How many trains that can run faster than its current top speed?

[AM9]

The governed speed depends on tyre wear - as new, it's 132mph, on minimum ~123mph.

ER/ScR sets had governors from new...

So do the current speed measurement devices fitted to trains compensate for that or are drivers only disciplined of the speed as displayed to them.

 

[hexagon789]

So do the current speed measurement devices fitted to trains compensate for that or are drivers only disciplined of the speed as displayed to them.

The speedometer has a wheel-wear compensator.

Much older classes of loco have them too, 47s for one.

 

[AM9]

The speedometer has a wheel-wear compensator.

Much older classes of loco have them too, 47s for one.

OK, so no loop hole there.

 

[GW43125]

Pretty much all LU stock can certainly go faster than their stated maximum. There’s plenty of stories of A stock in particular reaching 70+ mph. Likewise there are plenty of stories of trains being taken “off the clock”. It doesn’t really happen now, though I daresay it isn’t too uncommon to be on a 73 stock above 45 mph.

When growing up I always thought the 73 stock was 50mph because rarely did I not clock it at 50!

 

[bramling]

When growing up I always thought the 73 stock was 50mph because rarely did I not clock it at 50!

Yes there has been a tightening up of line speed being observed on LU over the last decade or so. A generation or so line speed was de-facto “as fast as the train will go”. This may occasionally still be seen on the Picc Line in a couple of places, but it’s now the exception rather than the rule. Heathrow T123 to Heathrow T5 is still often a fast section. Hounslow West to Hatton Cross was in the past, but less commonly seen nowadays.

 

[WarrenTManager]

also a 166 could hit 100 if you really gave it the beans.

Except Brian?

 

[Rhydgaled]

I suspect that a double green would be regarded as no safer than a single green. When seen at a speed significantly over 125mph, it woul;d be impossible to be sure that it was a double green until it was too late to correct the speed.

My understanding of multi-aspect signalling (correct me if I'm wrong) is that non-red signals meerly show how many clear blocks are ahead before the next red and are to do with the braking distance of the stock (and, if IC225 could brake from 140mph to a stand in the same distance as IC125 could stop from 125mph then the 5th (flashing green) aspect would not have been necessary); ie. for 4-aspect or 5-aspect signalling:

• single yellow - 1 clear block (ie. next signal may be at danger so prepare to stop)
• double yellow - 2 clear blocks (ie. next signal may be single yellow, so reduce speed accordingly ready to stop at the signal after next)
• single/solid green - 3 (or more, if on a line with no flashing greens) clear blocks - no need to reduce speed below 125mph
• flashing (or double, but as far as I know double-greens have never existed) green - 4 (or more) clear blocks - no need to reduce speed

In other words, if you were traveling at 140mph and saw that the next signal was a single/solid green you would not have to reduce speed to 125mph before the first solid green. You would have to start reducing speed to ensure that, by the time you saw a double-yellow, would be travelling at no more than 125mph.

I thought the problem was that, when travelling at high speed, I assume the driver would see the signal only for a few seconds. In that time it would be difficult to determine whether the light was flashing or not, so a green aspect could be mistaken for a flashing green; which would be rather dangerous. I suspect that is the issue, but without testing it for real you would not know for sure whether the drivers could reliably tell the difference between solid and flashing greens, hence the trail installation of flashing greens to see if that was a potential solution. As I say, I don't know any of this for sure, so correct me if I'm wrong.

 

[LiftFan]

Yes there has been a tightening up of line speed being observed on LU over the last decade or so. A generation or so line speed was de-facto “as fast as the train will go”. This may occasionally still be seen on the Picc Line in a couple of places, but it’s now the exception rather than the rule. Heathrow T123 to Heathrow T5 is still often a fast section. Hounslow West to Hatton Cross was in the past, but less commonly seen nowadays.

I usually get the impression on the Piccadilly and Bakerloo lines that it’s a more relaxed approach, especially late night services and on Sundays!

 

[coppercapped]

I'm probably teaching my grandmother to blow eggs, but...

In a series wound direct current electric motor, assuming the commutator and the armature windings are sufficiently strong to resist the centripetal forces generated by the rotational speed of the rotor, the maximum rotational speed is that achieved when the 'back electromotive force' exactly equals and opposes the applied voltage. At this point the current through the armature will drop to zero. The 'back emf' is generated by the armature windings by virtue of their movement in the stator's magnetic field.

The back emf can be reduced by weakening the stator's magnetic field by reducing the current through the windings, this is the field weakening used in many dc traction designs enabling to armature to rotate more quickly.

The above is true when the motor is tested against a brake.

In daily traffic the top speed achievable by a train powered by an old school straight dc unit is set by variations in the supply voltage from the third rail or overhead, the diameter of the driving wheels, the direction and strength of the wind, whether the train is ascending or descending a hill and whether any overspeed device is installed which reduces or cuts the power supply or applies the brakes. These factors explain the differences noted in the stock's performance from time to time.

Three phase alternating current motors, as used almost universally today, generate torque when the rotor 'slips' slightly behind the rotating magnetic field created by the stator coils from the three phases suppled by the power electronics. If the rotor and the fields rotate at the same speed the torque drops to zero. This means that the maximum rotational speed is defined by the power electronics and is no longer directly affected by the level of the supply voltage to the train. If a train's top speed is, say, 100mph then the maximum frequency the electronics will supply is that commensurate with that speed, similarly for a 140mph top speed. The caveats concerning wheel diameter, inclines and wind still hold!

 

[AM9]

The above is true when the motor is tested agaiThree phase alternating current motors, as used almost universally today, generate torque when the rotor 'slips' slightly behind the rotating magnetic field created by the stator coils from the three phases suppled by the power electronics. If the rotor and the fields rotate at the same speed the torque drops to zero. This means that the maximum rotational speed is defined by the power electronics and is no longer directly affected by the level of the supply voltage to the train. If a train's top speed is, say, 100mph then the maximum frequency the electronics will supply is that commensurate with that speed, similarly for a 140mph top speed. The caveats concerning wheel diameter, inclines and wind still hold!

For every ac traction system the maximum frequency that the inverter will provide is not only based on the maximum in-service speed required, but also the actual hardware of the system will have stress level limits that should be above those encountered at the maximum that the inverters can provide. Thus when the class 350 Desiro UKs were required to operate at 110mph service speed to inter work with the IC services, Siemens upgraded the motors with rotating parts modifications that would operate at higher spin rates, (commensurate with appropriate reliability levels for full in service operation). I presume that the temperature limits of the non-rotating components were compatible with the increased power that the high speed running would impose on them. The inverters would also have had control software changes to alter the highest frequency they output.

 

[coppercapped]

For every ac traction system the maximum frequency that the inverter will provide is not only based on the maximum in-service speed required, but also the actual hardware of the system will have stress level limits that should be above those encountered at the maximum that the inverters can provide. Thus when the class 350 Desiro UKs were required to operate at 110mph service speed to inter work with the IC services, Siemens upgraded the motors with rotating parts modifications that would operate at higher spin rates, (commensurate with appropriate reliability levels for full in service operation). I presume that the temperature limits of the non-rotating components were compatible with the increased power that the high speed running would impose on them. The inverters would also have had control software changes to alter the highest frequency they output.

Thank you for the additional information.

These don't contradict my statement that the maximum rotational speed of the armature in an induction motor is given by the rotational speed of the magnetic field in the stator windings. This is defined by the required maximum service speed of the train. This speed then defines the maximum rotational speed of the armature (given by the wheel diameter and the gear ratio) and the power required for the performance required. In turn this defines the heat that will be generated in the motor.

That is, the defining feature for a given top speed is the inverter frequency and the rest of the system is then designed to cope with mechanical and thermal stresses predicted. If a train's top speed is to be increased then it is clear that the mechanical and thermal stresses have to be re-calculated and any modifications made to ensure reliable service.

 

[AM9]

Thank you for the additional information.

These don't contradict my statement that the maximum rotational speed of the armature in an induction motor is given by the rotational speed of the magnetic field in the stator windings. This is defined by the required maximum service speed of the train. This speed then defines the maximum rotational speed of the armature (given by the wheel diameter and the gear ratio) and the power required for the performance required. In turn this defines the heat that will be generated in the motor.

That is, the defining feature for a given top speed is the inverter frequency and the rest of the system is then designed to cope with mechanical and thermal stresses predicted. If a train's top speed is to be increased then it is clear that the mechanical and thermal stresses have to be re-calculated and any modifications made to ensure reliable service.

The Desiro UK stock was fitted with 8 x 250kW motors, (their Bombardier equivalent class 375/377/387, had 20%-33% less total power), so as the motors were considered adequate for 110mph, it was a cost-effective upgrade because of a conservatively rated original design.

 

[778]

If a train is late running, would there be consequences for the driver if they went over the maximum speed to make up time, even it was only a few mph above?

 

[CBlue]

If a train is late running, would there be consequences for the driver if they went over the maximum speed to make up time, even it was only a few mph above?

The short answer is yes, there would be consequences for the driver from previous postings on here.
Not that a "few mph" will make any difference in trying to make up time, even over a longer distance. Just not worth it.

 

[D6130]

If a train is late running, would there be consequences for the driver if they went over the maximum speed to make up time, even it was only a few mph above?

There would be if they were downloaded....or caught by a radar gun.

 

[Jimini]

It used to be (I think based on old posts on here) that the SouthEastern Javelin services (on HS1 infrastructure only of course) were timetabled for 125mph operation, but are cleared to 140mph so would use this extra allowance to run at 140 in the event of late running (bearing in mind HS1 is 186mph for Eurostar services so the infrastructure can obviously accommodate it). Happy to be corrected though -- think I read that a good while ago! Wouldn't happen anywhere else on the network, of course. A speed limit's a speed limit.

 

[AM9]

It used to be (I think based on old posts on here) that the SouthEastern Javelin services (on HS1 infrastructure only of course) were timetabled for 125mph operation, but are cleared to 140mph so would use this extra allowance to run at 140 in the event of late running (bearing in mind HS1 is 186mph for Eurostar services so the infrastructure can obviously accommodate it). Happy to be corrected though -- think I read that a good while ago! Wouldn't happen anywhere else on the network, of course. A speed limit's a speed limit.

Well it could happen when a train is timetabled to take longer than the minimum legal time between two points to avoid conflicts at junctions etc..

 

[hexagon789]

It used to be (I think based on old posts on here) that the SouthEastern Javelin services (on HS1 infrastructure only of course) were timetabled for 125mph operation, but are cleared to 140mph so would use this extra allowance to run at 140 in the event of late running (bearing in mind HS1 is 186mph for Eurostar services so the infrastructure can obviously accommodate it). Happy to be corrected though -- think I read that a good while ago! Wouldn't happen anywhere else on the network, of course. A speed limit's a speed limit.

They are timed for 140mph, while they maybe don't always touch or hold the magic 225 (km/h) figure on every run, speeds into the 220s are very common.

Also, running at 140mph vs 125mph saves approx 3 secs per mile, so not going to significantly help regain time if that was a policy.

You need to run about 20 miles continuously at 140 to thus save just one minute over 125mph running. (Ignoring any acceleration and deceleration.)

 

[Jamesrob637]

Trying to picture a class 67 doing 143mph and the noise it’d make doing so

It was brand new at the time!

Railjet went over 270kmh back in 2008 on tests.

 

[SolomonSouth]

Wasn't a Class 321 tested up to 117 mph on Stoke Bank? Or is that an urban legend?

I suspect this is an urban legend. A 321 is extremely underpowered. The balancing speed for a 321 on level track is only just above 100mph. The RPS archives show it cannot exceed ~80mph up the Potters Bar climb of 1:200, and doesn't have any hope of getting past ~90mph on anything other than a flat/downhill gradient.

Now if you said the same for a 365, which can easily accelerate to 100 by Barnet Tunnel, and could exceed 100 up Potters Bar if left open, could reach 117, I would find it easier to believe.

 

[Mark J]

Is it true that the '90 mph' Class 165/166 can actually get nearer to 100mph if pushed hard by the driver.

I've been on them a few times in the past when you can tell the driver was really ragging the train to the max. Especially on late night Oxford to Reading non stop services (I once timed departing Oxford and arriving at Reading at 21 minutes on a 166) and the Kennet Valley line, non-stop between Thatcham and Theale. Various GPS speed tests seemed to indicate speeds in excess of 90mph - although not sure how accurate.

 

[SolomonSouth]

Is it true that the '90 mph' Class 165/166 can actually get nearer to 100mph if pushed hard by the driver.

I've been on them a few times in the past when you can tell the driver was really ragging the train to the max. Especially on late night Oxford to Reading non stop services (I once timed departing Oxford and arriving at Reading at 21 minutes on a 166) and the Kennet Valley line, non-stop between Thatcham and Theale. Various GPS speed tests seemed to indicate speeds in excess of 90mph - although not sure how accurate.

I don't think so. They only 350hp per car. I doubt they could get to 90mph on anything other than a nigh on flat profile, and I seriously, seriously doubt the balancing speed for a 165 is even close to 100mph.

 

[3RDGEN]

I suspect this is an urban legend. A 321 is extremely underpowered. The balancing speed for a 321 on level track is only just above 100mph. The RPS archives show it cannot exceed ~80mph up the Potters Bar climb of 1:200, and doesn't have any hope of getting past ~90mph on anything other than a flat/downhill gradient.

Now if you said the same for a 365, which can easily accelerate to 100 by Barnet Tunnel, and could exceed 100 up Potters Bar if left open, could reach 117, I would find it easier to believe.

In July 1990 the first Cl322 Stanstead Express unit was delivered and did a special press run from York to Kings Cross, it was reported to have reached 112mph down Stoke Bank under special approval. No idea if the special approval was for 110 and it overshot slightly or 112 was the max it could achieve, this might explain the claim of 117 perhaps?

I don't think so. They only 350hp per car. I doubt they could get to 90mph on anything other than a nigh on flat profile, and I seriously, seriously doubt the balancing speed for a 165 is even close to 100mph.

The Cl166 was tested at 100mph in both tare and crush laden conditions on the MML in 1993, everything was obviously new so in the best condition to achieve the speed. After 30 years you would expect them to have lost a bit somewhere.

 

[SolomonSouth]

In July 1990 the first Cl322 Stanstead Express unit was delivered and did a special press run from York to Kings Cross, it was reported to have reached 112mph down Stoke Bank under special approval. No idea if the special approval was for 110 and it overshot slightly or 112 was the max it could achieve, this might explain the claim of 117 perhaps?

If a 322 can do 112, a 365 can definitely do 120. They are much more powerful at the top end, and literally are minutes quicker from 85-100mph.

The Cl166 was tested at 100mph in both tare and crush laden conditions on the MML in 1993, everything was obviously new so in the best condition to achieve the speed. After 30 years you would expect them to have lost a bit somewhere.

Yes. But the engines have the same amount of power they always did.

 

[hexagon789]

The Cl166 was tested at 100mph in both tare and crush laden conditions on the MML in 1993, everything was obviously new so in the best condition to achieve the speed. After 30 years you would expect them to have lost a bit somewhere.

A pair of 158s used on an Glasgow/Edinburgh speed run in the 1990s touched 107mph and 108mph once each en route.

They have Cummins engines (the Scottish ones all did at least) but still 350hp engines and the transmission is the same as the 166s; tare weight is probably similar too.

 

[D6130]

A pair of 158s used on an Glasgow/Edinburgh speed run in the 1990s touched 107mph and 108mph once each en route.

They have Cummins engines (the Scottish ones all did at least) but still 350hp engines and the transmission is the same as the 166s; tare weight is probably similar too.

In my driving experience, the Perkins-engined units - although nominally more powerful than their Cummins-engined cousins - had a noticeably more sluggish rate of acceleration....resulting in a shorter time running at maximum line speed between stops.

 

[hexagon789]

In my driving experience, the Perkins-engined units - although nominally more powerful than their Cummins-engined cousins - had a noticeably more sluggish rate of acceleration....resulting in a shorter time running at maximum line speed between stops.

I thought the Perkins engines were also 350bhp?

The three engines variants being:

- Cummins 350bhp
- Perkins 350bhp
- Cummins 400bhp

 

[D6130]

I thought the Perkins engines were also 350bhp?

The three engines variants being:

- Cummins 350bhp
- Perkins 350bhp
- Cummins 400bhp

Yes, sorry.....the old memory 's getting a bit hazy after nearly eleven years of retirement. Let's start again: In my driving experience, the 350 bhp Perkins-engined units were noticeably more sluggish in their acceleration than their sisters fitted with identically-rated Cummins-engines.... resulting in shorter periods running at maximum line speed between stops.

 

[hexagon789]

Yes, sorry.....the old memory 's getting a bit hazy after nearly eleven years of retirement. Let's start again: In my driving experience, the 350 bhp Perkins-engined units were noticeably more sluggish in their acceleration than their sisters fitted with identically-rated Cummins-engines.... resulting in shorter periods running at maximum line speed between stops.

I've certainly read from a few drivers that the 400bhp variants were slower than the 350 ones, but also about the Perkins ones being slow to respond and being very unresponsive in low notches.

 

[D6130]

I've certainly read from a few drivers that the 400bhp variants were slower than the 350 ones, but also about the Perkins ones being slow to respond and being very unresponsive in low notches.

Yes, that corresponds with my experience....although I'm not sure whether I ever drove the 400 bhp variant. Did Northern have any of them eleven years or more ago?