Question on Alco's double engined 855 in Nov. TRAINS, page 98....

[Modelcar]

It is riding on four two-axle trucks. Question: If each truck is positioned on a pin enabling it to rotate...Are they then mounted on a subframe that is on a pivot....If not, how is the suspension of them positioned that enables them to follow the curvature of sharp turns....? I'm assuming the engine has a ridged frame along it's length.

[jchnhtfd]

I seem to recall a subframe for each pair of trucks. Not that unusual a set-up, really -- there were quite a number of Bo-Bo-Bo-Bo electrics with the same basic concept.

[Modelcar]

...Yes, we've seen several wheel arrangements similar as this but I'm trying to understand what set up they {the trucks}, were fastened to to allow turning and each follow the one in front of it if the engine had a rigid chassis......{That is if we're to assume they were pivited on pins....}.

[Overmod]

Span bolsters. Each truck has its own pivot pin (or attachment point for centerless trucks), around which it can turn. The two centers are joined by a common structure which itself is pivoted to the carbody proper. It's not uncommon to find the couplers on the span bolsters (which IIRC was the arrangement on the N&W 2300 steam turbine) rather than on the extended carbody.

My understanding is that this setup is as flexible as necessary. The history of the big double-engine GEs may be illustrative: the B-B+B-B trucked versions were much more successful than the C-C versions.

Where you get the weird truck arrangements is on the B-B-B locomotives with rigid carbodies, where some form of sophisticated lateral motion is generally used on the center truck, and the outer two are pivoted or otherwise allowed to turn in the 'standard' manner...

[Modelcar]

Overmod....You gave me the answer in the first 3 lines of your post....That's the way I thought it would have to be but didn't know....Thanks for that info.

[CSSHEGEWISCH]

The C855's, the U50's, and the exports to EFVM in Brazil all use span bolsters between the adjacent trucks. Each truck of a pair was attached to the span bolster and could rotate freely on its hinge point on the span bolster. The span bolster was in turn attached to the frame and could also rotate around its own hinge point on the frame. The coupler and draft gear are attached to the span bolster.

[Modelcar]

...Now we fully understand from the last posts.....I simply didn't see how with a rigid chassis and four pivot pins...it was possible to make any turns. Thanks.

[Anonymous]

To anyone's knowledge, did any of the builders consider the concept of articulation for the dual engined locomtives? I can see that working for a B-B-B or C-C-C setup. (A nine-axled C-C-C, now that would have been a locomotive to see!)

[M636C]

I understand the trucks and span bolsters on the C855 and U 50 were recycled from the GE gas turbines in the 51 and 61 series, just as the trucks from the two unit turbines were recycled on the U50C locomotives. Waste not, Want not!

There are good photos of the turbines in the recent "Classic Trains" issue.

Peter

[CSSHEGEWISCH]

Baldwin used articulation in the Centipede (2-D+D-2) and in its very first diesel-electric in the 1920's. The 1920's design had a B+B arrangement with the truck frames being linked together like an articulated steam locomotive. Couplers and draft gear were mounted on the truck frame and the carbody rested atop the trucks. All longitudinal forces were transmitted through the truck frames.

Most large straight electrics like the Joes, GG1's and others were also articulated. On the two three-truck designs of which I'm aware (PRR's E3b of the 1950's and the GM10B), was the center truck allowed any sideplay?

To Peter: Were there any articulated electrics or diesels in Australia?

[Modelcar]

....So what arrangement did the {2-three truck at each end}, of the DDA40X Centennials have.....Was it similar to what was described above for the big Alco 855....?

[Paul Milenkovic]

The DDA40X Centennials along with the other EMD double-engine entries (except for the E-units!) rode on D (4-axle) trucks.

That 2-D+D-2 arrangement was perhaps influenced by steam practices of using idler axles on a lead truck to help steer the whole works. The GG1 adopted that pattern (as electrics are bi-directional, you had two "lead" trucks), and they may have copied that from some electric on the New Haven. They went with that because experience showed it to be a stable truck arrangement, and heck, GG1-powered Congressionals probably had as good a schedule as everything from Metroliners through Acela.

Besides the 2-D+D-2 Centipedes (exotic for a Diesel but nothing unconventional for an electric), there were the Great Northern Cascades tunnel W-1 electrics (B-D+D-B -- all axles powered).

One of the first books I ever had as a child was Engines: Man's use of power from the water wheel to the atomic pile by L. Sprague de Camp and Jack Coggins. The section on electricity has a cutaway drawing of a W-1 electric: while the drawing only shows traction motors on the D truck, other sources indicated all axles were powered.

Those W-1's didn't stay in service very long. I guess when Diesels came, GN thought the electrics for the tunnels were a wasted effort. The 2nd Diesel Spotters guide shows the UP building a coal-fired gas turbine (yep, gas turbine) out of a PA as the lead unit and the shell of the W-1 as containing the gas turbine equipment. I guess the coal-fired gas turbine didn't work out -- the coal ash must of chewed up the turbine blades.

[Modelcar]

...Oops, my error on that one and thanks for the update data.....

[Anonymous]

QUOTE: Originally posted by CSSHEGEWISCH

Baldwin used articulation in the Centipede (2-D+D-2) and in its very first diesel-electric in the 1920's. The 1920's design had a B+B arrangement with the truck frames being linked together like an articulated steam locomotive. Couplers and draft gear were mounted on the truck frame and the carbody rested atop the trucks. All longitudinal forces were transmitted through the truck frames.

Most large straight electrics like the Joes, GG1's and others were also articulated. On the two three-truck designs of which I'm aware (PRR's E3b of the 1950's and the GM10B), was the center truck allowed any sideplay?

My understanding of the Centipedes, et al, was that the underframe was in two separate sections ie. not really articulated together with a common truck, and the single carbody itself "floated" on top of the mix. What I have always wodered with respect to the Centenials, 855's, et al, was why not simply articulate two separate engines (carbodys and underframes) onto a common third truck in the middle and operate it as a single B-B-B or C-C-C? If nothing else, it would reduce the rigid wheelbase of the D-D setup.

[Overmod]

Been trying to find time to answer a couple of these questions since early this morning..

One principle behind the Centipedes was the same as with GG1s (and others with those substantial cast underframes): all the buff and draft forces went through the articulated underframes (which is really what articulated *means* in this context). There is a drawbar between the two 'half' frames, and the carbody structure experiences no direct force (which allows it to be designed differently, and usually to weigh less, than it would if it had to take some component of traction or braking force directly.

My understanding was that the double diesels were built on a single, more-or-less unitized bed frame. This simplified construction and alignment of the machinery, and reduced the absolute number of joints and lubricated connections. Note that there is a 'packaging' formula for most diesel-electric locomotives: pivoted trucks (or span-bolster assemblies) somewhere near the quarter points of the bed frame, engine in the middle of the span, large fuel tank suspended between frame and rails. The first thing that happens with an articulated locomotive is that you lose the cantilever benefits of pivots at the quarter points where the frame bears on the articulated truck. You also will probably have to have a specialized bolster with two separate pivot locations, appropriate seals or bulkheads at each end of the separate unit, more need to balance components between the units if they are not absolutely common to each "end", etc. (My understanding is that it is more difficult to accompli***raction-motor cooling in a C truck articulated this way, for a variety of reasons).

I looked at articulated locomotives rather carefully in the early 1970s, and there are some other concerns. If you 'standardize' on a single design of carbody module for a given class of locomotive, you automatically have two cabs on the completed locomotive, or none if you go with boosters (which I have never particularly liked in high horsepowers) You have no capability of using the articulated underframes for other purposes -- not that you'd have much re-use for the single long bed frame either, but it's cheaper and gives a more rigid bed for the ancillaries. The weight-packaging problem is the real issue: it's almost impossible to get the weight properly balanced between the full truck on the end and the half-truck in the middle without cutting into allowable cab room, or increasing forward cantilever length (which has implications on tracking and equalization for the end trucks). My personal observation was that very careful extended side-bolster support for the middle truck was also necessary, but this might have been 'overkill' in design since my interest was in high-speed power at the time.

The D trucks on the Centennials were, afaik, entirely a matter of cost. As I recall, it was understood and accepted early on that the long wheelbase would restrict where the units could run -- and that there would be a limited market on other railroads for the D truck parts and technology.

Paul -- the unit you're describing is UP 80, which I was hoping would be covered in the Classic Trains turbine story, as it represented a very interesting experiment. Of course, that's ALL it was supposed to represent, as anyone ought to conclude from the way it was built -- it was a full-size proof-of-concept at minimum cost, not an attempt at a "practical" locomotive, or even a practical locomotive's configuration.

I was amused that MTH thought enough of this to model it in O scale -- rather well, imho. They did quite a bit of interesting research on the prototype, too...

I remember that the W-1s and the big electrics on the Virginian had a common characteristic -- the cab windows were all the way up at the top, and the locomotives were built very close to the loading-gauge limits... which in this area might as well have been dictated by tunnel clearances. There were stories about how new engineers riding these locomotives into tunnels had the urge to duck...

[M636C]

Guys,

We had two classes of electric locomotive in Australia with articulated trucks, NSW Railways 4501 (later 7100) and 4601-4640. The 46 class were built in England by the joint company Metropolitan-Vickers-Beyer Peacock, with GSI cast frames built by English Steel Corporation, using the US articulation arrangement. They were C+C, 3800 HP on 1500v DC. (4501 was a prototype with welded trucks, C+C, 2700 HP).

We have in Queensland a large number (186 ?) of B-B-B 4000 HP 25 kV AC electrics which are not articulated but which have extra side play and vertical motion in the middle truck. About half of these use ASEA equipment, similar to but lower powered than the GM10B EMD USA prototype.

New Zealand Railways had a 1000 HP Caterpillar engined road locomotive, class DJ, built by Mitsubishi in Japan, which also had the same B-B-B arrangement. A number of these operate a scenic railway out of Dunedin in the South Island, and I was able to ride the cab for much of the return journey down the Taieri Gorge.

The ride was quite strange and vaguely unsettling on the frequent sharp curves on that line, but I understand that the arrangement reduces curve forces and wear. There was no "Squealing" on curves from flange contact.

Peter

[CSSHEGEWISCH]

Another three-truck design would be the GE designs built for International Railways of Central America in the 1950's. They had a C-2-C wheel arrangement and were built just prior to the introduction of GE's Universal line in 1956.

[Overmod]

I expect that the engine you mention is similar to the ones built for Indonesia -- built by GE but equipped with the mighty 12-244! Look here

http://focc200.tripod.com/news.html

and keep going down the page until you find a reasonably-well-exposed picture of the running gear.

Looking at that picture, I'd SWEAR that's a pin-guided center truck -- and presumably, if so, it has lateral spring guidance like a steam-locomotive leading truck. Interesting!

[M636C]

Overmod,

I'd agree with your analysis about the arrangement for lateral movement, but how does it cope with humps and dips?

The NZ Mitsubishis and the QR Hitachi electrics used flexicoils to provide both lateral and vertical movement - the coils on the centre truck being longer with different spring rates to allow for humps and dips.

The ASEA units used double swing links on the secondary coils, as did the GM10B.

The Central American units were, I think hood units, and looked like overgrown GE 70 ton switchers, (although they probably weren't that much bigger).

Similar looking units to the Indonesian units ran in Thailand, but they were C-Cs and had twin Cummins diesels. They liked them, and bought more with Dash 7 electrics recently.

The White and Blue streamliner in the Indonesian photos is a standard export U20C (or something like that ) with a cab developed by Goninan, the Australian GE licensee, who also built the trucks for the new Thai units.

Peter

[Overmod]

QUOTE: Originally posted by M636C

Overmod,

I'd agree with your analysis about the arrangement for lateral movement, but how does it cope with humps and dips?

Presumably most of the equalization compensation would be handled in the 'normal' way for the illustrated truck design -- drop equalizer, coil springs from equalizer to truck frame, some sort of leaf or block to the bolster.

Looks to me as if there is some freedom for the whole truck frame and bolster to pitch relative to the carbody -- see all that light under there? That would give the desired longitudinal and lateral tilt to avoid unloading the C trucks, for example on a high center.

I would not have designed something like this if working from a clean sheet of paper -- but the clear implication is that someone did, and more than one railroad thought enough of it not only to buy it, but to keep it running lo these many years...

[Anonymous]

QUOTE: Originally posted by Overmod


Note that there is a 'packaging' formula for most diesel-electric locomotives: pivoted trucks (or span-bolster assemblies) somewhere near the quarter points of the bed frame, engine in the middle of the span, large fuel tank suspended between frame and rails. The first thing that happens with an articulated locomotive is that you lose the cantilever benefits of pivots at the quarter points where the frame bears on the articulated truck. You also will probably have to have a specialized bolster with two separate pivot locations, appropriate seals or bulkheads at each end of the separate unit, more need to balance components between the units if they are not absolutely common to each "end", etc. (My understanding is that it is more difficult to accompli***raction-motor cooling in a C truck articulated this way, for a variety of reasons).

I looked at articulated locomotives rather carefully in the early 1970s, and there are some other concerns. If you 'standardize' on a single design of carbody module for a given class of locomotive, you automatically have two cabs on the completed locomotive, or none if you go with boosters (which I have never particularly liked in high horsepowers) You have no capability of using the articulated underframes for other purposes -- not that you'd have much re-use for the single long bed frame either, but it's cheaper and gives a more rigid bed for the ancillaries. The weight-packaging problem is the real issue: it's almost impossible to get the weight properly balanced between the full truck on the end and the half-truck in the middle without cutting into allowable cab room, or increasing forward cantilever length (which has implications on tracking and equalization for the end trucks). My personal observation was that very careful extended side-bolster support for the middle truck was also necessary, but this might have been 'overkill' in design since my interest was in high-speed power at the time.

Overmod,

I'd be interested in seeing a picture or drawing of an articulated locomotive if such exists.

Regarding the use of standardized locomotive frames articulated together, it seems you are suggesting that to articulated two SD's together, you would practically have to cut each into a 3/4 length and articulated those together to retain the cantilever effect, except of course you are not cantilevering the articulated section. If I read you correctly, it is this cantilevering action that allows optimal adhesion of wheel to rail, and a true articulation e.g. two separate frames and carbodies wedded to a single center truck, would leave something lacking in that department.

[Anonymous]

By the way, weren't the Milwaukee's Bi-Polar electrics a double articulated locomotive in three sections, with the center cab and driving units on either end?

[Overmod]

Sort of, but not exactly the way you've worded it...

Look here for a pretty good illustration:

http://www.northeast.railfan.net/images/tr_milw_e2.jpg

Note that the 'cab' at each end is in unit with the hood. Each eight-wheel truck is rigidly attached to its respective end unit, with the 1-B truck allowed to swing with a centering device. There are 'ball-and-socket' joints between the truck frames, and my understanding is that all buff and draft forces go entirely through the underframe. The center "box" is carried entirely by the adjacent carbodies (and has, or had, the train-heat boiler etc. in it)

This really makes the locomotive more like two semipermanently-coupled 1-B+D units rather than an 'articulated' locomotive in the classical sense (which would involve the center unit being carried by pins or mountings on the trucks or on span bolsters, not on the adjacent carbodies). Of course, since the undercarriage IS fully articulated, I consider an EP-2 an articulated locomotive with 'somewhat unusual carbody structure'.

Perhaps interestingly, look at this locomotive, on the same site as the bipolar picture:

http://www.northeast.railfan.net/images/cnsm459.jpg

This illustrates a rather interesting variant of a 'span-bolster' idea -- these are full span frames, complete with 'front porches', and a shorter center-cab carbody.

[jchnhtfd]

back briefly to the Centennials... with the D trucks... if memory serves, they were occasionaly referred to as self-powered rail straighteners...

[M636C]

Overmod,

To get back to the CC200 and its centre truck, it struck me that there might be some vertical travel on the pivot, perhaps with a concentric coil spring to allow vertical translation as well as tilting to occupy all that space allowed.

The Japanese had some locomotives of this general type, with air bag secondary suspension on the centre truck which was deflated to increase adhesion on the driven trucks on track where higher loads were acceptable. This was presumably able to account for vertical curves with pressure relief valves.

Peter

[Overmod]

I was thinking exactly the same thing -- hey, just like an HO-scale lead truck...

The only thing is that I don't see any telltale spring silhouette in the picture, and I'd think a spring of the required diameter and strength would 'show'. Of course, the spring arrangement might easily be carried inside the carbody, with only the shaft of the pivot extending through a collar or bearing...

[Anonymous]

Any history of rail spreading with those center truck locomotives? I would think the thing would push outward on curves.

[M636C]

Dave,

The B-B-B locomotives are generally regarded as much easier on curves than the equivalent C-C, and no worse than than a B-B. The centre truck doesn't have to do anything other than hold up the centre of the unit. The two end trucks do all the guiding, and the centre truck can just follow the track. The suspension is designed to allow free lateral movement, and shouldn't apply any excess lateral force to the rails. They have been very successful in Europe, in Switzerland and Italy particularly (although the Italians also have a large number of articulated B-B-B locomotives as well as more recent rigid units).

Peter

[TH&B]

Big Jawn was a C-C-C-C , it must have used a span bolster the big N&W turbine.
Red + Ready 8 axle flat cars wich are commun today use span bolsters.

[Anonymous]

QUOTE: Originally posted by M636C

Dave,

The B-B-B locomotives are generally regarded as much easier on curves than the equivalent C-C, and no worse than than a B-B. The centre truck doesn't have to do anything other than hold up the centre of the unit. The two end trucks do all the guiding, and the centre truck can just follow the track. The suspension is designed to allow free lateral movement, and shouldn't apply any excess lateral force to the rails. They have been very successful in Europe, in Switzerland and Italy particularly (although the Italians also have a large number of articulated B-B-B locomotives as well as more recent rigid units).

Peter

Regarding the comparison of B-B-B being easier on curves than a C-C, does that include C-C's with radial steering?

One other point of interest. If this mid-truck concept works for locomotives, why not use it on freight cars to increase load limit above the current 286k/soon to be 315k limit? Frankly, with the advent of radial steering in three axle trucks, I would think the three axle truck would be the way to go for increasing load limits on freight cars. Then again, with standardization, it is probably cheaper to go 2-2-2 using run of the mill three piece trucks than to go with the hassles of radial steering components.