How far can a train roll?

[JB25]

Bit of a strange one and probably depends on various factors such as the train, it's formation, the weather conditions, gradient etc, but how far could a train roll under its own momentum before it would eventually come to stop?

I was thinking it when approaching Reigate recently, where beyond the station electrification stops... Say you were doing 70mph and shut off and let it roll. How far would a train get?

Just purely curious as it has always amazed me how little power needs to be taken on a train to get pretty far.

 

[BestWestern]

It would depend entirely on any gradients, as well as the other things you mention like the train itself and suchlike. There is no 'limit' though, as with anything that is freewheeling it would roll until the momentum ran out.

There was an incident maybe a year or so back involving a night freight train, somewhere up north I think. Travelling uphill, the Driver had failed to apply sufficient power - I believe the suggestion was that he was fatigued - and the train eventually slowed to a stop and began to roll backwards. It passed the second of two signals going the wrong way, at which point the Driver realised what had happened and applied the brake, a few miles before some pointwork which would have derailed it.

There was another recent incident, again probably a couple of years back I would think, involving an EMU operated by Southeastern I seem to recall. The sand hoppers had been emptied previously and not recharged for the next day's service. The train braked under severely bad railhead conditions and, without any grit under the wheels, slid straight through a station and a good couple of miles up the line. And that was with the brakes in!

 

[asylumxl]

On the Northern Line, 4 miles is the benchmark set by the runaway engineering train a short while back.

 

[yorkie]

Bit of a strange one and probably depends on various factors such as the train, it's formation, the weather conditions, gradient etc, but how far could a train roll under its own momentum before it would eventually come to stop?
I was thinking it when approaching Reigate recently, where beyond the station electrification stops... Say you were doing 70mph and shut off and let it roll. How far would a train get?

It appears the various factors mentioned are missing from the example.

 

[notadriver]

On an 8 mile trip scheduled to take 8 minutes I'll apply full power for first 3 minutes. Climbing at around 1 in 80 I'll top the summit at 65 mph. Descending the other side speed quickly builds to 80 mph and then I shut off the power. This will be after around 3 miles. With the falling gradient speed continues to rise and will hit the 85 limit just as the grade levels out. The limit rises to 90 but no more power is needed for the remaining 5 miles despite an uphill gradient into the next station.

Trains can roll incredibly well. This is part of what makes them so different to drive to road vehicles.

 

[DaveNewcastle]

When EastCoast's services are running at linespeed into London, the train requires a little breaking to reduce speed to 105mph after Potter Bar and before entering Potters Bar Tunnel. That's more than 12 miles out of Kings Cross, which is on a continuous descent all the way until the little jump up into the station after the Regent's Canal.

It's unlikely that any power would required during that 12 mile descent.

 

[1e10]

It would depend entirely on any gradients, as well as the other things you mention like the train itself and suchlike. There is no 'limit' though, as with anything that is freewheeling it would roll until the momentum ran out.

There was an incident maybe a year or so back involving a night freight train, somewhere up north I think. Travelling uphill, the Driver had failed to apply sufficient power - I believe the suggestion was that he was fatigued - and the train eventually slowed to a stop and began to roll backwards. It passed the second of two signals going the wrong way, at which point the Driver realised what had happened and applied the brake, a few miles before some pointwork which would have derailed it.

There was another recent incident, again probably a couple of years back I would think, involving an EMU operated by Southeastern I seem to recall. The sand hoppers had been emptied previously and not recharged for the next day's service. The train braked under severely bad railhead conditions and, without any grit under the wheels, slid straight through a station and a good couple of miles up the line. And that was with the brakes in!

http://www.theargus.co.uk/news/9371...rain_to_miss_platform_by_more_than_two_miles/

Here is what you're talking about.

 

[185143]

I was on a T68 the other day where this happened. We were approaching Shudehill, from Victoria, which as anyone who has travelled there will know, is quite a steep climb. The tram stalled just before Shudehill and rolled back about 50 cms until the driver applied the emergency brakes.

 

[Rugd1022]

On one of our (rare) Class 4 jobs we can roll pretty much from Hemel Hempstead to North Wembley before having to touch the brake, given a clear road.

 

[eastwestdivide]

Way back when I started reading railway mags, probably late 70s, there was one of the "train performance" columns, with speeds and logs etc, which I'm pretty sure had a section about a southbound WCML electric fail at full speed (no power) somewhere ridiculous like Tring, and the gradients and momentum carried it all the way in to Euston.
Tring's about the summit of the Chilterns round there, so it seems quite possible, especially in view of Rugd1022's comment above.

 

[edwin_m]

There was an incident maybe a year or so back involving a night freight train, somewhere up north I think. Travelling uphill, the Driver had failed to apply sufficient power - I believe the suggestion was that he was fatigued - and the train eventually slowed to a stop and began to roll backwards. It passed the second of two signals going the wrong way, at which point the Driver realised what had happened and applied the brake, a few miles before some pointwork which would have derailed it.

It was a class 92 on the climb to Shap. Rolled back for a couple of miles and reached 51mph.

http://www.raib.gov.uk/latest_news/news_archive/news_archive_2011/110815_pn_shap.cfm

This is part of the reason trains are more energy efficient than road vehicles. The steel wheel has a lot less resistance than a rubber tyre so a rail vehicle will roll much further.

 

[12CSVT]

AFAIK the longest continuous gradient on Network Rail is 26 miles (Pitlochry to Druimachdar summit)

 

[O L Leigh]

Yes, but if you have momentum you don't actually need a continuous falling gradient to roll for some very considerable distances.

A little trick I learned on the West Anglia is that you can get almost the entire way to Liverpool Street from Chingford with an empty train without making any control inputs whatsoever. You just get up to 5mph on your exit from the carriage sidings and then leave it alone and the train will coast all the way to town and observe all the speed restrictions without the driver having to intervene at all.

O L Leigh

 

[michael769]

With metal wheels on metal tracks there is next to no friction, so you really only have air resistance and the resistance in the axle bearings and transmission to slow it. The multi tonne mass means that even at low speeds the inertia is enormous so on the flat a train can keep going for a few miles.

I once travelled on a train which suffered compete loss of engine power on a morning commute. Aided by a downhill gradient, the driver kept it moving at speed for a good 25 miles to arrive at our destination several minutes early. (I suspect signallers gave us priority into the station to avoid getting a line blocked).

 

[edwin_m]

With metal wheels on metal tracks there is next to no friction, so you really only have air resistance and the resistance in the axle bearings and transmission to slow it. The multi tonne mass means that even at low speeds the inertia is enormous so on the flat a train can keep going for a few miles.

The energy loss between a wheel and the surface it is rolling on is not down to friction. Energy is only lost to friction if slipping takes place.

The way energy is lost by a wheel is that the bottom of the wheel, and to a lesser extent the surface it is running on, deforms as the wheel rolls along. If you look at a stationary car even with the tyres at the correct pressure the underneath of the wheel is flattened a bit. When it is moving this flat goes round and round the wheel as it rolls.

With a rubber tyre this deformation is quite large and most of the energy needed to cause it comes out as heat - if you bend a thick piece of rubber back and forth many times it will get hot. A piece of steel of similar dimensions will be much harder to bend, and will spring back more readily (returning the energy for re-use), so much less heat is created.

 

[michael769]

What you are describing is a form of frictional force.

 

[broadgage]

IIRC there was a case of Virgin Pendolinos that coasted for a considerable distance through a de-energised section of overhead.

This was not some fault or failure, but was a planned work around during engineering work. Much easier than attaching a diesel loco which would have been the obvious thing to do.

 

[davetheguard]

In the book West Highland Railway by John Thomas (ISBN 0 7153 7281 5), the author describes an incident where a guard's van became detatched from the rear of a train, and complete with snoring Guard, gathered speed, and rolled back from Corrour to south of Bridge of Orchy, where the now adverse gradient finally brought it to a stand.

There, the Stationmaster found the Guard still asleep. The guard's van had run back 25 miles......

 

[D6975]

Many years ago I read a book called 'Tales of the Glasgow and South Western' or something similar. Some very funny stories in there including one about a broken coupling causing some vehicles to get caught between two inclines, running back and forth for hours in the middle of the night.

 

[ChiefPlanner]

I had an unsecured Freightliner 10 set run away in a yard (no handbrakes applied and air leaked off in 10 mins !) - we stopped it after 100 yards. No details on a forum ....roller bearing fitted vehicles can go easily , as I learned....

 

[reb0118]

There, the Stationmaster found the Guard still asleep.

It was probably me!

 

[bronzeonion]

http://youtu.be/uylvUa_Dmf8?t=26s The obligatory video for any runaway train thread!

 

[Bald Rick]

Way back when I started reading railway mags, probably late 70s, there was one of the "train performance" columns, with speeds and logs etc, which I'm pretty sure had a section about a southbound WCML electric fail at full speed (no power) somewhere ridiculous like Tring, and the gradients and momentum carried it all the way in to Euston.
Tring's about the summit of the Chilterns round there, so it seems quite possible, especially in view of Rugd1022's comment above.

I've heard this too, from people who were working in LM control at the time. Apparently it was still doing 80 at Willesden.

 

[12CSVT]

It was a class 92 on the climb to Shap. Rolled back for a couple of miles and reached 51mph.

http://www.raib.gov.uk/latest_news/news_archive/news_archive_2011/110815_pn_shap.cfm

This is part of the reason trains are more energy efficient than road vehicles. The steel wheel has a lot less resistance than a rubber tyre so a rail vehicle will roll much further.

Nothing like as dramatic as the runaway freightliner wagons with isolated brakes over Shap in 1984. Train arrived at Preston with dragging brakes, local technical staff isolate brakes on rear 10 wagons but forget to tell the driver what they had done.

Somewhere between Shap and Penrith the strain on the couplings results in rear 10 wagons breaking away from the rest of the train. An eagle eyed signalman in Carlisle PSB spots this on his panel and the plan was that once the front of the train had cleared Upperby Junction, the runaway wagons would be diverted onto the goods avoiding line believing they would derail almost as soon as they were on the goods line. In fact the wagons, estimated to be travelling at 50 to 60 mph managed to round a curve with a 10 mph speed restriction between Bog Junction and Rome Street Junction and eventually derailed on a river bridge between Rome Street Junction and Caldew Junction. The driver wasn't even aware that some wagons were missing until a crew change took place in Carlisle station (possibly around the same time as the 'missing' wagons derailed).

 

[ChiefPlanner]

Nothing like as dramatic as the runaway freightliner wagons with isolated brakes over Shap in 1984. Train arrived at Preston with dragging brakes, local technical staff isolate brakes on rear 10 wagons but forget to tell the driver what they had done.

Somewhere between Shap and Penrith the strain on the couplings results in rear 10 wagons breaking away from the rest of the train. An eagle eyed signalman in Carlisle PSB spots this on his panel and the plan was that once the front of th train had cleared Upperby Junction, the runaway wagons would be diverted onto the goods avoiding line believing they would derail almost as soon as they were on the goods line. In fact the wagons, estimated to be travelling at 50 to 60 mph managed to round a curve with a 10 mph speed restriction between Bog Junction and Rome Street Junction and eventually derailed on a river bridge between Rome Street Junction and Caldew Junction. The driver wasn't even aware that some wagons were missing until a crew change took place in Carlisle station (possibly around the same time as the 'missing' wagons derailed).

That was quite an incident - apart from being wrongly coupled at Crewe (red passenger couplings vice shortened green - FLL couplings) - no brake test after isolation and so on - the redeeming factors were the staff at Carlisle PSB who acted commendably. The train had loaded OCTEL tank containers which did not breach - else a different story ...

 

[Wikipedia]

http://youtu.be/uylvUa_Dmf8?t=26s The obligatory video for any runaway train thread!

Agreed!!!

 

[D6975]

That was quite an incident - apart from being wrongly coupled at Crewe (red passenger couplings vice shortened green - FLL couplings) - no brake test after isolation and so on - the redeeming factors were the staff at Carlisle PSB who acted commendably. The train had loaded OCTEL tank containers which did not breach - else a different story ...

Wasn't it the damage caused by this incident that caused the closure of the avoid?

 

[Dieseldriver]

Had a bit of a test today on a generously timed ECS. From 70mph at a certain point I shut off power and let the train coast for a 40mph PSR about 4 miles away (pretty steep uphill gradient for about half that distance). I ended up hitting 40mph bang on the start of the restriction without touching the brakes, this was on a DMU, not renowned for their 'rolling' ability! Something I will remember for the future!
Most drivers will coast as much as they can, with knowledge of timetables/workings/route you can still arrive early/on time and encounter less restrictive aspects, use less fuel, give a smoother ride and to be brutally honest, give yourself a bit more job satisfaction

 

[Skoodle]

From Wandsworth Road to Clapham Junction on a 378 I depart taking power up to 15mph. I then shut off and coast the rest of the way. Downhill gradient the train increases to 20mph which is the line speed over Factory Junction. Line speed increases to 25 after but the train decreases to about 16-18 before approaching Longhedge Junction. I like to keep it low there as it's a late sighting for the signal to make sure I have the correct junction indicator.

The train then increases slowly up to about 25 as I pass the next signal. If it's a single yellow I know I have to slow down for the red at the top of the gradient, so still no further input until I'm down to about 10mph around 200m from the signal. If it's green, I'll take power and maintain 25. So that'd be about 2km coasting from 15mph before I have to do anything. Like Dieseldriver said it's all about route knowledge. I don't see the need for driving that section at full line speed, I have 6 minutes timetabled and know I'll end up stopped waiting for the previous train to depart anyway, but it does give a sense of satisfaction.

 

[notadriver]

Those Lorol trains certainly get up to mindblowingly high speeds Skoodle