Classic traction- real world performance ranking.

[mat12128]

This is aimed at Ex drivers and those with serious insight regarding the reality rather than on papers stats.
How would classes 20, 25, 26, 31, 33, 37, 37/9 (Ruston), 40, 45, 47, 50, 52, and 55 perform in shifting a 600 tonne train off the line in good traction conditions?
The caveat is that the 20s are a pair as typically seen- classed as a single unit.

A follow on (if the order would change),
What would be the estimated speed and finishing order topping Lickey if those locos did load 8 from Bromsgrove station standing start?

No bias, and let me know if you are having a casuals guess or if you have experience or deep mechanical/physics insight.

 

[Harpo]

Why 600 tonnes? If acceleration is being compared maybe aim for the 280-350 tons of a typical 8-10 coach train? Also with 600 tons you’ve probably passed the normal max load for a single type 2 on most routes and maybe beyond the max unassisted load for a pair on Lickey. (Max unassisted loads are based on the ability to restart from any location.)

As for pairs of 20s, various railtour experiences on stiff climbs suggest that they’ll plod along to summits at around 17mph, as the first stage of field weakening should happen but often can’t be sustained.

 

[EveningStar]

Trainspotting at Bromsgrove in the 1970s and into the 1980s, recall unassisted timing load was D455. Have seen 45, 46, 47 and 50 get to the summit from a standing start with varying degrees of ease. Imagine class 52 could do the same, except they were extremely rare at Bromsgrove in their later years. Class 31 and, even rarer on passenger trains, class 37 needed banking. Never personally observed class 20 or 25 on passenger workings at Bromsgrove, so no data. Daily sleeper, D560 as best I can recall, was banked, with exception of Friday when it ran in two parts.

 

[jfollows]

A booked class 31 on a D455 timing load was restricted to 220 tonnes, for example. Clearly if substituting for a more powerful locomotive with a heavier train it would struggle. Class 20 was 150 tonnes similarly.

 

[Magdalia]

A booked class 31 on a D455 timing load was restricted to 220 tonnes, for example. Clearly if substituting for a more powerful locomotive with a heavier train it would struggle. Class 20 was 150 tonnes similarly.

This was the LMR way of doing things, the timing load was for a Type 4 and the maximum permitted load for other classes was derived from a look up table. In this example class 31s frequently took 6 cars (210 tons) up the Lickey without assistance, similarly class 31 pairs up to 12 cars.

The ER were different. Each train had the timing load for the booked traction. For example A class 55 on a D280 timing for one of the crack business expresses would have a different schedule to a class 31 on a D280 timing on a Cambridge Buffet Express.

 

[AndrewE]

Daily sleeper, D560 as best I can recall, was banked, with exception of Friday when it ran in two parts.

Re the Bristol-Glasgow and Edinburgh sleeper, this doesn't fit with my memory (mid-70s) when I worked on Temple Meads. I agree it ran in 2 parts on summer Fridays, but I couldn't understand how both portions were bigger than the combined train on other days, the Edinburgh being longest.

I thought the Edinburgh train was unique in that it was the only passenger train booked to be banked at that time, which is why I and a friend caught it once just to hang out of the back windows from the standing start at Bromsgrove. The whole seats portion of the train seemed to be pretty empty from what I recall.

(However the 1979-80 Marshalling circular which I have doesn't support this memory of the train lengths in that year, I suppose a WTT for the summer of 1975 would have the timed stop to pick up the banker if it was planned. It could be that there was a Special Notice strengthening the Edinburgh train that I picked up on...)

 

[jfollows]

(However the 1979-80 Marhalling circular doesn't support this memory of the train lengths, I suppose a WTT for the summer of 1975 would have the timed stop to pick up the banker if it was planned. I suppose it could be that there was a Special Notice strengthening the Edinburgh train that I picked up on...)

1S19, M4, conveys sleeping cars, not to exceed 550 tonnes beyond Crewe, Bromsgrove a. 22:22.5, d. 22AE25.5. From the winter 75-76 PB working timetable. I don’t have the summer timetable. D600 on the London Midland Region.
I don’t understand the M4 designation.

AE - stops to attach/detach assisting locomotive.

 

[CW2]

An anecdotal response from the viewpoint of a crank that has experienced each of the classes concerned, but very few on trains as heavy as 600 tonnes:

The class 52 "Western" would be able to apply full power from a standing start in good rail conditions, thanks to its hydraulic transmission, so they would probably be fastest off the mark up to (say) 20 mph.
Classes 47 and 50 would be pretty much neck and neck after that.
Class 55 "Deltic" was notoriously difficult to get moving, with a tendency to overload if power applied too quickly, so 52/47/50 would be quicker to 20 mph, but the Deltic would swiftly overtake them after that.
Next comes the 45 (and 46), strong and steady acceleration, but significantly heavier than a 47 / 50.
A pair of 20s, with the same horsepower as a single 40, but more powered wheels and a lower maximum speed probably outperforms a class 40 from a standing start.
Following close behind comes the original unmodified 37, neck and neck with the class 33. Both classes are able to put the power down quite quickly.
The "slug" 37/9 heavyweight would round off the Type 3s. Low gearing and ballast weights = poor acceleration.
Probably the class 31 comes next - although as with the other type 2s, anything really heavy was too much for them.
The 25/26/27 (which you didn't mention) were all pretty much the same. Whenever a heavy train was involved they were used in pairs, so expecting anything much from a single loco on 600 tonnes is wishful thinking. Also they had a tendency to overload if opened up too quickly (and overheat if thrashed for too long, but that's another story).

I have no solid evidence to back up this order of merit, but it looks pretty sound to me. If anybody can produce some tractive effort / acceleration statistics, or logged runs over a specified piece of track from a standing start, that might be illuminating.

 

[EveningStar]

1S19, M4, conveys sleeping cars, not to exceed 550 tonnes beyond Crewe, Bromsgrove a. 22:22.5, d. 22AE25.5. From the winter 75-76 PB working timetable. I don’t have the summer timetable. D600 on the London Midland Region.
I don’t understand the M4 designation.

AE - stops to attach/detach assisting locomotive.

From personal memory, three minutes is about right, and mostly Bromsgrove crews could be in position within time. For those of us spotters old enough not to have a parental curfew, we tended to hang around for the sleeper, and quite often we would be invited onto the bankers for a round trip. Actual performance on the incline depended on the traction up front, although even that be variable, and some crews seemed minded to sit back and let the bankers do all the work.

 

[ac6000cw]

If you're interested in tractive effort and power-at-rail versus speed graphs for (most) 'Modernisation Plan' locos, take a look here - https://www.railtechnical.com/moderisation-plan-diesels