The End of Brass?

Roger T. wrote:


Like Roger, I am out of my depth here, never having had any experience with Mallet articulateds. However, going by what various publications have to say on the subject, I'm fairly certain that the equalisation/compensation arrangements on such engines are independent of each other, that is to say there is no connection between the equalising beams or rigging of each engine unit.
Cheers,
Mark .
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I think you're right about there being NO coupling of the separate engines' equalization systems between the 'halves' of a Mallet (or conventional simple articulated). The frames ARE connected, semi-rigidly', however. They DON'T just sort of float around like separate Diesel trucks, or Shay trucks. Also, since the rear engine is semi rigid under the boiler, any movement of the boiler initiated by the front engine is transferred to the rear engine through the boiler as well as the articulation joint. Thus weight transfer between frames is inevitable as each move. The frames are each part of a complex coupled system, formally equalized or not.
Dan Mitchell ========Mark Newton wrote:

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"Daniel A. Mitchell" wrote:

The rear frame is mounted rigidly on a Mallet. In theory, there should be no weight transfered through the articulation joint between the frames, but as that joint took care of the tractive forces, I'm sure there was some.

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The front support on some of the mallet type locos actually had a centering mechanism in there that pushed up the boiler when off of center - specifically the UP Challenger and Big Boy locos in particular. The rear joint was intended to hold the two loco chassis in alignment and thus the front loco frame was kept parallel to the rear frame at the minimum. I'll note also that European locos often had some strange suspension systems where they weren't fully equalized and thus often had problems from that aspect.
-- Bob May Losing weight is easy! If you ever want to lose weight, eat and drink less. Works evevery time it is tried!
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Tractive forces are not the issue.
Assume a Mallet style loco sitting on level track. The articulated joint (probably) has minimal VERTICAL load applied. The front engine is loaded by the front portion of the boiler weight, carried on the pedestal and cross-slide. The rear engine is loaded by the weight of the rear of the boiler applied directly to the rear frame. Within each frame, equalization will share the applied weight.
Now, move the entire front engine UPWARDS (bump in track). The articulated joint is now loaded so as to pull DOWN on the back of the front engine, and UP on the front of the rear engine. As little play is involved, actual motion will result. The front engine will carry MORE weight, and the rear engine LESS. This will be somewhat compensated for by the boiler motion that results. As the front of the rear engine frame is lifted, so will be the front of the boiler. This will REMOVE some of the front pedestal loading on the front engine. It gets complicated, basically an interconnected set of levers, but weight TRANSFER sure does occur. In effect, there *IS* an form of equalization between the front and rear engines, with the boiler as one lever. Within each frame, equalization will again share the applied weight, but the total weight on each frame changes, both in magnitude and points of application.
Total weight on drivers does not change, as what's gained by one engine is lost by the other.
Dan Mitchell ========Gregory Procter wrote:

<snip>
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You're right; there's clearly no inter-engine connection between the equalizers on a Mallet articulated. I guess somebody could have invented some that would compensate for the swivel, but they didn't. The front of the boiler sat on a kind of "shoe" on the front engine. Apparently the springs had to take up the slack as the boiler is pretty darn rigid.

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I'll be guessing a bit here. I've never read a GOOD dissertation on the Triplex design hopes.
Like all 'tank' type locos, including Garratts, the Triplexes suffered from both decreasing weight and weight transfer as coal and water were consumed. AT low fuel and water levels, the rear engine would have become very 'slippery'. By carrying some loco weight on the rear engine this effect would have been lessened.
Further speculation ...
The Triplexes were unusual in that they were Mallet locos (compound articulateds of mostly conventional design), but had 'all same size' cylinders. The compounding resulted from splitting the exhaust of the center high pressure engine and sending the (once expanded) steam to BOTH the front and real engines. Thus the total cylinder volume of the two low pressure sections was twice that of the high pressure section. IIRC, the rear engine got it's steam from ONE of the high pressure cylinders, while the front engine got it's from the other HP cylinder.
Now, if the rear engine slipped, and rapidly consumed the available low pressure steam, then the sudden loss of back pressure on the one high pressure center cylinder might also initiate a slip on THAT engine as well. It would also create larger than normal asymmetrical forces in the HP engine's frame and axles. None of these effects were good. Thus, I suspect, it was important to keep all three engines working as a team if decent performance was to be achieved. That implied some effort to keep weight distribution under control. I think that was the idea, anyway. It was NOT totally successful, but more-or-less worked. Anyway, that was not their major problem.
Their big limitation was steam production. The boilers of the time, with long narrow fireboxes, simply could not make enough steam to feed six cylinders at any respectable road speed.
The three Erie Triplex locos were semi successful. The VGN loco was not. It's not so much that the locos were very different, but their intended use was different.
Erie used theirs as pushers or helpers on hilly areas. They didn't have to exert full effort for long periods, and could 'recharge' steam pressure between assignments. They lasted in service for a number of years. VGN, on the other hand, wanted their triplex for road service, and it could not produce enough steam to SUSTAIN a road speed of more than 5 mph. That was too slow even for a VGN coal train in the mountains. This loco was a failure due to not meeting it's intended purpose. It was rejected, and later separated and modified into two conventional locos, a 2-8+8-0 and a 2-8-2, both of which were then used by VGN for years.
VGN solved their need for a massive 'coal pusher' loco by acquiring their several AE class 2-10+10-2 Mallets. The AE's were almost as effective starting a train as the Triplex, and could maintain their effort at 15 mph (three times the Triplex's speed) ... which was fast enough. The AE's had the greatest 'TE' of any conventional articulated loco. These engines were used for for years, and moved mountains of coal out of the eastern mountains.
The four Triplexes, while very impressive locos, were NOT large compared to several later Mallet and 'simple' articulated steamers. Even VGN's 'AE's, while having fewer wheels, were considerably larger locos than their Triplex. The Triplexes could produce MASSIVE (unmatched) tractive effort, at very low speeds, or for very short periods of time, but were not 'high horsepower' locos like the later Allegheneys, Challengers, and Big Boys. The Triplexes were great lumbering steam powered 'dinosaurs' whose time quickly passed.
They DO make GREAT models, though!
Dan Mitchell ========Gregory Procter wrote:

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Mark Newton wrote:

Thinking was all I was doing - didn't bother to check any books when I wrote the above. :-)
Regards, Greg.P.
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On Wed, 20 Aug 2003 10:56:15 -0400, "Daniel A. Mitchell"

Dan is right - and he's not using European notation. The + simply shows the point of articulation. Even in America.
In European notation a Pacific would be a 2C1. Americans use a subset of this for diesels, eg C-C although a European might say...
C-C if each 6-wheeled truck has the drive connected eg by side rods or a hydraulic drive
Co-Co if each axle on a 6-wheel truck is independantly driven eg by separate electric motors
A1A-A1A if the outer axles of 6-wheel truck are powered and the central one is not, like on the EMD E-units.

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Some years ago, the Trains editor, change the notation system from the American system th othe European system eg. - to +.
Much ink was spilled with people ranting about the change. No doubt that the European system is nore descriptive, albiet "foreign" to American railroaders .
As soon as David Morgan retired , Trains changed back to the American system. Why? My guess is that the new management didn't want to offend the readers who knew the American system from their first experience with steam.
Is the European system more informative? Yep. Fact is I don't need the extra info. I've been around long enough to know where an articulated bends.
John Glaab
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On 21 Aug 2003 02:08:11 GMT, snipped-for-privacy@aol.com (PEACHCREEK) wrote:

The Mallet-type isn't the only articulated.

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"Daniel A. Mitchell" wrote:

My prototype (Wrttemberg, S.Germany) used the "Klose" system where the end drivers were effectively on trucks and the side rods were given a system of elongation/shortening using a diamond "lozenge" on (a) crank-pin and a system of cranks/levers between the two sides. The locomotives all had 20-25 year life-spans so the system appears to have worked adequately.
Regards, Greg.P.
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You describe one of several schemes to allow the individual axles to swivel (align with curved track) while being driven by more-or-less rigid siderods. Other possibilities include variations "cone and cup" drives.
For long 'rigid' (again a misnomer) wheelbase locos often the front and rear, or perhaps the middle, axles were given what is referred to as a "lateral Motion device". A means whereby the wheels were allowed a certain amount of sideplay. This allowed the wheelbase more flexibility to conform to the curved track. This did not, in itself, imply any ANGULAR adjustment of the axles to keep them parallel to the track. That's doable too (as the system you describe proves), but is far more complicated.
Even today with Diesels these same problems arise. On curved track the axles in a rigid truck frame cannot all remain parallel and 'track' properly. For short wheelbases this was not much of a problem, except at high speeds or very high power loadings. Since both are now becoming more important, even modern Diesel trucks have 'steering' to allow the individual axles to pivot in the truck frames, and better follow the track.
With most Diesels at least you don't have to figure out how to couple siderods to the moving axles.
Dan Mitchell ========Gregory Procter wrote:

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"Daniel A. Mitchell" wrote:

It's one that worked.

The Golsdorf system replaced Klose's designs. (0-10-0 and 2-12-0)

There are examples of uncoupled steam locomotives and coupled Diesel locomotives - it's scarcely fair to compare designs/technologies 50-100 years apart and conclude the more modern one to be superior.
Regards, Greg.P.
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Mark Newton wrote:

Talking standard gauge, only one small batch of locos had inside cylinders and valve gear, the majority outside. None of them had Stutz tenders. Inside cylinders have the advantage of less side imbalances for a loco intended to run at higher speeds (entirely relative of course - 65Km/hr vs 45Km/hr) That advantage has to be balanced against higher maintainance costs. Most of the Klose "additional mechanisim" only moved on curves, otherwise it just sat there. It was simpler than the extra mechanisim of a Mallet, Meyer, Hagan etc which were the alternatives at the time.
Regards, Greg.P.
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Gregory Procter wrote:

Well, there you go - I didn't even realise that there were standard gauge locos with Klose mechanisms. I was only familiar of the Sachsen IIIks and the JZ 189s.

And the joys of digging out the smokebox lining to get at the valve chests!

Simple being a relative term in this context, eh? :-)
Cheers,
Mark
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Mark Newton wrote:

Sure, go compare the complexity of a Diseasel!
Regards, Greg.P.
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Gregory Procter wrote:

Granted - but I have someone else to delegate the diesel repairs to! <VBG!>
Cheers,
Mark.
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Mark Newton wrote:

When did you change your name from O.Bullied?
Regards, Greg.P.
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On Sat, 23 Aug 2003 08:45:50 UTC, Mark Newton

Yes, but a diesel is modular. When a steamer has a breakdown the whole loco is tied up in the shop. For many breakdowns on a diseasel a module (i.e engine, truck, etc.) can be replaced and it is on its way.
Frankly I would much rather try to maintain a diseasel than a steam boiler, especially in bad water country.
--
ernie fisch


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