Transport for Wales 769's

[Optom1]

Did the769 run the2F10 to Rhmney to Cardiff this morning? I wasnt watching rail cams this morning.

 

[Robert Ap Ioan]

I think it ran back late last night.

 

[Optom1]

Wasn’t shown onRTT

 

[Robert Ap Ioan]

I heard it go past around 10ish. I think it ran as 3z72

 

[Brissle Girl]

Post revised to reflect 769 rather than 230 usage - thanks gazthomas!

It certainly has. It took just 38 minutes from Pontlottyn and Cardiff Central, gaining 40 minutes! That said, it omitted at least eleven stops.

The top speed of a 769 is 90mph, but the ruling speed on the Rhymney branch (where most of the station stops are) is generally 75mph. This is equivalent to around 33.5 metres per second.

Let's allow around 23 seconds for the additional time to cover the distance from where braking commenced to the station stop itself. This reflects braking from 75mph at 0.75 metre per second per second (emergency braking is around 1.5 m/s/s). Note this is the additional time taken to cover the distance from where braking commenced to the station stop - not the total time it takes to cover that distance (I've calculated it by assuming constant deceleration, and halving the average speed over the braking distance, and subtracted the time taken to cover the braking distance at full speed from the time to cover the braking distance while braking to a standstill).

And it's reasonable to allow another 30+ seconds for the additional time required to reach 75 mph from each station stop. This assumes acceleration at 0.55 m/s/s - which is the rate at which 150s accelerate (although according to Porterbrook, the 769s will be faster accelerating than 150s). Again, please note that this is the additional time taken to cover the distance from the station stop to the point where top speed is reached - not the total time it takes to cover that distance (I've calculated it by assuming constant acceleration, and halving the average speed over the acceleration distance, and subtracted the time taken to cover the acceleration distance at full speed from the time to cover the acceleration distance while accelerating to top speed).

If we assume an average station dwell time of just over a minute (which is generous, given that according to RTT, many are scheduled to sop for only half a minute), that still means each station stop requires around an additional 2 minutes: 23 seconds lost braking from 75 mph, 1 minute to stand in the platform, and 30+ seconds lost while accelerating back to 75 mph. The reality, I suspect, is that the average station stop from top speed of 75 mph stop costs around an additional 90 seconds, and possibly a little less, over the time taken to cover the distance from where braking commences for the stop to the point where 75 mph is achieved again.

So had the 769 stopped at the 11 skipped stations this would have taken an additional 22 minutes (using 2 minutes per stop). As the 769 gained 40 minutes on its scheduled run, this means that it shaved at least 18 minutes off the journey time from Pontlottyn and Cardiff Central. And taking what I consider to be the more realistic figure of 90 seconds additional time per stop, this shows a time saving of an just over 23 minutes. Quite a feat.

But, pausing for a reality check, how long does a service train usually take to get from Pontlottyn and Cardiff Central? From RTT, 2P31, an off-peak train is scheduled to leave Pontlottyn at 10.13 (WTT), and to arrive at Cardiff Central at 11.09 (WTT), a journey time of 56 minutes. The 769 did it in 38 minutes, but skipped eleven stops. Adding back in the time for the station stops (using the same numbers as used above), would increase the journey time to 60 minutes (using generous numbers for the cost of each stop) or to 54 mins (using what I consider to be more realistic numbers).

So the big hurrah for the 769 seems to fall a little flat, in that the scheduled time for its return journey was somewhat leisurely. Yes, it gained a considerable amount of time, but on a fairly well padded schedule - NR anticipating some challenges along the way?

So on the face of it, it seems to me that switching to 769 usage will have little impact on journey times. That said, there are a host of other variables involved - not least driving techniques (loss powerful breaking / acceleration will increase the additional time required for each station stop), and realistic dwell times. Time will tell.

I think you're overthinking this somewhat.

Firstly, the padded scheduled timing is irrelevant. There would have been reasons why the padding was in there, and I'm guessing it wasn't needed.

As to the comparison with the normal time, you say it took 38 mins against a typical journey time of 56 mins. So an 18 min saving with 11 stops skipped. So around 90 secs a stop, which feels about right. Don't forget not all missed stops can be taken at a full 60 or 75mph line speed. That's all there is to it really. I'm sure the driver wasn't driving flat out either, but probably driving cautiously getting used to new unfamiliar rolling stock.

 

[Bob Price]

Another run due up and down tonight. These are the paths at Rhymney.
https://www.realtimetrains.co.uk/search/detailed/RYMYNGF/2020-03-24/1956

 

[PHILIPE]

Another run due up and down tonight. These are the paths at Rhymney.
https://www.realtimetrains.co.uk/search/detailed/RYMYNGF/2020-03-24/1956

Monday to Friday.

 

[Optom1]

Being a bit bored during wet weather did a few trips with 170’s(some of which have rear cab only door opening)acers:150,s:class37 locohauled stock.Outside of Central/Queen St most dwell times were40-50 secs.

 

[PHILIPE]

Did the769 run the2F10 to Rhmney to Cardiff this morning? I wasnt watching rail cams this morning.

I doubt it. They haven't been certified to operate in passenger service yet

 

[AM9]

So AM9, how do you get from 750V DC to the 1500V DC required for the traction motors, 240V AC for the house supply and 110V DC for other bits?
I did say that I wasn't an expert in the electrics side of things....

As samuelmorris has posted, the motors are 750VDC types, (like most BR MKI & III EMUs) the 319s are actually GEC but they are derivatives/alternatives to the classic Southern Electrics' English Electric EE507 type. Unlike camshaft traction control systems, I think that the motors are each fed by and are separately controlled by the GTO electronics, so they aren't put into series configuration for starting then switched to parallel for higher speeds and cruising. Other than higher (loco sized) motors, I think that 1500VDC motors on EMUs are relatively rare as there can be insulation problems when the peak voltages rise much above 1kV. The class 306 & 307 EMUs were originally 1500VDC designs (like the 506s on the Manchester, Glossop and Hyde line), and to reduce energy waste, the motors were 750VDC types but wired in series per bogie and the two bogies in series/parallel, starting in series and changing over to parallel st around 20mph, (often with much clacking and banging of contactors). When converted to ac, they were given a 1500VDC, fed from a 1500Vac tranformer and rectifier to enable the existing DC traction control to continue in use.
The 110 and 240V 'hotel'' supples were derived from auxiliary motor-generator sets.

 

[PHILIPE]

It doesn't seem to have set off from Canton tonight

 

[anamyd]

Top speed of a 769 is 100mph apparently

the 100mph top speed is on overhead electrification as in working like a 319; on Diesel the top speed is reduced in a similar way to 800s in that it's "as fast as the power generated for the motors by the engines will allow" - the Diesel top speed of a 769 is said to be "approximately 87mph".

 

[Philip Roberts]

the 100mph top speed is on overhead electrification as in working like a 319; on Diesel the top speed is reduced in a similar way to 800s in that it's "as fast as the power generated for the motors by the engines will allow" - the Diesel top speed of a 769 is said to be "approximately 87mph".

Ah, ok. Still, it's better than a 150.

 

[JN114]

the 100mph top speed is on overhead electrification as in working like a 319; on Diesel the top speed is reduced in a similar way to 800s in that it's "as fast as the power generated for the motors by the engines will allow" - the Diesel top speed of a 769 is said to be "approximately 87mph".

Source?

The 800s top speed on Diesel is 125, and they can achieve that; same as on Electric.

 

[samuelmorris]

Source?

The 800s top speed on Diesel is 125, and they can achieve that; same as on Electric.

There were suggestions that 800s topped out at 118mph on level ground but that was probably before the 800s were reprogrammed to behave the same way as 802s. I've seen the 87mph figure for 769s a few times. Given the 319s are known for accelerating very slowly beyond 90mph, I can believe it.

 

[JN114]

There were suggestions that 800s topped out at 118mph on level ground but that was probably before the 800s were reprogrammed to behave the same way as 802s. I've seen the 87mph figure for 769s a few times. Given the 319s are known for accelerating very slowly beyond 90mph, I can believe it.

I too can believe it. But the QP put it in quotation marks while correcting another poster and thus portrayed the matter as fact. It’s not, it’s hearsay; just as the 118mph Diesel top speed for IETs was incorrect hearsay.

 

[Nymanic]

I too can believe it. But the QP put it in quotation marks while correcting another poster and thus portrayed the matter as fact. It’s not, it’s hearsay; just as the 118mph Diesel top speed for IETs was incorrect hearsay.

While not proven fact, the 87mph figure does come from Porterbrook's own modelling data (source). The real-world figure appears yet to be divulged.

 

[yorkie]

Just a gentle reminder this thread is to discuss Transport for Wales 769's

We do welcome the discussion of other trains, e.g class 80x, but we do ask that these are posted in a seperate thread please.

 

[Senna1210]

While not proven fact, the 87mph figure does come from Porterbrook's own modelling data (source). The real-world figure appears yet to be divulged.

Its more than that real world

 

[Dai Corner]

Unless they start working on the main line they won't get anywhere near 87mph.

 

[AM9]

Unless they start working on the main line they won't get anywhere near 87mph.

On level track, the ultimate* maximum speed would be the same as they were as 319s less a small amount for lower power to overcome rolling resistance and aerodynamics. Thus 87mph on diesel isn't far out considering the 319s (and 769s on 25kV) would likely be somewhere in the 90s, in line with that during 25 years of Thameslink service.
* ultimate in terms of the asymptote on an unlimited length level track.

 

[Dai Corner]

On level track, the ultimate* maximum speed would be the same as they were as 319s less a small amount for lower power to overcome rolling resistance and aerodynamics. Thus 87mph on diesel isn't far out considering the 319s (and 769s on diesel) would likely be somewhere in the 90s, in line with that during 25 years of Thameslink service.
* ultimate in terms of the asymptote on an unlimited length level track.

I was thinking about the line speeds between Penarth and Rhymney rather than the capabilities of the units.

 

[Cardiff123]

Anyone want to make a prediction of whether we will see even one 769 in passenger service by the May TT change? Seeing as training runs only lasted a few days before they were stopped, and due to the current coronavirus situation, I'm going to guess it'll now be late summer or early autumn before any 769s are in passenger service.

 

[Bletchleyite]

Anyone want to make a prediction of whether we will see even one 769 in passenger service by the May TT change? Seeing as training runs only lasted a few days before they were stopped, and due to the current coronavirus situation, I'm going to guess it'll now be late summer or early autumn before any 769s are in passenger service.

On the basis that the reduced service doesn't need them and the social distance measures are likely to go on for some time, I suspect no we won't.

 

[Jamesrob637]

On the basis that the reduced service doesn't need them and the social distance measures are likely to go on for some time, I suspect no we won't.

Maybe just one to say that TfW meet the deadline and, because it's 4-car, at least it can't be short-formed?

 

[Brissle Girl]

Maybe just one to say that TfW meet the deadline and, because it's 4-car, at least it can't be short-formed?

I suspect meeting deadlines for introduction of trains is pretty low down anyone’s priorities at the moment. Don’t think anyone is going to be breathing down their neck to ensure it’s done in time.

 

[Anonymous10]

I suspect meeting deadlines for introduction of trains is pretty low down anyone’s priorities at the moment. Don’t think anyone is going to be breathing down their neck to ensure it’s done in time.

I have to agree with the virus it's likely things won't be particularly busy for a while

 

[Chris217]

I suspect meeting deadlines for introduction of trains is pretty low down anyone’s priorities at the moment. Don’t think anyone is going to be breathing down their neck to ensure it’s done in time.

Also,government relaxation of all rail franchise agreements due to covid-19
pandemic.

 

[craigybagel]

Amongst other restrictions brought in to cope with this crisis, at present no more then one person is permitted in either cab of a train at any time, except for emergencies obviously. It is therefore impossible to carry out any kind of training, since the instructors aren't allowed to have trainees with them. All trainee drivers and conductors are working from home, and I doubt you'll see any qualified train crew learning new traction any time soon.

 

[Robert Ap Ioan]

I'm wondering if something has changed. A Class 37 just went up the line.