How powerful were Modernization Era Diesel-Electrics and Hydraulics?

[Threepea51]

Hi, just wanted to ask a quick question regarding some modernization era diesels. I'm trying to modify the physics of these locomotives in Train Simulator Classic 2024 because currently the Class 52 model can go 100 mph pulling 20 coaches, which is something I don't even think a Deltic could do lol

How fast would these following BR Classes top out at pulling 10 Mk1 Carriages on level track?
Class 42/43
Class 44-46s
Class 47
Class 50
Class 52 Westerns
Class 55 Deltics

 

[norbitonflyer]

How fast they could go is not necessarily the same as how fast they were allowed to go. From memory, I believe most of the classes you asked about were limited to 90mph, with the 50s and Deltics allowed 100.

 

[Cowley]

How fast they could go is not necessarily the same as how fast they were allowed to go. From memory, I believe most of the classes you asked about were limited to 90mph, with the 50s and Deltics allowed 100.

Just to add that the 47s were 95mph apart the original batch of 47/7s which were rated at 100mph for the Edinburgh - Glasgow push pull services.

 

[Threepea51]

How fast they could go is not necessarily the same as how fast they were allowed to go. From memory, I believe most of the classes you asked about were limited to 90mph, with the 50s and Deltics allowed 100.

Well at some point or another they had to have gone faster than 90 mph. They might've been limited to 90 but I doubt they're top speed was 90. Like how the Deltics could reach well above 100 mph despite having a "top speed" of 100 mph

 

[hexagon789]

Hi, just wanted to ask a quick question regarding some modernization era diesels. I'm trying to modify the physics of these locomotives in Train Simulator Classic 2024 because currently the Class 52 model can go 100 mph pulling 20 coaches, which is something I don't even think a Deltic could do lol

How fast would these following BR Classes top out at pulling 10 Mk1 Carriages on level track?
Class 42/43
Class 44-46s
Class 47
Class 50
Class 52 Westerns
Class 55 Deltics

Design speed and actual achievable speed are of course different things.

Hydraulic transmission is also less efficient than electric generally, at converting engine power to usable traction power.

I'm quite interested in train performance generally, so I've read many books and articles on such matters.

Going off that, the maximum speeds I'm aware of that have been achieved by the classes you list are:

42/43, these were designed for 90mph, however the 42s experienced riding issues early on so were restricted to 80mph pending rectification. Nevertheless, some of the class were recorded topping 100mph on trains such as The Bristolian.

44-46s. The 44s had a poor reputation hence being largely restricted to freight from early on, the 45s were well liked and could outperform a 47 due to having more field diverts providing better acceleration throughout the speed range. 46s had a reputation as being notably weaker than 45s. 45s would top 100 easily, not so sure on 46s.

47s, obviously they were derated, so while in early years they could give Deltics a run for money on the more stopping ECML trains, afterwards they were notably more sluggish particularly above 80mph. The highest recorded speed I'm aware of is 115mph on 7 coaches.

52s, good at getting going and with heavy loads but the specific hydraulic transmission ratios used weren't well matched to the torque curves of the engine, consequently a Western nearing its overhaul could struggle to achieve its rated 90mph. A healthy one would touch 100 though, there are a few records of that in their early days; much less so in their last years.

55s, well so much power in a very light loco and completely unlike anything before in terms of performance, other than getting moving from a stand theory performance exceeds all the other classes mentioned. They were maintenance heavy, but would easily take 12/13 coaches to 100mph. Fastest speed I'm aware of is 125mph, albeit down Stoke Bank, but there are plenty of records of them topping 110mph in their later years when HSTs had ousted them from the top expresses and they were relegated to the York semi-fast and Hull services primarily.

 

[Shaw S Hunter]

The problem here is the OP talks about speeds on level track. Many here will be able to relate their own stories about timing trains running at above their official maximum speed but you can be sure almost all of these will have been on downhill stretches. To get a genuine answer to the question as posed you would probably need access to records of test runs conducted by the RTC.

 

[hexagon789]

Just to add that the 47s were 95mph apart the original batch of 47/7s which were rated at 100mph for the Edinburgh - Glasgow push pull services.

Only from May 1984, only on the E&G and only with special maintenance.

The 100mph authorisation was 'officially' rescinded if the maintenance lapsed and they would normally diagram such a loco on an Aberdeen or occasionally Highland Line working in such a case, not that drivers always paid that attention of course!

Performance was worse after 1984 as one (of the three) sets of field diverts was removed to reduce the motor current at high speed and reduce flashover risk. Thus, not without irony, a 47/7 would actually struggle to achieve 100mph more so than an unmodified 47/4!

It was only perhaps less noticeable due to the lightweight formations used.

The problem here is the OP talks about speeds on level track. Many here will be able to relate their own stories about timing trains running at above their official maximum speed but you can be sure almost all of these will have been on downhill stretches. To get a genuine answer to the question as posed you would probably need access to records of test runs conducted by the RTC.

The Railway Performance Society holds scores of logs and the Railway Magazine has been publishing logs and articles on train performance almost since its earliest publications.

 

[Threepea51]

Design speed and actual achievable speed are of course different things.

Hydraulic transmission is also less efficient than electric generally, at converting engine power to usable traction power.

I'm quite interested in train performance generally, so I've read many books and articles on such matters.

Going off that, the maximum speeds I'm aware of that have been achieved by the classes you list are:

42/43, these were designed for 90mph, however the 42s experienced riding issues early on so were restricted to 80mph pending rectification. Nevertheless, some of the class were recorded topping 100mph on trains such as The Bristolian.

44-46s. The 44s had a poor reputation hence being largely restricted to freight from early on, the 45s were well liked and could outperform a 47 due to having more field diverts providing better acceleration throughout the speed range. 46s had a reputation as being notably weaker than 45s. 45s would top 100 easily, not so sure on 46s.

47s, obviously they were derated, so while in early years they could give Deltics a run for money on the more stopping ECML trains, afterwards they were notably more sluggish particularly above 80mph. The highest recorded speed I'm aware of is 115mph on 7 coaches.

52s, good at getting going and with heavy loads but the specific hydraulic transmission ratios used weren't well matched to the torque curves of the engine, consequently a Western nearing its overhaul could struggle to achieve its rated 90mph. A healthy one would touch 100 though, there are a few records of that in their early days; much less so in their last years.

55s, well so much power in a very light loco and completely unlike anything before in terms of performance, other than getting moving from a stand theory performance exceeds all the other classes mentioned. They were maintenance heavy, but would easily take 12/13 coaches to 100mph. Fastest speed I'm aware of is 125mph, albeit down Stoke Bank, but there are plenty of records of them topping 110mph in their later years when HSTs had ousted them from the top expresses and they were relegated to the York semi-fast and Hull services primarily.

Wow! Thanks for the information! Very helpful and appreciated!

I always thought the 45s could reach around 90-ish tops, but didn't expect that they could reach 100 considering they weigh the same, if not more than the 40s

 

[Shaw S Hunter]

The Railway Performance Society holds scores of logs and the Railway Magazine has been publishing logs and articles on train performance almost since its earliest publications.

Very true. But how much effort is made to calculate in a scientific way what the balancing speed would be for a particular loco or type with different loads on different gradients. Enthusiast logs would often attempt to make allowances for passenger loads, adverse signals, etc but I don't recall seeing the above calculations worked out and presented in a user-friendly table. But you can be sure that data from official test runs would have been used in such a way because otherwise what was the point?

 

[hexagon789]

Wow! Thanks for the information! Very helpful and appreciated!

I always thought the 45s could reach around 90-ish tops, but didn't expect that they could reach 100 considering they weigh the same, if not more than the 40s

The 45s are heavier yes, but testing when new, anecdotal evidence and performance logs bear out their ability to exceed the hallowed 'ton' (100mph).

They have five fields diverts at 30, 40, 50, 60 and 70mph; this allows full generator output to be available right up to maximum speed. A 40 meanwhile, asides from having 500hp less at engine, cannot keep up its output to its rated 90mph and indeed even new many would struggle to touch 90mph with even modest loads.

Very true. But how much effort is made to calculate in a scientific way what the balancing speed would be for a particular loco or type with different loads on different gradients. Enthusiast logs would often attempt to make allowances for passenger loads, adverse signals, etc but I don't recall seeing the above calculations worked out and presented in a user-friendly table. But you can be sure that data from official test runs would have been used in such a way because otherwise what was the point?

Not in easily readable tables, no. Data on balancing speeds does exist though.

Some BR documentation lists these and I have read balancing speeds in some articles in the Railway Magazine P&P column and in Railperf's Milepost.

 

[matchmaker]

As a rough and ready calculation (mileposts and second hand on my watch!) I timed a pair of 50's on a Glasgow - London service at 107mph. From what I've read, the 40s were notoriously sluggish. Gerry Fiennes couldn't wait to get rid of them and introduce the Deltics. They went to the WCML where outright speed wasn't an issue, however a Coronation or Princess Royal would apparently run rings round them on the climbs.

 

[Harvester]

From what I've read, the 40s were notoriously sluggish. Gerry Fiennes couldn't wait to get rid of them and introduce the Deltics. They went to the WCML where outright speed wasn't an issue, however a Coronation or Princess Royal would apparently run rings round them on the climbs.

A perfect example of this was on the down ‘Midday Scot’ in 1964 on a run recorded from the footplate by O.S. Nock. The class 40 (D322) had to come off at Crewe due to a water tank leak, and was replaced by 46228 Duchess of Rutland. The Duchess was commandeered fully prepared as it was waiting to take over a later train, and set off with 12 coaches (455 tons gross) on type 4 timings. The 151 minute schedule from Crewe to Carlisle was run in 141 minutes 30 seconds a gain of nearly 10 minutes. However the tender tank was almost empty on arrival at Carlisle, and an extended water stop lost most of the time gained!

 

[norbitonflyer]

I understand the most famous 100mph run by a 46 involved some special adaptations.

 

[jfollows]

They have five fields duvets at 30, 40, 50, 60 and 70mph; this allows full generator output to be available right up to maximum speed. A 40 meanwhile, asides from having 500hp less at engine, cannot keep up its output to its rated 90mph and indeed even new many would struggle to touch 90mph with even modest loads.

The concept is interesting but you may want to edit your post!

 

[hexagon789]

The concept is interesting but you may want to edit your post!

Pesky autocorrect!

 

[Threepea51]

Pesky autocorrect!

What about the Class 50s? How did they perform with 10-ish coaches?

Also I fixed the physics of the engines you told me the performance of, and I got a Peak to reach 98 mph on level track hauling 11 Mk1s and I got a Deltic to reach 108 mph with 13 MK1s. I think these should be accurate performance figures lol

 

[Magdalia]

How fast would these following BR Classes top out at pulling 10 Mk1 Carriages on level track?

There is some relevant information in this recent discussion:

The effect of ETH-AirCon on locomotive performance, with an emphasis on classes 33, 47/4, 50 and 52.

There's been reference to the greater installed horsepower of 47s over 40s and the advantage of the former in also having ETH; but didn't ETH reduce the drawbar horsepower available? mods note - split from this thread...

www.railforums.co.uk

The Railway Performance Society holds scores of logs and the Railway Magazine has been publishing logs and articles on train performance almost since its earliest publications.

For high speed performance on level track two of the best routes are the Plain of York (north of York towards Thirsk) and the Somerset Levels (around Highbridge and Bridgewater), both of which have long stretches of uninterrupted level track.

 

[Snow1964]

Also I fixed the physics of the engines you told me the performance of, and I got a Peak to reach 98 mph on level track hauling 11 Mk1s and I got a Deltic to reach 108 mph with 13 MK1s. I think these should be accurate performance figures lol

It is not so much the power of the diesel unit, all would get up to a fair speed given a long enough time, and enough miles.

The real problem was the rapid drop off of acceleration rate as dc motors get near their top speed, as the magnet coils become too strong and the spinning rotor and coils are not pulled round by the magnets, but rotate so quickly they start the catch up the opposing one in front. (ok not in scientific terms, but easier to explain). So the ability the weaken the magnetic field at speed is big factor.

Typically the class 47 (which was everywhere in 1970s) would accelerate to about 85mph, then seem to take an eternity to edge close to the 95mph max. The acceleration graph almost flat lines at those last few mph

 

[Richard Scott]

I understand the most famous 100mph run by a 46 involved some special adaptations.

96mph was actual speed I believe!!

The 45s are heavier yes, but testing when new, anecdotal evidence and performance logs bear out their ability to exceed the hallowed 'ton' (100mph).

They have five fields diverts at 30, 40, 50, 60 and 70mph; this allows full generator output to be available right up to maximum speed. A 40 meanwhile, asides from having 500hp less at engine, cannot keep up its output to its rated 90mph and indeed even new many would struggle to touch 90mph with even modest loads.

45s also have a voltage raise on the generator at high speeds, coming in at about 75mph so overcomes the higher back emf from traction motors at this speed. Could cause generator issues and if one was going to fail, likely would do so when this happened as voltage rose from around 560V to 900V or so. This would allow a 45 to achieve a higher top speed than a 46. Definitely recorded one at 97mph but was on a liad of about 12 mark 1s.
Believe 5th divert actually comes in at 62mph, first one around or just under 25mph (they certainly will take the first divert on a heritage line with driver sticking to 25mph limit).
Apart from Deltics 50s were the locos to have for interesting speeds, have had them well over 110mph on many occasions and 116mph been reported by a number of different people (one being a driver on his last turn before retirement taking 50021 through Maidenhead at said speed and sticking two fingers up to the official with the speed gun, his story so unsubstantiated).

 

[hexagon789]

Believe 5th divert actually comes in at 62mph, first one around or just under 25mph (they certainly will take the first divert on a heritage line with driver sticking to 25mph limit).

Interesting, the speeds I outlined are from official documents but in reality the speeds vary loco to loco of course; I remember many 66 drivers in the psst commenting how variable the traction motor transition is on that class and they are a good bit newer than a 45! Similarly the speed at which weak field came in on 87s also apparently varied significantly enough loco to loco, one member of the class reputedly refused to weak field at anything less than 90mph!

Interestingly, going back to Sulzers, 62mph is actually the 'official' cut in speed of the third and final divert on a 47, first divert is supposed to be 26mph.

 

[D Mylchreest]

Hi, just wanted to ask a quick question regarding some modernization era diesels. I'm trying to modify the physics of these locomotives in Train Simulator Classic 2024 because currently the Class 52 model can go 100 mph pulling 20 coaches, which is something I don't even think a Deltic could do lol

How fast would these following BR Classes top out at pulling 10 Mk1 Carriages on level track?
Class 42/43
Class 44-46s
Class 47
Class 50
Class 52 Westerns
Class 55 Deltics

I'm no mathematician, so I can't do the sums myself, but I do remember reading a solution to the problem the OP has. The problem however is that I can't remember where I read it. Perhaps someone can help.

 

[70014IronDuke]

Design speed and actual achievable speed are of course different things.
...

44-46s. The 44s had a poor reputation hence being largely restricted to freight from early on,

Poor reputation? Can you put meat on that, please?
Perhaps in their early days the original steam heat boiler caused failures - but that occured with almost all steam-heat locos. And, of course, they were rated only 2,300 HP (no intercooler, as I'm sure you know). But I'd bet no driver noticed that when climbing Shap or Beattock vs a Class 8, and they surely performed better than a Cl 40.

I was under the impression they were sent to Toton to work mineral trains merely because they were a non-standard class. And at Toton they had an excellent record of (IIRC) c 45,000 miles per casualty, something like four times better than the 45 and 47. (Not sure about a freight only 47, would have been better than the boiler fitted.)

45s would top 100 easily, not so sure on 46s.

"easily" ? They could get to 100 ok, not sure how much they could top it without a long downgrade, such as on the down into Bedford. Like you, I'm blank on the 46s. Someone must have logs when they were regulars on the ECML.

47s, obviously they were derated, so while in early years they could give Deltics a run for money on the more stopping ECML trains, afterwards they were notably more sluggish particularly above 80mph. The highest recorded speed I'm aware of is 115mph on 7 coaches.

A 47/4 would have no problem reaching 100 and a bit more between Bristol Parkway and Paddington if the driver was prepared to give it a go. This with 10 or maybe 11 on. I'd guess the same applied to the relevant sections of the ECML, eg Darlington - York, and especially down Stoke, of course.

 

[Rescars]

This may be straying a bit, but I think I have read somewhere that the Southern's pioneer diesels 10201 and 10202 were originally specified with a top speed of 110mph, rather than 90mph, before their gear ratios were altered to improve tractive effort.

 

[Magdalia]

I'm no mathematician, so I can't do the sums myself, but I do remember reading a solution to the problem the OP has. The problem however is that I can't remember where I read it. Perhaps someone can help.

The mathematical solution exists in theory, the problem is obtaining accurate measurements. The advantage of using balanced speed on level track is that it eliminates some of the measurement errors.

 

[Richard Scott]

"easily" ? They could get to 100 ok, not sure how much they could top it without a long downgrade, such as on the down into Bedford. Like you, I'm blank on the 46s. Someone must have logs when they were regulars on the ECML.

A 47/4 would have no problem reaching 100 and a bit more between Bristol Parkway and Paddington if the driver was prepared to give it a go. This with 10 or maybe 11 on. I'd guess the same applied to the relevant sections of the ECML, eg Darlington - York, and especially down Stoke, of course.

In which case there is no reason to doubt a 45 would also reach 100mph easily with its superior electrical equipment, which would compensate for slightly lower power and increased mass. I'm fairly sure a 45 starts to unload at a similar speed to a 47.
Heard old drivers say that they reached an indicated 100mph on many occasions with a 45.

 

[Deepgreen]

55s, well so much power in a very light loco and completely unlike anything before in terms of performance, other than getting moving from a stand theory performance exceeds all the other classes mentioned. They were maintenance heavy, but would easily take 12/13 coaches to 100mph. Fastest speed I'm aware of is 125mph, albeit down Stoke Bank, but there are plenty of records of them topping 110mph in their later years when HSTs had ousted them from the top expresses and they were relegated to the York semi-fast and Hull services primarily.

Yes, and the very close similarity of that to 'Mallard' at 126mph at the same location is noteworthy. Talk of the 45s is interesting as I think they had the highest tractive effort of all the BR-era diesels, at 72,000lb. That doesn't affect top speed, of course, but it can affect the time taken to reach it in poor conditions. By contrast the highest steam TEs were around 40,000lb (43,000lb for the 2-8-2 P2s).

Hi, just wanted to ask a quick question regarding some modernization era diesels. I'm trying to modify the physics of these locomotives in Train Simulator Classic 2024 because currently the Class 52 model can go 100 mph pulling 20 coaches, which is something I don't even think a Deltic could do lol

How fast would these following BR Classes top out at pulling 10 Mk1 Carriages on level track?
Class 42/43
Class 44-46s
Class 47
Class 50
Class 52 Westerns
Class 55 Deltics

I would think a 'Deltic' could actually get to 100mph with 20 coaches on level track, it would just take longer. I haven't done the maths, but at 3,300hp it seems possible as a gut feeling.

 

[D Mylchreest]

The mathematical solution exists in theory, the problem is obtaining accurate measurements. The advantage of using balanced speed on level track is that it eliminates some of the measurement errors.

I think the theory would inform the design process, I'd be very surprised if it didn't. I would imagine that the design office would be given a set of requirements including such as speed on a (or more) given incline(s) with a given load or loads and then would come up with a diagram for their proposed locomotive. This would then form the basis for discussions between departments.
Whether the proposal would be taken forward is another matter, as is whether the design would actually meet the requirements when actually in service. In retrospect it's clear that most (but not all) of the BR Modernisation Plan Locomotives left a lot to be desired as did some later ones like the D1600 (Class 47) engines. This is particularly true in the area of reliability. But there was nothing else and BR had to move on from steam regardless.

 

[Magdalia]

I think the theory would inform the design process, I'd be very surprised if it didn't. I would imagine that the design office would be given a set of requirements including such as speed on a (or more) given incline(s) with a given load or loads and then would come up with a diagram for their proposed locomotive.

For the modernisation plan locomotives that's not how it worked. The process was much more empirical than theoretical. The specification was in parameters such as power unit output and axle load, not performance. The British Transport Commission (BTC) didn't find out what the locomotives could do until they put them on trains including tests with dynamometer cars, in the same way as what had happened with steam locomotives. Some of the results of these test were published by the BTC in Performance and Efficiency Test Bulletins.

Whether the proposal would be taken forward is another matter, as is whether the design would actually meet the requirements when actually in service.

And some of the modernisation plan locomotives did not get beyond the first order.

 

[Sun Chariot]

Talk of the 45s is interesting as I think they had the highest tractive effort of all the BR-era diesels, at 72,000lb

That TE figure seems steep. DerbySulzers site quotes:
Maximum Tractive Effort at rail (Class 45/46): 55,000lbs

class 44 class 45 class 46 details

Echoed by the info on Wikipedia.

 

[hexagon789]

Poor reputation? Can you put meat on that, please?
Perhaps in their early days the original steam heat boiler caused failures - but that occured with almost all steam-heat locos. And, of course, they were rated only 2,300 HP (no intercooler, as I'm sure you know). But I'd bet no driver noticed that when climbing Shap or Beattock vs a Class 8, and they surely performed better than a Cl 40.

One thing from the original testing data was a propensity to slip on the 44s, hence re-gearing of the traction motors to reduce the maximum and continuous tractive efforts to more usable levels (also enabled the full engine output to be used at higher speeds as well).

That TE figure seems steep. DerbySulzers site quotes:
Maximum Tractive Effort at rail (Class 45/46): 55,000lbs

class 44 class 45 class 46 details

Echoed by the info on Wikipedia.

55,000lbs all round, but the 44s were 72,000lbs as delivered until regearing reduced that figure.

"easily" ? They could get to 100 ok, not sure how much they could top it without a long downgrade, such as on the down into Bedford. Like you, I'm blank on the 46s. Someone must have logs when they were regulars on the ECML.

Easily yes, in the sense of not difficult for them to do so. 47s seem to have has a slight edge at the highest speeds and a higher top end but a 45 would reach 100mph perhaps as easily as a 47 or almost.

There are plenty of records of 100mph speeds attained on the Midland Main Line, even though it was a 90mph railway (and only 80 on the northern section) until 1983 when four sections of 100mph running were authorised.