# articulated question



## aionta (Apr 9, 2010)

Hello All I was just drooling ( all over the sofa) at the Class Z-6 Chalenger in Model Railroader July edition. and was wondering what is meant by anarticulated engine.

It would seem that at some point the engine can actually bend so as to go around corners better.

Way out of my price range.

Aaron


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## Reckers (Oct 11, 2009)

That's pretty much what it means, Aaron. As steam engines developed, they sort of ran into a roadblock: everyone wanted larger, more powerful engines to go faster, climb steeper grades, and pull more weight. The problem was, how do you make them larger? You can't really go taller or wider: the existing tunnels and bridges ruled both of those out. You could go longer: a longer frame allowed you to have a longer firebox and boiler and increase your power. Add extra wheels to support the weight as well as getting more iron against the rails for traction. The only drawback was that the curves in the rails limited how long you could get. When you have 4 drive wheels, you can cut a pretty tight curve. Those big puppies won't flex, though, so when you have eight drive wheels, you've cut your turning radius in half and can't go places you'd like to. The solution was to create a sort of hinge or pivot point under the engine to split the drivewheels into two groups, the front group being able to pivot. It required that they have their own sets of steam lines and valves, a pretty complicated arrangement. One of the early ones was designed by a Frenchman named Mallet (pronounced Mal lay). Sometimes you'll hear them called Mallets, like the hammer.


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## tjcruiser (Jan 10, 2010)

Reck --

Brilliant explanation, once again. Well done!

TJ


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## Reckers (Oct 11, 2009)

Thank you, TJ. I got interested in them a while back, wondering what kind of arrangement of valves or gears would get an engine named after a hammer!


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## shaygetz (Sep 23, 2007)

Great 'splainin'...:thumbsup:
One note to make about model articulateds---on models, both forward and rear engines are made to swivel for convenience and to help them get around our normally tight track radii. On real locomotives, only the forward engine is made to swivel, the rear one is fixed. The proper term for each group of drivers is "engine" as an articulated is considered two engines under one boiler. 

Interestingly, the Pennsy 4-4-4-4 T1, 4-4-6-4 Q2 and B&O 4-4-4-4 N1 are not articulated, they ride as two engines on a single fixed frame and are considered duplexes...the Beano built theirs to sit back to back, putting the cylinders to either end of the drivers, thereby shortening the length of the wheelbase. Only the models of the T1 and Q2 are articulated, incorrectly leading some to believe that the prototypes were.


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## aionta (Apr 9, 2010)

yes excellent explanation!

Thanks

Aaron


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## tjcruiser (Jan 10, 2010)

Thanks, Shay ... great info!

TJ


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## rbf (Feb 26, 2010)

Dos that translate the same into tighter turns on your layout? I have a 5' by 6' layout that is why I asked.


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## shaygetz (Sep 23, 2007)

My AHM articulateds all run very well on 20" radius curves, properly laid out with safe run offs for derailments, you could conceivably make your layout as narrow as 44". My layout is built on an oval that is about 5' x 43"...


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## rbf (Feb 26, 2010)

Thank You for the info. Your layout looks great! Looking forward in seeing pictures your layout as you complete it.


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## shaygetz (Sep 23, 2007)

Thanks...it actually gets finished once every 12 months...just in time for Thanksgiving and Christmas...



...the rest of the year it is my test bed for my little HO pets.


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## stationmaster (Dec 7, 2008)

Bob, are your articulated engines pre-RP25? My Rivrossi Red Box Mallets would never be able to handle a full 180*, 20r turn without a bit of rail climbing. The deeper flanges on the AHM's may help your engines with that problem.

Bob


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## shaygetz (Sep 23, 2007)

stationmaster said:


> Bob, are your articulated engines pre-RP25?
> 
> Bob


My Big Boy has the full circa 60s pizza cutters, my Mallet and Cab-Forward have the later .039" done through the 70s. Your Red Boxes were done for a different time, when folks could cough up more space for more generous curves and therefore demand scale sized drivers, making for less flexible tolerances.


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## stationmaster (Dec 7, 2008)

I didn't buy either of my Mallets. I traded an AHM Big Boy for one of the Mallets and a Red Box Clinchfield Challenger(rebadged for C&O). The other I bought as junk and rebuilt. I have another, but it needs a motor, a $20 junk special...

As far as building my layout around my engines, I don't think I even owned an SD when I built it, maybe an E7/8 or two. Much to the contrary, I was able to get larger engines BECAUSE of my larger radius turns.

Bob


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## tjcruiser (Jan 10, 2010)

Ha ha ... I'm sitting here chuckling to myself. I have yet to crack the secret lingo code that you gurus use. I've deciphered a few buzz words, but have to laugh at how this sounds for any non-train person eavesdropping in on the conversation:

"Bob ... My Big Boy has the full circa 60s pizza cutters ... Your Red Boxes were done for a different time, when folks could cough up more space for more generous curves ..."

And the coded reply ...

"I traded a ... Big Boy for one of the Mallets and a Red Box Clinchfield ..."

WHAAAATTTTT ????? 

Hmmmm ... I'm gonna jump in here (just for fun) with some pure gibberish just to see if I can fake my way into the conversation ...

"That's cool. Yeah, I've got some phinorcals on my Rotary Elbows, and the hyper-torque shoes on those Chugger Girls really gets 'em moving round the bend."

How'd I do? Code cracked? :laugh:

TJ


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## stationmaster (Dec 7, 2008)

Well, TJ, I guess our knowledge and wisdom, has yet to rub off on you. A Mallett is an articulated that uses both high pressure steam and low pressure steam to run. Norfolk and Western used these monstrosities for coal drags through the Appalachian Mountains. They were also used as "helpers" up grades. Behemoths, at best, these are normally considered some of the strongest engines ever built.

The Clinchfield RR used similar engines, normally referred to as Challengers, with a slightly different wheel configuration, 4-6-6-4 and 2-6-6-4's. These were less powerful than the Mallets, but did have a higher top speed.

There are some articulated engines that are not "compounds". Compound refers to the use of both high pressure and low pressure steam. These engines are thought to be more efficient as they use steam released from one set of drivers to power the second set. An engine can be an articulated and not be a compound, and visa versa. 

With the articulated engines, some even had a "split frame" that allowed the drivers, one set mounted to each "section", to be more able to negotiate tighter turns found on some mainlines, especially those found in hilly, mountainous areas of the coal mines.

Here area couple of links that may explain things a bit better.

Articulated engines:
http://en.wikipedia.org/wiki/Articulated_locomotive

Compound Steam Engines:
http://en.wikipedia.org/wiki/Compound_engine

By the way, you would never make a code breaker................ Stick to breaking wind.

Bob


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## Reckers (Oct 11, 2009)

Nice explanation, Bob!:thumbsup:


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## stationmaster (Dec 7, 2008)

Yeh, Reckers, sometimes I even amaze myself.

bob


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## tjcruiser (Jan 10, 2010)

Bob,

:thumbsup::thumbsup::thumbsup:

I'm in! To the lingo club! Awesome explanations! Many thanks!

TJ


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## tjcruiser (Jan 10, 2010)

Bob,

I read through that wiki link a bit. Fascinating. Thanks for the info.

So on a true Mallett (articulating, compound), with the fwd articulating truck having it's steam chest in the front, how does steam get to/from the chest? There must be some flexible insulated hoses or pipes???

Also, aren't there also articulated locos that have the steam chests next to each other, i.e., fwd truck with chest in rear; rear truck with chest in front?

Thanks!

TJ


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## tworail (Apr 13, 2006)

One that I know of where the steam chests are both outward (but not inward) is the Garrat. Here is a Aster/ LGB model - can't remember if this one is live steam or not.. still has the live steam price tag either way.










Here is a prototype:


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## tjcruiser (Jan 10, 2010)

Wow ... beautiful ... very different, but beautiful. There was a schematic, simply silhoette of a Garratt in the wiki link, and I grasped the concept, but couldn't imagine what that actually looked like. Your pic says all.

Great additional reading here:

http://en.wikipedia.org/wiki/Garratt

"Garratts enjoy an advantage over the Mallet system, because of the geometry of the design. When swinging around curves the boiler and cab unit move inward like a bowstring in the bow of a curve and this reduces the centrifugal force that would overturn a normal locomotive and which in turn permits faster running."

"A Garratt holds the world speed record for an articulated locomotive."

"Around 250 Garratts exist today. While many are stored or dumped in various stages of disrepair, more than 100 are preserved in museum collections or on heritage railways."

Fascinating!

Thanks, Bob!

TJ


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## stationmaster (Dec 7, 2008)

tjcruiser said:


> Bob,
> 
> I read through that wiki link a bit. Fascinating. Thanks for the info.
> 
> ...


TJ, I believe that the SP cab forwards had such an arrangement. (I'm too lazy to google pics to confirm an I don't have one here with me to scope out).

On some of the articulateds, including the Mallets and such, the steam was re-used from one set of drivers to the other, thus creating a compound, the use of both high pressure and low pressure steam. These were found to be the most efficient of the articulated configurations. The engines used both rigid and flexible pipe, depending on the placement of the steam chests on the engine, to allow for efficient usage of the "recycled" steam. (and we all thought recycling was a new idea!!!). This proved to be very beneficial in water(steam) usage and would allow these engines to carry less water to operate. Really, for its time, a very forward thinking and novel idea.

I have couple of "converted" a cab-forward for my roads. Though none ofthe roads operated any, I think these engines are a significant step in the progression of motive power and whose advent is very evident in today's modern diesel power, the crew is located in a cab at the front of the engine. 

The cab forward was introduced in primarily on western railroads, most significantly, the Southern Pacific, to prevent the extinguishing of firebox fires and asphyxiation of the crew when traversing long tunnels found on some of the routes taken by these trains. The design put the crew, and the firebox, ahead of the exhaust of these engines thus solving a serious problem.

On side note, I am "bashing" a 4-4-4-2 switch engine(no known prototype). I am having trouble finding a frame suitable for the project. I've tried, a couple of times, to create one from cast stock, only to screw it up. I want it to be a cab-forward switcher and am using an old boiler and cab that I have had laying around for years. It has been a project that I have been working on for about 5 years. I get frustrated and put it away and drag it back out, get frustrated again ...put it away... and endless cycle it seems. Being an ex-architectural designer, I think I can lay the frame out. I have a motor here meeting my needs since I intend to power both sets of drivers though some modification will also be necessary here also(one has to run "backward"). I also have the drivers from a pair of old Mantua 0-4-0's that will be laid out as you have already mentioned, with steam chests next to each other. I have problems with the frame "cracking" or "breaking" while I'm doing some of the grinding and filling necessary to get things together. Having no real plans, from others, for instruction, the project is "grind/file to fit". SLOW and bedeviling are very good words in this case.

Bob


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## tjcruiser (Jan 10, 2010)

stationmaster said:


> On side note, I am "bashing" a 4-4-4-2 switch engine(no known prototype). I am having trouble finding a frame suitable for the project.
> 
> Being an ex-architectural designer, I think I can lay the frame out.


Crazy thought ...

Here's a thought that grabbed me the other day. I was talking to a marine-techie buddy of mine who often needs small, custom fabricated waterproof plastic boxes. He develops the shapes in a 3D CAD software package, then sends the geometry file off to a company that generates a fully detailed, accurate part via Stereolithography. Basically, a pair of lasers heat up a molten bath of liquid resin, curing a thin layer in the process. A device lowers the bath a fraction of an inch, and the process repeats. It's essentially a fully-3D laser printer, generating whatever parts with complex shapes you feed it. And, get this:

My buddy is having custom boxes (with internal flanges, lips, etc.) made for him for around $15 each ... shipped to his door in 2 days.

The company has a separate process where they can "sinter" the resin, coating it with metal for improved structural rigidity.

Anyway ... the light bulb's gone off in my head, and I'm thinking wouldn't this be a fabulous way to generate missing / needed parts for model trains?

Do you know how to drive any 3D CAD software?

http://www.protocam.com/html/slapro.html

http://www.protocam.com/html/services.html

Hmmmm ...

TJ


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## stationmaster (Dec 7, 2008)

TJ, I have AutoCad, with 3-D capability.

Bob


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## tjcruiser (Jan 10, 2010)

Hmmm ...

I'm running AutoCAD LT 2D along with MultiSurf 3D.

I think the stereolith guys need a gridded solid model, rather than just a surface model.

This idea is gonna gnaw at me for a while ... hmmm ...

TJ


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## rayins (Dec 31, 2010)

*Thank you brother*

I just want to thank you brother for your openness about your love for our great Creator and God. Another believer.
Ray:thumbsup:






shaygetz said:


> Great 'splainin'...:thumbsup:
> One note to make about model articulateds---on models, both forward and rear engines are made to swivel for convenience and to help them get around our normally tight track radii. On real locomotives, only the forward engine is made to swivel, the rear one is fixed. The proper term for each group of drivers is "engine" as an articulated is considered two engines under one boiler.
> 
> Interestingly, the Pennsy 4-4-4-4 T1, 4-4-6-4 Q2 and B&O 4-4-4-4 N1 are not articulated, they ride as two engines on a single fixed frame and are considered duplexes...the Beano built theirs to sit back to back, putting the cylinders to either end of the drivers, thereby shortening the length of the wheelbase. Only the models of the T1 and Q2 are articulated, incorrectly leading some to believe that the prototypes were.


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