp-c.../Table-1-Hitachi-800-802-orders-V3-Avenir.pdf

Note the diesel power is the engine output - the 'power available for traction' (after the auxiliary loads and transmission losses are subtracted) will be somewhat lower, probably at least 10% less. So the continuous 'power at rail' on diesel for say a 5-car 802 (with all three engines working!) might be as low as 2/3 that on OHLE - anyone got any hard figures?

 

[Railperf]

In 2013 typical journey times,

London - Swansea was 3hrs now 2hr 45.

London - Cardiff was 2hrs now 1hr 50.

London - Bristol was 1hr 45 now 1hr 35.

Times vary but in general electrification and the new fleet has cut journey times and capacity increased too.

Yes the London to xxxx times are quicker, thanks to the better electric performance. Not sure about times between stations on the diesel sections though.

== Doublepost prevention - post automatically merged: 25 Jun 2023 ==

I'm not sure this is correct. I'm not familiar with the specific train setup, but I'm familar with motors in general.

From what I understand, the GUs only generate electricity to power the motors. Therefore the torque output of a GU is not so critical on its own, but the power output is more important.

The high acceleration at low speeds is because modern motors (post 1980s, power electronics controlled) give maximum torque from standstill until maximum power is reached, after which it operates at maximum power, and torque (and therefore acceleration) decreases.

My suspicion is that maximum power under diesel is lower than under wires, because the power output of the GUs are limited. Therefore, you will feel an acceleration (motor torque) drop off at 40mph under diesel. Under wires, the drop off would be at higher speeds.

Here is an explanation from another driver (as explained on another forum) about the torque surge issue.

"the Power Brake Controller on 80x will only allow 90% power demand. Basically the driver sets a power demand on the PBC and the TMS / Traction system does the rest, including telling the GUs how fast they need to run to produce the power output the Traction equipment requires, the idea being that unlike Voyagers the engines only run as fast as they are required to to produce the required kW output, including that required for saloon HVAC etc.

The torque fluctuations on the engines seem to eminate from wheelslip, obviously if the vehicle wheelsets start to slip you need to remove the power to regain traction and the GU will obviously unload when this happens. Torque fluctuations probably therefore don't do the engines and their charge air systems any favours."