I was reading the section on the Bessemer and Lake Erie Railroad in Kalmbach’s Guide to North American Steam Locomotives and encountered the following statement regarding that road’s 2-6-6-2 and 2-10-2 locomotives:
Is this statement a unique reference to the B&LE’s Mallet or was instability an inherent characteristic of most articulated lokes?
Wouldn’t this draw more responses in the “STEAM & PRESERVATION” section? Many of the Steam fans seem to hang out there…There’s also the “CLASSIC TRAINS” section of the forums which hosts a lot of Steam loving regulars…although O.C the locomotives forum is in no way “diesel only”.
Older compound articulated engines were basically ‘slow motion’ machines that were not built for speed. Many had very small drivers. The B&LE 2-10-4 engines were quite modern, balanced and while not speed demons, could move at track speed with their 63" drivers. The DM&IR later got them and used them in Northern Minnesota ore service.
Modern simple articulates like the 4-6-6-4 ‘Challenger’ were good riding engines with high speed capability.
Jim
Jim, I have the impression that the N&W A’s were also good riding. Am I right? I know that they were used for both passenger and fast freight service.
Incidentally, this morning, RFDTV had a fine half-hour program on N&W freight steam. It was primarily Y6b’s, but I think they had an A or two as well. The description had promised some electric locomotives, but the presentation was all steam.
Johnny
I guess since N&W had 190 2-6-6-2s they must have been pretty happy with their fleet since they warranted multiple orders over the course of five years; I will conclude, therefore, that the instability of the B&LE units were a somewhat unique phenomena and that generally articulateds were no more and no less unstable than steam locomotives in general.
The statement in the Guide is ambiguous as written. Unstable riding qualities could mean “hunting”, or side to side movement of the front engine as speed increases. It could also refer to vertical movement caused by the generally poor counterbalancing of small drivers as speed increases. A third observation would be a combination of vertical and horizontal movements caused by the shuttling action of the pistons (for 90 deg they move in the same direction forward and back) on either engine. The latter is particularly apparent on locos with no trailing truck, so it may not apply to 2-6-6-2’s.
Along with others here, I don’t know of any modern 4-6-6-4 or 2-6-6-4 that had any problem with front engine instability (hunting). All had well-supported reputations of being able to run 70 mph or higher. They were properly designed to take care of the potential problem.
I think that RFDTV program Saturday morning was just the first half-hour of an hour-long program shown earlier in the week. The second half-hour had the electrics. It’s worth watching if you get the chance.
Here’s a link to the book mentioned, for those not familiar: Guide to North American Steam Locomotives
Bergie
The Garrett engines of South Africa ran at speeds of 70 MPH.
Most if not all Garretts were simple articulateds, not mallets. Mallets are 4-cylinder compound articulateds.
Would compounding make a difference?
There is a great difference in the construction of a Beyer-Garrett and the articulated engines used in this country, which, I understand, made them comparatively easy riders. The boiler was suspended between the two engines and had an articulated connection with both, as I recall. Of course, as the train moved towards it destination, the weight on the drivers of both engines was reduced as the front engine crarried the water and the rear engine carried the fuel. Would this have had an effect on the ride?
Johnny
I recommend reading the book Perfecting the American Steam Locomotive by J. Parker Lamb, which was published in 2003 by the Indiana University Press. Lamb, who is a well known railroad photographer, was chairman of the Department of Mechanical Engineering at the University of Texas. The book traces the development of compound and simple articulateds and discusses the issue of instability of the early articulateds.
Simple and compound engines refer to how the steam was used to power the cylinders.
Simple = high pressure steam to all cylinders.
compound = High pressure to one set and the exhusted lower pressure to the other set of cylinders.
Articulated engines meant one set of drivers moved right or left and some up and down independent of the fixed rear set of drivers.
As far as I know the Garretts were the only engines in service that both sets of drivers moved independently.
Mallet was the name of the man (English)(Correction French) credited with the design of the double set of drivers for one boiler.
All articulated had a power cylinder for each set of driver wheels (4 or 6 cylinders).
?? three sets of cylinders per driver truck??? I was wondering if any articulated had three cylinders per truck…
The engines with powered trailing boster trucks were not considered articulated.
No, there were three engines–the front engine was articulated to the middle engine, and the third engine was beneath the tender. The Erie had, I believe ,three triplexes, the Virginian ahd one, and I believe that the Santa Fe also experimented with triplexes. All cylinders were the same size, for one high pressure cylinder exhausted to the front engine which, of course, exhausted tothe smokebox. The other high pressure cylinder exhausted into the tank, and served as something of a feedwater heater.
The great failing of the triplex was that the boilers were not designed to provide enough steam to keep the locomotive going, and it was necessary to stop and build up steam. Also, as the water in the tank was used up, the tender engine lost tractive effort as the weight on it was reduced.
Johnny
The smaller drivers on the early mallets would have a greater dynamic augment (rod pounding) at faster speeds than the later locos with larger drivers.
You also would have to look at the track structure. Early locos were smaller and lighter in total weight even though they had the same weight on drivers as mallets. The total engine weight of the mallets was greater and tended to transfer the instability of the roadbed to the cab.
One more point is the cab placement to the center of gravity to the locomotive. The cab being so far from the center when entering a curve or crossover would toss the crew to one side or the other.
Pete
Anatole Mallet, was FRENCH, NOT ENGLISH.
The rear set of drivers was not always fixed. On the German “Hagans Patent” design the leading driver set was fixed and the rear set articulated.
No: the double Fairlie and Modified Fairlie types and some Mason Bogie types could move both sets of driving wheels independently.
No the Hagans Patent used a complicated set of levers to drive the rear drivers from the front cylinders. The Luttermoller patent used gear drive to a leading and trailing axle while up to three conventional axles (in the middle) were rod driven.
The London and North Eastern Railway had a 2-8-0+0-8-2 Beyer Garratt with three (simple - not compound) cylinders per engine unit and the New Zealand Railways had three 4-6-2+2-6-4 Beyer Garratts with three simple cylinders to each engine unit.
As far as I know, the maximum achieved was the eight cylinder 4-4-2+2-4-4 of the Tasmanian Government Railways which had four simple cylinders per engine unit.
M636C
Well that is what I like about this forum.
People can find out information about everything and there is someone out there with a bit more knowledge.
As there is some one out there attempting to do something different or attempted to it better.
It was also done with out computers, just a pencil and paper.
What was the timing of the cylnders and the position of the drivers with three cylinders? Two cylinders were set at 90 deg.
Ya I think the key issue is the driver size. Early Mallets with small (50-some inches) driving wheels were used for “drag freights” only. It just wasn’t possible to add enough counterweight to offset the weight of the rods. They were generally restricted to 20 MPH or less.
Later engines like Challengers with large wheels (similar in size to passenger engine wheels) rode much better and could run at passenger train speeds.
Remember at top speed an engine’s wheels could rotate something like 13 times a second.
70" drivers at 100 mph are rotating at 8.0 revs/second, so 13 rev/sec is a bit high, equivalent of 162 mph.
57" drivers at 100 mph (!!!) are rotating at 9.8 rev/sec, likely long after rods and crankpins have been distributed to the adjacent countryside. Here, 13 rev/sec is equivalent of 133 mph. Pretty fast for a 2-6-6-2 or 2-8-8-2