Is this acceptable?

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jonb

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Just noticed this whilst checking my train home on the 'one' website, surely they cant be kidding............

18:30 London Liverpool Street to Norwich due 20:26
This train is run short formed with 4 carriages.

This is due to an earlier train failure.

this train will be formed with a 4 car emu set instead of a loco hauled set.

Message received: 12/06/2006 at 15:19:25

Scheduled Expected Station
18:30 18:30 London Liverpool Street
19:23 19:23 Colchester
19:40 19:40 Ipswich
19:51 19:51 Stowmarket
20:03 20:03 Diss
20:26 20:26 Norwich
 
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Julian G

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jonb said:
Just noticed this whilst checking my train home on the 'one' website, surely they cant be kidding............

18:30 London Liverpool Street to Norwich due 20:26
This train is run short formed with 4 carriages.

This is due to an earlier train failure.

this train will be formed with a 4 car emu set instead of a loco hauled set.

Message received: 12/06/2006 at 15:19:25

Scheduled Expected Station
18:30 18:30 London Liverpool Street
19:23 19:23 Colchester
19:40 19:40 Ipswich
19:51 19:51 Stowmarket
20:03 20:03 Diss
20:26 20:26 Norwich
OoOo
317!! :razz:
No it's not acceptable and i hope a Stansted Express Unit will be allocated to the Service
 

Tomnick

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Well it's not the first time! I'm sure the Norwich farmers won't be too impressed, but I'm sure they'd prefer it to no train, a packed following service, or even a bus.
 

jonb

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True but 18.30 right in the peak - Nice! wouldnt like to be on that one home. As for 360's during the day theres plenty lying about at Clacton/Ilford/Colchester........
 

ChrisCooper

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Nick W said:
Yeah unless the linespeed goes up to 110mph, a 360 or 321 will always beat a 90 hauled, Sad I think.
A 321 won't be a 90. On basic power-weight ratio you're talking about 10.5hp/t for the 321, wheras a 90 with 8 Mk3s and a DVT is just over 12hp/t. Timings back this up aswell. The 321s will have an advantage up to a certain speed, but then it's acceleration will start falling off just as the 90 is really getting going (they don't give maximum tractive effort until 87mph, wheras the 321s will do so much lower). At 100mph, the 321 will be almost flat out, but the 90 will still have a good 10mph to spair. The 90s do well on the braking front aswell with powerful rheostatic braking on the loco. Oviously on a short, start stop run, the 321 would win easily, but with a half decent gap between stations the 90 will start gaining the advantage. 317s, which usually substitute on the Norwich runs (since CSR isn't provided north of Ipswich and the 321s don't have NRN) are even slower than the 321s.
 

David

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AlexS said:
Yars, but do the 90s not have to accelerate *much* slower so as not to exert too much force on the coupling?
Debatable that. After all, 90s can keep to 125mph times on KX - Leeds service because of their faster acceleration.
 

matt

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The 90 can also keep to Voyager timings on the Birmingham to Manchester route
 

O L Leigh

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Just to pick up a few points.

While Cl321's used to be the EMU of choice to deputise on London-Norwich runs, this has fallen by the wayside. I'm not entirely sure why Cl317's took over this role but, with last year's summer timetable and the end of loaning units out to c2c and Thameslink, there seemed to be units to spare. These were stabled out at Colchester and operated by Mainline traincrew from the same location. Since the end of that timetable, the requirement for Cl317's on the WA division has increased. Therefore, I would be very surprised if there was still a specific allocation of standby units (although we do keep at one on standby at Liv St should the need for it arise).

There are technical issues over the choice of substitute. Currently, Cl360's are not cleared to operate north of East Suffolk Junction, which puts their northernmost limit at Ipswich. Like the Cl321's, Cl317's are fitted with CSR only and do not carry NRN equipment. However, I believe that the real deciding factor is down to the traction knowledge of the Mainline crews that are expected to operate them. They "sign" Cl317's because of the pool of substitute units used last summer, but I don't think that they "sign" Cl321's.

As for the relative acceleration of a Cl90 compared to other traction combinations, this is a complex topic and not just down to maximum speed or power-to-weight ratios. Mk2's and Mk3's were never designed with push-pull operation in mind. Therefore, there is an amount of "give" in the couplings. This isn't to much of a problem when pulling, but it requires careful driving when pushing to avoid any stressful or uncomfortable "snatches", meaning that they have to accelerate gradually. Either way, an EMU is certainly capable of maintaining Cl90 timings.

The IC225 sets are the only trains designed from the outset for push-pull operation and, from my experience riding them, it seems that the operation of the Cl91 and the train's brakes have been carefully tuned so that they work together. It always seemed to me that the train's brakes were bled out slowly rather than the air being dumped in one huge gasp, while the Cl91 gently applied pressure. It was always possible to tell when the Cl91 had been swapped out for a Cl90, as there was always a hard thud from the back as the loco seemed to be trying to accelerate hard against the train's brakes (although they may have improved the situation since the mid 1990's when I last experienced this form of traction). Once the brakes were all bled out, the Cl90 would then accelerate the train in short order up to, presumably, 110mph, and almost certainly attaining that speed more quickly than would have been the case with a Cl91 providing the motive power.

HTH

one TN
 
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