P2 Locomotive Company and related matters

Metal fatigue is independent of speed.

 

Entirely agree with no wish to go there again, now if only a moderator would see this they could delete the associated posts....

 

Definitely no plans to ask if the P2 can be allowed above 75....

 

Don't you mean the conductor rail?

 

But stress may be dependent on speed and increasing stress will reduce the time to fatigue failure

 

The P2 (if it eventually runs) is seen as a hauler, not a racehorse like Tornado. If my memory is correct, the late David Elliott once told me that there was no evidence that the P2s had ever run faster than 80mph.

 

However speed on a loco is linked to rotation of wheels and rotation is linked to cycles and fatigue is linked to cycles

 

But if you do a journey of a given length, don’t you do the same number of wheel rotations and therefore cycles? So if a loco covers 100 miles in two hours at 50mph or in 1h 20 at 75mph, it has done the same number of cycles …

Tom

 

This non-engineer, who understands that the faster something goes the more energy it uses, doesn't quite understand how fatigue in a moving part can't be linked to the amount of energy going through it.

 

Come on - think about it. The only way that a steam loco running at 90 mph is going to be of any benefit/compatability with the modern railway is if there is a diesel on the back powering like hell. A steam loco on its own just does not have the acceleration charastics of modern traction and there is no point in pretending otherwise. If Tornado takes say 10 miles to get up to 90 mph when the following train does it in less than a mile you are not that compatable. Granted it is better if you use a diesel on the back to aid acceleration but..... that is not what people (at least on here) want. Oh, the realities of main line steam in the 2020s!

Peter

 

Surely acceleration is only half of the issue? Isn't the other about the ability of a train, once at speed, to stay out of the way of other services?

 

My old man was saying, even when we started doing tours in the late 70's, that it would be acceleration (or lack thereof) which would eventually see steam off the mainline... And its hugely worse now electric has replaced diesel on many mainlines.

Oh and stop calling @torgormaig Shirley....

 

Running faster downhill, as in steam days, would make a difference, but possibly not much.

 

Just applying a fag packet calculation: Let’s take @torgormaig numbers - a steam hauled train that takes 10 miles to reach 90mph, vs a modern unit that gets there in 1 mile. Let’s also assume the acceleration is linear (unlikely, but fag packet calculation).

The electric train takes 80 seconds to run the first mile, and 40 seconds for each of the 9 subsequent miles - 440 seconds in total to run 10 miles (or about 7m 20s)

The steam-hauled train takes 800 seconds to get to 90 mph - or 13 minutes 20 seconds.

In other words - the steam special could be given a six minute head start and the electric would catch it after ten miles …

Tom

 

But my post was simply in relation to speed not time or distance. The reality is that they are all interlinked, along with stress variation and even design which, badly done, creates stress raisers.

 

This is veering very close to laden vs unladen African or European Swallows.....

 

At the time of the run that was suspected to have been an unintentional consequence of the general restriction of steam to 75 mph. It did seem illogical that both Tornado and Mk Is were allowed to do 90 mph but not together.

 

That sounds awfully like a Nat Pres urban myth to me. I have never heard of Mark 1s being limited to 75 mph specifically behind steam. They are normally 100 mph vehicles and the only limiting factor in them not running at that speed behind steam is the limit imposed on the the loco itself and not on the stock. Just like they are limited to 95 mph behind a Class 47 diesel.

Peter

 

It's specifically included in the regulation 4 exemptions, extract from the current LSL document available online:
"(d) The operator must ensure that the Rolling Stock shall not be operated:

(i) at a speed exceeding 75 mph (120 kph) for steam operations: or
(ii) at a speed exceeding the plated speed of the coach for electric or diesel operations."​

 

I'm surprised you say that Peter. I thought the model was that if you can run at 75mph max with steam, you can have a 60mph path. Whereas if you can run at 90max,you can step up to a 75mph path and probably run for the most part at 80-85 well within the performance rating of an A1. So the model was York in four hours, 100 mins to Grantham, 40mins to water while two LNER flights pass, another 100 mins to York. There are 75mph schedules on the ECML,there must have been discussions about what would be possible say on a Saturday. It wasn't complete cloud cuckoo land either commercially or operationally ten years ago.

Peter