European freight yard operations vs US Operations



The Garrat is effectively a 'tank locomotive' whereas the US Mallets, (excluding the Triplex) are 'tender locomotives'. The same problem of reducing tractive effort occurs with almost every tank locomotive ever in operation. Simply moving the boiler/engine unit pivots outwards and placing the supplies in a seperate tender would solve that "problem". The Triplex Mallet had the same problem, but in that case it really would have been a problem as all the loss of weight was from just one engine unit.
Regards, Greg.P.
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Well, no, had circumstances differed, the triplex *might* have demonstrated that problem eventually, but since the inadequate boiler never could supply enough steam for sustained running anyway, that difficulty rarely -if ever- arose.
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Whatever the boiler's failings, assuming it could raise enough pressure to slip the drivers on starting, the major change in weight on the tender driving wheels would have created traction problems with that group. If I remember rightly, the main frame drivers cylinders feed the two outer pairs of cylinders in compound form. If the rear driver set lacked weight then either those drivers would slip, causing a drop in the mid pressure receiver, which would effectively drop steam pressure to the front engine unit and raise pressure to the main engine unit, or the maximum throttle and cut-off would have to be kept below the rear engine's traction limit.
Regards, Greg.P.
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Hi,
Greg.Procter wrote:

Well, but let's just assume these steam engines were used just for helping to push trains up a ramp. There is a yard with service facilities at the bottom of the ramp and after pushing the train up these locos just "drift" back down or probably help a down train by supplying additional brakes and air...
In that scenario, the boiler gets re-filled below, so the adhesion is good while pushing up and it doesn't matter for the downhill part, anyway.
So, while it is a very limited use, such locomotives may actually work in this scenario. AFAIK the triplex locos (2-8-8-8-2) were used by Virginian in such a way.
Ciao...
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A good point. However, the power trains (engines) would always be more or less well balanced, which is a great deal more than could be be said for some Mallets which were woefully ill balanced. I think that I am correct in saying one or two were very nearly unusable because of that and had to be modified or abandoned. My memory is rather shaky here. Perhaps someone else can shed further light on the aspect of well balanced Mallets, or otherwise.
Oh! I just happened to thumb through a copy of Train Shed Encyclopedia to check a point and, referring to an earlier comment I made, I note the Allegheny H8's were designed for 60 mph max. and 30-35 max. continuous power output. Why then run them for long periods, or any other locomotive, at crawling speed - it just doesn't make sense

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Back when the USRA designs were done, there wasn't much interest in really high speed for freight trains - cars had friction bearings on the axles as well as the locos - so the need for a good balancing of the drivers really hadn't become critical. It wasn't later till some of the western roads wanted to get their trains over the track faster that the latest techniques weree applied to dynamically balance freight haulers.
-- Bob May
rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net
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Hi Bob,

I think that we are at cross purposes, maybe?
I was talking about balanced power distribution to individual engines related to balanced weight distribution of the boiler/main frames to achieve equalised traction without slippage, particularly on Mallets where, if my memory serves me correctly, some locomotives were notoriously poor in this regard. I should have made my point clearer!
I think that you are talking about wheel balancing, yes?
Brian
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Looks like it.
Mallets had the problems you're speaking of not so much because of unbalanced weight distribution, but because the low-pressure cylinders on the front engines had to be much larger in diameter than the high- pressure rear cylinders, and figuring out just *how* much larger in those days was largely (pun intended) a matter of cut-and-try to see what worked.
If you guessed wrong in the design phase, the front cylinders might well have more (or less) thrust than you intended them to, and would pull harder than the rear engine as a result; breaking traction every time the front engine (A) hit slippery track (which it would hit first, remember), (B) started up a steep grade where there was now less weight on the front engine due to weight-transfer, or, (C) the steam lines running from the rear cylinders to the front ones developed leaks (and they did), in which case the front engine might pull so poorly that the rear engine was the one that kept slipping.
As you can see, most of these problems could be (and were) solved by using simple articulation -where all the cylinders use the same high- pressure steam- and by increasing the sophistication of the locomotive's articulated suspension system as well.
In an interesting and little-known sidelight; the Southern Pacific's cab-forwards had a built-in advantage in the weight-transfer department: where a normally oriented articulated would *lose* weight on the pivoting driver set as the locomotive climbed a grade -possibly causing a loss of traction- the pivoting set on cab-forwards actually *gained* more traction on grades, which explains why these locos had such an outstanding reputation for not slipping.
~Pete
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On 9/3/2009 12:48 AM Twibil spake thus:

Warning: tangent.
Speaking of cab-forwards: in retrospect, with 20-20 hindsight, that design makes *so* much more sense than the traditional cab-behind one (including the weight advantage you mentioned). Makes me wonder, naively, why it wasn't adopted much earlier and universally. Why was a clearly inferior arrangement taken as "the way it must be done"? Why force the engine driver to control a huge locomotive with its train from a vantage point with limited sight, as if peering through a small peephole?
(As a further tangent, it always cracks me up to think of all those letter "F"s painted on early diesel locomotives, so the hidebound steam engineers would know which way was supposed to point forwards. When was this practice dropped?)
--
Found--the gene that causes belief in genetic determinism

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On Thu, 03 Sep 2009 10:18:23 -0700, David Nebenzahl wrote:

The cab forwards had the best safety record of all SP steam.
--
Steve

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On Thu, 03 Sep 2009 10:18:23 -0700, David Nebenzahl

Not with coal firing. Many "standard" locomotives could be supplied for oil or coal.
There were problems with this layout though - there was at least one fatality when oil pipes under the engine leaked causing wheel slip in a tunnel.
From Wikipedia:
One problematic aspect of the design, however, was the routing of the oil lines; because the firebox was located ahead of the driving wheels (instead of behind them, the usual practice), oil leaks could cause the wheels to slip. A nuisance under most conditions, it resulted in at least one fatal accident. This occurred in 1941 when a cab-forward with leaking steam and oil lines entered the tunnel at Santa Susana Pass near Los Angeles. The tunnel was on a grade, and as the slow-moving train ascended the tunnel, oil on the rails caused the wheels to slip and spin. The train slipped backwards and a coupler knuckle broke, separating the air line, causing an emergency brake application and stalling the train in a tunnel that was rapidly filling with exhaust fumes and steam. The oil dripping on the rails and ties then ignited beneath the engine cab, killing the crew.
And I think there were crew concerns about safety in a collision. I know there was a fatality when a cab forward hit a flat car.
Also they weren't used to a truck under the firebox that "steered" the engine into curves instead of just carrying the weight so there were some early problems with this.

Heck, Union Pacific steam locomotives had "UP" painted on the back of the tender to show which way to re-rail it.
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(Note to self: remember to point this out to the die-hard U.P. fanatics at out next club meeting...)
Thanx, Chris. That's a good one!
~Pete
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On Fri, 04 Sep 2009 05:18:23 +1200, David Nebenzahl

The Brits did it in the first decade of the 19th century :-) It was only when Stephenson's boiler showed the (best) way that the "U" flue boilers went out of fashion. The Italians tried it pre-1900 with 4-6-0s (0-6-4?) and 0-10-0s (0-10-0s) but the coal bunker beside the firebox severely limited the range. The Germans tried blowing pulverized coal from a rear coupled tender to the cab-forward firebox BR05 4-6-4 but the trunking tended to block up. Cab-forwards really need to be oil fired!

Loco drivers don't really need wide vision - it only enables them to see things like semi-trailers parked across level crossings. All they need to see are the signals.
Regards, Greg.P.
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On Fri, 04 Sep 2009 09:15:20 +1200, Greg.Procter wrote:

Luckily for SP, they'd switched to ol by 1903, so when the Baldwin 2-8-8-2s they got in 1908 resulted in near asphyxiation of the engine crews they went looking for solutions and were able to go with a cab forward design.
--
Steve

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In article

Fascinating stuff. Thanks. But I was actually thinking about simple Mallets rather than compound. Didn't some of these come well and truly unstuck too (no pun intended)?
Personally, I've always thought that the Garratt was a fundamentally sounder design, from several points of view, but I wouldn't argue the case. I guess it's very much 'horses for courses' and there must have been successes and failures in both camps.
Brian
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On Thu, 03 Sep 2009 18:57:49 +0100, Brian Bailey

Americans tend to use the word "articulated" where other countries use Mallet because other kinds are uncommon there.
Mallet's original patent was for a compound, not the articulation method he used.
Some of the last compound Mallets had low pressure cylinders to the limit even of the large American loading gauge.
http://www.retroweb.com/trains/y6_2136_m.jpg

It's not articulated, but Churchward showed that a well designed simple engine was just as good and a lot cheaper to build - he used two cylinders with a very long piston stroke giving the save volume as the de Glehn compound's four. The de Glehn was a far smoother running engine and being a balanced design gave negligable hammer blow due the two cylinders on each side operating at 180 degrees to each other, balancing each other out.
So Churchward came up with simple 4-cylinder engines with the same layout.

I've heard that.
They were certainly very good engines. Californian friends my age who saw them in operation speak very highly of them.

It's an inherently less stable design than the Garratt which is more like two locomotives with a boiler slung berween them rather than a single flexible one. Garratts, Fairlies and and Meyers run more like bogie passenger carriages.

Me too. Outside the USA it pretty well superceded the Mallet. I suspect there might also have been patent royalties.
There were a few other kinds in the USA. The Denver and Rio Grande had a Fairlie that was shipped out from the UK but this didn't have enough fuel or water capacity. Mason built one double Fairlie and a lot of single Fairlies. And don't forget the Heislers, Shays and Climaxes.

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A "Mallet", by definition, *is* a compound Mallet, although simple articulateds were also sometimes misnomered as Mallets by folks who didn't really understand the difference. In their minds two or more sets of drivers with a hinge in between equaled a "Mallet".
http://loggingmallets.railfan.net/sub/malletinfo.htm
From what I've read, some early simple articulateds were indeed prone to slipping the front engine under some circumstances, but I never heard of them having that problem to the same extent as did compound mallets.
But the causes of loss of traction on the front engine are immediately obvious if you look at the side elevation of practically any articulated design: the rear engine supports much of the weight of the cab, the firebox, and the largest diameter portion of the boiler, while the front engine has only the lighter portion of the boiler and the smokebox (which is hollow) above it to provide downforce. And in most articulated designs at least the first set of drivers hang clear out beyond the front of the smokebox!
I've never seen any figures on what the weight differential between sets of drivers was on the various articulated designs, but it's a safe bet to say that the less weight the front engine carried in proportion to the rear engine the more prone it was to slip the drivers.
BTW: It was easier to slip a set of steam engine drivers than most people suppose. In the video listed below you can see an over- enthusiastic hand on the throttle break one set (I can't tell for sure which set) of drivers loose under a cab-forward while it's still on the roundhouse lead track and is barely off of the turntable! Listen to the exhaust note suddenly speed up...

http://www.youtube.com/watch?v=n_ErZ5SgkVw

~Pete
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wrote:

No.
While his patent was for compounding which he didn't originate, it is his system of articulation.

What kind of articulateds? Surely not Fairlies, Haywoods, Garratts, Meyers etc?
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Yes.
From the URL listed below: "While it is not technically correct to call them Mallets since they are not compounds as per the Mallet patent, simple articulateds like Weyerhaeuser #111 were identical in design concept to a regular Mallet except for the fact that live steam was delivered to both sets of cylinders at the same time."
What part of this did you not understand?

You don't know what sort of locos we're talking about in this portion of the thread even after reading the URL?
http://loggingmallets.railfan.net/sub/malletinfo.htm
If so, you need more help than I can give you.
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wrote:

And they got it wrong. What's your point?

I know perfectly well what I'm talking about.
Mallet's system of articulation is not the only kind.

What part of that did YOU not understand?
Just because there was (mostly) just one articulation system used in the US, doesn't mean they have exclusive use of the term to mean Mallet's articulation system.
Tell me, what would YOU call a simple engine using Mallet's articulation system given that "articulated" does not exclusively describe it?
Well?

Articulated on its own means generic articulated.
I'm not the one who jumped in to insist that "Mallet" really meant compound Mallet articulated.

Hardly.
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