Articulated diesel?

[MidlandMike]

Your tractor example has its wheels fixed mounted, and turning is done at the pivot.  This is like the AT&SF flexible boiler experiment, except that the flexible boiler was not really a pivot.  It was a failed experiment, whereas the articulated locos with the articulation at the frames became the standard.  The articulated frame carried thru to early heavy electrics, and even a few Baldwin diesels.  The Balldwin centipede perhaps could have been fully (body) articulated since it had two diesel engines, and it had enough axels to support a split body.  However, if you look at the DD40X, you will see the small footprint of the 4 axel trucks at each end.  If you tried to balance each half of the articulated bodies over the (fixed mounted ?) truck, the ends of the loco would have large overhang that would work aginst smooth coupling force transfer.

[mudchicken]

Euclid

The AT&SF experimented with articulated steam locomotives where the two frames were rigidly attached to the boiler, but the boiler itself articulated by the hinge effect of a bellows connection in the boiler barrel.  See Figure 4 here:

http://www.catskillarchive.com/rrextra/blwmal00.Html

 

bendy-boilers and the prairie mallets were a disaster. Thankfully the 4x and 5x bendy boilers never even got off the drawing board.

[Paul_D_North_Jr]

Euclid

With a diesel locomotive, D-D trucks are likely to be too long to negotiate curves, so each truck must be articulated. . . . [snipped - PDN]

The 1960's "2 locomotives on 1 frame" period in the US did have these 2 EMD models with D-D trucks:

http://www.thedieselshop.us/Data%20EMD%20DD35A.HTML

http://www.thedieselshop.us/Data%20EMD%20DDA40X.HTML "Centennial"

- Paul North. 

[Euclid]

Re- AT&SF locomotives #1158 and 1159:

Yes, the bellows connection to achieve a flexible boiler was indeed a failed experiment.  I understand that it failed because the inner “V” pockets of the bellows filled with packed cinders, preventing the “V” pockets to collapse when rounding curves.  So the resulting counterforce pulled the bellows ring rivets in two.

The bellows were primarily intended to be the mechanical joint for the boiler articulation.  Inside of the bellows was a form of ball-and-socket slip joint nearly as large as the boiler barrel.  That detail, I do not exactly understand.

In any case, I assume that this flexible bellows was just connecting an open fire throat, and that the fire tubes terminated in tube sheets on each side of the bellows.  So the joint was not under steam pressure.

I assume that the engine sets also were hinged in the same location as the boiler bellows.  What this would have achieved all together is reducing the lateral boiler displacement on curves that is a characteristic of typical articulated steam locomotives where the engines articulate, but the boiler does not. 

https://books.google.com/books?id=Y30hAQAAMAAJ&pg=RA4-PA50&lpg=RA4-PA50&dq=flexible+boiler+connection+atsf+locomotive&source=bl&ots=fMejNuNh6k&sig=T4V8ymot6HVvAJv_1OZ5iBhPQF0&hl=en&sa=X&ved=0ahUKEwj86d2Ntp_KAhXDKh4KHZRLAWYQ6AEIJTAC#v=onepage&q=flexible%20boiler%20connection%20atsf%20locomotive&f=false

[dehusman]

From a purely technical standpoint virtually every diesel bought by class 1 railroads ARE articulated engines already, the drivers are not rigidly attached to the frame of the locomotive and can rotate with respect to the frame.

[samfp1943]

It seems that the EMD TR1 [Cow&Calf]  has not been mentioned as a type in this Thread. 

ICRR had two pair, on Blomberg-style Trucks, used originally around Chicago and then St. Louis until retired.

UPRR had some that they referred to as 'Transfer Sets'  (total 8(?) were used as helpers on Cajon Pass, and were specially equipped for that service-see note on linked 'Railpictures' photo- @ http://www.railpictures.net/viewphoto.php?id=516942&nseq=1

ALCO had also made Cow&Calf models for Oliver Mining Co in Minnesota (see note) @"... Baldwin VO-1000, DS-4-4-10, S-12 and S-8 cow/calf locomotives compromised a majority of the mine railroad power, followed by EMD SW-9, SW-1200 and TR-6 cow/calf models and in third place were Alco S-2, RS-2 and S-6 cow/calf models..." 

from link @ http://www.missabe.com/cms/about-oliver

[DS4-4-1000]

Paul_D_North_Jr

 

Euclid

With a diesel locomotive, D-D trucks are likely to be too long to negotiate curves, so each truck must be articulated. . . . [snipped - PDN]

 

 

The 1960's "2 locomotives on 1 frame" period in the US did have these 2 EMD models with D-D trucks:

 

http://www.thedieselshop.us/Data%20EMD%20DD35A.HTML

http://www.thedieselshop.us/Data%20EMD%20DDA40X.HTML "Centennial"

- Paul North. 

Don't forget that the Baldwin Centipedes had "D" trucks as did the Little Joe electrics and those two giant electrics that GN had.

[CSSHEGEWISCH]

I'll throw out the following proposal to see if we can get some sort of consensus.  Since Wiener's definition of an articulated locomotive is overly broad when applied to diesels, an articulated diesel may be defined as either:  A. an inseparable jointed arrangement such as ATSF M-190, or B. a jointed arrangement in which tractive or buff forces are transmitted through the truck frames only such as a
Baldwin Centipede or the Baldwin experimentals like BLW 58501.

Note that this excludes multiple units linked by drawbars such as FT sets or cow-calf sets.  Drawbars were often replaced by couplers in many of such sets.

[carnej1]

From a purely operational perspective any M.U'd multi-locomotive consist could be considered "articulated" as it is a modular tractive effort producing system intended to pull(or push if the units are DPU's/Helpers) a train of unpowered vehicles with flexible linkages between the power units..

About the only modern idea I can think of that might meet the exact definition is this:

https://patents.google.com/patent/US20110067390A1/en?q=mobile&q=diesel&q=power+system&q=separated&q=engine&q=exhaust&assignee=Clean+Rolling+Power%2c+LLC

The patent describes installing auxiliary cooling, exhaust after-treatment and waste heat recovery systems on a tender unit coupled to the locomotive and connected by flexible piping.

The industry doesn't seem to be showing any interest in the idea. Given the added complexity one can see why.......