Class 377 Stopping Distances

[Lufcman]

Anyone know where I can find the stopping distances at various speeds for the Class 377?

 

[bigdelboy]

you might find some information in this incident report .... (or you may not):

http://www.raib.gov.uk/cms_resources.cfm?file=/111117_R182011_Stonegate.pdf

Possibly more detailed in some circumstances and not in others.

I certainly not recommend doing a field test on the Brighton main Line Jenny Agutter style!

 

[notadriver]

12%g on a dry rail

 

[user15681]

To put it into context, I was told that during trials of the new 377s, braking in full step 3, the unit got from 90mph to 0 in 36 seconds.

 

[Lufcman]

Would like to know speed/ distance ie. 50mph:100metres etc

 

[bangor-toad]

To put it into context, I was told that during trials of the new 377s, braking in full step 3, the unit got from 90mph to 0 in 36 seconds.

Really? Wow.
If my maths is right that's 90mph to stop in a bit over half a mile. That's far quicker than I'd have thought.

How does this compare to other types / classes of train?

Cheers
Mr Toad

 

[cossie4i]

Really? Wow.
If my maths is right that's 90mph to stop in a bit over half a mile. That's far quicker than I'd have thought.

How does this compare to other types / classes of train?

Cheers
Mr Toad

A 395 will stop from 75mph to 0 in 15 coach lengths (emergency stop).

 

[deltic08]

Conversely, can anybody tell me please how long in time and distance does a 377 take to accelerate to 90mph.

 

[455driver]

Really? Wow.
If my maths is right that's 90mph to stop in a bit over half a mile. That's far quicker than I'd have thought.

How does this compare to other types / classes of train?

Cheers
Mr Toad

A 444 leaving Popham no2 tunnel at 100mph will be able to stop at Micheldever if full service is used, it was done several times when the trains were on trial/driver training runs when they were new, it is not recommended in normal service though!

 

[Skoodle]

Conversely, can anybody tell me please how long in time and distance does a 377 take to accelerate to 90mph.

On a 378 it takes me roughly 600m to get to 50mph from 0. I worked this out briefly using google maps. I would say about 1.1km to get to 90mph. There are more traction motors on a 4 car 378 compared to a 377 so I would say just a little bit longer. It's hard to work out exactly as the faster the unit goes, the less force the motors use so I could be way off the mark!

 

[deltic08]

On a 378 it takes me roughly 600m to get to 50mph from 0. I worked this out briefly using google maps. I would say about 1.1km to get to 90mph. There are more traction motors on a 4 car 378 compared to a 377 so I would say just a little bit longer. It's hard to work out exactly as the faster the unit goes, the less force the motors use so I could be way off the mark!

Many thanks. I did hear that acceleration was 1mph/second but this is not true above 60-65mph.

 

[edwin_m]

If you choose a station which is reasonably level and free from speed restrictions, you can work out the acceleration quite easily. Position yourself on the side with the mileposts and record the exact time of each one with a stopwatch. You can then draw a graph of distance against time, which can be converted into distance against speed.

 

[Bald Rick]

If you choose a station which is reasonably level and free from speed restrictions, you can work out the acceleration quite easily. Position yourself on the side with the mileposts and record the exact time of each one with a stopwatch. You can then draw a graph of distance against time, which can be converted into distance against speed.

That does assume that mileposts are positioned accurately!

 

[bigdelboy]

If you choose a station which is reasonably level and free from speed restrictions, you can work out the acceleration quite easily. Position yourself on the side with the mileposts and record the exact time of each one with a stopwatch. You can then draw a graph of distance against time, which can be converted into distance against speed.

• Class 377 with a pantograph will normally accelerate to 90mph better north of the Thames
• Class 377 without a pantograph will normally accelerate to 90 mph better south of the Thames
• A train which is late (and especially at end of drivers shift ) may accelerate faster

...

In the stopping game there are a lot of variables ... gradient, rail conditions, reaction time, brake condition ( I understand this varies with wear, heat, recent usage..... etc). Also my understanding (often flawed) is Time to stop from say 60mph may be different if the brakes were initially applied at say 90mph rather than if the train was doing 60mph when breaking commenced (assume zero reaction time) due to typical brake characteristics. In practice a driver will brake harder than he deems necessary initially so to avoid hard braking at the last moment.

 

[edwin_m]

• Class 377 without a pantograph will normally accelerate to 90 mph better south of the Thames

These trains also lack the transformer so they are a bit lighter, which makes a difference to acceleration at the top of the speed range.

• 
  In the stopping game there are a lot of variables ... gradient, rail conditions, reaction time, brake condition ( I understand this varies with wear, heat, recent usage..... etc). Also my understanding (often flawed) is Time to stop from say 60mph may be different if the brakes were initially applied at say 90mph rather than if the train was doing 60mph when breaking commenced (assume zero reaction time) due to typical brake characteristics. In practice a driver will brake harder than he deems necessary initially so to avoid hard braking at the last moment.

• 
  
  I agree you can't get a good understanding of the braking characteristics of trains by a mlepost-and-stopwatch technique. Even full service brake will rarely be used because drivers are trained to brake light and early in case of hitting poor adhesion nearer to the intended stopping point. However it usually isn't necessary to try this because braking rates are generally clearly defined and constant across the speed range (full service is 9% of gravity for modern EMUs, although HSTs have a different braking curve above 100mph).
  
  By contrast acceleration reduces at higher speeds and may also depend on factors such as passenger load and line voltage, although modern traction packages tend to compensate for these. Modern EMUs on the DC network are also current-limited to avoid overloading the supply.

 

[MCR247]

These trains also lack the transformer so they are a bit lighter, which makes a difference to acceleration at the top of the speed range.

I was under the impression that dc only units had ballast in place of the transformer? Or is this just rubbish? (it was on here I read this after all )

 

[bigdelboy]

These trains also lack the transformer so they are a bit lighter, which makes a difference to acceleration at the top of the speed range.

My thinking was because there isn't a good stretch of 3rd rail north of the thames these units wouldn't go anywhere fast north of the thames

 

[edwin_m]

My thinking was because there isn't a good stretch of 3rd rail north of the thames these units wouldn't go anywhere fast north of the thames

That's what I thought when I read your post first time. Then I decided you were saying that units without a pantograph would accelerate better south of the Thames than units with a pantograph.

 

[bigdelboy]

That's what I thought when I read your post first time. Then I decided you were saying that units without a pantograph would accelerate better south of the Thames than units with a pantograph.

.... actually I had left it like that so people might think that .... then you have j(unexpectedly for me) just given a reason why those without pantographs might accelerate a tad quicker on third rail, and I suppose also in the context of original poster's requirement may also brake a little quicker ...

 

[notadriver]

This is a class 378 accelerating to 60 mph on a downhill gradient on DC third rail

http://youtu.be/b5Pk-_bgrZk

This is a pair of 375s (identical in power to 377s) accelerating to 90 mph

http://youtu.be/wwSSUd5kwX4

This is on a downhill gradient and due to current restrictions is about 5 mph slower than a 4 car would be above 50 mph.

My personal experiences with 378s have shown that the dual voltage models are slightly slower to accelerate on third rail than the ones that are DC only (378/1s).

However I can't say the same for 375/6s which are dual voltage vs the rest of the fleet and it is the third rail only 375/9s which just lack a bit of puff at higher speeds.

 

[deltic08]

If you choose a station which is reasonably level and free from speed restrictions, you can work out the acceleration quite easily. Position yourself on the side with the mileposts and record the exact time of each one with a stopwatch. You can then draw a graph of distance against time, which can be converted into distance against speed.

Thank you for the advice. I have been timing trains for the last 50 years and used to correspond with Ossie Nock who wrote a performance column in Railway Magazine. He published quote a few of my logs mostly on NE-SW trains.

My problem is that I do not live near a 377 route so was asking those who do live on a route.
--- old post above --- --- new post below ---

This is a class 378 accelerating to 60 mph on a downhill gradient on DC third rail

http://youtu.be/b5Pk-_bgrZk

This is a pair of 375s (identical in power to 377s) accelerating to 90 mph

http://youtu.be/wwSSUd5kwX4

This is on a downhill gradient and due to current restrictions is about 5 mph slower than a 4 car would be above 50 mph.

My personal experiences with 378s have shown that the dual voltage models are slightly slower to accelerate on third rail than the ones that are DC only (378/1s).

However I can't say the same for 375/6s which are dual voltage vs the rest of the fleet and it is the third rail only 375/9s which just lack a bit of puff at higher speeds.

Thank you, this is very useful. I assume ac only units would accelerate slightly better if and when they are built.

 

[edwin_m]

Thank you for the advice. I have been timing trains for the last 50 years and used to correspond with Ossie Nock who wrote a performance column in Railway Magazine. He published quote a few of my logs mostly on NE-SW trains.

My problem is that I do not live near a 377 route so was asking those who do live on a route.

Obviously teaching grandmother to suck eggs in that case then, but it might be of use to others reading the topic!

 

[deltic08]

Obviously teaching grandmother to suck eggs in that case then, but it might be of use to others reading the topic!

Yep, I agree with you there. Sincere apologies.

 

[bigdelboy]

.... I assume ac only units would accelerate slightly better if and when they are built.

Yes ... that would be because they could run without shoes on.

More seriously I believe the 377's are nobbled on dc at reduced power, the same way 444's and 450's are. I get the impression they accelerate with more punch on the WCML to Bletchley. If you can find timings from the brighton-london high speed run they you may also be able to glean information from that.

Oh ... look what i've found ....

Searching on youtube ... http://www.youtube.com/watch?v=Jl9wBpvu86U (It is just possible the you tube footage time might be fractionally out and a proper timing log of the run might be needed.

Last time I recall seeing one of these units was on the Reigate shuttle ... what a come down!

 

[notadriver]

Units always accelerate better on AC. I'll give an example of what I saw from the TMS of a 378 which isn't current restricted as it doesn't normally operate in multiple.

Tractive effort starts falling away at 25 mph on DC. This didn't happen until 35 mph on AC. Maximum power showing from the DMOS vehicle was around 500 KW whereas under AC I saw a peak of 700 KW.

Railway express shows a class 357 reaching 60 mph in 50 seconds on AC and a 375 took 70 seconds on DC and that wasn't restricted.

Strangely though a 379 doesn't feel as swift off the mark as a 357. Can anyone comment ?

 

[edwin_m]

Strangely though a 379 doesn't feel as swift off the mark as a 357. Can anyone comment ?

Speculation: Possibly the traction control software has been tweaked to give a softer start from rest, so although the eventual acceleration is more it takes longer to build up so is less noticeable.

 

[Kite159]

Units always accelerate better on AC. I'll give an example of what I saw from the TMS of a 378 which isn't current restricted as it doesn't normally operate in multiple.

Tractive effort starts falling away at 25 mph on DC. This didn't happen until 35 mph on AC. Maximum power showing from the DMOS vehicle was around 500 KW whereas under AC I saw a peak of 700 KW.

Railway express shows a class 357 reaching 60 mph in 50 seconds on AC and a 375 took 70 seconds on DC and that wasn't restricted.

Strangely though a 379 doesn't feel as swift off the mark as a 357. Can anyone comment ?

I can notice it when travelling on the 395, the acceleration when it's on the AC wires feels much greater than it's in DC rail mode

 

[cossie4i]

I can notice it when travelling on the 395, the acceleration when it's on the AC wires feels much greater than it's in DC rail mode

That it is, 0-100kph in 38secs on the level.

12car on DC is very painful lol

 

[Dieseldriver]

The stock I drive (3 step disc braked) will do 90mph - 0 in about half a mile on a dry rail with an emergency brake application. Last leaffall it took me a mile a and quarter to stop from 70...