What makes a rebuild of an existing loco/multiple unit a complete new class of loco/MU

[Bessie]

Sorry if this been asked before on a previous thread but with the likes of Class 69s, 230's and 769's being "built" from existing machines what makes them get a new TOPS classification versus say HSTs back in the day which were re-engined and retained their same numbers. We had class 57's from re-engined class 47's but the re-engined 73's became 73/9's rather than a new TOPS classification.

 

[swt_passenger]

Change of overall functionality drives a class change I think is the main answer.

A 769 is no longer just an EMU, but it’s not just become a straight DEMU either, so 2xx would not be appropriate - 750-799 has been introduced to cope with such bi-mode units.

AIUI locomotive classes correspond broadly to power bands, so maybe a re-engined 56 needs to go into a new range, but a 73 doesn’t?

A 230 didn’t have a real previous class, because it was an LU train, but as a DEMU 2xx is correct.

 

[D6975]

Class 30s became 31s when re-engined, but stayed in the same type 2 power band, so that theory doesn't hold water.
While class 47s re-engined became 57s, but also stayed in the same power band as 47s.
One class given a new number, the other not when re-engined in the same power range as the original.

 

[gingertom]

would I be right in saying that the VP185 engine was detuned to match the performance of the Valenta it replaced in the class 43? Would have made an interesting machine if left at full grunt, possibly necessitating a new TOPS number and enlarged coolers.

 

[D365]

At the end of the day, decisions on TOPS reclassification are entirely down to the owner of the vehicles and the regulatory bodies.

 

[themiller]

Class 73 locos are supposed to be 3rd rail electro-diesels but the CS 73s can no longer pick up from 3rd rail. I would have thought that they should have been allocated a class in the diesel loco series

 

[xotGD]

In the blue corner, Classes 37/9, 73/9 and 47601/901

In the red corner, Classes 29, 31, 57 and 69

Conclusion: Pass.

 

[CBlue]

Class 73 locos are supposed to be 3rd rail electro-diesels but the CS 73s can no longer pick up from 3rd rail. I would have thought that they should have been allocated a class in the diesel loco series

If their 3rd rail pickup ability is gone simply because the shoes have been removed, is that really justifying a full renumbering?

As far as I know GBRF have other 73/9's that can run on 3rd rail?

At the end of the day, decisions on TOPS reclassification are entirely down to the owner of the vehicles and the regulatory bodies.

Exactly. As much as some enthusiasts would love to renumber everything on TOPS into neat little groups (much like the ones who want to chop services about so they look tidy on a map), there's no practical reason why any vehicle owner should do so.

 

[Cowley]

In the blue corner, Classes 37/9, 73/9 and 47601/901

In the red corner, Classes 29, 31, 57 and 69

Conclusion: Pass.

Yes. I don’t think there’s any set parameters on this subject. As you say. Pass...

 

[Western Sunset]

And the class 70 (diesel) appeared in the seventies series (dc electrics) for, presumably, vanity reasons.

 

[randyrippley]

Class 30s became 31s when re-engined, but stayed in the same type 2 power band, so that theory doesn't hold water.
While class 47s re-engined became 57s, but also stayed in the same power band as 47s.
One class given a new number, the other not when re-engined in the same power range as the original.

At the time it was said in the specialist press that despite the type 4 power rating, the 57s were capable of type 5 freight haulage tasks so were deliberately given a type 5 class number to reflect this. Presumably they were judging the loco on tractive effort, not engine power.

When the 30s were reengined there was no significant change in performance

Class 73 locos are supposed to be 3rd rail electro-diesels but the CS 73s can no longer pick up from 3rd rail. I would have thought that they should have been allocated a class in the diesel loco series

They could if they put the pickup shoes back on

 

[themiller]

If their 3rd rail pickup ability is gone simply because the shoes have been removed, is that really justifying a full renumbering?

As far as I know GBRF have other 73/9's that can run on 3rd rail?

I believe that the ‘gubbins*‘ has been removed from within the locos thus rendering them impotent as far as 3rd rail is concerned.
*please excuse the technical jargon.

 

[millemille]

The National Technical Rules, in this case "Rail Industry Standard" RIS-3453-RST "Vehicle Registration, Marking and Numbering", define the how/what/why of vehicle numbering.

 

[JohnMcL7]

I believe that the ‘gubbins*‘ has been removed from within the locos thus rendering them impotent as far as 3rd rail is concerned.
*please excuse the technical jargon.

The third rail equipment has not been removed from the CS 73/9's, only the shoes have been removed (they were initially present on the rebuild - https://www.rmweb.co.uk/community/i...modifications/&do=findComment&comment=3768986) so they're still electro-diesels and could be returned to third rail if needed.

 

[themiller]

The third rail equipment has not been removed from the CS 73/9's, only the shoes have been removed (they were initially present on the rebuild - https://www.rmweb.co.uk/community/i...modifications/&do=findComment&comment=3768986) so they're still electro-diesels and could be returned to third rail if needed.

Sorry, that was a misinterpretation on my part of a statement that I read (can’t remember where, now) that the electrics had been removed when the new engines were fitted. The article didn’t say that the electrics had been replaced afterwards.

 

[507021]

I don't think there was ever any logic when it came to renumbering rolling stock.

The way the 769s have been numbered is utterly bizarre in my opinion.

 

[D365]

I don't think there was ever any logic when it came to renumbering rolling stock.

The way the 769s have been numbered is utterly bizarre in my opinion.

Cl319 + 450

 

[507021]

Cl319 + 450

Oh I get that completely.

I just find it odd the GWR units have their own subclass because they've retained their pick-up shoes, particularly when the 319/3s which had theirs removed when they came up here weren't given their own subclass to differentiate them from other 319s which still had theirs. The freight units should be the 769/9s, in my view, but it is what it is.

 

[grumpyoldman01]

This might just be a matter of timing

If you thank back to the early days of TOPS numbering, you had 47s/48s even though the only difference was the engine (48s had a Sulzer 'V' whereas 47s had twin bank ones), and the Peak's were split between 44s, 45s, and 46; consequently renumbering re-engines Brush 2s as 31s would make sense. However, at some point something changed, and so by the time the HSTs were built, if I remember correctly the fact that some had GEC traction motors wasn't even recognised, and the 314 and 315 EMUs were numbered consecutively even though some had GEC electrics and others Brush.

 

[jopsuk]

Re-built locos/MUs get a new class number if their owner/operators want it to have a new class number

 

[D365]

Oh I get that completely.

I just find it odd the GWR units have their own subclass because they've retained their pick-up shoes, particularly when the 319/3s which had theirs removed when they came up here weren't given their own subclass to differentiate them from other 319s which still had theirs. The freight units should be the 769/9s, in my view, but it is what it is.

The GWR units have other changes compared to the earlier orders. Not sure why they went for /9, but the GWR units have gone through their own testing and certification programmes.

 

[507021]

The GWR units have other changes compared to the earlier orders. Not sure why they went for /9, but the GWR units have gone through their own testing and certification programmes.

Fair enough, I wasn't aware of any other differences beyond the pickup shoes!

 

[Journeyman]

Class 73 locos are supposed to be 3rd rail electro-diesels but the CS 73s can no longer pick up from 3rd rail. I would have thought that they should have been allocated a class in the diesel loco series

As others have mentioned, they're still electro-diesels, although not much original equipment remains on board, and they're now crammed full of modern electronics. It's surprising they weren't given new class numbers, but they do retain certain grandfather rights in terms of technical standards, so retention of the same class number has something to do with that.

 

[plugwash]

Fair enough, I wasn't aware of any other differences beyond the pickup shoes!

My understanding is that the original 769 design was done for a customer who would never need third rail. So on the original 769 design the diesel replaced the third rail. The GWR variant had to support both at the same time which meant extra switchgear. I seem to remeber they also had to put the shoegear on the opposite end of the car from where it was originally on the 319s due to space constraints.

 

[D365]

My understanding is that the original 769 design was done for a customer who would never need third rail. So on the original 769 design the diesel replaced the third rail. The GWR variant had to support both at the same time which meant extra switchgear. I seem to remeber they also had to put the shoegear on the opposite end of the car from where it was originally on the 319s due to space constraints.

Indeed. You don’t want the risk of third rail back-feeding the engines, or vice versa!

 

[507021]

My understanding is that the original 769 design was done for a customer who would never need third rail. So on the original 769 design the diesel replaced the third rail. The GWR variant had to support both at the same time which meant extra switchgear. I seem to remeber they also had to put the shoegear on the opposite end of the car from where it was originally on the 319s due to space constraints.

Thanks for the clarification.