class387
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Is the 745 running as planned today?
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Class 745 Stadler FLIRTs
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dk1
Veteran Member
11:30, 13:00, 16:30 & 17:50 all booked to be 321s.
10:00, 15:00 & 20:00 booked to be 745s.
Why is that? At 236.6m, they are typical of full length trains everywhere.
For example:
class801 - 23m
class 390 - 265.3m
class 700 - 242.6m
class395x2 - 242.6m
Even the normal peak trains on GE trains are/were as long, - class321x3 - 239.4m, and from the '60s class305x3 - 232m. Also the normal complement of LST-NRW fasts before electrification was comprised of a class47 plus a mix of MK1 and/or MK2 LHCS totalling from 232.23m to 235.64mclass 390 - 265.3m
class 700 - 242.6m
class395x2 - 242.6m
So there's nothing special about the length of the 745s.
RailWonderer
Established Member
I think drivers are being careful with them now, it was raining quite hard when we left as well. I think they can still accelerate faster, in time we’ll see.
What left the most impression on me was the vestibule doors that make every seating area like a big compartment. The doors being in the centre and not the ends like on other ICs make a big difference.
dk1
Veteran Member
Yes mate. The 1100 & 1102 ex-Lst are both 90/DVT sets.
captainbigun
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Why accelerate hard when the timings don't need it, only leads to more use of the brake and increased energy usage.
The days of smashing the power controller wide open on any rail vehicle are long long gone. Drivers have standards to follow and are closely monitored. The environmental issues we are all well aware of also mean that energy usage is important - don't forget this is directly charged through metering on the vehicle.
More important than hp/tonne is CO2/km.
The days of smashing the power controller wide open on any rail vehicle are long long gone. Drivers have standards to follow and are closely monitored. The environmental issues we are all well aware of also mean that energy usage is important - don't forget this is directly charged through metering on the vehicle.
More important than hp/tonne is CO2/km.
samuelmorris
Established Member
Technically even more than that due to more efficient use of 'vestibule space'.
Perhaps there's some careful driving, although probably more due to low speed limits and a congested railway on the exit from Liv St rather than any lack of confidence in the units. I've certainly enjoyed some very spirited driving on 755s.
Yes the vestibule doors do make for quite a cosy feel. And it's immediately apparent how much extra seating only 1 set of doors allows.
bahnause
Member
Accelerating hard is very efficient on electric trains. They don‘t have the narrow optimum power range a diesel unit has. The time you save when accelerating hard can be used later, coasting for longer or braking earlier and using more of the regenerative capavilities.
captainbigun
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Yes, but there are other factors including passenger comfort. The GE is so heavily utilised, especially Shenfield to Colchester that defensive driving is inevitable.
ashkeba
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For fun!
Southeastern's Javaline drivers don't need to push you back into your seats accelerating away from Ashford but some still do. Are you one of the grumps who complains about odd PA announcements?
dk1
Veteran Member
Nothing changed this end. We wack them open and smash the power controller especially when running late or on the last bit. Those Stadlers are fast in diesel mode and exhilarating in electric.
He/she may be, but the important part of the post is that hard acceleration doesn't help anybody on a fully loaded line as it just wastes energy, causes more wear and tear on brakes, wheels and track, and of course can make the ride unpleasant for some. Trains are not fairground rides. The acceleratrion is there to be used when needed rather than a p***s extension for drivers and enthusiasts.For fun!
I don't think much of that is actually true.
Acceleration does not involve braking. And a lot of braking is regenerative on modern stock anyway.
I highly doubt that acceleration has any impact at all on track or wheel wear, unless the wheels are slipping, which again modern electronics takes care of.
Accelerating away quickly rather than dawdling means junctions and sections will be cleared more quickly, helping to keep other traffic flowing smoothly.
Ultimately, it takes the same amount of energy to accelerate several hundred tonnes of train from rest to 100mph, regardless of whether you do that quickly or slowly.
If there was no good reason to have such acceleration rates available, they wouldn't have installed 5.2MW of traction equipment and could have saved lots of money by chopping half of it out.
In short, quick acceleration does not "waste energy" in the slightest.
Railperf
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The modern AC traction motor systems are much more efficient than the old DC Motors. You cannot be serious by saying that consuming 7000 horsepower for 2 minutes accelerating to 100mph uses more energy then a 5000 horsepower locomotive accelerating for 4 minutes at full power.
Railperf
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Yes the 755 4-car are amazingly fast in diesel mode. Only 20 seconds slower from a standing start to 3 miles than on electric! I haven't yet analysed how much faster the 4 car 755 is on diesel than a class 321 but it must be at least 40 seconds.
On the Cambridge to Ipswich services you actually spend more time running at line speed. Whereas before you were spending more time accelerating and braking between the shorter stops
samuelmorris
Established Member
For EVs on the road, excessive acceleration does have a range impact, therefore is less efficient. I see no reason why the same wouldn't be true of rail.
Correct. I'm not suggesting that at all, someone else did and I was refuting that.
ashkeba
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Less traction available from metal wheel on rail so not the same level of excess? As mentioned, getting the vehicle past certain junctions sooner can reduce the power demands of other vehicles too. Plus I suspect regenerative braking putting back into overhead lines is more efficient than road EVs that can only charge batteries at 20-30% loss in and out.
squizzler
Established Member
Maybe that is due to the internal resistance of the batteries: rapid acceleration causes the voltage across the terminals to drop, hence reducing that available across the motor?
samuelmorris
Established Member
I would have thought there'd be more efficiency losses with rail as the energy needs to pass back through the transformer, but I haven't seen any numbers on it. You're right that rail doesn't have anything like the excess acceleration that EVs can produce but I'd expect there still be to some degree of efficiency loss due to the enormous amount of current involved. I expect it's probably negligible, however, to operational benefits like, as you say, being out of the way of junctions / power sections.
ExCommuter
New Member
One area where increased acceleration will cause additional energy loss is in the resistive losses in the overhead line. If you compare the same train accelerating at one rate with it accelerating at twice the rate (to make the sums simpler) then the harder acceleration will require twice the power and hence twice the current. As resistive losses are proportional to the current squared, then the losses will go up by a factor of 4 (2^2). As it will take twice as long at the lower acceleration rate to achieve the desire line speed then the losses will continue for twice the period, so the net result is that the resistive losses will be double when using the higher acceleration. In reality, the additional losses may be even higher if the voltage on the overhead line drops due to the higher power draw requiring even more current to achieve twice the power.
The same applies anywhere there are resistive losses in the electrical circuits.
Also, the quicker a train accelerates the sooner air resistance starts becoming significant. As air resistance is generally taken as being proportional to the cube of the speed (speed x speed x speed) then the faster acceleration will result in these additional losses being encountered earlier. Again while the longer acceleration period will mitigate some of this i=t will not mitigate all of it.
Please note I am not saying that there are not other reasons why a driver may need to accelerate faster but only clarifying that higher acceleration invariably will result in higher energy use particularly if you take into account the overhead line losses etc.
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Oh for all sorts of reasons.
Like the energy consumed keeping the battery cool at high current flow.
Hysteresis in rubber tyres.
Wheel slip.
"Electronic differential" (which is usually just a brake acting on whichever wheel is about to slip) keeping the car in a straight line.
Etc
Not the same thing at all.
Railperf
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The rate of acceleration can be managed by software if train operators want to save energy.
Pendolinos have an eco mode. But to be honest the amount of energy used often depends on the state of the road ahead and whether there are any out of course slowings for delayed trains ahead or temporary speed restrictions.
ZL exile
Member
before retiring, I always drove to the schedule not the line speed as that is what we were judged against on a download, even though some of the schedules were so slow, you could actually run at less than 50 on the ECML. Some were even worse than that. No point in burning resources just to get to a red signal early. It’s about professionalism and avoiding risk.
D365
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Exactly; end of the day, you are indeed driving to a timetable.
Railperf
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Yes..and that is why many drivers running into and out of Liverpool Street coast along at around 70 or 80mph instead of the the full 90mph.
An HS1 driver shared me his download, and it was clear that observing speed limits was checked for. But also stuff like leaving a good 20 second gap from doors closing to applying power. Dwell times were also looked at closely. As it happens..they are not (currently judged more postively by maintaining the schedule by driving at the lowest speed possible or slowest braking rate or slowest acceleration. Definitely do not exceed speed limits. That is for sure!
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