todays point question..

[whole diary]

[BerkshireBugsy]

Following on from the resturant car noise question I though I would ask this one

If an overhead powered train (such as a westbound heathrow express) was able to proceed past the end of the overhead power lines without the brakes how long would it take.for it to come to a stop ? Are we talking almost immediately? 100 yards or so? More ? And why?!

Have a good Friday everyone!

[Maxwell P]

You need to get out more BB

Fortunately, there are electric tram er sorry train gurus amongst members who will no doubt be able to answer your current question.



Have you considered www.reading-forum.co.uk btw?

They too seem obsessed with the arcane.

Have a good weekend!

[BerkshireBugsy]

You need to get out more BB
Have a good weekend!

You are certainly right about getting out more - and maybe spending less time commuting on trains!

[6 OF 2 redundant adjunct of unimatrix 01]

unless its up hill ... without any brakes on you could actually push a railway carriage....couldn't stop it tho   

[Maxwell P]

unless its up hill ... without any brakes on you could actually push a railway carriage....couldn't stop it tho   

In the same vein, I could easily drive an HST^▸ (High Speed Train), until I had to stop it that is.

[eightf48544]

I reckon from the full 100 at Hayes with the pan lowered and not touching the brakes bearing in mind it's basically flat (1:1700 up) somewhere around Langley maybe Slough even.

[BerkshireBugsy]

Just out of curosity is there any form of very short term battery back up on electric trains to ciao with any short term power loss?

You can tell I am stuck on a train and bored !

[Brucey]

Just out of curosity is there any form of very short term battery back up on electric trains to ciao with any short term power loss?

I actually wondered the same when travelling on a Pendo last week.  My thought was that there would be a short power loss at points on overhead wires.  Battery or not?  No idea.

In third rail land, there are typically enough shoes to collect from a rail either side at any end of the train.

[6 OF 2 redundant adjunct of unimatrix 01]

unless its up hill ... without any brakes on you could actually push a railway carriage....couldn't stop it tho   

In the same vein, I could easily drive an HST^▸ (High Speed Train), until I had to stop it that is.

stopping a hst is easyer than driving it.... just dont do the dead mans pedal when your supposed to .... i think? .... im not a driver

[readytostart]

Just out of curosity is there any form of very short term battery back up on electric trains to ciao with any short term power loss?

I actually wondered the same when travelling on a Pendo last week.  My thought was that there would be a short power loss at points on overhead wires.  Battery or not?  No idea.

In third rail land, there are typically enough shoes to collect from a rail either side at any end of the train.

In OHLE land there are neutral sections where power changes from one substation to another, typically located where the train would not usually need to stop to prevent it ending up in just the wrong spot and with no power. A pendo is equipped with two pantographs so in effect would be able to rescue itself using the other pan.
Pendos are permitted (with very strict controls being imposed by the signaller) to 'high speed coast' through an isolated section of OHLE and my understanding (gradients permitting) is that they can go for a good few miles before a) they lose momentum or b) the lack of power to the compressors leads to a loss of air and the brakes apply.

[smokey]

One advantage of the Virgin Pendolino's is that they have Two Pantographs, Only One can be in use at a Time as there are power busbars from end to end, however should a Pendo stop with the (in use) Pantograph on a neutral section, if on the level or an uphill gradiant, the Pantographs could be changed over to get the Unit moving again. Not sure if the driver would have to go to rear car to change Pantographs.
If on a Down hill section of Line Just releasing the brakes would do 

[tramway]

Eurostar Calss 373's had quite a coasting distance on the original CTRL^▸ (Channel Tunnel Rail Link) (before HS1^▸ (High Speed line 1 - St Pancras to Channel Tunnel)) when changing from 3rd rail to OHLE around Fawkham junction.

There are details somewhere on how long this actually took, can't seem to find it at the moment but other members may have exact details to hand.

I never actually timed it but at a guess it might have been anything up to a minute to accomplish.

[rogerpatenall]

When Eurostars coasted over the neutral section at Fawkham there was a very noticeable change from 'being powered' to 'coasting' and a 'pull' as the power came back on.

[Trowres]

From 100mph a train could coast for around 10 miles, depending on gradient, wind etc. On a 1 in 200 down gradient it may go on indefinitely. Of course, considerations like route setting and obstructions might affect the outcome!!

If my rough guesstimate isn't good enough, you could plug your chosen values into the formula in:
http://www.easts.info/2003proceedings/papers/0091.pdf 

[readytostart]

From 100mph a train could coast for around 10 miles, depending on gradient, wind etc. On a 1 in 200 down gradient it may go on indefinitely. Of course, considerations like route setting and obstructions might affect the outcome!!

If my rough guesstimate isn't good enough, you could plug your chosen values into the formula in:
http://www.easts.info/2003proceedings/papers/0091.pdf 

Only thing stopping it on a straight downward gradient is when the air drops due to a lack of power to the compressors and the brakes apply.