HST 'racing' a new GWR set

[keefer]

Would the Pendo/LH difference be down to Virgin seeking the use of 9xxx headcodes as showing priority over 'normal' Class 1 trains?

[caradoc]

3 hours ago, Zomboid said:

They were in different paths I assume, so the chance of hitting a double yellow would be different on the LHCS compared to the Pendo, so it could actually be signals.

 

But Pete the Elaner stated the trains were forming the same services (which also negates the 9xxx vice 1xxx headcode theory) ! I can't see any other explanation other than Enhanced Permissible Speeds. 

 

[Ken.W]

On 02/01/2021 at 14:55, Bomag said:

 

According to a few sources I have seen (including P5 combined) all engines on 800/801/802 are now rated at 940hp

 

I'm sure I've seen that clip before, and it was early on in the introduction of 800s on GWR, so would have been before the 800s engines were uprated, if indeed they have been.

 

AIUI, the GWR 800s were initially 750, but were later uprated to 900 but only up to 40mph. Only the GWR 802s were uprated to start with, as these were not part of the IEP order. I've seen nothing to suggest LNER sets were uprated. However, I doubt if anyone outside of Hitachi actually know what the situation is, as they seem highly reluctant to give out any information if they can help it (as evidenced in the Neville Hill inquiry).

When the LNER training was being set up, there were problems getting the relevant instructions from Hitachi, and even when the courses were going on there was still a dribble of information coming from them.

They're also very averse to making any changes at all to the sets, even this long after Neville Hill some issues of unnecessary distractions from the TMS are still unresolved, and after over a year they still won't put in extra luggage racks LNER have requested as being needed - hence the end seats with a vinyl cover over for luggage to be placed on them.

[Ken.W]

On 03/12/2020 at 00:45, Bomag said:

 

I have to say the driving on the GW HST was being a bit limp on the video. Compare that to a ECML HST from Newark, Grantham or Stevenage leaving on full bung

 

Looking at that video again, although it claims to show the difference in capability between an 800 and a HST, the HST does look slow in starting away to me, probably not more than notch 3 (of 5), and that's just an 8 car set, I was used to the 9 car EC sets and worked HSTs regularly from '86

 

The speeds I quoted earlier for the climb to Durham are personal experience and clearly show the 800 is significantly slower on diesel. However, where the 91 and HST figures are in service, loaded, the 800s an empty set on training runs - they were on electric on this section by the time they entered service.

 

17 hours ago, DY444 said:

I don't think the IET in diesel being faster off the mark is anything to do with distributed traction.  Rather it's to do with design decisions as to how the available diesel power was to be deployed in the IET and the need to limit traction motor current in the HST power cars at low speed. 

 

The IET traction software was set up specifically to give fast acceleration from rest on diesel with the engine power being deliberately restricted above a certain speed.  By contrast the HST power cars have a system which deliberately restricts traction motor current up to a certain speed.  I can't remember the numbers but it's something like a max current of 1500A up to 35mph ish.  Or put another way the IET was deliberately set up to accelerate rapidly up to about 40mph on diesel and the HST was deliberately constrained.  This is why in original trim the IET took off quickly and then quickly ran out of puff and the HST did the opposite.  The increase to 940hp has made most difference to the IET diesel performance at higher speeds as you'd expect.

 

The HST doesnt constrain power up to a certain speed then increase to full power (the 91 does this, as I posted earlier). The governor / load regulator simply limit power to the maximum rating of the motors, and then, as with any electric transmission, amps will gradually fall as speed increases.

It's possible to give them full power at quite low speed, which clearly isnt happening in this example

[DavidB-AU]

It was clearly staged and the HST was probably in notch 3. Took under a minute to see what an HST can really do.

 

 

 

And even on one engine seems to be able to match the GWR "test".

 

 

[DY444]

5 hours ago, Ken.W said:

The HST doesnt constrain power up to a certain speed then increase to full power (the 91 does this, as I posted earlier). The governor / load regulator simply limit power to the maximum rating of the motors, and then, as with any electric transmission, amps will gradually fall as speed increases.

It's possible to give them full power at quite low speed, which clearly isnt happening in this example

 

Fair enough, a bad choice of words on my part.  What I was getting at is that unlike on say a class 87 where the driver can play chicken with the traction motor overload relays by juggling the tap changer to extract maximum performance if the load and road conditions allow, on an HST the maximum motor current is constrained in a pre-determined way at lower speeds.  This, together with the deliberate decision to optimise the IET diesel performance for starting from rest, gives the HST an inherent disadvantage at low speeds.

 

As an aside does motor current fall gradually as speed increases on an AC motored electric transmission?  Not my area of expertise but I didn't think it did.

Edited January 4, 2021 by DY444

[Zomboid]

35 minutes ago, DY444 said:

an aside does motor current fall gradually as speed increases on an AC motored electric transmission?  Not my area of expertise but I didn't think it did.

The short answer is "yes", though the current Vs speed profile is quite different, they do have the same basic shape.

 

Edit - I don't know specifically about 80xs, the profiles I have seen are for AC motored stock which runs on the DC network. Since the drive part is the same there's no reason to think physics would be different, but I haven't seen any Hitachi profiles.

Edited January 4, 2021 by Zomboid