If all locos under a certain class were made equal, why did some last 30 years longer than others?

[richieb1971]

So I guess what I am asking is if locos are not made equal, and that some are more prone to withdrawal from an earlier time. Or perhaps maintenance depots had their favourites they looked after whilst letting others rot.

Obviously its very complicated as many years and scenarios played out. The reason I ask is that it seems like any loco can be made brand new again on the outside, the engines can be upgraded inside. Yet still some classes had examples that lasted 3 or 4 decades longer than other examples.

 

[hexagon789]

So I guess what I am asking is if locos are not made equal, and that some are more prone to withdrawal from an earlier time. Or perhaps maintenance depots had their favourites they looked after whilst letting others rot.

Obviously its very complicated as many years and scenarios played out. The reason I ask is that it seems like any loco can be made brand new again on the outside, the engines can be upgraded inside. Yet still some classes had examples that lasted 3 or 4 decades longer than other examples.

Could be a number of things -

Accident/collision damage, sometimes certain damage isn't evident until years later and is bad enough to require withdrawal as repair is uneconomic.

Non-standard equipment/fittings and a desire to standardise on members of a class with the most common fittings.

Surplus to requirements in one area and nowhere for them to be moved to.

I'm sure there are plenty of other reasons as well.

 

[Deepgreen]

I think it's fundamentally whether a class is all withdrawn simultaneously or not. If not, there are obviously going to be some that go sooner, and there may be policy changes during the process which see some last far longer than earlier thought. If a class was built in batches there may be detail differences, plus different maintenance regimes at different depots, modifications that either worked or didn't, damage, random major failures, etc. So many reasons.

 

[The exile]

So I guess what I am asking is if locos are not made equal, and that some are more prone to withdrawal from an earlier time. Or perhaps maintenance depots had their favourites they looked after whilst letting others rot.

Obviously its very complicated as many years and scenarios played out. The reason I ask is that it seems like any loco can be made brand new again on the outside, the engines can be upgraded inside. Yet still some classes had examples that lasted 3 or 4 decades longer than other examples.

Currently 49 years and counting between withdrawal of the first 08 and the last ( whenever that’s going to be).

 

[xotGD]

For some classes, some locos were vacuum brake only while others were dual braked. The vac only were typically culled first.

 

[D1537]

For Class 47

47401-420 (D1500-D1519) were completely non standard and were all withdrawn quite early.

When the class was being reduced in the late 1980s the hit list included the minority fitted with series-parallel traction-motors (there were 86 of them: 47001-47019, 47096-47113, 47115-47124, 47421-454, 47485-488, 47529). Any SP loco that needed expensive repairs was withdrawn, even recently overhauled examples with minor damage such as 47428.

Despite that some of the SP locomotives went on to survive into the later 90s, although only two survived to see in the year 2000 (celebrities 47004 and 47488).

Currently 49 years and counting between withdrawal of the first 08 and the last ( whenever that’s going to be).

Currently 55 years and counting between the first Class 37 and 47 withdrawals (D6983 and D1671, though admittedly this was due to severe accident damage)

 

[The exile]

For Class 47

47401-420 (D1500-D1519) were completely non standard and were all withdrawn quite early.

When the class was being reduced in the late 1980s the hit list included the minority fitted with series-parallel traction-motors (there were 86 of them: 47001-47019, 47096-47113, 47115-47124, 47421-454, 47485-488, 47529). Any SP loco that needed expensive repairs was withdrawn, even recently overhauled examples with minor damage such as 47428.

Despite that some of the SP locomotives went on to survive into the later 90s, although only two survived to see in the year 2000 (celebrities 47004 and 47488).



Currently 55 years and counting between the first Class 37 and 47 withdrawals (D6983 and D1671, though admittedly this was due to severe accident damage)

The same accident, I believe! I guess that first 08 may also have been accident-related, though the first withdrawals en bloc followed a few months later.

 

[thedbdiboy]

Class 08s were built over a period of 10 years so that has an effect but I think maybe you need to look at it another way, it's dictated as much by the work the locos are needed for. The most extreme examples concern Shunters and Type 1 / Type 2 diesels, but even amongst Type 3 and Type 4 models, once technology allowed the industry to pack more power in there was no need to build more of these. The utter transformation and contraction of the rail network from the 1950s to the 1980s (particularly freight) meant that there were literally hundreds more of these locos built than were eventually needed even within an average service life. So first of all the most troublesome classes were eliminated; followed by picking off examples of other classes where they get damaged, suffer major failure or simply decay at a faster rate than their class siblings. BR never built another loco under Type 5 rating after 1968 - the industry instead since repurposed what was already there from a vast pool of existing locos.
Once the Class 66 was established, the only reason for retaining any other motive power was for the handful of jobs that a 66 was not optimised for. So, for example, whilst there was no need for 100 class 60s, there were some workings for which this class was suited, so a limited number of the class were cherry picked for overhaul based on condition to meet this need. Similarly, whilst there was no need for 308 Class 37s, there was a economic case to life-extend a small number of them to provide a flexible go-anywhere 1750hp of power where a class 66 isn't the right answer.
The planned Stadler Class 93 looks to be a fascinating loco, combining powerful electric traction and battery capability with Type 2 standalone diesel power, and would therefore eventually supplant the work being done by the remaining lower powered diesel examples, but until then a few of them get the lucky golden ticket and live decades beyond their classmates.

 

[tbtc]

Could also be a bell curve situation - e.g. you have a class where the average locomotive lasts thirty years, but some last fifteen/twenty years whilst others last forty/forty five years - that kind of deviation may be expected (rather than everything lasting precisely thirty years)

As @thedbdiboy says above, some classes took a long time to be built (which means that, even if the standards didn't change during that time, there may be some that are several years older than others - the 170s were built over seven years - a longer period if you include the 168s - so I wouldn't expect them all to be withdrawn in the same year)

Some stock is built to meet a need today (e.g. we need x number of locomotives/ units to perform a current role), but as they are cascaded onto "secondary" routes over the years, fewer and fewer are required in regular service, so you don't need so many, which means that there's no urgency to repair every bump/scratch/ bit that falls off... sometimes the loss of a key freight contract will mean significantly fewer locos required so some scrapped before their time (e.g. the 58s may have been built with the expectation of many years of coal but when that dried up the locos weren't required

Then. at mid life, the fact that a class of locomotives/ units are no longer being produced means that it's simpler to "borrow" a working part from an unused machine, which means the depot has a "Christmas Tree" which donates its windscreen wipers etc to locomotives/units in need of replacement ones...

You might keep a number of locomotives/ units sat in a yard without being used (as the work dries up for that kind of train), which is fine for a while - dump them in a pile at Toton etc - but then things need an overhaul/ passing an "exam" etc to tick a box and a decision needs to be taken whether to spend money on it to keep it going or give up on it, so some things will get scrapped before their time, because it's not economic to keep them - same goes for accident damaged stuff - you might justify a new fuel tank for something ten years old but not at twenty years old

So, to take the example of the 170s, private TOCs ordered enough to meet the PVR on certain routes - now that they are around twenty years old, they have been replaced on some routes either by electrification (e.g. Edinburgh - Glasgow, Rugely - Birmingham) or by a cascade of more suitable stock (e.g. Hull - London), some of the routes that they were ordered for don't exist (e.g. Barnsley/ Matlock/ Burton no longer have London services) - some of them have been cascaded onto services that they're not really suited to (e.g. Harrogate stoppers) - if one is in an accident today then I guess it'd be worth repairing it but there'll come a time when it'd be dumped in a siding at Tyseley and was slowly robbed of parts (because it's simpler to pinch components than order new parts, especially a one-off) - then as the 170s run out of "flagship" routes to operate they'll move onto services where they can do an okay job but probably won't require so many to run them - so they might not have any money spent on them to meet exam requirements (since there are a surplus of such units) - the class will dwindle down from hundreds to dozens

Then again, I guess there's a risk that something might be withdrawn en-masse if a safety critical fault is found or a route is closed (e.g. the 76/77s didn't hang around after Woodhead, for obvious reasons)

 

[Julia]

Other wide lifespan variations might include where an individual example has been re-purposed for something out of the ordinary and that requirement persists long after the class as a whole has become redundant - the 05 on the Isle of Wight (in fact pretty much anything that ends up on the Isle of Wight!), the 15s used as static boilers, and so on. I guess it happens less for EMUs as they are usually one-class-per-route and get replaced en masse when the time comes for an upgrade. The more "go anywhere, do anything" a class is, the more likely they will stray from their original duties, split up as a group and find new roles as time goes on.