Articulated Steam Locomotives of North America

I think most of us share your scepticism about the 140 mph. But some of the American railroads did run very fast services prior to WW2, comparable with those run at the time in Britain and Europe.

Most of the super-fast trains were run by diesel units, but the Milwaukee Road retained steam power into the 1940s on its "Twin Cities Hiawatha" service, which in 1939-41 provided the fastest-ever regular scheduled steam service - 81 mph on the 78 mile section eastbound from Sparta to Portage.

https://en.wikipedia.org/wiki/Twin_Cities_Hiawatha

Motive power was the A-class 4-4-2 and F7-class 4-6-4, both specially built for high-speed service with 7-ft driving wheels. One of the Atlantics was recorded by dynamometer-car at 112 mph, while there was a stop-watch timing of one of the Baltics getting close to Mallard's speed. These engines make an interesting comparison with Gresley's A4, but had 32-ton axle-loads and only two cylinders.

https://en.wikipedia.org/wiki/Milwaukee_Road_class_A
https://en.wikipedia.org/wiki/Milwaukee_Road_class_F7

 

Another interesting concept experimented with by the AT&SF was that of a jointed boiler to allow more flexibility and presumably reduce frontal overswing.
Several were built with a bellows type joint (made up of bolted metal rings) and one with a Ball and Socket set up.
They were less than successful

It is interesting that more of the American Railroad Companies did not attempt a world speed record, perhaps after the war.
At the risk of upsetting Gresley devotees, Mallard appeared to be at the limit of its abilities when gaining the record.

Considering that the Americans were designing Locomotives that could exert 5000+ drawbar horsepower, utilised roller bearings on axle and motion surfaces, equipped locos with mechanical stokers and a plethora of other technology one has to assume it was the lineside infrastructure that set the limits.

 

It would still be wrong. Tractive effort (or tractive force) is a purely calculated number based on boiler pressure; cylinder dimensions (stroke and diameter); number of cylinders and wheel diameter. As such, the locomotive weight is irrelevant, as can be noted if you compare, say, 2-6-0 and 2-6-4T versions of basically equivalent locos, which have different weights but the same TE.

What you might be thinking of is the factor of adhesion, which is TE divided by the adhesive weight (i.e. weight on the driving wheels). Adding axle load to the driving wheels improves the factor of adhesion since while the TE remains the same (nothing changes in boiler pressure, cylinder size or wheel diameter), the weight on the wheel increases which reduces the propensity to slip for a given force applied at the rim.

Tom

 

If you had said traction you might have just got away with it. If you had said adhesive weight you would have been right. Tractive effort is purely a function of cylinder size and number, wheel diameter and boiler pressure although there is also a relationship between TE and weight, generally referred to as the adhesion ratio.

 

The 60 Class Garratts were the last of the NSW locomotives to receive the cast frames with integral cylinders, the 57 Class 4-8-2 being the first - these incidentally being inspired by the UP 8000 Class which also had the Gresley-Holcroft valve gear.

The later 58 and 59 class also had the cast frames, although the 58 was a modified 57, and the 59 was a US-built machine so naturally had them, but the most famous exponents of this technique were the 38 Class Pacifics.

 

Nominal TE is calculated as you say, but adding weight could increase the actual deliverable effective TE.

 

Hey I'm no engineer, I'm just going on what the books say!

Getting my head around this though , TE appears to be a "superfluous" figure then, because if weight has no bearing TE is purely a "potential" and without weight cannot be transferred to railhead?

What he said!

 

There’s a relationship between TE and weight. Too little and you can’t deliver the TE, too much and you are using more TE to move the loco than necessary. As a rule, you are trying to reduce the weight of a steam loco and increase the weight of a diesel to reach the optimum ratio. But not always.

 

High horsepower is no guarantee of high speed.
Having said that, IIRC the NYC Niagaras could cruise at 100 mph with 1000 short tons on the drawbar. Pretty impressive but no guarantee they could have gone at 120+ on a lighter load.

 

This is what i have been looking for, for a couple of days.

A group well down the route of building a new T1, these are the lot hollering on about doing 140mph, soon....

The T1 Trust (prrt1steamlocomotivetrust.org)

 

But that's my point exactly: 81mph is not exactly 110 or 140mph?

Yes, but these are not duplex locomotives like the T1 where 140mph is being claimed. If anything, you'd see more evidence for these locomotives having authenticated speed records but it simply does not exist the other side of the pond.

I think trying to take the speed record these days is daft, to be honest. Too many factors of safety for a 126mph+ run in my view.

 

The weights of many steam locos were determined by what the civil engineers could accept, and (at least in Britain, I don't know about elsewhere) some consequently had adhesion factors rather below the optimum.

 

Yet we get regularly reminded that for their weight, British locos were puny in comparison to what the sainted Chapelon produced! Hordes of 4000hp 100 ton locos heading every which way around France! Maybe with all that power and so little weight they could do 140mph indicated on the speedo even if proceeding rather more sedately over the ground …

Tom

 

The Chapelon improvements would have greatly increased the power outputs at moderate and high speeds without involving very high TE at low speeds.

 

Whilst I sort of agree with you, that is the nature of human endeavour.
Why go to Mars for instance?
We are doing a good enough job of b*ggering up this planet without exporting more trash into outer space - but without pushing boundaries technology does not evolve.

Arguments have been posted on NP about new builds - the whys and wherefores etc. At the end of the day if it catches peoples imagination and they are willing to expend time and money that is their prerogative.
Personally I cannot see why there was a need to build Tornado but respect those that achieved it.
Why are there groups replicating a Baby Deltic or Class 22 or a Class 29 etc? Hardly successful traction!
Personally I would like to see a replicated Blue Pullman and yes perish the thought a modern interpretation on "Leader", perish the thought. (Just to see if modern materials and technology could make it work!!!!!!!)

Outside Railways what is it about Land Speed Records etc?

Regards safety of running at 126+ MPH cannot see that safety should be an insurmountable problem? If a line straight and flat enough can be found, and the owner of that line is agreeable, safety precautions can be put in place! These days it might even be possible to control the loco remotely perhaps?
After all Mallard didn't explode on its run!

And Civil Engineers didn't always get it right! I think I am correct in saying the Highland Railway "River" class were sold on to the Caley because their axle weights were too high for the Civil Engineers liking, but subsequently found to produce less hammer blow, because of superior balancing, compared to other HR loco stock.

Of course not, many other factors are involved I should imagine ie. breathing, reciprocating masses, steam production ........ but certainly having a high BHP helps, I would imagine, if all other factors are optimised!
Certainly with road vehicle technology having a high BHP is no substitute for Torque (Grunt).

 

I'm loathe to get into this debate again, but everything my research is telling me with regards to the Gresley days on the L.N.E.R. is that the so-called Chapelon improvements didn't translate into real world work. The best example of Chapelon's work is the one he shares with Kylala in my opinion - the Kylchap. That is what helped Mallard achieve 126mph, ultimately.

In L.N.E.R. days, there wasn't a requirement for 4000HP locomotives. By 1948, you could argue cogently for a 3000HP locomotive, but by then probably diesel electric in nature and for the speeding up of express passenger services more than freight at that point. The mammoth steam locomotives of the United States worked on entirely different infrastructure: longer consists required more powerful locomotives.

I've just finished a chapter on Gresley's P1s and, though in my view they represent some of the best Gresley designed (booster issues aside), the infrastructure in terms of the track layout, sidings, and more were simply not in place for the trains they were best suited to pulling (100 wagons or more).

I think enthusiasts often forget that locomotives and rolling stock are constrained by the limits and needs of the working railway, and not the other way around...

 

Of course enthusiasts' needs should come first !

 

For most of the steam era, French trains were subject to a national speed limit of 75 mph (120 km/hr). The 1930s brought some relaxations and some high-speed trials, but i don't recall seeing any report of a French steam loco reaching 100 mph.

So the focus of French designers had to be on achieving acceptable end-to-end times through relatively high uphill speeds with heavy loads. So Chapelon produced plenty of horse-power, but not Mallard-type speeds.

It was only when main-line electrification was well advanced in the 1950s that the French seemed to become interested in rail speed records - but not with steam engines.

 

I see parochialism is alive and well in pre grouping Brighton territory.