Maximum speed on 750V DC third rail routes

[bengley]

Not in mine (2015 edition), at least not where it used to be in the older editions.

First page of the Victoria to Brighton maps

 

[Deepgreen]

Why is it only 100mph on the down? And what is the limit on the up line?

I think the point was that 100mph is only attained on the down (Hildenborough bank - 1 in 100 falling), it won't be attainable on the climb (up line).
--- old post above --- --- new post below ---
I had an exceptional short run in the winter of 1981/2, when heavy snow had caused severe disruption. I was at Sutton, waiting for a trian to Epsom. This was in the days of the peak Bognor Regis trains and one hove into view (CIG, BIG, CIG formation) and stopped as usual at Sutton, and should have then been fast to Dorking. However, owing to the lack of other trains around, we were told it woud call at Epsom as well. I happened to board the buffet car and we then rocketed away to Epsom. I recorded 90mph around Ewell East on the downhill section before the brakes slammed on! Very surreal, a short suburban run in an operating buffet car, a blizzard blowing outside and us hurtling along at well over the line speed!

 

[Taunton]

I experienced a sub-one hour REP/TC/TC run from Southampton to Waterloo once and that was with sitting outside Waterloo for a few minutes waiting for a platform...

When nonstops ran from Southampton Parkway (maybe still called Southampton Airport then) to Waterloo I once had just a 4 car 4-VEP turn up on a REP/TC diagram. Bit of a squash as you can imagine. But did it move, and I felt beyond Basingstoke we were up towards 100 mph, finally stopping in Waterloo just on 60 minutes from Parkway. That was quite a ride.

The REP/TC formations were surely quite regularly up at these speeds as well, on the same stretch eastbound or through Winchester on the Down journey. All this stock had B4 bogies and should have been fine for 100 mph.

 

[Bald Rick]

First page of the Victoria to Brighton maps

So it does, thanks.

 

[Kentish Paul]

When the REPs were being tested in 1967, I've heard stories of speeds considerably in excess of 100 mph, though none of it was officially authenticated.

I seem to remember a story of a 4REP being tested between Tonbridge and Ashford. It was overnight and a speedgun at Staplehurst clocked it at 112mph.
Something to do with Eurostar 3rd rail pick up trials.

 

[61653 HTAFC]

I seem to remember a story of a 4REP being tested between Tonbridge and Ashford. It was overnight and a speedgun at Staplehurst clocked it at 112mph.
Something to do with Eurostar 3rd rail pick up trials.

Would 4REPs have still been capable of running then? Given that they donated their running gear to the 442s I'd be surprised, as 73+TC formations had to deputise during the transition because a 432 had to be taken off before the next 442 off the production line could be finished!

 

[tsr]

So it does, thanks.

I believe GTR route knowledge documentation states a linespeed of 100mph between the South end of the platforms at Three Bridges and Balcombe Tunnel Junction, on the Fast lines. Interestingly, I do not believe this is based on rolling stock classes either.

 

[jopsuk]

My understanding is that it's less a problem of shoegear staying in contact, that the issue is the impact on the ramps. That >100mph would be easily do-able, but for reliability you'd want much longer, shallower gradient ramps. Which means longer gaps between sections, which in turn means more chance of being gapped if a train has to make an unplanned stop.

 

[HSTEd]

My understanding is that it's less a problem of shoegear staying in contact, that the issue is the impact on the ramps. That >100mph would be easily do-able, but for reliability you'd want much longer, shallower gradient ramps. Which means longer gaps between sections, which in turn means more chance of being gapped if a train has to make an unplanned stop.

If you go down that route you could potentially have switched overlap rails so that one side of the train always has a shoe in contact with a live conductor rail, but that would require in line rail insulators, I imagine they could exist but I have never seen one.

Of course a two track railway can have no breaks at all if it wants if it puts the rails on the left hand side (in the direction of running) - the rail could run for many miles unbroken since crossovers will not require a break.

 

[D1009]

If you go down that route you could potentially have switched overlap rails so that one side of the train always has a shoe in contact with a live conductor rail, but that would require in line rail insulators, I imagine they could exist but I have never seen one.

Of course a two track railway can have no breaks at all if it wants if it puts the rails on the left hand side (in the direction of running) - the rail could run for many miles unbroken since crossovers will not require a break.

What about level crossings, though?

 

[Kentish Paul]

Would 4REPs have still been capable of running then? Given that they donated their running gear to the 442s I'd be surprised, as 73+TC formations had to deputise during the transition because a 432 had to be taken off before the next 442 off the production line could be finished!

My quote about Eurostar testing is no doubt wrong. Still trying to find the original story about the REP testing between Tonbridge and Ashford. Even so, 3200hp over 4 cars must have been quite nifty. Almost as good as 4500hp in a 6 car class 395. (AC only).

 

[HSTEd]

What about level crossings, though?

That would depend on the third rail shoe gauging and if the road deck could reasonably ride as high as the top of the third rail.
THen you just use the in line rail insulators to ensure the third rail over the crossing is dead unless a train bridges it. Or is even made entirely out of a non conductive material.

 

[D1009]

That would depend on the third rail shoe gauging and if the road deck could reasonably ride as high as the top of the third rail.
THen you just use the in line rail insulators to ensure the third rail over the crossing is dead unless a train bridges it. Or is even made entirely out of a non conductive material.

Is that actually used anywhere, or is it just your suggestion?

 

[HSTEd]

Is that actually used anywhere, or is it just your suggestion?

Its not used that I know of, but I assume there is no hard physical reason the required in line rail insulators cannot exist.

 

[urpert]

What about level crossings, though?

Not to mention stations (where the 3rd rail is normally kept on the opposite side to the platform)

 

[HSTEd]

Not to mention stations (where the 3rd rail is normally kept on the opposite side to the platform)

How many stations exist where 125mph is required through platform faces?
And how many seconds would be lost requiring a slowing to 100mph through them?
And there would be no problem with switching sides there using very gentle third rail ramps since you don't care about isolation in that case.

 

[Peter Mugridge]

When nonstops ran from Southampton Parkway (maybe still called Southampton Airport then) to Waterloo I once had just a 4 car 4-VEP turn up on a REP/TC diagram. Bit of a squash as you can imagine. But did it move, and I felt beyond Basingstoke we were up towards 100 mph, finally stopping in Waterloo just on 60 minutes from Parkway. That was quite a ride.

The run I was talking about, however, was from Southampton Central to Waterloo, not from Parkway. In those days there was one an hour non stop each way to / from Central.

 

[notadriver]

The run I was talking about, however, was from Southampton Central to Waterloo, not from Parkway. In those days there was one an hour non stop each way to / from Central.

I'm not sure VEPs would attain 100 mph on the up beyond Basingstoke. They have trouble maintaining 90 on the level.

 

[61653 HTAFC]

My quote about Eurostar testing is no doubt wrong. Still trying to find the original story about the REP testing between Tonbridge and Ashford. Even so, 3200hp over 4 cars must have been quite nifty. Almost as good as 4500hp in a 6 car class 395. (AC only).

Could the unit used in the Eurostar tests you mentioned have been one of the "Greyhound" 421 units? As I understand it they could shift a bit...

 

[nlogax]

My quote about Eurostar testing is no doubt wrong. Still trying to find the original story about the REP testing between Tonbridge and Ashford. Even so, 3200hp over 4 cars must have been quite nifty. Almost as good as 4500hp in a 6 car class 395. (AC only).

This?

"..

In the build up to the Eurostar build, Alsthom engineers and SNCF were
sceptical about the ability to achieve satisfactory current collection
from the third rail so we arranged an overhauled 4 REP with maximum
diameter whelsets to go flat out between Tonbridge and Ashford in a
night time possession. The result was entertaining to say the least.
The speedo was off the clock (100 mph +) and a radar gun at
Staplehurst clocked us at 117 MPH. Ride was bloody awful and I'm sure
that had the straight been longer we could have cracked 120MPH. This
sort of performance is why 4 REP's were never supposed to run alone,
always with one or more TC's.

Another point to bear in mind is that 4xx stock has a balancing speed
on the level of 80 mph or 86 mph for "greyhound" units with a second
field weakening stage, whilst the Electrostars and Desiros will
balance at 100MPH."

https://groups.google.com/d/msg/uk.railway/7uPYi1m4xY0/dGVlJPO4oyQJ

 

[Peter Mugridge]

I'm not sure VEPs would attain 100 mph on the up beyond Basingstoke. They have trouble maintaining 90 on the level.

True, but I was talking about a REP/TC/TC rake...

 

[notadriver]

True, but I was talking about a REP/TC/TC rake...

Someone mentioned a VEP in place of a REP/TC combo.

 

[HarleyDavidson]

Could the unit used in the Eurostar tests you mentioned have been one of the "Greyhound" 421 units? As I understand it they could shift a bit...

Greyhound units were very good and quick.

I'm saying nothing more.

 

[Islineclear3_1]

Greyhound units were very good and quick.

I'm saying nothing more.

You beat me to it! I'm sure Greyhound Cigs with their additional field weakening were capable (and did) 95mph++

 

[Nym]

This?

"..

In the build up to the Eurostar build, Alsthom engineers and SNCF were
sceptical about the ability to achieve satisfactory current collection
from the third rail so we arranged an overhauled 4 REP with maximum
diameter whelsets to go flat out between Tonbridge and Ashford in a
night time possession. The result was entertaining to say the least.
The speedo was off the clock (100 mph +) and a radar gun at
Staplehurst clocked us at 117 MPH. Ride was bloody awful and I'm sure
that had the straight been longer we could have cracked 120MPH. This
sort of performance is why 4 REP's were never supposed to run alone,
always with one or more TC's.

Another point to bear in mind is that 4xx stock has a balancing speed
on the level of 80 mph or 86 mph for "greyhound" units with a second
field weakening stage, whilst the Electrostars and Desiros will
balance at 100MPH."

https://groups.google.com/d/msg/uk.railway/7uPYi1m4xY0/dGVlJPO4oyQJ

Point of pedantry, electrostars and desiros won't balance at all, they're AC machines driven from inverters, they'll drive to and usually beyond their nameplate ratings, that's more than 100mph.

 

[notadriver]

Point of pedantry, electrostars and desiros won't balance at all, they're AC machines driven from inverters, they'll drive to and usually beyond their nameplate ratings, that's more than 100mph.

Absolutely agreed and Greyhounds will exceed 90 mph on the level whilst the logs I've seen of slam door trains are varied. A 4-CEP seemed to have trouble managing 80 but a 4-CIG was good for 5 mph more.

 

[Nym]

Absolutely agreed and Greyhounds will exceed 90 mph on the level whilst the logs I've seen of slam door trains are varied. A 4-CEP seemed to have trouble managing 80 but a 4-CIG was good for 5 mph more.

Quite...

If one looks at the likes of LUL stock, some stocks will easilly exceed their top speed to a high balancing speed, such as 1972TS, built for 45mph, but still has plenty to give on the flat at that speed. 1 car less but the same power as 1967 Tube Stock.

 

[HarleyDavidson]

Absolutely agreed and Greyhounds will exceed 90 mph on the level whilst the logs I've seen of slam door trains are varied. A 4-CEP seemed to have trouble managing 80 but a 4-CIG was good for 5 mph more.

Well the South Central's might, Fratton's would clock up 90 quite readily. If they didn't you just had a word with the lads down the shed and they'd sort it. Much better than the manky Wimbledon VEPs.

 

[Taunton]

As I understand it a 4-REP had 1,600 hp in each of its end power cars, each power car was essentially a Class 73 loco electrically with no diesel and a passenger body. With a REP/TC/TC combo you thus had 3,200 hp for 12 cars.

A 4-VEP had 1,000 hp, so a 12-car set had 3,000hp, for pretty much the same overall weight, the difference being probably within the tolerances of individual units. Both types had B4 bogies which were good for 100mph elsewhere.

So what accounts for any difference in performance? Gearing? Field weakening?

 

[notadriver]

As I understand it a 4-REP had 1,600 hp in each of its end power cars, each power car was essentially a Class 73 loco electrically with no diesel and a passenger body. With a REP/TC/TC combo you thus had 3,200 hp for 12 cars.



A 4-VEP had 1,000 hp, so a 12-car set had 3,000hp, for pretty much the same overall weight, the difference being probably within the tolerances of individual units. Both types had B4 bogies which were good for 100mph elsewhere.



So what accounts for any difference in performance? Gearing? Field weakening?

The 4-REPs did have a higher gear ratio than other VEPs or even the class 73. The logs I've seen show them to be slightly slower to accelerate a 12 car train than a traditional formation but able to maintain level speeds of 90 mph plus.