Steam speed records including City of Truro and Mallard

That might confirm whether or not the speed of the chart paper varied, but that is irrelevant to the speed calculations, which were and are made from the time and distance traces. Whether there is a systematic variation in the distance trace, as argued by Andrews, or not, as argued by Simon, is of some interest, but it is of little relevance to the 125/126 question. The most telling argument there is the impossibility of the speed really increasing and decreasing much over a few seconds.
I agree with Simon that Mallard's performance over the whole run deserves more attention.
If we wish to speculate, we could speculate what Mallard (or any A4 with the double Kylchap exhaust and after receiving the improved middle big-end) could have achieved if given the chance .

 

A happy Xmas and nice new year.

 

We have sister engine 656 at the Nene Valley Railway.

 

I'm in a Facebook group about the LMS and old one about the Aspinall LYR Atlantic has resurfaced. Didn't we discount this on here a while back?

 

Link to the discussion?

I don’t think the LYR Atlantics were capable of 90mph, but we keep getting lots of claims about high speeds with little evidence.

 

plenty from the USA too at that time

 

Why not? 90 mph is less than 360 rev/min which is the traditional design speed for reciprocating steam engines (not simply locomotives.) so should be achievable as a piece of mechanical equipment.

 

The Belgian SNCB 12 inside two cylindered was measured doing 103 mph and had drivers of 2100mm

https://www.altaplana.be/_media/documents/atlantic1201.pdf

LYR had 2210mm drivers

Who, by the way, are WE getting lots of fake informations?

In Germany it was clearly specified before WW1 that two cylindred locomotives were not to go faster than 5 rev per second and max hammerblow per wheel not to exced 15% of stationary load on same.
Three and fourcylindered were allowed 6 rev per second.
These speeds were sometimes execed on police acceptance prototype test,but only by accident in normal use.

 

Because the more I look into Mallards run and what was actually required to achieve the comparatively high speeds the more sceptical I become to the 90+mph claims that are not authenticated by dynamometer car or similar.

In the round I don’t think enough consideration has been given to air resistance, rolling resistance, ability of a boiler to maintain the required rates to achieve these speeds, and a lot more besides.

In short, I think steam locomotives likely got to the early 90s and hung around those speeds for a very long period of time before the size of the boilers increased enough to supply steam to the required rate to accelerate and maintain those speeds.

 

I'm inclined to agree, Steve, but quite frankly the thoughts of the jack pin in the connecting rods driving the Joy valve gear flailing around at those speeds and under the power that would be required makes me wince a bit!

But the real problem would be finding a sufficient length of suitable track on the L&YR, which was a medium speed, medium to short distance workings line. Unlike the GNR or, for that matter, LNWR, it was a bit short of long stretches of straight, slightly falling track over which to do this.

 

OTOH - find a suitable gradient...

In the case of Mallard, it was probably getting about 3,100hp from the cylinders - but also another 1,500hp from the gradient, and in railway terms that wasn't even a very steep downhill. I don't know the L&YR case well enough to comment, but I don't in principle feel that 90 mph from an Edwardian loco on a suitable road is that far fetched. I wouldn't be that surprised for example to find a T9 doing those sorts of speeds through Axminster with a light load aiming to charge Honiton Bank.

There are cases with well-attested high start-to-stop average speeds over fairly long distances from that era. To make them, you have to either assume that when the running was favourable they ran at very high speeds downhill; or else they were able to sustain rapid acceleration from a stand and high speeds uphill - which feels less likely.

Thought experiment: suppose you wish to run at an average of 60mph - and bear in mind Hardwicke managed 67mph over 141 miles on its famous run.

- Each mile takes 60 seconds
- Hit a mile of gradient that knocks you back to 45mph, and you take 80 seconds for a mile, i.e. every mile loses you 20 seconds on your schedule
- To get that 20 seconds back, you need to run a mile in 40 seconds, which is 90mph.

In other words, on a line with equivalent amounts of uphill and downhill, every mile you run at 45 mph requires you to run another mile at 90mph to maintain your 60mph schedule.

Tom

 

This was a the chart prepared by Harry Ivatt to demonstrate the speed needed to make up lost time, as given in H.A.V. Bulleid's 'The Aspinall Era'.

 

So far.........

Mallard & the German 05 went very fast

Even if it didnt go quite as fast as Mallard the 05 was timed at over 110mph on several occasions.

Als after its High Speed run Mallard had failed unlike the 05.

BUT only 3 05's were built whereas there were 35 A4's in front line service for over 30 years

Then the high speed runs are all very well but what the paying passenger wants was summarised by Herbert Walker, the regular service, punctuality and a decent but not excessive speed.

To what extent did railways other than The Southern aim for this and how did these runs contribute to it?

In particular what was the best point to point timings reasonably achievable day in day out, what was done to improve these both in terms of increasing the power of locomotives but also reliability.

 

Max continious with two firemen on postWW2 test stand V2 was 1990 ihp.
Is there any information how much extra for how long by lowering water level and pressure?

 

I’m not saying that an L&Y Atlantic did 90 mph; I am saying that one would be capable of doing so which was in contradiction to your earlier post. There are a lot of extraneous things that contribute to how fast a loco can go ranging from train weight through to gradient to curvature with a lot of parameters in between. The L&Y was not a high speed line. Stick the loco on the GN down Stoke with a light load or billiard table GC and 90 should/would be achievable. 360 rpm was a norm with steam engines in Victorian times.

 

But markets vary. Short distance--frequency and reliability are king. London to Scotland in the steam era is going to be six hours plus so for the end to end traffic you need departures at say 1000, 1600 and 2200. In that type of market, journey time is very important whereas frequency isn't.

Of interest is the intermediate case eg London-Birmingham or London-Bristol where there is more of a blend of journey time and frequency.

Whether it's a King, a Duchess, a MN or an A4, the practical requirement is to be able to run reliably in the 8os over many miles. Mallard put up a tremendous technical and publicity achievement for a rather grey and battered country. We were still Great Britain. The implications for everyday railway running were zilch.

 

Wasn't it supposedly somewhere between Liverpool and either Southport or Ormskirk?

 

Oh, I don't know, Steve. L & Y Atlantics did Liverpool (Exchange) to Manchester (Victoria) non-stop, via the Wigan avoiding line, in 40 minutes, regularly.

 

The reported track was that between Liverpool Exchange and Southport - specifically between Seaforth & Litherland and Birkdale where the track is fairly straight and gradients IIRC are minimal. The train concerned was a test train to check possible electric timings hence no claim for the first 100 mph was made at the time.

 

As a matter of interest what is the current line speed limit on Seaforth to Birkdale section?