Does anyone know what we hit?

[colin penfold]

Soon after Maidenhead the HST forming the 0800 Pad-Bristol hit an obstruction on the track which could be felt quite violently in the train. It took out a brake pipe causing an emergency brake application and also smashed a window towards the rear of the train. We were lucky that there were engineers on the train who repaired the broken pipe and got us to Reading where the train was taken out of service.

 

I am curious as to what we hit. The train manager suggested ballast, but I don't think ballast is in the habit of rising up and striking trains?

[Andy Hayter]

I cannot answer the specific question Colin, but there is experience of ballast piercing brake pipes.

 

When the first section of TGV Est in France had been completed it was earmarked for the then next TGV high speed record attempt - 150 = 150m/second.

 

In one of the test runs prior to the attempt proper  the 5 car specially adapted TGV kicked up a piece of ballast which cut into the brake pipe at around 500kph.  The stopping distance is something I relate to folk who seem to think trains stop on a sixpence in an emergency.  At 500kph=/- the stopping distance was 15kilometres at full emergency braking.

Edited June 22, 2018 by Andy Hayter

[Trog]

If the ballast is left piled above the level of the rails in the 4' after relaying work trains can hit it. Or if left high in the cess it can shake down under the vibration of passing trains until it gets on the rail head. Where it goes next is any bodies guess but it will probably be at a very high speed.

 

Once had a job where we stored the sleepers from the road we were reballasting in the 4' of the other road. We had failed to take account of a scattering of ballast on the sleepers, and the loco of the first spoil train started pushing the sleepers down the track I think with its fuel tanks. Que some urgent French Army gestures followed by a set back, and a bit of sleeper shuffling.

[colin penfold]

Thanks chaps, you learn something new every day

[wirey33]

 

When the first section of TGV Est in France had been completed it was earmarked for the then next TGV high speed record attempt - 150 = 150m/second.

 

In one of the test runs prior to the attempt proper  the 5 car specially adapted TGV kicked up a piece of ballast which cut into the brake pipe at around 500kph.  The stopping distance is something I relate to folk who seem to think trains stop on a sixpence in an emergency.  At 500kph=/- the stopping distance was 15kilometres at full emergency braking.

 

This seems an extraordinary distance ? 15 km is over 9 miles.

 

As a comparison, an aircraft landing at 200 mph certainly doesn't need miles and miles of runway to come to a halt.

 

Now obviously momentum has something to do with it, but 15km seems excessive ??

[Gareth Collier]

But jets have reverse thrust, flaps and rubber tyres on tarmac to slow them down, not metal on metal. Probably lighter too.

[Pete the Elaner]

9 miles to stop does sound a very long way doesn't it?

500kmh is about 310mph. Slowing by 100mph is putting a huge amount of energy into the braking system, but even when you're done with that, the train is still moving at 210mph, which is over 3 miles per minute. If this takes 1 minute (is that reasonable?), then the average speed during this deceleration is about 260mph, in which time the train has travelled well over 4 miles. That is half the 9 miles gone.

 

Stopping from a higher speed within existing braking distances was a significant, but often overlooked, design challenge of the APT project.

[Andy Hayter]

https://www.dailymotion.com/video/x1mlov

 

 

This was the actual record breaking run, so going a bit faster than when the accident occurred, but I think you might begin to see why the stopping distance is so long.  The video is very short and for most of it there is just empty track.

 

Incidentally the landing speed of passenger aircraft is usually well below 200mph.  Even a heavy jumbo jet lands at around 160mph.  

Edited June 27, 2018 by Andy Hayter

[Edwin_m]

Distance to stop is v²/2a where v is the speed in m/s and a is the acceleration (deceleration), 0.9m/s² being typical for a service brake on a modern unit.  From 150m/s this gives 12.5km.  However the record run may have braked more gently, perhaps using regenerative braking only, so as to reduce the heat dissipation in the friction brakes. 

[ejstubbs]

https://www.dailymotion.com/video/x4nwv8m

 

Er, that plays a video called "2 filles 1 carrotte" - I don't think that is the link you meant to post!  NSFW, though I believe (I closed the tab pretty smartish!) not nearly as rude as it might at first appear (which I think is given away by the title, assuming you understand enough French).

Edited June 27, 2018 by ejstubbs

[Joseph_Pestell]

Er, that plays a video called "2 filles 1 carrotte" - I don't think that is the link you meant to post!  NSFW, though I believe (I closed the tab pretty smartish!) not nearly as rude as it might at first appear (which I think is given away by the title, assuming you understand enough French).

 

I think that must be one of those kitchens that feature in Gordon Ramsay's programmes.

[Andy Hayter]

Er, that plays a video called "2 filles 1 carrotte" - I don't think that is the link you meant to post!  NSFW, though I believe (I closed the tab pretty smartish!) not nearly as rude as it might at first appear (which I think is given away by the title, assuming you understand enough French).

 

Ooops

 

Now corrected with the right link

 

https://www.dailymotion.com/video/x1mlov

[woodenhead]

Er, that plays a video called "2 filles 1 carrotte" - I don't think that is the link you meant to post! NSFW, though I believe (I closed the tab pretty smartish!) not nearly as rude as it might at first appear (which I think is given away by the title, assuming you understand enough French).

The vegan version of deux filles et un sausicon

[101]

Ooops

 

Now corrected with the right link

 

https://www.dailymotion.com/video/x1mlov

Watching that video actually made me swear! That's a ridiculous speed

[Grovenor]

Watching that video actually made me swear! That's a ridiculous speed

 

Plenty of better shots of the TGV record on you tube

eg.

https://youtu.be/sE4A0nPjyqQ

 

[Andy Hayter]

I agree the quality of my link is poor, but somehow it seems to me to convey the real speed in a way that side on and head on shots do not.  Nor really do the through the cab window shots.  The passing catenary mast go faster and faster for sure, but really taking in the real speed is more of a challenge.

Everyone will have their own favourites. 

[E3109]

As thoroughly impressive as that is, I still prefer the 1955 version, featuring CC7107 and BB9004...

331klicks/hour ain't bad at all.

Also remember that those old girls were running on plain bearings too, albeit of the absolutely superb Athermos design.

 

There's a bit of stuff on YT about it, can't recall the channel but the narration is definitely the Gallic version of Mr Chomley-Warner!

[keefer]

Remember reading about those attempts - one of the limiting factors being the pantograph heads glowing red hot with sparks and molten metal flying off!

Were those done on 1500V DC or 25kV AC?

[E3109]

1500 DC I think, given the lovely arched portals down south, as depicted in the vids.

[E3109]

https://m.youtube.com/watch?v=2cRDeFKR2Q8

[Fat Controller]

1500 DC I think, given the lovely arched portals down south, as depicted in the vids.

Confirmed; the line used was the one from Bordeaux towards the Spanish border, I believe. The track took a pounding as well.

Apparently, to supplement the train brakes, technicians on board were instructed to open all drop-lights on the coaches to increase drag.