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A 3 car HST calls at Ealing Broadway


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I bet that had some acceleration!

Acceleration maybe but being such a short formation  it would have not much more stopping power than a push bike so very heavily speed restricted (the minimum formation you can run with an HST before having to reduce speeds is 5 trailers - anything fewer than that and stopping distances start going off the graph and you bring in big reductions below line speed).  Probably just as well for a Driver having to stop at a lot of unfamiliar places!

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It's not the first time it has happened.

 

One other time was when a driver was booked to do a turn using a DMU that he did not sign, so they put out a 2+2 formation to keep the service running.

 

Alistair

 

Probably the 2+2 that turned up on a VT operated Manchester Airport-Glasgow, vice a 158, but as Mike says, the braking capability is somewhat compromised in short formations.

 

Cheers,

Mick

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Hi, Latest fun size operation was on FGW due traction knowledge in last 6 months or so if my memeory serves ok. Yes VT and ICXC before run fun size for many reasons most famous after axlebox failure fears so many MK3 trailers stopped , remember the HST parked on Newton Abott bridge?. VTXC flirtation with 158s on Birmingham - Swindons saw a few short forms as well.

A well known short form HST was the pint size for the launch of the dyamic lines livery 2+3 set...

but wether it stopped at EB?

Robert

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It's not the first time it has happened.

 

One other time was when a driver was booked to do a turn using a DMU that he did not sign, so they put out a 2+2 formation to keep the service running.

 

Alistair

And this is the FGW that everyone was knocking in another thread for not providing customer service?

 

Dear-oh-dear.

 

Stewart

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Acceleration maybe but being such a short formation  it would have not much more stopping power than a push bike so very heavily speed restricted (the minimum formation you can run with an HST before having to reduce speeds is 5 trailers - anything fewer than that and stopping distances start going off the graph and you bring in big reductions below line speed).  Probably just as well for a Driver having to stop at a lot of unfamiliar places!

Interesting but I'm wondering why, given that power cars and coaches all have their own brakes? I'm guessing it's to do with the greater weight of the two power cars compared with the coaches or is there a more subtle reason? (My bushbike stops far more quickly than a train but I don't very often take it up to 125MPH!!  )

Edited by Pacific231G
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Interesting but I'm wondering why, given that power cars and coaches all have their own brakes? I'm guessing it's to do with the greater weight of the two power cars compared with the coaches or is there a more subtle reason? (My bushbike stops far more quickly than a train but I don't very often take it up to 125MPH!!  )

Put simply, each axle has a certain brake force, which varies from vehicle to vehicle. For example, say each trailer car has a brake force of 45 tonnes, and the power cars a brake force of 45 tonnes. If the power car has a mass of 70 tonnes, and each trailer a mass of 30 tonnes. To run at the line speed, the brake force must equal or exceed the mass of the train. So if you do the Maths, 2 power cars and 3 trailers mass 230 tonnes. The brake force of this setup would add upto 235 tonnes. Now if you removed a trailer car, the mass would drop to 200 tonnes, but the brake force would drop to 190 tonnes. Because of the reduced braking force available, you would have to reduce the max speed of the train until the braking performance matched the distance available to stop in.

 

The above is a very simplified explanation, and there has to be a allowance for a train running with one or more brake isolated. A train would be allowed to run with a certain percentage of its brakes isolated and if there was more isolated than normal, the speed of the train would also have to be reduced. The braking curve is also calculated under poor rail head conditions, which explains why most trains normally stop quicker than allowed for in the timetable. All this is worked out automatically when TOPS came into operation. Before this, it had to be worked out manually, a pain for freight trains.

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to add speeds to the above One or two locomotives with one, two or three vehicles OR Three or more locomotives and any number of vehicles have to run at reduced speed:

 

75mph for linespeed 90mph and above

 

60mph for 85mph and below

 

(same as running light engine)

 

and from the rulebook......

 

imagejpg1.jpg

 

These restrictions apply to locomotive-hauled trains formed of:

• mark 1 coaching vehicles

• mark 2 coaching vehicles

• mark 3 sleeper vehicles

• postal or parcel vehicles hauled by a locomotive (not including class 325 electric multiple-unit (EMU) vehicles).

 

no mention of reduced speeds for MK3 day coaches!

 

and the above restrictions do not apply to class 67s as they have very good brakes!!

 

its a minefield

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and the above restrictions do not apply to class 67s as they have very good brakes!!

 

its a minefield

 

Unless it's the Scottish sleeper locos with cast iron blocks....

 

Cheers,

Mick

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I only discovered the concept of 'flailing' thanks to the recent thread about K&WVR diesel galas, but now I'm noticing it all the time!

 

This website has lots of photos of strange HST (amongst others) formations. As the name suggests, the photos all seem to be taken at Totnes!

 

http://www.totnestrains.com/

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In BR days, when the EC sets were 8-car and XC ones 7-car, at line speed you could tell the difference...

by the brakes!

 

, and there has to be a allowance for a train running with one or more brake isolated. A train would be allowed to run with a certain percentage of its brakes isolated and if there was more isolated than normal, the speed of the train would also have to be reduced.

 

The speed's reduced for any brakes isolated, 10 below linespeed for one coach, and 20 below for two. 'At caution' beyond that

 

 

and the above restrictions do not apply to class 67s as they have very good brakes!!
 

 

67s have special dispensation to run at 100 light engine when on Thunderbird duties

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