Maximum speed on 750V DC third rail routes

[Harlesden]

I was always under the impression that high speed was not possible on third rail routes. However, I've just noticed the Class 450 units can do 100mph - but do they ever?

 

[61653 HTAFC]

The speed record on 3rd rail is 108mph, recorded in 1988 by a 442 on test. However running regularly at such speeds creates issues with the interface between juice rail and shoegear, particularly at the starts of a new run of rail when the rail switches sides. I believe parts of both the SWML and Brighton Main Line see 100mph running but someone who works the lines there might know better.

 

[Bald Rick]

SWML sees regular 100mph operation; Up Fast cleared from Basingstoke to Byfleet & New Haw, Down Fast from Farnboro' - Hook(ish).

BML doesn't; its max 90 now. Used to be 100mph, for 319s only, for a few miles either side of Gatwick. However for the last decade all 319s called at Gatwick, so couldn't achieve it, so it is permanently back at 90 now.

The SE main line from Sevenoaks Tunnel to Sandlong tunnel is also 100, with a few restrictions (notably Tonbridge and Ashford).

 

[30907]

The blanket limit for EMUs was 75mph until around 1962 when it was raised to 90 (Tonbridge-Ashford was the most likely place to experience it IIRC). The 442s were the first units with 100mph permitted.

 

[HarleyDavidson]

Used to do 100 quite regularly with 442s and both 444/450s, you can get just about 95 mph with an 4/5 or 8 car set from a standing start at Woking around the West Byfleet area, before you have to drop to 90.

What is odd is that with 444/450 you can leave the PBC wide open on the downhill stretch from Wallers Ash loop going down towards Winchester and be at 100 and they won't go above the 100, they don't apply the brake either, they just power back & hold.

 

[6Gman]

The blanket limit for EMUs was 75mph until around 1962 when it was raised to 90 (Tonbridge-Ashford was the most likely place to experience it IIRC). The 442s were the first units with 100mph permitted.

What were the REP/TCs allowed to do?

 

[dgl]

What were the REP/TCs allowed to do?

I believe 90mph

 

[61653 HTAFC]

What were the REP/TCs allowed to do?

I believe 90mph

They were technically capable of a fair bit more, and in the days of no "black boxes" often did!

 

[dgl]

They were technically capable of a fair bit more, and in the days of no "black boxes" often did!

I suppose a 4REP on it's own would be quite 'lively'

 

[yorksrob]

SWML sees regular 100mph operation; Up Fast cleared from Basingstoke to Byfleet & New Haw, Down Fast from Farnboro' - Hook(ish).

BML doesn't; its max 90 now. Used to be 100mph, for 319s only, for a few miles either side of Gatwick. However for the last decade all 319s called at Gatwick, so couldn't achieve it, so it is permanently back at 90 now.

The SE main line from Sevenoaks Tunnel to Sandlong tunnel is also 100, with a few restrictions (notably Tonbridge and Ashford).

Ah, the good old days, before HS1 turned the mainline into a branch.

 

[notadriver]

Used to do 100 quite regularly with 442s and both 444/450s, you can get just about 95 mph with an 4/5 or 8 car set from a standing start at Woking around the West Byfleet area, before you have to drop to 90.

What is odd is that with 444/450 you can leave the PBC wide open on the downhill stretch from Wallers Ash loop going down towards Winchester and be at 100 and they won't go above the 100, they don't apply the brake either, they just power back & hold.

I'm guessing the 1/250 falling gradient probably isn't steep enough for speed to rise above 100 coasting. That and they have a speed limiter fitted.
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Ah, the good old days, before HS1 turned the mainline into a branch.

Only two sections where 100 is attained now. Sevenoaks to Tonbridge (down) and between Ashford and Westenhanger (up and down)

 

[nlogax]

What were the REP/TCs allowed to do?

In addition to this, was 90mph still the limit for REPs and double-headed 73s (+ TCs) when they were running the remaining fast services during the early years of the 442s?

 

[Peter Mugridge]

They were technically capable of a fair bit more, and in the days of no "black boxes" often did!

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...

 

[MrB]

I'm guessing the 1/250 falling gradient probably isn't steep enough for speed to rise above 100 coasting. That and they have a speed limiter fitted.
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Sevenoaks to Tonbridge (down)

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

 

[HarleyDavidson]

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...

That wasn't uncommon. I managed to do Waterloo - Southampton Ctl, in just about 65' with a 442 set and that was driving it like I stole it, a clear run and using every bit of route knowledge I had to the max.

Now as I've got older & wiser, I just cannot be bothered to chase time up, you don't get any extra money for it and you never get any thanks for making it back up so what's the darn point. In fact you're just as likely to make a mistake and get downloaded and done for something trivial! :roll:

 

[contrex]

They were technically capable of a fair bit more, and in the days of no "black boxes" often did!

There was an up REP + TC run reported in the Railway Magazine around 1970 which included 105 after Roundwood.

 

[375610]

In the pre HS1 days, a fast Ramsgate to Charing Cross 375 would manage 100mph at around the Sellindge HVDC station between Westenhanger and Ashford. It would then sit at 100 all the way from Ashford to Tonbridge. These days both a 375 and a 395 will, on a good run, touch 100 between Westenhanger and Ashford, but only for seconds before having to brake. The 395s seem slightly slower on DC than the 375s.

 

[MikePJ]

I'm pretty sure the VEPs, CEPs and CIGs on the Portsmouth Direct line used to exceed 90mph downhill either side of Buriton Tunnel in the 1990s. My train home from school used to be an eight or twelve-car formation and I remember peering through the window at the speedometer in one of the cabs where the two units were coupled. Quite a lively ride when compared with modern stock at that speed!

 

[Nym]

In the pre HS1 days, a fast Ramsgate to Charing Cross 375 would manage 100mph at around the Sellindge HVDC station between Westenhanger and Ashford. It would then sit at 100 all the way from Ashford to Tonbridge. These days both a 375 and a 395 will, on a good run, touch 100 between Westenhanger and Ashford, but only for seconds before having to brake. The 395s seem slightly slower on DC than the 375s.

Would make sense, I expect they're heavier?

 

[Trog]

Part of the North London DC electric network had a line speed of 110MPH. Although I think the con rail is down now.

 

[HarleyDavidson]

I'm pretty sure the VEPs, CEPs and CIGs on the Portsmouth Direct line used to exceed 90mph downhill either side of Buriton Tunnel in the 1990s. My train home from school used to be an eight or twelve-car formation and I remember peering through the window at the speedometer in one of the cabs where the two units were coupled. Quite a lively ride when compared with modern stock at that speed!

You can do 90 just after the bottom of Ditcham bank/curves, there's a 75 then a 90, to just outside Rowlands Castle, where it's 70 around the curve to Durrants then up to 85, which is pointless because SN are always running late at Havant.

In the up direction it's 40 through Buriton, then 85 to just before Petersfield then 80 through the up platform and it stays there to Sheet AHB, 85 to Prince's Bridge AHB, 80 through Liss, 85 after Liss Common, which is impossible due to the grade up to Langley, where you can get 85. On leaving Haslemere you have to keep a sharp eye on the speedo as it's quite easy to accidentally do 90 if you're not careful.

In the past 90 down the bank towards Witley wasn't uncommon.

 

[bengley]

SWML sees regular 100mph operation; Up Fast cleared from Basingstoke to Byfleet & New Haw, Down Fast from Farnboro' - Hook(ish).

BML doesn't; its max 90 now. Used to be 100mph, for 319s only, for a few miles either side of Gatwick. However for the last decade all 319s called at Gatwick, so couldn't achieve it, so it is permanently back at 90 now.

The SE main line from Sevenoaks Tunnel to Sandlong tunnel is also 100, with a few restrictions (notably Tonbridge and Ashford).

319 100mph is still in the sectional appendix for Earlswood North Junction to Balcombe Tunnel Junction

 

[SpacePhoenix]

Above 100mph would Desiros and Electrostars start to draw enough power to trip the local power supplies?

 

[HSTEd]

I doubt it considering some of the circuit breakers now have trouble detecting shorts let alone trains.

I imagine you could go faster if you had a line with long continuous conductor rails and less side switching, but you would probably need more sophisticated pick up shoes with some sort of tensioning system along the lines of those on pantographs.

 

[notadriver]

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

Gradients and 90 mph limit on the up.
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Would make sense, I expect they're heavier?

Interesting that if you couple together two class 375/3s the total is about 266 tons. A 395 weighs about 10 tons more.

Of course it is well known the 395 is heavily restricted on the current it can draw at higher speeds on DC. This also affects longer Electrostar formations.

 

[Nym]

I doubt it considering some of the circuit breakers now have trouble detecting shorts let alone trains.

I imagine you could go faster if you had a line with long continuous conductor rails and less side switching, but you would probably need more sophisticated pick up shoes with some sort of tensioning system along the lines of those on pantographs.

You can already get spring balanced shoegear for DC 3rd rail pickups.

 

[D1009]

What were the REP/TCs allowed to do?

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.

 

[HarleyDavidson]

I'd say that it was more along the lines of comfortably above 100 mph and still going strong.

 

[Bald Rick]

319 100mph is still in the sectional appendix for Earlswood North Junction to Balcombe Tunnel Junction

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

 

[HarleyDavidson]

IMHO the sectional appendix only has one use and that's as a door stop because of the number of errors in it. :roll: