Why Class 37s?

[driverd]

A pretty simple question popped into my head today - no doubt someone here will be able to give me a very thorough answer! What particular facet of Class 37s sees them continue so persistently in service, some 60 or so years after introduction?

I'm really struggling to think what they offer above and beyond modern locos, but I'm figuring it must be something, as companies using them are precisely that; competitive companies, not just lethargic TOCs that can't justify buying something newer.

I'm specifically curious what they bring to RHTT runs and the test trains. In both these cases, one would (perhaps wrongly) assume a class 68 or Class 67 would present a more cost effective solution? I'm aware the axle load of a 37 is lower, but does this actually prohibit a higher RA loco from going on a certain route, or is it just a case of travelling at a lower speed etc (sorry, question in a question there)?

 

[K.o.R]

If the RA of a vehicle is too high for a given route it (and any train it is a part of) is prohibited from using that route.

 

[driverd]

If the RA of a vehicle is too high for a given route it (and any train it is a part of) is prohibited from using that route.

How does that work, though?

The axle load of certain units (185s I'm looking at you), is way higher than anything else that uses certain routes. In these cases, the solution is a lower PSR. Equally, on the likes of the WHL, locos have highly specified PSRs as detailed in the Route Clearance section of the sectional appendix (Eg: 5mph over bridge x).

I don't think to say a high RA means no go is strictly correct. Yes, if I rocked up with a 67 wanting to go somewhere it's not cleared, I'm not going to be allowed to go. But if I'm Mr DB Cargo and enter into talks with NR, I'm asking what the process would be and how costly this would be. What are the economic considerations that makes it continue to be sensible to use 37s?

 

[K.o.R]

Wiki so apply salt as necessary:

Route availability - Wikipedia

en.wikipedia.org

Route Availability (RA) is the system by which the permanent way and supporting works (bridges, embankments, etc.) of the railway network of Great Britain are graded. All routes are allocated an RA number between 1 and 10.

Rolling stock is also allocated an RA (again between 1 and 10) and the RA of a train is the highest RA of any of its elements. The train must have a route availability (RA) lower than or equal to the RA of a line to be allowed to use it. The RA is primarily related to the axle load of the vehicle, although axle spacing is also taken into consideration. In practice it is the locomotive which governs where trains may operate, although many high capacity 4 axle wagons have high RAs when fully loaded. (When considering the operation of trains the loading gauge must also be considered.)

Also has a table of axle loads for several RA numbers, and lists a class 185 as the highest RA multiple unit at 5, with all others in the list being 4 or lower (but no 7xx or 8xx listed).

I would surmise that the closer to the route's RA the train is, the more likely to be working under restrictions, but once it exceeds the RA then even with restrictions it would be too damaging to the track.

 

[driverd]

Wiki so apply salt as necessary:

Route availability - Wikipedia

en.wikipedia.org

Also has a table of axle loads for several RA numbers, and lists a class 185 as the highest RA multiple unit at 5, with all others in the list being 4 or lower (but no 7xx or 8xx listed).

I would surmise that the closer to the route's RA the train is, the more likely to be working under restrictions, but once it exceeds the RA then even with restrictions it would be too damaging to the track.

I think you're missing my question slightly - what would then be required to lift the RA, or accommodate a particular loco specifically, and at what cost?

I know when I was a train planner, in some cases route clearance was a paper exercise - basically no one had asked to take train x on route y before, but it fit, so NR just update the tables. In other cases you may have one bit of infrastructure, in other cases you may have a whole route built to a particular vehicle profile.

How does RA fit into this equation? It's not something I've ever worked with so it's not something I'm overly familiar with.

 

[brad465]

We can't get enough of the sound of tractors.

 

[Bessie]

Most Class 37s are RA5 so I assume they can go anywhere on the network. I assume supply of parts is good. Perhaps drivers at the TOCs enjoy them in same way as driving an old classic car. Its a purer driving experience and you have that sound. PS: I’m writing purely as an enthusiast!

 

[Magdalia]

What I know is from historical research rather than knowing the details of the engineering processes.

Route availability is primarily but not entirely based on axle load. There is (or at least was) also something called the hammer blow effect which depends on how close together the axles are. Both routes and rolling stock are assessed for route availability, and assigned a number on a scale. Low RA numbers indicate low axle load and high RA numbers indicate high axle load. For routes this is about civil engineering particularly bridges, and a low RA is bad because the rolling stock that can use the line is restricted. For rolling stock it is basically about putting it on a weighbridge and counting the axles, and a low RA is good because that means it can go on more routes. As others have said, RA has got more sophisticated in recent years for example with variable speed limits over structures.

The boundary between RA5 and RA6 is at 18 tons axle load and is particularly important operationally, because there are very few routes below RA5. As has already been said, any rolling stock that is RA5 can go just about anywhere.

At the time of the Modernisation Plan 18 ton axle load was part of the specification for Type 2 locomotives. This means that a 4 axle locomotive can weigh no more than 72 tons and all of the 4 axle Type 2s struggled to meet this. Even with 6 axles the 18 ton axle load can be hard to hit: bigger power units and extra auxiliary machines add to weight.

For many years the class 37 has been the most powerful locomotive still around that is RA5, and that's why it has survived. But it does have a rival now because HST power cars are also RA5.

 

[Spartacus]

I think you're missing my question slightly - what would then be required to lift the RA, or accommodate a particular loco specifically, and at what cost?

I know when I was a train planner, in some cases route clearance was a paper exercise - basically no one had asked to take train x on route y before, but it fit, so NR just update the tables. In other cases you may have one bit of infrastructure, in other cases you may have a whole route built to a particular vehicle profile.

How does RA fit into this equation? It's not something I've ever worked with so it's not something I'm overly familiar with.

Route clearance is usually about the loading gauge, what's above the track, and getting clearance is often a case of just checking one against the other and adding that particular stock to the list of cleared stock.

Route availability is usually about what's below the track, bridges, culverts etc. As the RA of the route is always knows, and is that of the stock, there's no paper exercise that's going to get something cleared that's too heavy. What do you do to get things cleared? Unless you've a loco that can shed weight (freight wagons have run only part loaded in the past where if fully loaded they would be above the route's RA) it's a matter of rebuilding the permanent way to some degree, which can rather expensive.

On occasions you have something of a halfway house with high RA stock stock, usually locos, banned from a route except under special circumstances, such as a failure, the High Level Bridge at Newcastle's an example of this, but these type of arrangements are rare.

 

[Cheshire Scot]

The axle load of certain units (185s I'm looking at you), is way higher than anything else that uses certain routes. In these cases, the solution is a lower PSR.

For class 185s it is not a lower PSR, they take the PSR - the PSR applies to all trains including e.g. freight or loco hauled passenger unless specified otherwise which in the case of higher speeds for non 185 trains on e.g. the Hope Valley, speeds higher than the PSR are permitted by use differential speeds such as SP or MU.

 

[37114]

A couple of other builds;
- They are reliable
- They are readily available
- It is virtually impossible to buy a Tier IIIB emissions compliant power unit to fit inside the body of a loco in the UK loading gauge
- The work they are used on would not cover the cost of depreciation of newer locos.

 

[DanNCL]

On occasions you have something of a halfway house with high RA stock stock, usually locos, banned from a route except under special circumstances, such as a failure, the High Level Bridge at Newcastle's an example of this, but these type of arrangements are rare.

What makes the High Level Bridge even more of an anomaly is that 91s at RA7 are exempt from most of the restrictions that prevent other locos from using the bridge.

- They are reliable

Anyone who used them regularly on the Cumbrian Coast in the 2010s would disagree!

 

[Snow1964]

They were built well, long before computer design, and in a way were a scaled down class 40. And as so often happens if you reduce a bigger design but save money by continuing to use the same basic design and parts end up with something over engineered, but sturdy and reliable

 

[zwk500]

Route clearance is usually about the loading gauge, what's above the track, and getting clearance is often a case of just checking one against the other and adding that particular stock to the list of cleared stock.

Route clearance is, strictly speaking, the combination of Route Availability and Gauge Clearance

Route availability is usually about what's below the track, bridges, culverts etc. As the RA of the route is always knows, and is that of the stock, there's no paper exercise that's going to get something cleared that's too heavy. What do you do to get things cleared? Unless you've a loco that can shed weight (freight wagons have run only part loaded in the past where if fully loaded they would be above the route's RA) it's a matter of rebuilding the permanent way to some degree, which can rather expensive.

In between running lighter or rebuilding the line you can put a speed restriction over the specific problem bridges. It depends on the design and strength of the materials and bearings, among other things to do with load distribution. Also sometimes you have restrictions on too many locos travelling too close together (e.g. No double-heading).

 

[L401CJF]

Anyone who used them regularly on the Cumbrian Coast in the 2010s would disagree!

Weren't a lot of the failings with that operation a result of a fault between the 37 and DBSO rather than the loco itself?

 

[Lucy1501]

Weren't a lot of the failings with that operation a result of a fault between the 37 and DBSO rather than the loco itself?

I believe a lot of the issues on the Cumbrian Coast were due to Northern pushing the limits of the 37s too much. The timetable Northern were running was designed for a modern DMU, not a 60s locomotive.

The 37s could barely keep up with the timetable as Northern didn’t change it to suit the different rolling stock’s abilities.

 

[D365]

If the RA of a vehicle is too high for a given route it (and any train it is a part of) is prohibited from using that route.

This. If a Class 38 fleet had been built in the 80s or 90s, they would have seen off the 37s. But it didn’t happen, and here we are.

 

[_toommm_]

Weren't a lot of the failings with that operation a result of a fault between the 37 and DBSO rather than the loco itself?

The few times I’ve seen failures was where the DBSO couldn’t communicate with the 37 (or vice versa). I ended up stuck in Foxfield one evening for about four hours because of it, which scuppered the service from Carlisle from about 14:00 until the end of service. The signaller at Foxfield refused to implement SLW.

 

[12LDA28C]

A pretty simple question popped into my head today - no doubt someone here will be able to give me a very thorough answer! What particular facet of Class 37s sees them continue so persistently in service, some 60 or so years after introduction?

I'm really struggling to think what they offer above and beyond modern locos, but I'm figuring it must be something, as companies using them are precisely that; competitive companies, not just lethargic TOCs that can't justify buying something newer.

I'm specifically curious what they bring to RHTT runs and the test trains. In both these cases, one would (perhaps wrongly) assume a class 68 or Class 67 would present a more cost effective solution? I'm aware the axle load of a 37 is lower, but does this actually prohibit a higher RA loco from going on a certain route, or is it just a case of travelling at a lower speed etc (sorry, question in a question there)?

You could ask exactly the same question about Class 47s, or any other heritage diesel that is still active on the main line.

Class 37s are not unique in that respect, although to be fair 37s and 47s are really the only heritage fleets used in any numbers by both freight and passenger (charter) operators.

 

[ac6000cw]

A couple of other builds;
- They are reliable
- They are readily available
- It is virtually impossible to buy a Tier IIIB emissions compliant power unit to fit inside the body of a loco in the UK loading gauge
- The work they are used on would not cover the cost of depreciation of newer locos.

That's not really true - the GBRf class 73/9 conversions (using an MTU R4000 V8 I think) were done after the Euro stage IIIB limits came into force in 2012, and more recently the cl. 93 and cl. 99 have been developed.

Also the diesel 'power pack' car in a 755/4 produces 2570hp/1920kW (from 4 x Deutz V8s) in less than 7m of length - AFAIK that includes the engines, alternators, cooling system and fuel tanks.

I'd be pretty surprised if Stadler couldn't build you an RA5 compliant class 37 replacement - doubt it would be cheap though (which is why it hasn't happened yet...)

 

[driverd]

You could ask exactly the same question about Class 47s, or any other heritage diesel that is still active on the main line.

Class 37s are not unique in that respect, although to be fair 37s and 47s are really the only heritage fleets used in any numbers by both freight and passenger (charter) operators.

Thats not really true, though. The 47s are all but retired. The 37s are still employed by modern companies that are seeking to modernise and improve the carbon credentials of their fleet (eg: DRS, who are pushing a decade since the withdrawl of 47s). They seem to have a niche in terms of the non-railtour work they do and this thread is all about why 37s fill this niche, and the economic arguments that favour their retention, as opposed to a new build locos or infrastructure modifications.

Thanks all for the informative replies so far. I understand RA plays a part here but as noted up thread, it's not an insurmountable problem and it'd be really interesting to hear what the costs would look like, for instance, to swap a RHTT circuit from 37s to 68s - and where the break even roughly falls with that - from anyone who may know.

 

[Ken H]

It aint broke. dont fix it.

 

[66701GBRF]

I'm specifically curious what they bring to RHTT runs and the test trains. In both these cases, one would (perhaps wrongly) assume a class 68 or Class 67 would present a more cost effective solution? I'm aware the axle load of a 37 is lower, but does this actually prohibit a higher RA loco from going on a certain route, or is it just a case of travelling at a lower speed etc (sorry, question in a question there)?

General loco availability is one reason. RHTT's have very little weight but need two locos in top and tail. Why use 2 expensive locos that could be better utilised elsewhere when you can use 2 cheaper ones? As for the test train, it is its go pretty much anywhere RA5 without restriction that makes them more suitable. No use having a test train that has to significantly reduce its speed all the time.

 

[12LDA28C]

Thats not really true, though. The 47s are all but retired. The 37s are still employed by modern companies that are seeking to modernise and improve the carbon credentials of their fleet (eg: DRS, who are pushing a decade since the withdrawl of 47s). They seem to have a niche in terms of the non-railtour work they do and this thread is all about why 37s fill this niche, and the economic arguments that favour their retention, as opposed to a new build locos or infrastructure modifications.

Thanks all for the informative replies so far. I understand RA plays a part here but as noted up thread, it's not an insurmountable problem and it'd be really interesting to hear what the costs would look like, for instance, to swap a RHTT circuit from 37s to 68s - and where the break even roughly falls with that - from anyone who may know.

Interesting that you quote DRS. I was under the impression that they were in the process of getting rid of all their Class 37s, despite having spent vast amounts of money resurrecting some of them (eg 37424) from near-scrap condition.

 

[D365]

Interesting that you quote DRS. I was under the impression that they were in the process of getting rid of all their Class 37s, despite having spent vast amounts of money resurrecting some of them (eg 37424) from near-scrap condition.

AFAIK they’re keeping them for a few more years of RHTT.

 

[Richard Scott]

Think the question's been answered, they were incredibly reliable (believe around 40000 miles per failure in 1980s) and low Route Availability. Many also had a lot of money spent on them refurbishing them in mid to late 1980s, if anything was an issue it was the generator so replacing with an alternator made them more reliable (I assume as don't have any figures to back this up). Also regeared bogies meant greater hauling power and alternator would mean marginally more power at rail.
Slightly off topic but believe 20s and 40s were also very reliable.

 

[D365]

Given that DRS and Colas had to spend money overhauling ’unrefurbished’ Class 37/0s in the 00s and 10s, there certainly weren’t enough 37/5s to go round!

 

[driverd]

Lovely, thanks for the answers so far.

I'm basing a lot of this on the assumption that a 37 with a 60s power plant is a gas guzzler compared to modern alternatives (eg: a 68) - is this a fair assumption?

If so, would anyone in the know be able to advise on the true cost analysis of replacement? For example, at what point would it be more efficient to commision a whole new build super-light loco? (I'm coining the term seeing as 68s are "UK light" but still a hefty RA8) I presume the 37s can't go on forever, so there's gotta be a point where the financial scales tip away from them? (Even better if anyone could support an answer with figures)

 

[D6130]

I ended up stuck in Foxfield one evening for about four hours because of it, which scuppered the service from Carlisle from about 14:00 until the end of service.

I hope the Prince of Wales was open....sadly it isn't any more.

 

[Bill57p9]

General loco availability is one reason. RHTT's have very little weight but need two locos in top and tail. Why use 2 expensive locos that could be better utilised elsewhere when you can use 2 cheaper ones? As for the test train, it is its go pretty much anywhere RA5 without restriction that makes them more suitable. No use having a test train that has to significantly reduce its speed all the time.

This answer touches on another reason for 37 use: the niches they are still employed on are low trailing weight, hence their relatively low power compared to modern build mainline diesel locomotives isn't a constraint.
As a mixed traffic design they also have a reasonable top speed and many of those still on the mainline have ETS, adding to flexibility.

They are serviceable, available, evidently affordable and fit for these niche purposes: 66s are slow and largely in use, 60s are limited to 60 whilst 67s have a very unappealing axle load.

Re. The Cumbrian Coast 37 reliability issues: I was under the impression that the intensive cycle of hard acceleration and breaking of the stoppers also contributed.