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The pros and cons of class 37 v class 40 locomotives

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Inversnecky

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Not sure if this works as a topic, but interested in the ‘pros’ and ‘cons’ of each. Which was better? Reliable? Why were there more 37s made and used than 40s, which seemed to have a limited lifespan like the peaks?

On another thread, the propensity of 40s to derail on throat trackwork was a point against them.
 

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jopsuk

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Class 40s were heavier (though on two more axles), less powerful and the eight wheel bogies won't have been nice on the tracks
 

43096

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Class 40s were heavier (though on two more axles), less powerful and the eight wheel bogies won't have been nice on the tracks
Less powerful? 2000hp Class 40 vs 1750hp Class 37 says otherwise!
 

36270k

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Although 30 tons heavier , the 40 has about the same brake force as the 37 due to the outer axles being unbraked on the 40
 

Cowley

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Although 30 tons heavier , the 40 has about the same brake force as the 37 due to the outer axles being unbraked on the 40

I didn’t realise that the pony wheels on the 40 were unbraked? I suppose that’s the same on the Peaks as well then?
 

Richard Scott

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I didn’t realise that the pony wheels on the 40 were unbraked? I suppose that’s the same on the Peaks as well then?
Correct, no brakes on pony truck on peaks either but they have much greater brake force than the 40. Think the 37 shows how quickly diesel technology was developing then. 37 in real world probably easily as capable as a 40.
 

Cowley

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Correct, no brakes on pony truck on peaks either but they have much greater brake force than the 40. Think the 37 shows how quickly diesel technology was developing then. 37 in real world probably easily as capable as a 40.
I always find it interesting how large some of the trains entrusted to some of these locos were back in the day. You’d often see them on 12 mk1s on a summer Saturday.
 

Richard Scott

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I always find it interesting how large some of the trains entrusted to some of these locos were back in the day. You’d often see them on 12 mk1s on a summer Saturday.
Agree, think a lot of modern trains are totally overpowered to the detriment of fuel consumption. Know modern engines will use less fuel but still unnecessarily overpowered e.g. 185s. Remember having 37376 towing a dead 47 and load 7 up the Lickey unassisted. Quite a trailing load, especially when had 31407 on load 6 and would've been quicker to walk!.
 

hexagon789

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I didn’t realise that the pony wheels on the 40 were unbraked? I suppose that’s the same on the Peaks as well then?
Correct, no brakes on pony truck on peaks either but they have much greater brake force than the 40. Think the 37 shows how quickly diesel technology was developing then. 37 in real world probably easily as capable as a 40.

I'm not sure, 40s are shown in the diagram books as 51 tons brakeforce (64%), 44-46s are shown as 63 tons (78%). I wonder how you get such a difference?
 

Richard Scott

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I'm not sure, 40s are shown in the diagram books as 51 tons brakeforce (64%), 44-46s are shown as 63 tons (78%). I wonder how you get such a difference?
Possibly brake cylinders, peaks have 24, 2 for each wheel on a powered axle? Peaks are slightly heavier but only a matter of a couple of tons do doubt that'll have much impact?
 

hexagon789

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Possibly brake cylinders, peaks have 24, 2 for each wheel on a powered axle? Peaks are slightly heavier but only a matter of a couple of tons do doubt that'll have much impact?
Could be something like that, just seemed like quite a difference
 

pdeaves

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Not really a pro/con thing and purely subjective, but the 40 always looked better proportioned to me. Looking nicer to one person does not make for a better locomotive, though!
 

Cowley

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Is the nose on the 40 idential in proportions to that on the 37?
They always looked slightly longer on a 40 than they did on a 37 to me but I’m not sure?
 

Inversnecky

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They always looked slightly longer on a 40 than they did on a 37 to me but I’m not sure?

The 40 is three metres longer than the 37, so perhaps that can make a 40’s nose appear shorter than it is.

Here’s a plan of the 37, have drawn a blank with the 40, maybe someone else can help out? Failing a direct measurement of ‘nose length’, it could be estimated from measuring the scale diagram.

ETA some prototypical 40 plans.
 

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Cowley

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The 40 is three metres longer than the 37, so perhaps that can make a 40’s nose appear shorter than it is.

Here’s a plan of the 37, have drawn a blank with the 40, maybe someone else can help out? Failing a direct measurement of ‘nose length’, it could be estimated from measuring the scale diagram.
I meant that I thought the nose on a 40 looked slightly longer... :)
 

chorleyjeff

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I always find it interesting how large some of the trains entrusted to some of these locos were back in the day. You’d often see them on 12 mk1s on a summer Saturday.

And further back lower powered steamers were frequently diagrammed for 16 coaches in regular traffic. Acceleration was dire compared to 40s on the same trains.
 

randyrippley

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You need to look at the background reasons for why the 37s and 40s were built.

The 40s were an insurance policy using known safe technology in case the untried and unproven Peak design failed.
The 40s were the Bullied SR design with an understressed off-the-shelf engine and off-the-shelf EE parts-bin cab added. Nothing to go wrong except a lack of performance.
The Peaks were a new design, built on a new production line by a team with no previous diesel experience, using a licenced engine also built on a new production line. Many things to go wrong - and they did. The engines suffered serious crankshaft and crankcase failures. Crompton-Parkinson couldn't deliver the electrics quickly enough. And even with a second production line set up, the BR workshops couldn't hit delivery targets, running at least a year behind schedule.
BR had no choice but to order more batches of class 40 even though they were inferior on paper - but at least could be delivered on schedule and worked. EE even offered to fit the later builds with uprated engines - an offer BR declined on grounds of risk reduction.
However when someone finally came up with the definitive type 4 design - the 47 - production of both designs closed, with EE losing work while the BR workshops got a large part of the 47 order.

When the 37s were ordered, things had moved on, the BR workshops were full building classes 24/25 and later 47, so the job was inevitably going to go to an outside contractor. There weren't many bidders as by then the building of diesels was proving to be a financial black hole. EE offered a cut-price design based on bits from their parts bin and got the offer - which filled the hole left by then impending closure of the class 40 line. The request was for a type 3, EE actually offered an engine which had been running at 2000hp in hot-high conditions in East Africa, but BR insisted it be derated. Whether this was for reliability, or whether the government authority was for a type 3 and nothing else is debatable. Whatever the truth, the 37s could have been built as type 4 machines but weren't.
The key thing is that this time the EE design became the standard production design for type 3, hence the numbers.

In essence, the difference is the 40s were an unwanted, but needed, insurance backstop, while the 37s were a successful main production run
 

Helvellyn

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You need to look at the background reasons for why the 37s and 40s were built.

The 40s were an insurance policy using known safe technology in case the untried and unproven Peak design failed.
The 40s were the Bullied SR design with an understressed off-the-shelf engine and off-the-shelf EE parts-bin cab added. Nothing to go wrong except a lack of performance.
The Peaks were a new design, built on a new production line by a team with no previous diesel experience, using a licenced engine also built on a new production line. Many things to go wrong - and they did. The engines suffered serious crankshaft and crankcase failures. Crompton-Parkinson couldn't deliver the electrics quickly enough. And even with a second production line set up, the BR workshops couldn't hit delivery targets, running at least a year behind schedule.
BR had no choice but to order more batches of class 40 even though they were inferior on paper - but at least could be delivered on schedule and worked. EE even offered to fit the later builds with uprated engines - an offer BR declined on grounds of risk reduction.
However when someone finally came up with the definitive type 4 design - the 47 - production of both designs closed, with EE losing work while the BR workshops got a large part of the 47 order.

When the 37s were ordered, things had moved on, the BR workshops were full building classes 24/25 and later 47, so the job was inevitably going to go to an outside contractor. There weren't many bidders as by then the building of diesels was proving to be a financial black hole. EE offered a cut-price design based on bits from their parts bin and got the offer - which filled the hole left by then impending closure of the class 40 line. The request was for a type 3, EE actually offered an engine which had been running at 2000hp in hot-high conditions in East Africa, but BR insisted it be derated. Whether this was for reliability, or whether the government authority was for a type 3 and nothing else is debatable. Whatever the truth, the 37s could have been built as type 4 machines but weren't.
The key thing is that this time the EE design became the standard production design for type 3, hence the numbers.

In essence, the difference is the 40s were an unwanted, but needed, insurance backstop, while the 37s were a successful main production run
In another universe the Class 45 fleet could have been quite large if those additional Class 40s hadn't been ordered and Crompton-Parkinson could have kept up with supply (negating the need for the Class 46 variant of the peak).

Wonder what a Class 47 with Crompton-Parkinson electrical equipment could have been like.
 

randyrippley

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In another universe the Class 45 fleet could have been quite large if those additional Class 40s hadn't been ordered and Crompton-Parkinson could have kept up with supply (negating the need for the Class 46 variant of the peak).

Wonder what a Class 47 with Crompton-Parkinson electrical equipment could have been like.
It would have been a lot more reliable...but would still have the weakness of the Sulzer diesel
 

CW2

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There was the subsequent experimental uprating of 37292 to 2000 hp in the early 1980s, which proved that the class 37 power unit could cope with more load.
Does anybody have any further info on this? Was this a precursor to fitting ETH to the 37/4s?.
 

Kingspanner

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Wasn't that a Mirrlees power unit and the loco named "Mirrlees Pioneer" as a result? Or was that different project?
 

Cowley

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I did read a couple of days ago (I think maybe on wnxx) that BR were offered an upgraded 2400hp version of the class 40 while they were still in production, but BR turned it down due to worries about reliability of the power unit and traction motors.
I wondered about that upthread and was surprised to read it a day or two later so it stuck in my mind.

Wasn't that a Mirrlees power unit and the loco named "Mirrlees Pioneer" as a result? Or was that different project?
A different project I think. Those were the six refurbished class 37/9s,
four were fitted with Mirrlees engines and two with Ruston ones in the mid 80s.
 

Dr Hoo

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I never worked 'on the ground' with Class 37s but took it as an omen that literally when I arrived for my first ever supervisory shift there was a derailed Class 40 blocking the job and someone had to pick me up in a yellow BR van from a station along the line. A bogie problem had caused the '40 to drop on the deck on a crossover.

Needless to say the M&EE representative denied that there was a problem with the locomotive whatsoever and blamed the track.

On my third day I arrived at work to discover the same Class 40 derailed again on another crossover a couple of miles away.

At that point the M&EE representative conceded that there might be a rotational stiffness issue.

Never really trusted them after that but have to concede that they could shift a chunky freight train.
 
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