Questions about driving trains.

[RPM]

Here's one that I feel I should know but don't: is the power control lever a continuous range (like the accelerator in a car) or does it have a series of steps/gears?

The combined power/brake controller (PBC) on a modern (class 165 onwards) DMU has 7 power notches, a neutral position, and 4 brake steps.

Normally the unit is started from a stand in notch 4, then the notches are increased incrementally to notch 7. Local instructions in my part of the world specify that notch 7 should not be selected until the speed exceeds 10mph. In practise I usually select notch 7 somewhere between 15 and 20mph, but that is just my personal choice of driving style. Notches 1 and 2 are used when shunting, reforming units or coupling. Notches 1, 2 or 3 may also be selected when running at speed on a level or gently rising gradient in order to maintain linespeed.

Most braking is done in step 1 as per defensive driving instructions. Steps 2 and 3 are used in small doses to correct retardation as required. Notch 4 is the emergency brake. This cannot be deselected once engaged, until the speed drops below 5mph. In practical terms this means the train will come to a stand before the emergency brake releases. In low adhesion conditions brake steps 2 and 3 can be used more liberally as the automatic sanders operate in these steps, but not in step 1.

There is also an emergency brake plunger which can be hit in an emergency situation and puts the unit straight into step 4. This is usually (but not always) situated centrally in the cab so it can be operated by a conductor driver, second man etc.

Units with a combined PBC also have a hill start button, usually situated on the end of the controller's handle, a bit like the release button often seen on the gear selector on automatic cars. The function of this is to allow a step 1 brake application to be briefly maintained whilst the revs build up so the unit does not roll backwards. On older units with separate power and brake controllers this is obviously not necessary.
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Go on then, how realistic would you as a driver rate a simulation game such as train simulator? What are the key differences between driving a train from your laptop or computer in your living room to sitting in the cab of an actual train and driving it?

I find train simulator games completely and utterly unrealistic. This is probably grossly unfair to those who have slaved over their creation, but without the movement, the feel of the track, the sheer sense or responsibility and the slightly surreal uncertainty of how a steel wheel will interact with a steel rail, the games just don't cut it.

To be fair though, I find the proper company simulator equally unrealistic.

 

[Eagle]

So how is the voltage to the motors reduced? The 455's are DC trains and transformers don't work with direct current!

As a complete guess, I'd assume that there's an inverter that converts DC to AC, which then goes through a transformer; and then if it's needed to go back to DC it goes through a rectifier.

 

[455driver]

As a complete guess, I'd assume that there's an inverter that converts DC to AC, which then goes through a transformer; and then if it's needed to go back to DC it goes through a rectifier.

That is how the electrics are configured on the 444 and 450 units.

Nothing as posh on a 455 its 750V DC across the board (except control circuits, lighting and heaters)

 

[RPM]

This might be of some interest to folks curious about driving. It is slightly out of date now with GSMR and one or two other things having been introduced since the picture was taken. This is a 168/1. One day I will get round to doing the other 168 subclasses (which are laid out differently) and the 165s and 121s.

http://www.flickr.com/photos/rpmarks/2851378601/

 

[Pumbaa]

Are you allowed to use the DSD holdover in normal service on Chiltern land, ie looking back when departing?

 

[Eagle]

http://www.flickr.com/photos/rpmarks/2851378601/

That horn lever looks incredibly satisfying

 

[michael769]

As a complete guess, I'd assume that there's an inverter that converts DC to AC, which then goes through a transformer; and then if it's needed to go back to DC it goes through a rectifier.

I have no idea what they actually use on trains, but this can also be achieved using a DC to DC convertor. Most achieve it by storing the power in some way and then releasing it at a different voltage (one example is a charge pump as used in camera flashes, another is a magnetic induction switch as used in transformer less switching power supplies), but you can also do it mechanically by coupling a motor and a generator together.

Sorry for the electronics lesson now back to driving :razz:

 

[Temple Meads]

Is there a limit on how long a driver can be at the controls for before requiring relief (and no, not the bladder variety..)?

 

[4-6-2 Coast]

This is my first post on railforums so please be gentle

What is the meaning of the signal that's an illuminated circle with a horizontal or diagonal dark bar, often seen part way along platforms (at least that's where I see them.) Thanks.

 

[notadriver]

Those are called banner repeaters. Usually situated on a bend before a signal it is an advance warning of whether the signal ahead is 'on' - showing a red or 'off' ie not red.
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Is there a limit on how long a driver can be at the controls for before requiring relief (and no, not the bladder variety..)?

Depending on the company, the usual maximum is 4hrs 30. It's unusual to go that much without any kind of break.

 

[RPM]

Are you allowed to use the DSD holdover in normal service on Chiltern land, ie looking back when departing?

Yes. Normal practise here. Having said that, whilst it is routinely used on 165s, the fact that the holdover button is inconveniently placed on 168s means that it is easier to select neutral on the power/rake controller on these units.
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Is there a limit on how long a driver can be at the controls for before requiring relief (and no, not the bladder variety..)?

Yes, but complicated and (to an extent) company-specific. I'll leave it to somebody else to explain the details.
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That horn lever looks incredibly satisfying

What could you mean?

 

[rebmcr]

That horn lever looks incredibly satisfying

What could you mean?

Does it click, or just pivot/bend?

 

[Cherry_Picker]

On a 168 it kinda farts. A 67 horn is incredibly satisfying though, you could knock down the walls of jericho with that thing.

 

[t_star2001uk]

On a 168 it kinda farts. A 67 horn is incredibly satisfying though, you could knock down the walls of jericho with that thing.

Myself, i prefer the DVT end. A much more satisfying sound.
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Class 67 Desk



DVT Desk

 

[Kneedown]

It depends on the traction of course. Electric multiple units tend to have 4 power notches or steps. Each step is approximately 25% up to 100 % on modern multiple units. (1990 onwards). Diesel multiple units have more power notches - 7 tends to be the usual.

Locomotives often have a continuous range.

Some loco's, for instance 31's and 47's, have a combination. A few notches followed by a continuous range. All other loco's i've driven have a notch/detente at the first power setting, followed by continuous range, although on some of the 20's i drove the first notch was quite worn and took some delicate finding.

 

[Nym]

I see. I've not heard of Back EMF before- you learn something new everday! So how is the voltage to the motors reduced? The 455's are DC trains and transformers don't work with direct current!

As a complete guess, I'd assume that there's an inverter that converts DC to AC, which then goes through a transformer; and then if it's needed to go back to DC it goes through a rectifier.

I have no idea what they actually use on trains, but this can also be achieved using a DC to DC convertor. Most achieve it by storing the power in some way and then releasing it at a different voltage (one example is a charge pump as used in camera flashes, another is a magnetic induction switch as used in transformer less switching power supplies), but you can also do it mechanically by coupling a motor and a generator together.

Sorry for the electronics lesson now back to driving :razz:

You're all thinking too complicated for the 455s. I beleive that earlier it was told that there are the motoring positions of...
Shunt
Series
Paralell
Weak Feild

This would indicate that these units use RPAs or Rotary Pneumatic Accelarators or the electrical equivilant but this is rare.

This system switches a series of resistors in and out of circuit with the rotor windings and sometimes the stator windings depending on the motor configuration. Usually this is the case as Series DC motors would be used, not to be confused with series operation where motors are wired in series with eachother.

The switching contacts are air powered and step through according to a timer, enhncements have included shunt resistance current monitoring with a wound component triggering the switching to the next contactor step.

This can be overidden by using the 'Shunt Holding Relay' that will prevent further operation of the camshaft and the current resistance would be held in place.

The TBC or TC will control if this relay is held in or not and indirectly the S1 and P1 contactors to wire motors in series or paralell.

Weak feild contactor(s) are in place to bring a paralell resistance in/out next to the stator winding to reduce the feild current, therefore the static magnetic flux, therefore the back EMF. This gives a larger potential difference across the rotor coil, inducing additional current and allowing the motor to spin faster, while reducing torque.

Anyway getting off my train now...

Nym,
(Not a driver but well qualified to answer)

 

[Kneedown]

It's a valid question. It will be the power controller and the brake controller. On multiple units they maybe combined.

On a loco there are two brake controllers.
The "Straight" or "Direct" brake which applies brakes on the loco only. This is used when running light engine, or when working unfitted "Class 9b" trains. It was also used on vacuum braked freight trains, a gentle application being made to buffer all wagons up to one another before applying the vacuum auto brake.

The "Auto" or "Train" brake is the larger of the two brake handles, although on a 58 or 60 it is a tiny joystick. It applies the brakes on the train vehicles and also a proportionate amount on the loco, and is the one you'd use on any passenger or fitted freight train.

There is also a brake changeover switch some where in the loco with 2 or 4 settings depending on whether it is an air brake only loco or dual braked loco. The 2 settings are "Goods" and "Passenger", with "Air Goods, Air Pass, Vacuum Goods, Vacuum Pass" on dual braked loco's.
On passenger or parcels services, and also freightliner or other class 4 trains the "Passenger" setting will be used. On freight trains up to and including class 6 (60 mph max) the "Goods" setting should be used, which will release the train brakes more slowly to avoid "snatching" therefore minimising the risk of breaking couplings and dividing your train. Basically, when you release the brakes they will release from the front of the train going backwards, and on a long train it can take a good while for the brakes to fully release at the rear of the train, so if the brakes have fully released at the front and not at the back, there is a risk of breaking the coupling if you take power. The Goods setting overcomes this "Choking" the air/vac system, providing a slower, more gradual brake release.
If a Driver Manager (or Traction Inspector as they were known as then) popped up for an assessment ride or to say hello, the first thing they would do is disappear into the engine room to check the position of the switch as on some loco's they were located in awkward to get at places, resulting in a minority of Drivers not bothering to change them over.

 

[Nym]

Do you know I am not sure

Remember there are 2 seperate feeds to the traction motors, the normal 2 wires going to the brushes (as in a model loco) and 2 going to the magnets to creat the field (these are permanent magnets and so dont have a feed on models), these are the ones that are reduced to weaken the field.

See above for detail.

You are correct about the four wires. One will be connected to the other as thr rotor and stator are normally wound in series but the four wire arrangement allows for weak feilding and quick diagnosis (as above)

 

[notadriver]

Remember the 4-CIG 'Greyhounds'? These had additional field weakening to improve acceleration. A standard '400' series was unable to attain its nominal maximum of 90 mph on level track. These could exceed it.

 

[CCF23]

I drive London Underground trains, so if anyone has any questions regarding LU driving, fire away

 

[notadriver]

I drive London Underground trains, so if anyone has any questions regarding LU driving, fire away

Great which line are you on? If you can't say I understand.

 

[bronzeonion]

A question for you more veteran drivers. What do you think of the modern 3 step disc brake/stepless on a Desiro compared to the older EP on units/Automatic brake on loco haul? In terms of responsiveness, control, smoothness and easiest to come out of a slide?

 

[atlasduff47]

Hi all,

A two pronged one for all you drivers. What would be your traction of choice past or present and why?

 

[Kneedown]

A question for you more veteran drivers. What do you think of the modern 3 step disc brake/stepless on a Desiro compared to the older EP on units/Automatic brake on loco haul? In terms of responsiveness, control, smoothness and easiest to come out of a slide?

3 step is nice and user friendly. You apply it, it goes on. Release it it comes off, all pretty much instantaneously. There is a lot more time delay with auto on a loco, even with an E70 brake control unit. That said wheelslide is a nightmare. Disc brakes are better for bringing a train down from speed, but tread brakes are more positive a lower speeds and slightly less inclined to slide due to the conditioning of the wheels from the brake blocks.
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Hi all,

A two pronged one for all you drivers. What would be your traction of choice past or present and why?

From my own experience, 56 for freight as they will pull anything. Romanian for power delivery, BREL for user friendliness.
Express passenger HST or 45. Both solid performers and a 45 will outperform a 47 most days despite 5mph less speed.
Local passenger i'd have to say 150's, although i believe any EMU would do tje job better if the wires were there.

 

[455driver]

Seen that, thanks Nym.
?

Remember the 4-CIG 'Greyhounds'? These had additional field weakening to improve acceleration. A standard '400' series was unable to attain its nominal maximum of 90 mph on level track. These could exceed it.

Oh they used to fly along, pity the brakes were not upgraded at the same time, I have heard of many a driver comming unstuck when they arrive at their normal braking point going a lot quicker than they were expecting, not that it ever happened to me, honest!

 

[atillathehunn]

Thanks for the offer to answer all our silly questions. Potentially ridiculous question, but is there a cruise control function? Select a speed and the train will accelerate to the speed and remain there? On many of the trains here, the driver will select a speed target. Not to mention how much I appreciate the cruise control function on my car...

 

[notadriver]

Only certain trains have it. Here's a few

Class 357/375/376/377/379

'Disconnected on 375s and not permitted to be used on 376s or 377s on DC due to high power consumption' (so I understand)

Also disconnected on Networkers

Pendolino and class 90/91 locos.

I don't think any diesels have it although I'm told 185s do.

Desiro multiple units have a top speed limiter set at their maximum service speed.

 

[jopsuk]

Here's one (and if there's any ATW Cambrian line drivers they'll be especially able to answer):
Do you fear that the introduction of ERTMS, giving you constant target speeds (rather than your own judgement) will make the job deathly dull? I appreciate a greater fear would be automisation, but I reckon whilst we've got level crossings and other level access there's going to be someone up the front doing stuff!

 

[AndyLandy]

OK, here's my silly question I'd like to know the answer to.

Do you guys driving get a CD player or radio or whatever in the cab? Can you listen to music as you drive? Or is it forbidden on safety grounds?

 

[notadriver]

Absolutely forbidden to have any electronic devices on in the cab at all.