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EMD SD40-2 with B-B trucks at both ends

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Posted by Overmod on Saturday, October 3, 2020 6:37 AM

CSSHEGEWISCH
I'd have to check my copy of "Articulated Locomotives" but I think that Wiener [note sp.] classified locomotives equipped with Klien-Lindner axles in normal fashion since they had rigid side frames. 

He did not, and went into some detail about the conventions he proposed for distinguishing radiating axles (which with rod drive required rigid frame for the cranks). I wish I had my copy handy so I could review the specific 'syntax' of his extensions to Whyte coding.  
There were wackier versions than Klien-Lindner or Schwartzkopff-Eckhardt; consider arrangements that dropped a powered axle as 'booster' and raised it when undesired, or analogues to the Swiss electrics with idler wheels between drivers...

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Posted by CSSHEGEWISCH on Friday, October 2, 2020 10:03 AM

I'd have to check my copy of "Articulated Locomotives" but I think that Weiner classified locomotives equipped with Klien-Lindner axles in normal fashion since they had rigid side frames. 

The daily commute is part of everyday life but I get two rides a day out of it. Paul
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Posted by Overmod on Thursday, October 1, 2020 11:29 AM

steve-in-kville
Okay... from the pictures online it looks like there are four axles per truck. Makes sense.

As part of your education, I recommend that you read Lionel Wiener's Articulated Locomotives with a particular eye towards his 'taxonomy' of various approaches and his proposed notation.  That is where the le Massena kerfuffle about using the plus sign for an articulated joint (as in 2-6+6-4 instead of 2-6-6-4 for Whyte-coding a simple articulated with Mallet-style articulation, or in a different system that counts axles, 2-C+C-2 instead of 2-C-C-2 for a GG1) that caused so much confusion and delay in the 1970s came from.

Now on reflection I may have been using the convention almost precisely backward, but we will take up why this might be a failure in a bit:  let it be illustrative of the difference here.

The Flexicoil three-axle truck you understand, and a locomotive with two of these that has a fuel tank between them is properly C-C when all six axles are motored.

EMD in building two-motored DD35s and 40s could manage four motored axles in a rigid sideframe (essentially like an extension of a three-axle Flexicoil frame, although different in detail design) and hence we can correctly call this a D truck.  (Some European systems distinguish conjugated or coupled axles, so a "D" truck would have to have the wheelsets geared or rodded together, and one with individual noise-suspended traction motors would be denoted "Do", but we don't use that convention here yet...)

Now Mr. Goding built his more flexible truck by taking a couple of shorter-wheelbase Flexicoil C trucks and lopping one outer axle off each (which converted them into B trucks) and arranging a revised pivot location.  He then had to mount these to a typical 'older' SD chassis that still used pin swivel truck mounting, so he used a longitudinal beam, called a span bolster, to link the two trucks together but still allow each to pivot around its own center pin location.  The span bolster has its own pin connection which links to the locomotive frame just as a regular truck would do.

This is the critical difference between a "B-B" truck and a D truck: the ability of the 'halves' to pivot independently.

Now for the fun: there have been locomotives with multiple B trucks in which not all of them pivot: a couple of the PRR experimental electrics of the early '50s were built that way and, more interestingly, a locomotive Mr. Goding knows, the 'white wonder' GM10B.  Here the center truck has considerable lateral play, but is not articulated to its neighbors, so we can call the locomotive a B-B-B all day long and be justified.

But when we put the two trucks on the span bolster we effectively articulated them, just not directly 'frame to frame' as in true truck articulation (which, remember, is what that plus sign is supposed to denote in Wiener).  And just as on the original C-C version of the SD, there is a fuel tank between the two trucks still, so the result is not a B-B-B-B and can't really be a B-B+B-B as the two span-bolstered assemblies are not linked; it is a B+B-B+B ... reaching for the aspirin bottle yet? ... if we want a consistent notation that tells us how the driving axles are mechanically arranged under a locomotive.

At some point we should probably develop a notation for rigid-frame radial-guiding trucks like the HTCR family; we might even have a convention for those with steering levers vs. those without.  Wiener took up the issue (there was a whole set of steam locomotives that had 'radiating' axles, some of which accomplished the feat with side rod drive!) but the result he arrived at in 1930 has not been generally adopted (or recognized, at least) and may be too weird for normal use.

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Posted by steve-in-kville on Thursday, October 1, 2020 6:14 AM
Okay... from the pictures online it looks like there are four axles per truck. Makes sense.

Regards - Steve

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Posted by CSSHEGEWISCH on Thursday, October 1, 2020 5:53 AM

D-D is two trucks with four motored axles each. B+B-B+B four trucks with two motored axles each with two trucks connected by a span bolster.

The daily commute is part of everyday life but I get two rides a day out of it. Paul
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Posted by steve-in-kville on Thursday, October 1, 2020 5:08 AM
Help me understand this.... how is a 4-axled truck still considered a B-B? Why not D-D? Just when I thought I understood this stuff....

Regards - Steve

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Posted by bogie_engineer on Sunday, September 27, 2020 7:45 PM

I did the testing of the seven axle SDP45 BN 6599 with the HT-BB (built from a pair of SD Flexicoil trucks) at the rear in 1984 - the results showed superior curving performance as measured with instrumented wheelsets when compared to the rigid SD Flexicoil at the cab end. But the testing of the HTCR truck a few years later with the same instrumented wheelsets showed the radial truck to curve with lower forces than the HT-BB or a GP two axle truck. Testing more recently after removal of the inter-axle link connecting the steering beams showed no significant change in performance of the HTCR truck which is why it was not included in HTCR-6 truck developed for the EMD Tier 4 locomotive, really simplifying the design.

Dave

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Posted by Overmod on Sunday, September 27, 2020 6:18 PM

Incidentally while Mr. Goding is reading this thread he might address the OP's implicit premise that a B-B+B-B "SDP45" would be easier on the track or better-guiding than with a good C truck, even a three-axle radial-guided truck -- either with or without steering levers.

I would immediately favor a truck with zero rigid wheelbase over one with implicit B-truck even for very short B wheelbase as in the old EMD '80s test and presumably Flexicoil primary suspension.

For branch lines you might still want a pivoting main truck frame rather than the shear-spring limited rotation in modern EMD practice; I think this would require relatively capable frame yaw damping or equivalent and I believe Mr. Goding has previously discussed best practice...

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Posted by bogie_engineer on Sunday, September 27, 2020 4:51 PM

samfp1943

In Brazil, IIRC they operate with metre gauge on many of the heavy haulage mining railroads.  VAQLE and MRC are a couple, I remember.Whistling

At one time we had a regular contributor to this FORUM (pedrop). I have not seen his name pop up in some time...He was a correspondent of edblysard's, and had supplied this Forum with many photographs of the Briziian railroad system.  Particularly, he had provided a series of photos of conversions of re-sold American locomotives ; while thwy were convereted to the BB+BB wheel arrangement for service in Brazil.  

Here is a linked site that has photos of new GE's in route for export to Brazil. @

https://www.railpictures.net/viewphoto.php?id=287170

Here is a YT video, (Close-up views; of the BB+BB wheel sets) of that series (ES58ACi's)in BB+BB wheel arrangements.  in service for Vale in Brazil @https://www.youtube.com/watch?v=VBVZG5Gugkk

 

 
Pedro still posts regularly on Trainorders.com. The picture of the new GE's in route are broad gauge six axle locos. In the video of the GE's with the four axle trucks you can see how high they sit due to the span bolster being totally under the bottom plate.
 
At about the 8 minute mark, this video has a good picture of the GBB truck:
 
 
Dave
 
Edit - video link added
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Posted by samfp1943 on Sunday, September 27, 2020 4:42 PM

In Brazil, IIRC they operate with metre gauge on many of the heavy haulage mining railroads.  VAQLE and MRC are a couple, I remember.Whistling

At one time we had a regular contributor to this FORUM (pedrop). I have not seen his name pop up in some time...He was a correspondent of edblysard's, and had supplied this Forum with many photographs of the Briziian railroad system.  Particularly, he had provided a series of photos of conversions of re-sold American locomotives ; while thwy were convereted to the BB+BB wheel arrangement for service in Brazil.  

Here is a linked site that has photos of new GE's in route for export to Brazil. @

https://www.railpictures.net/viewphoto.php?id=287170

Here is a YT video, (Close-up views; of the BB+BB wheel sets) of that series (ES58ACi's)in BB+BB wheel arrangements.  in service for Vale in Brazil @https://www.youtube.com/watch?v=VBVZG5Gugkk

 

 


 

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Posted by bogie_engineer on Sunday, September 27, 2020 1:02 PM

IA and eastern

If i went to EMD and want to buy SD40-2 locomotives on SDP45 frames with B-B trucks on both ends. This locomotive would be real good on curving branchlines and tranfers runs. What EMD would charge me for such a locomotive. Gary

Progress Rail/EMD has an 8-axle locomotive, the SD70ACe-BB in the catalog today:
I designed this truck and the modifications to the underframe to accept it as one of my last designs before I retired (again) in 2015. It's available off the shelf where Tier 4 emissions aren't required (Brazil) in meter gauge. Making a standard gauge version is simpler than the meter gauge since there's more space between the wheels; I did some preliminary layouts but no drawings for it were made. There was some fleeting interest for high TE applications but nothing came of it. It's used in Brazil where high TE in meter gauge is desired - the narrower motors required don't produce the same TE as standard gauge so having two more is an advantage; also spreading the weight over 8 axles allows NA style locos and their more comfortable cabs at the meter gauge axle load limits, 54,000 lbs. in Brazil, compared to 70,000+ in NA.
 
The GBB truck is much different than the retrofit truck used in Brazil on NA locos converted to 8-axle in that the span bolster tucks up into the underframe to keep the underframe height the same as current production NA locos - the retrofit truck raises the bottom plate several inches even with smaller wheels. It also has a high traction motor arrangement for much better weight shift performance and a fully fabricated truck frames and bolster.
 
Dave
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Posted by IA and eastern on Sunday, September 27, 2020 12:27 PM

I was looking at standard gauge and what would be the cost. Would it be double the cost of a regular SD40-2. Gary

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Posted by CSSHEGEWISCH on Sunday, September 27, 2020 10:06 AM

EFVM in Brazil is a meter-gauge railroad that could be considered to be DM&IR in the tropics.  Quite a few years after the DDM45's were purchased, they began acquiring various EMD and GE second-generation C-C units and retrucked them as B+B-B+B with meter gauge two-axle trucks and span bolsters.  To keep things interesting, they will operate in multiple with stock export models.

The daily commute is part of everyday life but I get two rides a day out of it. Paul
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Posted by Overmod on Saturday, September 26, 2020 6:20 PM

Something like this (but on test, only one end) was actually tried at one point.  I only know second-hand; I think Mr. Goding knows directly.

Some engines this size not only were converted to B-B span-bolster-style, but as narrow as meter-gauge!  But to my knowledge that was an 'aftermarket' conversion of used -- sometimes very used -- locomotives.

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EMD SD40-2 with B-B trucks at both ends
Posted by IA and eastern on Saturday, September 26, 2020 5:37 PM

If i went to EMD and want to buy SD40-2 locomotives on SDP45 frames with B-B trucks on both ends. This locomotive would be real good on curving branchlines and tranfers runs. What EMD would charge me for such a locomotive. Gary

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