Question about Class 55 locomotive "Deltic"

tom73 · 12 Nov 2019

If this locomotive had been configured while still on the drawing board for 125mph running rather than 100mph (maybe with the 12-cylinder Paxman Valenta engines, running at 1,500 rpm and developing 2,250 bhp) rather than the 1,650 bhp engines they were eventually given would their replacement after just 16 years or so been considered necessary? Could they have remained until the advent of overhead electrification?
The replacement for the Class 55, the Class 43, looked good and could go faster but it was still a diesel just as the Class 55 was,

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hexagon789 · 12 Nov 2019

tom73 said:
If this locomotive had been configured while still on the drawing board for 125mph running rather than 100mph (maybe with the 12-cylinder Paxman Valenta engines, running at 1,500 rpm and developing 2,250 bhp) rather than the 1,650 bhp engines they were eventually given would their replacement after just 16 years or so been considered necessary? Could they have remained until the advent of overhead electrification?
The replacement for the Class 55, the Class 43, looked good and could go faster but it was still a diesel just as the Class 55 was,

The problem was both power and axle-loadings. At the time the HST was developed no single engine could produce the 4,500hp needed for sustained 125mph in a light enough loco. The solution was to split the power between two power cars which enabled light enough track loadings to satisfy the permanent way engineers.

Kestrel was 4,000 metric hp but it was heavier than its specificaction, even after swapping it's bogies for those of a Class 47.

delt1c · 12 Nov 2019

Design speed was actually 105mph

randyrippley · 12 Nov 2019

tom73 said:
If this locomotive had been configured while still on the drawing board for 125mph running rather than 100mph (maybe with the 12-cylinder Paxman Valenta engines, running at 1,500 rpm and developing 2,250 bhp) rather than the 1,650 bhp engines they were eventually given would their replacement after just 16 years or so been considered necessary? Could they have remained until the advent of overhead electrification?
The replacement for the Class 55, the Class 43, looked good and could go faster but it was still a diesel just as the Class 55 was,

The class 55 was designed in the 1950s. The Valenta didn't come into production until the 1970s, so no possibility of fitting it to a 55.
The Valenta was roughly based on the Ventura, as used in the class 29 and one class 42, but which by the early 1960s was only developing 1350 bhp out of a V12. So you'd need two V12 units to equal the power of a Peak or 47. Besides which Paxman engines had an awful reliability record especially in earlier use in the various modernisation plan type 1 locos.
Based on previous form, putting a Paxman engine into the HST was a heck of a gamble, whoever took the decision to do it was brave.

coppercapped · 12 Nov 2019

tom73 said:
If this locomotive had been configured while still on the drawing board for 125mph running rather than 100mph (maybe with the 12-cylinder Paxman Valenta engines, running at 1,500 rpm and developing 2,250 bhp) rather than the 1,650 bhp engines they were eventually given would their replacement after just 16 years or so been considered necessary? Could they have remained until the advent of overhead electrification?
The replacement for the Class 55, the Class 43, looked good and could go faster but it was still a diesel just as the Class 55 was,

I think your timeline is adrift!

Development of the Deltic engine started in 1947 and was first used on minesweepers in 1951. The prototype Deltic locomotive was built in 1955.

Development of Paxman's YJ engine, later the Ventura, started around 1956 and test running commenced in 1958, some ten years after the Deltic.

It would have been impossible to configure the Deltic locomotive body to take the Ventura engine as when the body was being designed the Ventura did not even exist.

In 1954/5, when the Deltic locomotive was being designed, there was little experience of designing locomotive bogies to run at 100mph, let alone 125mph. A reliable and safe 125mph locomotive bogie in 1955 would not have been possible.

The Class 43/HST bogies benefitted from the fundamental theoretical studies of wheelset and bogie behaviour carried out by Wickens and others at BR's Technical Centre at Derby in the mid-1960s. These studies made it possible for the Advanced Passenger Train to run at speeds of 150mph and for the 4-wheel Pacers to run stably at 75mph.

Your question is based on a misunderstanding of the times scales and therefore cannot be answered.

Helvellyn · 12 Nov 2019

Always thought it was a shame they couldn't be retained for the secondary ECML services that remained Class 47 hauled when the HSTs were introduced. Or possibly used on the MML. But I get they were a small class when BR was trying to standardise to as few classes as possible.

Spartacus · 13 Nov 2019

tom73 said:
If this locomotive had been configured while still on the drawing board for 125mph running rather than 100mph (maybe with the 12-cylinder Paxman Valenta engines, running at 1,500 rpm and developing 2,250 bhp) rather than the 1,650 bhp engines they were eventually given would their replacement after just 16 years or so been considered necessary? Could they have remained until the advent of overhead electrification?
The replacement for the Class 55, the Class 43, looked good and could go faster but it was still a diesel just as the Class 55 was,

Yes, that would have worked, but in addition they’d also have needed a flux capacitor. Don’t forget that the Deltics were a ruddy big step up, 3300hp from 2000hp Class 40s when first designed. Perhaps they could have been designed for 125mph if they’d used higher rated Napiers, but their reliability or cost of operating due to length between services and overhauls would have been prohibitive, as would the lack of 125mph stock or track.

kermit · 13 Nov 2019

Was an increase in line speed to 125mph also dependent on use of continuous welded rail rather than the jointed track still in use when the Deltics entered service? Not to mention improved signalling?

pdeaves · 13 Nov 2019

kermit said:
Not to mention improved signalling?

The HST was specially designed to stop from higher speeds within the existing signal spacing.

randyrippley · 13 Nov 2019

Spartacus said:
Yes, that would have worked, but in addition they’d also have needed a flux capacitor. Don’t forget that the Deltics were a ruddy big step up, 3300hp from 2000hp Class 40s when first designed. Perhaps they could have been designed for 125mph if they’d used higher rated Napiers, but their reliability or cost of operating due to length between services and overhauls would have been prohibitive, as would the lack of 125mph stock or track.

Its telling that the SuperDeltic was never built, despite I think three attempts at designing one. Hard to imagine that a pair of larger deltic engines would stay within gauge

hexagon789 · 13 Nov 2019

coppercapped said:
In 1954/5, when the Deltic locomotive was being designed, there was little experience of designing locomotive bogies to run at 100mph, let alone 125mph. A reliable and safe 125mph locomotive bogie in 1955 would not have been possible.

In 1955 the French had already managed over 200mph, twice

kermit said:
Was an increase in line speed to 125mph also dependent on use of continuous welded rail rather than the jointed track still in use when the Deltics entered service? Not to mention improved signalling?

No alterations to the signalling generally, the HST was specifically designed to be able to stop from 125mph in the same distance (it was proved to do better) as a vacuum, tread braked train from 100. The things that enabled this were - air braking, disc brakes and E70 electric brake control units.

Journeyman · 13 Nov 2019

Helvellyn said:
Always thought it was a shame they couldn't be retained for the secondary ECML services that remained Class 47 hauled when the HSTs were introduced. Or possibly used on the MML. But I get they were a small class when BR was trying to standardise to as few classes as possible.

Secondary services wouldn't have needed the high performance of the Deltics, so it wasn't possible to justify the cost of keeping a small nonstandard fleet.

swt_passenger · 13 Nov 2019

kermit said:
Was an increase in line speed to 125mph also dependent on use of continuous welded rail rather than the jointed track still in use when the Deltics entered service? Not to mention improved signalling?

I also read a while ago that up in the north east they even had to raise bridges, to allow the track to be properly ballasted to modern standards, before the Deltics could enter service. So they took advantage of that to lift many bridges high enough for electrification at the same time.

Merthyr Imp · 13 Nov 2019

Helvellyn said:
Always thought it was a shame they couldn't be retained for the secondary ECML services that remained Class 47 hauled when the HSTs were introduced. Or possibly used on the MML. But I get they were a small class when BR was trying to standardise to as few classes as possible.

They were used for a year or two on the services to York, Hull and Cleethorpes before the HSTs took them over. I seem to remember the 'Hull Executive' for a time was the fastest non-HST service in the country.

Here's a photo I took of 55007 at Cleethorpes in May 1979:

coppercapped · 13 Nov 2019

hexagon789 said:
In 1955 the French had already managed over 200mph, twice
SNIPPED

Have you seen photographs of the state of the track after these high speed runs?

30907 · 14 Nov 2019

coppercapped said:
Have you seen photographs of the state of the track after these high speed runs?

Thanks for the tipoff; I Googled french speed record 1955; no wonder SNCF waited 12 years before trying 125mph!
(The first link I could make work is this - scroll down for the pic:
https://www.railforums.co.uk/thread...est-verified-recorded-speed-in-a-mk-1.104370/)

hexagon789 · 14 Nov 2019

coppercapped said:
Have you seen photographs of the state of the track after these high speed runs?

Yes, but that was from doing over 300km/h, 200km/h would've been far more doable. Indeed West Germany started running at such a speed from 1962, Japan at 210 from 1964 and France at 200 from 1967.

70014IronDuke · 14 Nov 2019

Journeyman said:
Secondary services wouldn't have needed the high performance of the Deltics, so it wasn't possible to justify the cost of keeping a small nonstandard fleet.

A former BR engineer and friend did tell me that the Cl 55s had been under consideration for transfer to the MML in the late 70s. I don't know if this was merely a suggestion at a management meeting that was then ignored, or if any serious thought was given to the idea - potential costings, timings etc.

To be frank, it would be a surprise for the idea NOT to have been bandied about, but I suspect the costs of all the training and displacement for the time the locos would have been expected to remain in service prior to HSTs coming over anyway meant the idea was abandonned. Of course, 22 Deltics would have been too many for the MML in any case. I suppose they could have been put on NE - SW services too, but then there would not have been enough of them to make reliable schedule improvements. Would have been nice to hear them climbing the Lickey, or roaring through the tunnels out of St Pancras though.

Western Lord · 14 Nov 2019

randyrippley said:
Its telling that the SuperDeltic was never built, despite I think three attempts at designing one. Hard to imagine that a pair of larger deltic engines would stay within gauge

The engines would not have been physically larger, just higher rated.

ac6000cw · 14 Nov 2019

Western Lord said:
The engines would not have been physically larger, just higher rated.

Yes, turbocharged versions of the 18-cylinder supercharged engines in the class 55's

But also more diesel power means larger cooling systems to deal with the increased waste heat, and larger fuel tanks to maintain the range. You reach a point where the design gets too long and heavy to be sensible as a high-speed passenger loco.

(As an aside, that last point is what drove American freight railroads to eventually abandon the use of 4-axle diesel locos on intermodal trains in favour of 6-axle locos - as the power of the 4-axle locos increased progressively, they reached a point when the fuel tanks got too small to provide the range they needed on the long hauls).

43096 · 14 Nov 2019

70014IronDuke said:
A former BR engineer and friend did tell me that the Cl 55s had been under consideration for transfer to the MML in the late 70s. I don't know if this was merely a suggestion at a management meeting that was then ignored, or if any serious thought was given to the idea - potential costings, timings etc.

To be frank, it would be a surprise for the idea NOT to have been bandied about, but I suspect the costs of all the training and displacement for the time the locos would have been expected to remain in service prior to HSTs coming over anyway meant the idea was abandonned. Of course, 22 Deltics would have been too many for the MML in any case. I suppose they could have been put on NE - SW services too, but then there would not have been enough of them to make reliable schedule improvements. Would have been nice to hear them climbing the Lickey, or roaring through the tunnels out of St Pancras though.

The chronic unreliability of the 55s also counted against them, as well as the cost of maintaining them: at times availability struggled to be at 50%.

Don’t forget that BR was hoping to order more HST sets than the 95 it got, including a batch for the MML.

Clarence Yard · 15 Nov 2019

They did not suffer from "chronic unreliability" - they had the highest MPC (by a long way) of all the passenger diesels on ER for several years and their availability only suffered badly when the 1970's materials shortages kicked in and getting parts for smaller (in number) classes became a real issue, both in works and at depot.

As specialised locos, they needed a highly trained workforce at depots to keep them on the go and this really did count against them being redeployed. Personally, I don't think their move to York did them any favours at all and they really weren't best suited to stop start secondary express work. They worked better on, for example, the triple Edinburgh diagrams where you would get three trips out of them in 24 hours and then you kept them nice and warm, working at a fairly constant high speed thrash.

They were well worn when they were finally withdrawn, which wasn't a surprise considering the many hard miles they had done and also the curtailment of the HG overhaul programme a few years earlier. Towards the end of their days there were quite a few age related faults creeping in.

jimm · 15 Nov 2019

43096 said:
Don’t forget that BR was hoping to order more HST sets than the 95 it got, including a batch for the MML.

They also wanted some HSTs for TransPennine services - I think Modern Railways published a table showing all the routes that BR hoped to operate with HSTs and how many sets that would add up to in an issue at the end of 1975 or early in 1976, if anyone can track it down.

The Deltics were certainly pretty handy on their occasional excursions across the Pennines from York in their last few years and, not surprisingly, always seemed to go much better up the hills than the 47s and Peaks

43096 · 15 Nov 2019

jimm said:
They also wanted some for TransPennine services - I think Modern Railways published a table showing all the routes that BR hoped to operate with HSTs and how many sets that would add up to in an issue at the end of 1975 or early in 1976.

Something like 161 sets in total, rather than the 95 they actually got. There was an extra 18 for Cross-Country, 10 for the MML and 30 for Trans-Pennine and Edinburgh-Glasgow that were never built.

sprinterguy · 15 Nov 2019

jimm said:
They also wanted some for TransPennine services - I think Modern Railways published a table showing all the routes that BR hoped to operate with HSTs and how many sets that would add up to in an issue at the end of 1975 or early in 1976.

Off topic, but just for reference the original 1972 submission from the BRB was for 161 sets, formed thus:

27: Western Region, Paddington-Bristol/Swansea (27 built)
42: Eastern Region, Kings Cross-Leeds/Edinburgh (32+4 additional built)
16: Western Region, Paddington-Paignton/Plymouth/Penzance (14 built)
10: Midland Region, St Pancras-Nottingham/Sheffield (Not proceeded with)
18: Cross-country North East-South West (18 sets built)
18: Cross-country North West-South Coast (Not proceeded with)
30: Regional, Transpennine North, Edinburgh-Glasgow and possibly others (Not proceeded with)

EDIT: 43096 beat me to it!

Shaw S Hunter · 15 Nov 2019

Clarence Yard said:
They did not suffer from "chronic unreliability" - they had the highest MPC (by a long way) of all the passenger diesels on ER for several years and their availability only suffered badly when the 1970's materials shortages kicked in and getting parts for smaller (in number) classes became a real issue, both in works and at depot.

As specialised locos, they needed a highly trained workforce at depots to keep them on the go and this really did count against them being redeployed. Personally, I don't think their move to York did them any favours at all and they really weren't best suited to stop start secondary express work. They worked better on, for example, the triple Edinburgh diagrams where you would get three trips out of them in 24 hours and then you kept them nice and warm, working at a fairly constant high speed thrash.

They were well worn when they were finally withdrawn, which wasn't a surprise considering the many hard miles they had done and also the curtailment of the HG overhaul programme a few years earlier. Towards the end of their days there were quite a few age related faults creeping in.

You are quite right to say that they were not unreliable as such. They were however rather expensive to maintain. Of course sustained running was better for them but that is true of all diesels! But the Deltics had the added complexity of opposed pistons and the phasing gears. I suspect that many senior maintenance engineers breathed a huge sigh of relief when they were withdrawn.

Cowley · 15 Nov 2019

Shaw S Hunter said:
You are quite right to say that they were not unreliable as such. They were however rather expensive to maintain. Of course sustained running was better for them but that is true of all diesels! But the Deltics had the added complexity of opposed pistons and the phasing gears. I suspect that many senior maintenance engineers breathed a huge sigh of relief when they were withdrawn.

(Apart from 31s.

)

Shaw S Hunter · 15 Nov 2019

Cowley said:
(Apart from 31s. )

Not for nothing were they known as "Peds"! [/OT]

47271 · 15 Nov 2019

sprinterguy said:
Off topic, but just for reference the original 1972 submission from the BRB was for 161 sets, formed thus:

27: Western Region, Paddington-Bristol/Swansea (27 built)
42: Eastern Region, Kings Cross-Leeds/Edinburgh (32+4 additional built)
16: Western Region, Paddington-Paignton/Plymouth/Penzance (14 built)
10: Midland Region, St Pancras-Nottingham/Sheffield (Not proceeded with)
18: Cross-country North East-South West (18 sets built)
18: Cross-country North West-South Coast (Not proceeded with)
30: Regional, Transpennine North, Edinburgh-Glasgow and possibly others (Not proceeded with)

EDIT: 43096 beat me to it!

So, just out of interest, if the 10 originally intended for the St Pancras services were never built, where did the Midland Main Line sets come from?

Peter Mugridge · 16 Nov 2019

47271 said:
So, just out of interest, if the 10 originally intended for the St Pancras services were never built, where did the Midland Main Line sets come from?

They were from the East Coast, displaced by the 91s.

Question about Class 55 locomotive "Deltic"

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