Articulated Steam Locomotives of North America

There you go again. I made no such assumption and no such link. If you think I did, quote me. A little bit of honesty might help. It's exasperating because you continue to make (the same) unjustified comments.

Incidentally, Holcroft's patent conveniently expired in 1913.

 

Excellent find. Thanks for sharing.

 

There's an excellent account of the Pennsy's Duplexes in the late Bill Withuhn's (former Curator of Railways at the Smithsonian and a qualified steam driver) American Steam Locomotives. The T1s, with a poppet valve system supplied by Franklin, had continual problems with valve breakages. After a study by a company called Batelle, it was proven that these problems were caused by the drivers exceeding an rpm of 550, a speed equivalent to 130mph. The material used for the valves turned out to be almost incidental.

A few times each month a T1 limped into a terminal with a broken valve, the valve body shattered against its seat. Maintenance practices and inspections were tightened up, but the breakages continued. The Chief Engineer at Franklin, Julius Kirchoff, and his colleagues were not only embarrassed but profoundly puzzled. Based on six years testing of a locomotive fitted with Franklin poppet valves and elaborate bench testing with the first T1s, Franklin had warranted the new T1 valves for sustained speeds up to 100 mph and short durations of 125 mph.

By late 1946, elaborate analysis of production and maintenance records had yielded little insight, and nearly every valve in the T1 fleet had been individually inspected for flaws. The valve breakages seemed to occur randomly, but they were concentrated on the high speed line between Crestline and Fort Wayne where the authorised speed was 100mph. Kirchoff decided to send out a "spy" - a Franklin staffer to ride trains anonymously for a month on the Fort Wayne Division and to clock their actual speed.

In telephone and letter reports, the staffer verified the not infrequent slipping at speed, as well as numerous milepost timings of 100mph and above. Some of his reports seemed unbelievable, including some instances of speeds up to 140mph. When he returned to Baltimore, he met with the group and presented his findings, and he gave his log and watch to Kirchoff for verification. Once or twice per week in the recorded month, when a train was 10 cars or less in length and running behind schedule, the engineer had made up time by exceeding 125mph. Twice that month, with short trains of six or seven cars, speed had reached 135 to 142 mph, as clocked over several miles. Careful inspection of logged entries and watch, as well as the consistency of successive time intervals between mileposts on all the timed runs, attested to the veracity of the log.

In Kirchoff's strongly held opinion, the fallacy of the duplex idea was having two independent drive-systems in the same frame. Rather, the two cylinder pairs and all the driving wheels should have been synchronised as one mechanical group, not two.

https://www.amazon.co.uk/American-S...757216&sprefix=American+steam+,aps,246&sr=8-1

 

It looks as though slipping was the predominant cause of valve breakage. It seems that valves broke, whatever material was used, at above rpm equivalent to 130 mph. It also seems more than possible that the speed record could have been claimed but not when the line limit was 100 mph. Someone would have been fired!

 

Progress on T1 5550:

 

Curiouser and curiouiser!
I do sometime wonder whether British ( or is it just English) exceptionalism creeps into discussions on this site on occasions!

Any Locomotive can slip and I certainly read that the EAR class 59 Garretts could slip but whether one engine slipping induced the other to slip I know not. The engines on a Garrett could certainly get out of phase with each other, as on any other Garrett and presumably any articulated locomotive .
Don't the BR class 60s possess a creep facility that allows a very small amount of very controlled slip to increase traction?

Brilliant Photos. Thanks for posting!

As were some of the Class 37s in Britain for freight work (Class 37/7s)

 

Whilst I am no engineer, and am willing to be proven wrong, wasn't the use of the undriven axles, at least on Mallets, to
1) guide the engines on curves
2) support the weight of the massive fireboxes required to produce the steam to move these behemoths.
3) to reduce axle loading to acceptable levels for the track, given that extra driving axles would be superfluous for the desired "TE, Tractive Force or BHP" whichever are the correct methods of measurement.
Many of the Mallets were no slouches, able to hustle along at 70+ mph and at home on timed freights and passenger loading.
In addition Mallets were transferred from some railway companies to others to help the war effort, despite perhaps being less suited for the task confronting them. Needs must.
Obviously those companies "donating" motive power were unlikely to offer their top notch stock!

 

Parallel this to valve gear bending or breaking at excessive speed. The 9Fs were recorded as unofficially reaching speeds in the 80s, with enthusiastic loco crew, and were then restricted by diktats from the management, because of worries of the forces exerted by reciprocating masses.

 

I remember reading somewhere that when Blue Peter went into that uncontrollable slip, the rpm, just before the valve gear broke up, would have been the equivalent of 140mph

 

Forgive me if I am mistaken, but several of your posts suggest that you may be confusing the terms "Mallet" and "articulated", they are not synonymous. Mallets are by definition compound (double or triple expansion) and articulated, most articulated locomotives (especially those built with speed in mind) were simple (single expansion) and therefore not Mallets.

 

A Big Boy is a Mallet and is not a compound

 

ALCO had the sole US licence for the Gresley conjugated valve gear and promoted it vigorously in the 1920s as part of its 3-cylinder campaign when 2-cylinder locos had reached their effective limits of TE capacity. There were various 3-cylinder locos built by ALCO with Gresley gear, the most significant being the 4-10-2 classes for the SP and UP and the UP's spectacular 9000 series of 4-12-2 locos.

The Gresley gear on the earlier locos was always prone to extreme accelerated wear, probably due to US operating conditions, and was not really satisfactory until the second batch of 9000s when roller bearings were fitted to the motion pins. The accelerated wear resulted in all 15 of the first batch of 9000s being rebuilt c.1935 as "third link" locos with three sets of motion, two on one side and one on the other.

The 9000s sent by the UP to the OW were also fitted with two-axle boosters on the leading tender truck (bogie on this side of the pond) making their tenders one their own notionally more powerful than many British main line locos.

 

A Big Boy is categorically NOT a Mallet, it is a simple-articulated locomotive.

For the record and to correct several other popular Big Boy misconceptions, neither were the Big Boys the largest, the longest, the heaviest, or the most powerful locomotives, all of which accolades are regularly and erroneously applied to them, although it is true that 4014 can claim most of these in terms of locomotives currently operational.

It is, I believe, possible to demonstrate that a Big Boy boiler would theoretically fit inside the boiler of an Allegheny.

 

Technically it’s not but we’re in danger of splitting hairs. A true Mallett is a compound, Big Boys were not compounds.

 

It is far from splitting hairs. In the taxonomy of steam locos they are specific terms meaning different things and should be used properly, it is not splitting hairs. All dogs are mammals but not all mammals are dogs. All Mallets are articulated but not all articulated locomotives are Mallets. (Since this thread has also diversified I could add that all duplexes are divided-drive rigid locomotives and are neither articulated nor Mallets).

Technical accuracy is a good thing and should be encouraged.

Neither is it splitting hairs to point out that the term Mallet has a single "t".

 

There’s nothing wrong with accuracy, but I’ve seen the term “simple mallet” used of classes like the Big Boy, where the dominant feature is not compounding but the form of articulation.


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There is no such thing as a "simple Mallet", although I suppose the term could refer to a Mallet which lacks complexity, or possibly a Mallet which is running "simple" whilst accelerating a train from rest. Some compounds including articulated compounds (such as the celebrated N&W Y6B) had this facility.

Otherwise the fact that you've seen the term is irrelevant, it simply casts doubt on the competence of the author and does not make it right.

 

Or perhaps it could refer to a locomotive using Mallet’s articulation principles but with only simple expansion.

I’m not arguing it’s strictly correct - it isn’t - but that nomenclature evolves beyond the strictly correct.

That people here - an informed audience - are using the term in this way suggests that, like “hoover” or “google”, the term has outgrown its original precise meaning.


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