Transport for Wales 769's

[samuelmorris]

Can I get rid of following pics to restrict it to the 769 video

I'm not sure I understand what you mean - do you mean stop youtube from suggesting other videos to play after it's finished? Not that I'm aware of.

 

[Greybeard33]

But only when decelerating, and not when stationary?
All the reasons above are I imagine why the engines are "idling" at 1100rpm rather than the 700-800 mark used by Sprinters, that makes sense. It just doesn't make any sense to me under braking outside the context of mechanical transmission. It's not like you can use engine braking with electric traction...

The brake compressor is a large intermittent load on the DC traction supply.

 

[Cardiff123]

Has the 769 run this morning? It seems to have disappeared from RTT

 

[Jamesrob637]

Is it a good idea to run stuff like these training runs now under the current circumstances, given there'll be no passengers on board and TOCs are reducing frequencies?

 

[PHILIPE]

Has the 769 run this morning? It seems to have disappeared from RTT

They are shown in RTT but cancelled due to "Delay not investigated".

 

[Bob Price]

Is it a good idea to run stuff like these training runs now under the current circumstances, given there'll be no passengers on board and TOCs are reducing frequencies?

ideal time IMHO. Less trains to get in the way if it breakdown and a fleet of trains ready for when we do all go back to work.

 

[PHILIPE]

Seems to have been abandoned for now as 37025, the Thunderbird ar Rhymney, on it's way back to Canton

 

[AM9]

In a conventional diesel electric vehicle the engine generates power which is passed directly to the traction motors to convert into motion through the axles (keeping it simple before anyone says more), a higher moving speed (as an example) requires more power to the traction motors so a higher demand on the engine. On a 769 the diesel engines are generating a constant 750v DC to be passed down the bus line (the high voltage cable) to the transformer traction electronics (see note 1), at this point the unit works like a 319 electric unit in that the power is passed through the transformer traction electronics See note 2) to be used from there; which is why a 769 still generates the buzzing noise like a 319.(see note 3)
The voltage output is a constant 750v which is why it should rev at it's maximum speed most of the time, there will be something technical around electric demand on the supply which means it does sometimes rev down and up but that's electrical and I haven't seen the 769 manual(see note 4)

note 1 - the DC bus does not connect the transformer to anything, the transformer feeds alternating current to the rectifiers which in turn feed DC to the DC bus
note 2 - you cannot pass DC through a transformer, it is an AC only device and in the class 319, it transforms (hence the name) the 25kV ac at a fairly low current (up to a maximum of about 45Amps) down to a voltage that feeds the rectifiers (with a maximum current around 1300Amps) to create the 750VDC for the bus.
note 3 - the buzzing noise is around 300Hz which is the frequency of the GTO Thyristor chopper circuits that regulate the power to the DC motors and is heard in the trailer car (TSO). The transformer 'buzz' is a much deeper (100Hz) noise and is heard when in the motor car (MSO).
note 4 - the diesel engine and the generator are both controlled together. The output voltage is held (as near as is practicable) to 750VDC by a) adjusting the excitation of the generator which alters its power output partly independent of its rotational speed and b) by adjusting the diesel engines fuel injection rate which changes both the speed and its torque. The genset controller does this according to the demands on the DC bus and for a giver demand can spin the motor faster and back off the generator excitation or increase the excitation and increase the engine's torque. The exact levels are programmed in the controller with regard to fuel efficiency, engine stress, temperature etc., so it is quite possible that the engines* on the video were spinning with a low'ish load on their output.​

* The early testing of the genset was delayed by a technical problem where the two gensets were interfering with each other's efforts to stabilise the bus voltage and continually cycling up and down. This cause a minor delay in the design phase.

 

[Senna1210]

Seems to have been abandoned for now as 37025, the Thunderbird ar Rhymney, on it's way back to Canton

Abandoned this week due to current driver situation and paths restarting next week but in the PM

 

[krus_aragon]

Seems to have been abandoned for now as 37025, the Thunderbird ar Rhymney, on it's way back to Canton

That 37 is to be a useful bellwether.

 

[Bikeman78]

Is it a good idea to run stuff like these training runs now under the current circumstances, given there'll be no passengers on board and TOCs are reducing frequencies?

In the short term, it would appear to be an ideal time to do training runs. Last week the valleys ran a near normal weekday service. This week is a Sunday service with a few peak extras so there will be a lot of spare crew. Also the fleet mileage will plummet so fewer exams will be required.

Of course, if the instructor drivers/conductors go sick then training will stop. Also, if Canton do get short of staff the priority will be running the service rather than babysitting the 769.

 

[PHILIPE]

In the short term, it would appear to be an ideal time to do training runs. Last week the valleys ran a near normal weekday service. This week is a Sunday service with a few peak extras so there will be a lot of spare crew. Also the fleet mileage will plummet so fewer exams will be required.

Of course, if the instructor drivers/conductors go sick then training will stop. Also, if Canton do get short of staff the priority will be running the service rather than babysitting the 769.

There is an evening trip from Canton to Rhymney and return scheduled this week.

 

[AMD]

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....

 

[samuelmorris]

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....

The 240V AC etc. is provided via a motor alternator on the 319s I believe. I wasn't aware the traction motors were 1500V, I thought they were 750V driven directly (well, after a PWM system) from a rectifier off the transformer but I could be wrong about that.

 

[aleggatta]

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....

The 240V AC etc. is provided via a motor alternator on the 319s I believe. I wasn't aware the traction motors were 1500V, I thought they were 750V driven directly (well, after a PWM system) from a rectifier off the transformer but I could be wrong about that.

AFAIK 319s are camshaft/resistor bank control, as it was the only standard control system that would work on AC and DC supply systems at the time

 

[samuelmorris]

AFAIK 319s are camshaft/resistor bank control, as it was the only standard control system that would work on AC and DC supply systems at the time

No, they're definitely PWM controlled, I know that much - the 300Hz or so PWM frequency is clearly audible, and was even moreso when they ran on DC power. I think you may be thinking of 313s there.

 

[aleggatta]

No, they're definitely PWM controlled, I know that much - the 300Hz or so PWM frequency is clearly audible, and was even moreso when they ran on DC power. I think you may be thinking of 313s there.

Do apologise! just checked the training material and they are GTO(Gate Turn Off) thyristor controlled. My confusion came from the old southern training material being the same for classes 319 and 456, and assuming it was the same as the 455 traction electronics!

 

[PHILIPE]

There is an evening trip from Canton to Rhymney and return scheduled this week.

realtimetrains.co.uk/train/V01055/2020-03-23/detailed

It has left Canton so fingers crossed

 

[Adlee Turner]

I was just wondering, I looked on real time trains and could see the 2nd run back up to Rhymney later from Canton but couldn’t see a return back to Canton? Does that mean the 769 will be potentially staying overnight at Rhymney, If so I presume to train the staff there?

 

[krus_aragon]

I was just wondering, I looked on real time trains and could see the 2nd run back up to Rhymney later from Canton but couldn’t see a return back to Canton? Does that mean the 769 will be potentially staying overnight at Rhymney, If so I presume to train the staff there?

That second run up is also missing a return journey tomorrow and further on in the week. (There's no morning working for an overnight stay, either.) That working must not have been uploaded yet, either that or they'll end up with the entire 769 fleet transferred north one at a time!

 

[PHILIPE]

That second run up is also missing a return journey tomorrow and further on in the week. (There's no morning working for an overnight stay, either.) That working must not have been uploaded yet, either that or they'll end up with the entire 769 fleet transferred north one at a time!

Perhaps it's going to work the first one Down

 

[krus_aragon]

Perhaps it's going to work the first one Down

Ooh, you optimist, you!

 

[gazthomas]

realtimetrains.co.uk/train/V01055/2020-03-23/detailed

It has left Canton so fingers crossed

It seems to have has a storming run back

 

[Roger B]

It seems to have has a storming run back

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.

 

[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 230 is 60mph, according to wikipedia. This is equivalent to around 26.8 metres per second.

Let's allow 30 seconds for the additional time to cover the distance from where braking commenced to the station stop itself. This is pretty generous if braking is at 1 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 60 mph from each station stop. This assumes acceleration at 1 m/s/s - which is faster than most other emus. But D78s from which the 230s have been created are quite light-weight vehicles, and Vivarail make much of the enhanced acceleration capabilities of class 230 in press releases, etc - although they seem to be very careful not to publish any related data. 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 one 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 an additional 2 minutes: 30 seconds lost braking from 60 mph, 1 minute to stand in the platform, and 30 seconds lost while accelerating back to 60 mph. And as stated above, these are generous numbers. The reality, I suspect, is that the average station stop from top speed of 60 mph stop costs an additional 90 seconds, and probably a little less, over the time taken to cover the distance from where braking commences for the stop to the point where 60 mph is achieved again.

So had the 230 stopped at the 11 skipped stations this would have taken an additional 22 minutes (using 2 minutes per stop). As the 230 gained 40 minutes on it's 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 230 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 230 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 230 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.

Roger I thought this was a 769 running? 230s are for Wrexham to Bidston only now?

 

[Bletchleyite]

Roger I thought this was a 769 running? 230s are for Wrexham to Bidston only now?

I thought the same, I suspect a typo.

 

[Philip Roberts]

Revising this post to reflect 769 rather than 230 data - I'll re-post shortly!

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 230 is 60mph, according to wikipedia. This is equivalent to around 26.8 metres per second.

Let's allow 30 seconds for the additional time to cover the distance from where braking commenced to the station stop itself. This is pretty generous if braking is at 1 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 60 mph from each station stop. This assumes acceleration at 1 m/s/s - which is faster than most other emus. But D78s from which the 230s have been created are quite light-weight vehicles, and Vivarail make much of the enhanced acceleration capabilities of class 230 in press releases, etc - although they seem to be very careful not to publish any related data. 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 one 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 an additional 2 minutes: 30 seconds lost braking from 60 mph, 1 minute to stand in the platform, and 30 seconds lost while accelerating back to 60 mph. And as stated above, these are generous numbers. The reality, I suspect, is that the average station stop from top speed of 60 mph stop costs an additional 90 seconds, and probably a little less, over the time taken to cover the distance from where braking commences for the stop to the point where 60 mph is achieved again.

So had the 230 stopped at the 11 skipped stations this would have taken an additional 22 minutes (using 2 minutes per stop). As the 230 gained 40 minutes on it's 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 230 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 230 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 230 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.

Top speed of a 769 is 100mph apparently

 

[Roger B]

Roger I thought this was a 769 running? 230s are for Wrexham to Bidston only now?

Thanks gazthomas. I'm revising with 769 data - I'll re-post shortly.

 

[craigybagel]

Other then a short bit of 75 coming down the hill from Heath to Queen Street I don't believe there's much if any parts of that route with a speed higher then 60 anyway.

 

[Roger B]

Thanks gazthomas. I'm revising with 769 data - I'll re-post shortly.

Revised post (see above), using 769 data.