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GWR Class 769 information. (Units no longer with GWR - Off Lease March 23)

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cactustwirly

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How is capacity then maintained on the 2315 from Paddington to Oxford which uses the Greenford and Bourne End units and the 0030 from Paddington to Oxford if there are no 3-car Turbos and the Bourne End working becomes a 769?

That Basingstoke unit must go to Oxford for a reason.

I suspect the diagrams will be changed up so that the 0030 is operated by a class 800?
 
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Ladder23

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I grew up in Luton and remember the 319s being introduced fresh from the factory. Everything about this video is 'Just Wrong' to me - wrong sounds, wrong colours, wrong electrification (i.e. neither OLE nor 3rd rail), even wrong class number! It will take some getting used to.
Exactly the same as me!!! Luton also, so very used to these and the distinctive noise when pulling off and screaming at full speed ha. I miss them on our route, they don’t look right in the video.
 

AM9

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Definitely the transformer hum I'm thinking of, it resonates really nicely with the classic DC traction motor sound.
I think the 'transformer' noise is the 100Hz buzz that can be heard in the PMS when on ac only. It isn't there when on DC and wouldn't be there owhen running as a DEMU. The higher pitch tone (about 300Hz) is the traction electronics under the TS which can be heard from adjacent cars. The noise itself I suspect is magnetostriction from the various would components in the electronics. That is present whenever the traction system is loaded, whether under DC, ac or the 3 phase diesel genset. The traction system (motors and electronics) is likely to be quieter under diesel as there is about 30-40% less power available than throuigh line power collection.
 

Bletchleyite

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I think the 'transformer' noise is the 100Hz buzz that can be heard in the PMS when on ac only. It isn't there when on DC and wouldn't be there owhen running as a DEMU. The higher pitch tone (about 300Hz) is the traction electronics under the TS which can be heard from adjacent cars. The noise itself I suspect is magnetostriction from the various would components in the electronics. That is present whenever the traction system is loaded, whether under DC, ac or the 3 phase diesel genset. The traction system (motors and electronics) is likely to be quieter under diesel as there is about 30-40% less power available than throuigh line power collection.

Cheers. Having just played a couple of test tone YouTubes, it's the 300Hz tone I refer to. I just find it a really, really nice sound for some reason, it's almost like a violin and quite relaxing. It only seems to be 319s that have it - the very similar 321s don't, just the 100Hz buzz.
 

cactustwirly

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Cheers. Having just played a couple of test tone YouTubes, it's the 300Hz tone I refer to. I just find it a really, really nice sound for some reason, it's almost like a violin and quite relaxing. It only seems to be 319s that have it - the very similar 321s don't, just the 100Hz buzz.

I think I know what you mean, the 456s have it as well, despite having the same motors as the 455s.
I remember it's got something to do with the newer type of traction control system that the 321s (& 455s) don't have.
 

59CosG95

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I think I know what you mean, the 456s have it as well, despite having the same motors as the 455s.
I remember it's got something to do with the newer type of traction control system that the 321s (& 455s) don't have.
Indeed; 319s and 456s use GTO (Gate Turn Off) Choppers for traction motor control, while 314s, 315s, 317s, 318s, and all of Classes 320-322 (as built) have Thyristor control. 455s have more in common with 313s in this field, utilising camshaft control.

Early 3-phase AC drive units (Networkers, 323s, 373s, and also Class 92s ) used GTO Inverter control; every design since uses more efficient IGBT (Insulated Gate Bipolar Transistor) Inverters.
 

AM9

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Indeed; 319s and 456s use GTO (Gate Turn Off) Choppers for traction motor control, while 314s, 315s, 317s, 318s, and all of Classes 320-322 (as built) have Thyristor control. 455s have more in common with 313s in this field, utilising camshaft control.
That makes more sense. The 319s are the only MKIII class EMU that runs under both ac and DC. The DC-only 455s* and 456s have conventional EE507 motors/camshaft controllers and resistance banks as a traction system, (as had been standard SR and BR practice since 1935)! The ac-only MKIII EMUs (317, 318,320,321 & 322) had a thyristor control because they only ever ran on ac from the transformer. The 319s have a 750VDC bus which is either rectified ac from the transformer or DC direct from the 3rd rail collector shoes. In an earlier age, (MKI days?) they could then have a camshaft and resistor bank control, but as energy conservation and more performance was required in the late '80s, the GTO chopper enabled a more efficient control to be used. This is why they have been chosen for the diesel conversion.
The 300Hz sound comes from the magnetic components in the traction control - including the motor windings, when they carry high current pulses at six times the ac frequency (three positive and three negative), 50 x 2 x 3 Hz.
* the 455/9s have been modified and fitted with modern Vossloh 3phase motors and system.
 
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FGW_DID

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769943 'should' be making an appearance at Reading towards the end of this week. This will be GWR's first 769 to be delivered.
 

FGW_DID

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Is it all ready to be run or do they need further modifications?

RTR (AFAIK). Don't expect to see it in traffic straight away though, Drivers (Mainline & Depot) need to be trained up first!
 

Ladder23

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Why are these in progress 769‘s scattered amongst Wolverton, Crewe, and other places?
 

Bob Price

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There are now 7 of the 9 TfW ones delivered and they arrived in Thameslink colours for them to repaint. Training may be an issue as all has been stopped due to social distancing in the cabs.
 

JN114

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For GWR Wolverton has been the site doing bodywork corrosion repairs and repaint (as 319s), Loughborough are doing the 319 to 769 conversion mods. Crewe seems to be a storage intermediary; I’m guessing not masses of room at Loughborough for storing vehicles waiting mods.
 

Bob Price

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So do we think it will be a Loughborough to Reading move? Scrap that thought, they are being delivered by road to TfW and guess they will be to Reading.
 
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JN114

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I’d expect it to be Loughborough to Reading TCD, then spend a few weeks just on the depot getting engineering staff familiar, then engineering drivers etc etc

The Welsh ones went by road after track renewals somewhere in the Birmingham area invalidated the 769 gauging certificate - I don’t know though if that will preclude a Loughborough to Reading move, which I’d expect to go direct up the MML to Dudding Hill, across to Acton Wells then down the GWML from Acton.
 

Bob Price

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Could be. Nothing in the schedules for a Loughborough to Reading move this week as yet. If it does use that route it will pass the Slough cameras. Snaps to follow
 

Ladder23

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I would love to witness a move from wolverton!

I did notice one unit outside was painted and its since gone or been moved? I don't suppose that's left and I missed it?
 

aleggatta

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Well isn't this a whole lot of pedantry for the sake of it. It's a train and it moves, it has been branded 'tri mode' by the owners, who I'm sure don't really care about the technical accuracies and were more interested in making a bold statement to lease trains out.

What I'm interested in is how exactly they have set up the contactor arrangement to switch between 750/genset and what the earthing arrangements are, also if they have gone for fixed or retractable shoe ear (a first for a 31/76-9)
 

samuelmorris

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Well isn't this a whole lot of pedantry for the sake of it. It's a train and it moves, it has been branded 'tri mode' by the owners, who I'm sure don't really care about the technical accuracies and were more interested in making a bold statement to lease trains out.

What I'm interested in is how exactly they have set up the contactor arrangement to switch between 750/genset and what the earthing arrangements are, also if they have gone for fixed or retractable shoe ear (a first for a 31/76-9)
It's also incorrect, because tri-mode should really mean electric feed, diesel generator and battery power, as per the 756.
 
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