European freight yard operations vs US Operations

Yeah, they're pounds.

Reply to
Steve Caple
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Har de har-har. :-)

Reply to
Roger T.

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

Reply to
Brian Bailey

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

Reply to
Twibil

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...

Reply to
Bernhard Agthe

Hi,

Greg.Procter wrote: (center couplers vs. buffer-and-screw)

Not necessarily...

Well, in a badly tightened train I'd say up to 1/2" of loose slack and some more slack at the point where the buffers just start to compress until they reach the "norm" compression, so about 1" would be what I often see a freight train's rear wagons "bounce" back after stopping, accumulated to more than 1ft. in a normal (10-15 car) train... Especially fancy to watch when it's tank cars that are about half full...

Well, I'd consider 1mm of slack to be less than what I regularly see (or think I see).

Apart from that, you can build a center coupler with some buffering properties (spring), and this is being done with Scharfenberg couplers. So basically you could have little "free" slack (a few mm) and some sprung slack (which would negate most of the free slack). But this is more expensive than...

Sure ;-)

(automated brake line coupling)

Yeah, but my argument was along the line of a few wagons separating from the end of a train at speed - the automated valves need to stay open for long enough to put the whole train (both parts) into emergency braking - as would happen when a train separates nowadays)... But if the brake valves shut upon the separation, both parts of the train would continue to "run" at speed which is not good ;-)

That was about the point - it would have been too expensive to change millions of couplers...

So, I have all winter to either change my model railroad's couplers (N-Scale Rapido to Kadee-style) or to repair my broken Rapido couplers ;-)

Ciao...

Reply to
Bernhard Agthe

(fully automatic couplers)

...

Yeah, I know, but I do see one problem with fully automatic couplers - as explained, they may not "open" the brake line in case of unwanted train separation at speed or they would "open" the brake line in case of (controlled) hump yard shunting...

So, two different ways of uncoupling have to be implemented:

(1) "controlled" uncoupling with the valves closed before uncoupling the brake lines and

(2) "unwanted" uncoupling with the valves staying open long enough to put the train into emergency braking after uncoupling the brake lines.

But I'm sure the designers of the system did thing about this ;-)

Ciao..

Reply to
Bernhard Agthe

On 9/3/2009 2:20 AM Bernhard Agthe spake thus:

In the case of a "break-in-two" at speed, the brake lines certainly would open, albeit destructively: the hoses would simply be ripped from the trainline.

Reply to
David Nebenzahl

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?)

Reply to
David Nebenzahl

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

Reply to
Steve Caple

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.

Reply to
Christopher A. Lee

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

Reply to
Brian Bailey

(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

Reply to
Twibil

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.

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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.

Reply to
Christopher A. Lee

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".

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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...

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~Pete

Reply to
Twibil

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?

Reply to
Christopher A. Lee

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.

Reply to
Greg.Procter

One can make "hooking up" automatic but accidental uncoupling (or deliberate uncoupling) manual. We have "pre-uncoupling" available in HO scale!

You could invent something better! I use Rapido coupler (heads) on my HO British rolling stock. The slack is about right to represent the slack of historic British goods trains. ;-) I tried HO Kadees but they required nasty alterations to the wagons, and the Rapidos will couple to HO NEM couplers if I ever want to do that.

Regards, Greg.P.

Reply to
Greg.Procter

The European center coupler had the airlines and several dozen electrical connections mounted on the "glad-hand" so that they connected automatically. Presumably uncoupling disconnected them automatically? With the precision engineering to eliminate almost all the free slack and all those automatic connections, it was an expensive coupler and that's not counting the cost of wagon conversion.

Reply to
Greg.Procter

We're off on severa tangents here i in this thread. As to weight balance, Mallets (the engines with high pressure cylinders on one set of drivers and a low pressure cylinders on another set of drivers) have the problem of not having the ability to provide equal power to the two sets of drivers. This is because the high pressure vylinders have steam and the low pressure cylinders don't. Some work was done to provide high pressure steam to the low pressure cylinders to provide that power but then it was easy to overdo it and get the low pressure engine to slip instead. In addition, some engines weren't balanced properly to provide the right amount of TE at running speeds and the setting of the Johnson bar didn't help in that regard either. After all of that, you also have the effforts of stupidity by the engineering staft making the loco to over/under power the loco engine compared to the boiler cap. and so forth and things are all over the place. In all, the idea of using steam is a good idea which has been well used in stationary and marine applications but due to the way that railroad locos were run, they really didn't do all that great.

-- Bob May

rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net

Reply to
Bob May

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