Class 41 HST prototypes

[daveyb]

Good morning all,

 

With Rails of Sheffield and the Science Museum group doing the Class 41 in OO soon, I have been looking at web sources to find out about the life size units. As a relative youth on this forum (of nearly 55 years😆) I remember seeing the prototype set and it has always been of interest.

 

What I'm not really finding on the net is how different they were to the production Class 43 units. How 'one off' were they? They used a similar power unit, but there are obvious differences in vent placements and other indicators of equipment positioning.

 

Were there any significant challenges with cooling the Valenta in the prototype? The Class 43 models had terrible issues even into the early 80s and the changed cooler groups and more than 10 years of experience saw issues on MML upon introduction of HST services. Were the prototype HST power cars ever trialled there from Derby?

 

Lastly, how bad was the condition of the power car that was scrapped in 1990? 

 

Thanks

[rodent279]

Others will no doubt correct me, but I think the prototype set was nowhere as intensively used as the production sets, and that is why the cooling issues arose.

[daveyb]

Probably a fair assessment of the use of a prototype, but also that is the point of trialling or at least bench cycling such key components.  I'm sure that there have been advances in testing methodology in the last 50 years.  Reading through some of the Class 91 selection memos in Traction magazine from a few editions ago it took a while to sink in (also the Class 60s and 92s had many issues to rectify ata similar era).

[woodenhead]

It's nothing new - Stanier's Jubillees were dogs out of the workshop and were outperformed by Patriots until the problems were sorted.

[Lemmy282]

It was inevitable that there would be changes between the prototype and production versions, bear in mind the HST was a "stop gap" because the APT project was running way behind schedule. It was only decided to go ahead with the HST in 1970, and the prototypes were running in 1972, so no prolonged testing period. They seemed to do most of their testing on the East Coast before moving to the Western mainline, I don't remember seeing them on the MML, fairly certain they never came to Sheffield at any rate.

The production versions came into service in 1975, so all in all a very quick prototype to production period. It must have been a very good basic design though to have lasted so long.

[Davexoc]

The cooling on the power cars was driven via a carden shaft off the engine via a viscous coupling. I don't think this really helped with the heat cycling on the Western, where it was Padd flat out to Reading, short stop then flat out to Swindon, and so on. With the viscous coupling, while sat in the station with the engine idling, the fan isn't really dealing with the heat build up from the last blast, only really working hard on departure. The youtube link below is one of several shows this, with the cooling fan almost drowning out a Valenta, and that takes some doing.....

 

https://www.youtube.com/watch?v=7haUvUi2nZk

 

[daveyb]

I don't think the prototypes did much testing on the MML, certainly very few pictures on the usual sources.  I did work experience at St Pancras and Cricklewood in 1984 and one of my 'jobs' was filling the new extra header tank on the HSTs on the new MML runs upon their arrival at St.P.  I seem to remember there were two different cooling sets and one was better than the other, and these sets went to Bounds Green each night.

 

The fleet was introduced quickly and fairly successfully showing the soundness of the original design but it would seem that areas were not tested to a point where weaknesses showed up - always a difficult thing to work out as it's trying to prove something you haven't seen!

 

I thought the main driver was the lack of cash for the ECML electrification that drove the HSDT, more so than the APT problems.  The APT was in its infancy when the HSDT prototypes were built and designed as a stop gap to the electrification of the ECML and GWML (I'm not sure the MML was being considered back then as it was in the era where GC and MML were being run down) with a view to either converting them or replacing them with OHLE pick up for lines other than the WCML with its curves needing thetilt mechanism.

 

I read a comment that the Deltic were a stop gap measure waiting for ECML wires, too.

 

That is certainly a wail on the Youtube clip!

[keefer]

Don't forget too, the APT concept was gas turbine - so as well as the general delays with the whole project, it was effectively killed off with the Oil Crisis in 1973.

So while the HST was a stop-gap anyway, it meant it would have to be one for longer until the electric APT could be designed.

Of course, the other good thing that came out of the HST was the Mk3 carriage which came into service (loco-hauled) in 1974/5, although only on top WCML trains.

Edited February 5 by keefer

[ISW]

On 01/02/2024 at 18:16, daveyb said:

Good morning all,

 

With Rails of Sheffield and the Science Museum group doing the Class 41 in OO soon, I have been looking at web sources to find out about the life size units. As a relative youth on this forum (of nearly 55 years😆) I remember seeing the prototype set and it has always been of interest.

 

What I'm not really finding on the net is how different they were to the production Class 43 units. How 'one off' were they? They used a similar power unit, but there are obvious differences in vent placements and other indicators of equipment positioning.

 

Were there any significant challenges with cooling the Valenta in the prototype? The Class 43 models had terrible issues even into the early 80s and the changed cooler groups and more than 10 years of experience saw issues on MML upon introduction of HST services. Were the prototype HST power cars ever trialled there from Derby?

 

Lastly, how bad was the condition of the power car that was scrapped in 1990? 

 

Thanks

 

Have you seen the 'bookazine' "HST - The Definitive Guide" from ~May 2022? It contains quite a bit of useful information.

 

Ian

[daveyb]

Thanks! I had not, but I have downloaded it for a spot of light reading.

[45125]

On 03/02/2024 at 17:30, Davexoc said:

The cooling on the power cars was driven via a carden shaft off the engine via a viscous coupling. I don't think this really helped with the heat cycling on the Western, where it was Padd flat out to Reading, short stop then flat out to Swindon, and so on. With the viscous coupling, while sat in the station with the engine idling, the fan isn't really dealing with the heat build up from the last blast, only really working hard on departure. The youtube link below is one of several shows this, with the cooling fan almost drowning out a Valenta, and that takes some doing.....

 

https://www.youtube.com/watch?v=7haUvUi2nZk

 

This form of drive will always been a problem. As some one fro Old Oak you will know all the other issues with the Marston cooler groups. Blocked rad panels both internally and externally, fan control not working correctly, loss of fan oil, coolant leaks from the S and J couplings and the panels not having a large surface area for the duty required in summer, the Serck cooler group performed better but suffered from blocked panels, loos of fan oil, secondary water pump drive problems. 

 

Most of these problems vanished with the fitting of Brush and Voith cooler groups, but these did have a few minor problems of their own.

 

Al Taylor