Tech Info about BB 8 axle loco please .

Trains Magazine Locomotives
1

Hi all , I was looking around earlier and noticed that Wabtec and Progress build export locomotives with 4 trucks and 8 powered axles .

I am interested to know how the four bogie systems work as in how they articulate for track curvature .

Here in Australia our axle loads are lower at around 22-22.3 metric tonnes vs 30 plus in the US .

I’m wondering how we would go with 8 axle units that would maintain up to 22.3 TAL (178T gross) but give us better adhesion performance . In theory it would allow us to use smaller lighter AC traction motors than current in US but still have decent performance .

The down side could be less space for a decent sized fuel tank but that would depend upon frame length . Recently Progress made the narrow gauge GT46ACe for Adani and its frame was a bit longer than our standard gauge units . It’d be interesting to see what could be done with the same frame length but laid out more like the GT46ACe they are currently making for Australian operators , but in BB configuration . Wabtec has been doing similar things to Progress with GE Evo based units on Metre gauge export units .

Thoughts ?

2

It was GE that originated the four truck design, using the standard truck they used on small narrow gauge units linked by a span bolster, much as the UP Gas Turbines used. EMD started off by building the DDM45, an SD45 on the four axle Flexicoil. Later they copied the GE design.

In the case of the DDM45, which ran on a metre gauge iron ore line, the problem was that the motors weren’t powerful enough, so four motors were needed to deliver the engine power to the track. While the axle load was reduced, that wasn’t the main problem.

Vitoria a Minas had a number of Krauss Maffei 4000 HP diesel hydraulics, basically the same as the second Southern Pacific order, which retained the three axle tr

3

Part of the reason for the double-B systems was certainly the traction-motor capability possible on the narrower gauge with wheelbarrow-suspended motors. However, we should consider the EMD experimentation with the arrangement (at one end of a test locomotive) – we have had both threads and informed discussion about this.

I think we’ve covered the ‘alternative’ to using span bolsters (which can increase height) on some of these locomotives. One alternative is to pivot only the outboard trucks (the inside ones could be, but guiding would be sadly affected!) with the inner trucks free to ‘float’ transversely, as on the three-truck PRR experimental electric. Those inside trucks could be allowed some controlled rotation as well as lateral accommodation without compromising ZWT tractive effort to the locomotive chassis. I doubt you would see any modern diesel locomotive or conversion with the trucks articulated in line, with couplers on the truck framing, since the fuel tankage would be in the way.

4

About 12 years ago I was tasked with designing a 4-axle meter gauge bogie for the SD70ACe-BB Progress Rail sold to VLI in Brazil. Axle load was limited to 24.5 metric tons. The meter gauge AC motors used were the SD70MAC cross-section with 43" wheels. I was able to keep the bottom plate height the same as the standard SD70ACe by using a fabricated span bolster that is partially tucked into the underframe and is hollow to distribute the cooling air to the TM’s which receive full ventilation regardless of bogie rotation. To keep the 2-axle sub-bogies compact and low, they use drop equalizers with the primary springs below the H-shaped bogie frame. The motor arrangement is unique in that all motors are on the same side of the axle as is common on low weight shift 3-axle bogies. To optimize weight shift performance with the axle hung motors, the motor nose supports are connected to the bogie frames at axles 1 and 3 - the nose supports for axles 2 and 4 are connected to the span bolster. Weight shift performance is equal to high adhesion 3-axle bogies, unlike the typical span bolster arrangement using two axle bogies with facing motors.

The span bolster has a pin on top that engages a pivot with fore and aft rubber pads that transmit the tractive force into the underframe but allow for lateral motion. Rubber compression springs on “wings” at the bolster ends support the underframe and transfer the load directly to a second set of rubber compression springs on the underside of the “wings” that engage the bogie frames. This allows for a simple bogie frame with short bending moments between spring sets. The equalizer suspension is unique in that the axle bearing adapters connect directly for traction thru a rubber bushing pinned to the equalizer and a rubber pad carrying the vertical load from equalizer to bearing adapter. Lateral thrust pads handle lateral forces between bearing adapter and bogie frame. A rubber bushed link connects the equalizer with the bogie frame to tran

5

We already have weight and fuel tank capacity issues at 134 metric tonnes on 6 axles . From what I’ve read our new Evolution based units won’t have the US std AC traction motors and are going to be limited to 7800 litres of fuel .

This won’t work on our interstate trains without in line fueling so an even smaller (shorter) tank may not make much difference .

Another two axles/traction motors and 44 tonnes definately would .

I can’t see any other way around the performance issues on our lighter 60 kg/meter rail etc .

6

Not directly addressing the primary topic, but I think providing some pertinent background, here is a “potted history” of span bolster running gear.

As far as locomotives are concerned, span bolster running gear appears to have originated in the first half of the 1920s in American interurban practice. A non-exhaustive search shows that in 1924, Piedmont Northern used the B-B+B-B wheel arrangement, with articulated span bolsters, whilst in the same year, Illinois Terminal used B-B-B-B, with independent span bolsters. In some of these cases then span bolsters may have been associated with lateral motion trucks. There may well have been earlier applications. Span bolsters were also used for freight cars, in for example 4-4-4-4 and 8-8-8-8 configurations, but I do not know the timelines. Four-truck interurban locomotives were built until at least 1941-42, e.g. Piedmont & Northern #5600 by GE,

The NYC T class electric locomotives of 1913 and up had a single-frame B-B+B-B wheel arrangement, but it was not of the span bolster type. Rather the inner axles were rigidly mounted to the beams, with the outers in non-lateral notion trucks that acted as pilots to the inners. (1) One could say that it was more-or-less a 2-B+B-2 wheel arrangement but with powered outer trucks, although 2-B+B-2 itself did not arrive until 1921 (GE for Paulista, Brasil).

The solitary EMD (Winton/GE/St. Louis) model T (was it painted black?) transfer locomotive of 1936 for the IC had the span bolster B-B+B-B wheel arrangement, with as best I can tell, rigid bolster trucks.

Post-WWII GE used the B-B+B-B span bolster wheel arrangement, with articulated span bolsters and rigid-bolster trucks, for the VGN EL-2B electric locomotives. (2) Then it used the non-articulated B-B-B-B form, with swing bolster trucks, for the Alco-GE GTEL4500 prototype (3), carried over to the GE production machines.

In that time period, Brown Boveri also proposed various GTEL designs, including some aimed at the US market which had span-bolster A1A-B-B-A1A running gear, as well as a D-D. (4)

Overmod has mentioned the Westinghouse non-span bolster B-B-B-B wheel arrangement used on its solitary GTEL prototype. That was derived from a Westinghouse proposal for a homologous series of electric locomotives (AC and DC) that all used the same standard B truck with non-lifting lateral motion. The range went from B-B, through B-B-B to B-B-B-B, and most improbably to articulated span bolster B-B-B+B-B-B and B-B-B-B+B-B-B-B versions. (5) The single-frame tribo form – with extended lateral motion centre-truck - was by that time well-established, although not widespread, in worldwide practice (GE appears to have been first, with a B+B+B for Mexicano c.1924). The Westinghouse B-B-B-B was an extension of that. (In respect of the tribo form, the articulated body type was also known pre-WWII, but the semi-articulated body form was yet to come.)

The Baldwin STEL prototype for N&W had (non-articulated) span bolster C-C-C-C running gear.

In 1962, the UP proposed using (in fact re-using) the same GTEL4500 B-B-B-B running gear for its desired twin-engine 5000 hp diesel-electric locomotives. (6) It had to order prototypes from Alco and GE, who thus did use this running gear. EMD chose to build prototypes on its own account, thus got to choose, and developed its own D-D approach. There is some evidence that UP might have preferred B-B-B-B for the DDA40X, but not unexpectedly, that followed EMD’s preferred D-D approach. (7)

In the late 1960s, French builder CEM developed a span-bolster B-B-B-B locomotive for service on the African Outre Mer metre and Cape gauge lines. The B trucks were of the monomoteur type. Lateral motion swing links were placed between the body and the span bolsters, not between the span bolsters and the trucks. Also, I think for the first time on a span-bolster locomotive, the couplers were mounted on the mainframe, not the outer ends of the span bolsters. This locomotive, designated the 4B type by CEM, was part of a family, which included the 2B and 3B types. The 2B type simply used two of the B trucks with swing link assemblies. The 3B type had a single B truck, as on the 2B, at one end, and a span-bolster B-B assembly, as on the 4B, at the other end. This made it the most ersatz form in the tribo group, and probably the most asymmetrical of the asymmetrical wheel arrangement locomotives – certainly more so than the Hungarian and British C-B examples.

Next came the GE export BB locomotives, which also had the couplers mounted on the mainframes, then the (I think – and this is strictly a layperson’s viewpoint – very neat) EMD export arrangement described above by Dave.

The D-D wheel arrangement (with true D trucks, not D wheelbases in a rigid frame), an alternative to B-B-B-B, was quite rare. As best I can determine, EMD was the only user. British Rail designed a swing bolster D truck c.1950, (8) but in the event never applied it. Otherwise D trucks have almost always appeared in pilot-truck arrangements, such as 2-D+D-2 and B-D+D-2. Baldwin also proposed, but never used 1-D+D-1. There was a solitary Russian prototype diesel-electric (the so-called Gakkel locomotive) of c.1924, single-frame with the 1-C+D+C-1 wheel arrangement, so this did have a D truck (It was an actual truck, not part of the frame, but one could say that it was piloted by the outer 1-C trucks.) (9)

By the way, GE referred to the GTEL4500 and U50 running gear as B-B-B-B, not B+B-B+B, as used in some publications. Whether the latter is a railfan derivative , or change made by AAR I do not know. In the British Commonwealth wheel arrangement system, with which I am more familiar, it would definitely be Bo-Bo-Bo-Bo, no ‘+’ sign anywhere.

(1) See US patent 1026552.

(2) The reasons for this choice were provided in ASME paper 49-SA-7, ‘Motor-Generator Locomotives, Their Design and Operating Characteristics’, by Fox (VGN), Gaynor (GN) & Gowans (GE).

(3) See AIEE paper 50-77, ‘The Alco-GE 4,500-Horsepower Gas-Turbine Electric Locomotive’, by Morey (GE).

(4) See Railway Mechanical Engineer, 1946 August, ‘Gas Turbine locomotives’, by Giger, p.394ff; also Brown Boveri Review 1945 October-November ‘The Brown Boveri Gas Turbine Locomotive’, p.353ff.

(5) See AIEE paper 48-54, ‘Electric Locomotives with Identical Basic Components’, by Brecht & Kerr (both Wemco)

(6) See: UP Miscellaneous - donstrack

(7) The span bolster possibility was mentioned in Railway Locomotives & Cars 1968 December in an item ‘Two-engine, 6600-hp Locomotives for UP’, pp5 & 6.

(8) See IEE paper #967, 1950, ‘Mechanical Design of Electric and Diesel-Electric Locomotives’, by Cox (BR).

(9) See Railway Mechanical Engineer 1927 July pp.435-437.

Cheers,

7

As far as I know, the use of + to denote articulation comes from Wiener, in Articulated Locomotives (1930), in part as revived and promulgated by Bob LeMassena around the time Kalmbach republished that book in 1970. I recall a certain amount of pushback and mockery expressed from the railfan community about this, as they were used to 2-8-8-2s and 2-6-6-4s and were upset when they sprouted plus signs.

Note might also be made of the convention of using subscript o for unconnected powered axles in a truck, as in Bo-Bo or Co-Co for most American diesel-electrics. This is where that term ‘tribo’ comes from (it has nothing to do with lubrication).

I don’t have my copy of Wiener handy, but as I recall he used an apostrophe for individual powered axles in a common frame, so the B&O constant-torque W-1 would not have been 2-Do-2 but 4-2’2’2’2-4. This is kinda like different forms of calculus notation…

Can you edit the post to clarify where the swing links run on the CEM locomotives? I think that last word is meant to be ‘trucks’ or ‘truck bolsters’…

I confess to having been impressed at the principle of CEM standardizing on one type of span-bolster arrangement and using it on their smaller ‘tribo-size’ locomotive. It certainly gets around issues of lateral accommodation, even if swing is greater at one end than the other…

8

In the late 1960s, French builder CEM developed a span-bolster B-B-B-B locomotive for service on the African Outre Mer metre and Cape gauge lines. The B trucks were of the monomoteur type. Lateral motion swing links were placed between the body and the span bolsters, not between the span bolsters and the bogies(?). Also, I think for the first time on a span-bolster locomotive, the couplers were mounted on the mainframe, not the outer ends of the span bolsters. This locomotive, designated the 4B type by CEM, was part of a family, which included the 2B and 3B types. The 2B type simply used two of the B trucks with swing link assemblies. The 3B type had a single B truck, as on the 2B, at one end, and a span-bolster B-B assembly, as on the 4B, at the other end. This made it the most ersatz form in the tribo group, and probably the most asymmetrical of the asymmetrical wheel arrangement locomotives – certainly more so than the Hungarian and British C-B examples.

I recall this design. I don’t think any locomotives were built to this design. I seem to recall that it was to be offered, among others, with a Pielstick 18 PA6 engine of 6000 HP and was available in standard gauge form as well. The feature that comes to mind is that the monomoteur bogies, like all of their type, were quite tall, projecting up into the locomotive cab type body well beyond the base of the engine and generator and the span bolsters were above this, occupying most of the locomotive up to the roof mounted radiators and air intakes at both ends. Given how far up into the body the span bolster was located, it would have been easy to arrange swing hangers r

9

One other, much less obvious use of span bolsters not listed above was in the Union Pacific Streamliner trains.

The two units of M 10002 were articulated onto a span bolster which carried the end inner trucks, although from the outside, it looks like a pair of locomotives coupled together.

This feature also applied to the two units of the M10004 series, although these later received a genuine third booster unit coupled to the leading pair.

Amazingly, it appears that the first booster unit for the M 10004 units was run (in undercoat) coupled by span bolster to the M 10002 lead unit for trials on the City trains. M 10002’s “booster” was only 900HP, so this might have been to get early test results from a 2400HP pair.

Peter

10

Thanks for adding the UP Streamliner case to the span-bolster list – I was previously unaware of those.

Regarding the CEM locomotives, as best I can determine the builds (all CM (Cape/metre) gauge) were:

27 of the 4B (two span bolsters) type with SACM AGO 230 V16 or 240 V16 engine.
22 of the 3B (one span bolster) type with the SACM 195 V12 engine.
20 of the 2B (no span bolsters) type with the SACM 195 V12 engine.

More powerful standard gauge diesel-electric as well as electric 4B types were proposed, but none of those were built.

On the use of the ‘+’ sign in wheel arrangements, this from an article ‘Electric Locomotive Classification’ in ‘Railway Age’ 1926 February 27, pp.525-6, proposing a new system for electric locomotives:

‘The connection between trucks or motive power units, constituting an articulated joint (a flexible connection through which propulsive forces are transmitted to the drawbars) is indicated by a plus (+) sign. Example B+B – two trucks connected by an articulated joint.’’

And:

‘The separation between swivel type trucks is represented by a minus (-) sign. Example B-B – a locomotive with two swivel type trucks.’

On that basis, one may see why GE used B-B+B-B to describe for example the VGN EL2B, and B-B-B-B to describe the GTEL4500. In the EL2B case, the two span-bolsters are connected by an articulated joint through which passes all buff and drag forces, which completely bypass the main structure. But under each span bolster, the two trucks are independent of each other. In the GTEL 4500 case, the two span bolsters are unconnected, hence the minus sign in the middle. As with the VGN EL-2B case, the two trucks under each span bolster are also independent. The pathway for buff and drag forces is coupler to span bolster outer section to span bolster pivot, thence via the mainframe to span bolster pivot and via the span bolster outer section to coupler.

Cheers,

11

Re the UP Streamliners, I retrieved my copy of the book ‘The Union Pacific Streamliners’ by Rank and Kratville. This has detailed information, including good photographs, of the span bolster assembly used on the M-10002/3/4/5/6 power cars, which were in fact locomotives.

The UP had evidently chosen the articulated body arrangement generally for the streamliners because it was thought to aid stability at very high speeds (100 mile/h and above). Presumably it wanted to retain this for the double power car case, and so the span bolster was required to accommodate two power trucks under the articulation point. Evidently the span bolster assembly, with carefully controlled lateral motion trucks, was also sufficiently stable at very high speeds. The streamliner span bolsters had 8’4” wheelbase trucks at 16’0” centres. The conventional wisdom is that B-B locomotives with short truck centres are prone to oscillation (perhaps a combination of yaw and longitudinal side-to-side) at higher speeds, but this did not seem to afflict the span bolster B-B combination, perhaps because effectively, most of the mass it was carrying was concentrated at the span bolster centre, rather than distributed along and beyond its length.

This experience may have predisposed the UP to accepting the span bolster running gear arrangement for the GTEL4500. Here, 9’4” wheelbase swing bolster trucks were used at 15’4” centres. The same running gear then became its preferred type for its “double diesels”, so it would seem to have worked well in practice.

Those Streamliner power cars then belonged to three groups:

  1.          Four-truck locomotives

  2.          Locomotives with span-bolsters

  3.          Articulated body diesel locomotives

The third group is quite small, the other examples I know of being two Krupp diesel-hydraulic prototypes, B-B-B (with the Krupp characteristic of the time of having a torque converter for each axle), one each for SNCFA, Algeria and EFVM, Brasil, and five Alsthom diesel-electrics, B-B-B, for FE, Ecuador. On the other hand, there were many more articulated body electric locomotives, mostly because FS, Italy had a very large fleet built up over 50 years or so. (The FS locomotives had fairly short truck centres, and eventually FS switched to the single-frame tribo (triple bogie/triple truck) type for better stability at very high speeds.)

I think that the Streamliner power cars could also be described as being of the quasi-(articulated body) tribo type. From the viewpoint of the body structure, its rests on three truck assembles, with the centre “truck” under the body articulation point. The centre point of the body assembly does not “know” whether it is resting upon a single truck or on a span bolster in turn resting upon a pair of trucks.

Returning to the wheel arrangement designation issue, I had a quick look at various sources to see how that for the GTEL4500 and subsequently the GE U50 and Alco C855 diesels changed over time.

Railway Age (RA) 1948 November 27 and 1949 June 18 had the GTEL4500 as B-B-B-B.

Locomotive Cyclopedia 1950-52 had the GTEL4500 as B-B-B-B.

RA 1963 September 09 had the diesels as B-B+B-B.

RA 1963 October 07 had the diesels as B-B-B-B.

Railway Locomotives and Cars (RLC) 1963 November had the diesels as B-B+B-B.

RLC 1964 July had the diesels as B-B-B-B.

Lee, in ‘Turbines Westward’, 2nd, 1975, had the GTEL4500 as B-B-B-B, I suspect copied over from UP documentation.

Kratville & Ranks, in ‘Motive Power of the Union Pacific’, 1977 had the GTEL4500 as B-B-B-B, again I suspect copied over from UP documentation.

Keekley, in ‘Roaring U50’s’, 1978, described the U50 (or U50D, as he called it), as having a B+B B+B (space, no sign between the two B+B groups) wheel arrangement.

Cockle, in ‘Giants of the West’, 1981, used B+B B+B for the GTEL4500, Alco C855 and GE ‘U50D’.

Marre, in ‘Diesel Locomotives: The First Fifty Years’, 1995, used B+B-B+B (with a dash between the two B+B groups) for the GE U50 and Alco C855.

I think it is a case of ‘take your pick’ from:

B-B-B-B
B-B+B-B
B+B B+B
B+B-B+B

Whether the changes were the results of rethinking the situation or just random errors is unknown.

I have not seen any GE literature in respect of the BB40 series export models, so do not know how it described their span bolster wheel arrangements.

As the ‘U50D’ alternative designation for the U50 has come up in some of the above sources, the earliest use that I have seen was in the RA 1969 February 24 and RLC 1969 March articles on the GE U50C. Both referred to its predecessor as the U50D, without further explanation.

Keekley said: ‘The U50D was originally introduced to the Union Pacific by General Electric as simply the U50. It was only after General Electric built the U50C model in 1969 that the earlier model was referred to as the U50D.’ He does not say by whom, though.

And Cockle: ‘While properly classified as U50’s, when the U50C was introduced this model became known as the U50D (improper, as it did not have D-type trucks) or sometimes called a U50 B+B B+B’.

Early GE literature (e.g. GEA-7842 of 1963 September) referred to the model as simply the U50. And its never-built successor was the U56, e.g. as referred to in RLC 1965 September and 1966 March.

But GE did use the U50D designation in its 1985 May ‘Universal World Users Brochure’ and again in its 1991 September 21 ‘World Users List’. How that came about is unknown, but de facto it legitimized this designation, notwithstanding its origin, whether it was from GE, the trade press or the railfan world.

In general though, the evidence over many years is that the span bolster wheel B-B-B-B arrangement is quite satisfactory in riding and tracking terms for high-powered diesel-electric locomotives in situations where eight axles rather than six are required in order to meet axle-loading constraints. And as the EMD case shows, they can be built without requiring a higher frame height than for homologous C-C locomotives, and with tandem-mounted traction motors. Whether the extra axles and extra complexity for extra power is justified in any given situation would be for the individual railroad operators to decide.

Cheers,

12

I should have credited the Kratville “Steamliners” book as my source for the span bolsters on the later M10000 series locomotives, although I think the feature was mentioned in most references. However, the photos in the Kratville book made things quite clear. That book is an excellent source for most things related to the UP Streamliners, although the change from head end power in dedicated power cars to steam heating and axle generators, a retrograde step in nearly every way, is only indicated by a careful reading of the actual vehicle diagrams. This occurred between the LA 1-2-3 and SF 1-2-3 sets and the following 4-5-6 sets (so before WWII).

Regarding the use of “+” in wheel arrangements, the rationale used in Australia was that “+” was used where a hinge was present, and if not a “-” was used. Thus electric locomotives with connected bogies were Co+Co but those without connection between bogies were Co-Co. There were some diesel locomotives with bogies connected, but not many. Some of these had couplers carried by the bogies, and some did not. Some diesels with couplers carried by the bogies did not have an interconnection.

One very common usage was 4-8-4+4-8-4 for Beyer Garratt locomotives. This would be incorrect by the above definition, since Garratts were supported on pivots with no hinge involved. However most Mallets and simple articulated locomotives had a hinge connection and could be shown as 4-8+8-4 using this definition.

I’m not sure that even the very compact span bolster arrangement would suit the limited headroom of the general Australian loading gauge, as suggested by the original poster. Just the loss of fuel capacity would be a problem owing the the shorter tank required.

One further point about the Gas Turbines and U50s. My understanding was that the U50s used the same trucks as the turbines, these being fitted to the U50s and the Alco C855 units as the turbines that has used them were withdrawn and scrapped. Whe

13

I’ve also found Kratville’s “Streamliners” book to be very informative, picked up my copy in spring of 1977 and didn’t fully realize how detailed the book was until getting White’s book(s) on American RR pasenger cars.

From my reading, the motive to go back to steam heat and axle generators was to allow interchange with UP’s existing passenger car fleet (and the fleets of the C&NW and Espee). What amazed me about the head end ower was that using electric resistance heat from the diesel generators used less fuel than steam heat despite the inefficient conversion of diesel fuel to electric power. I’d also expect that the head end power used less fuel than what was needed to overcome the drag of axle driven generators.

14

I guess UP finally realised that with the LA & SF 4-5-6 sets, they were dealing with full size trains, not dedicated articulated lightweight trains. All the E3s and E6s had steam heating and could be used on any passenger train. While the fuel consumption increased, it was still far less than would be used by oil burning steam power, and they could stop maintaining the power vans and convert them to baggage cars. The overall simplification might have saved money in 1941 terms.

In Australia, the broad gauge states went with axle driven air conditioning, there was no steam heat used in Australia in the early 1950s, but the standard gauge operations decided on power vans as the source of power. This situation changed in 1962 when trains began to run from Sydney to Melbourne without change at the border, and the cars converted from broad gauge were fitted for HEP. By 1970, the Melbourne Adelaide broad gauge “Overland” was converted to HEP. In the early 1950s it gained the nickname of “Overdue” since two 1500HP EMDs lost time dragging the heavy train with axle driven generators up the steep grades at each end of the line. When 1800HP units arrived around 1960, things improved but by 1970 they decided they had to make the change.

In Australia the various governments are encouraging homeowners to change from gas heating to electric, although there are relatively few locations where real heating is needed even in Winter. Oil heating died out quickly due to the oil price increases in the 1970s.

Peter

15

As I understand it, all 23 of the GE U50 model built for the UP had running gear, mostly complete but in some cases just the span bolsters, recycled from the GTEL4500 fleet (including the prototype), as did the three Alco C855. But the three U50 for the SP had new-built running gear. Evidently there was no problem with supplying to the same pattern, with GSC the presumed, but not confirmed, supplier.

Also, the catalogued-but-never-built successor models, GE U56 and Alco C860, had the same span bolster running gear, this indicating that there was no problem with its availability if wanted.

Re the GE U50C, the available evidence is that GE started with the idea developing a lighter, shorter and lower cost 5000 hp twin-engined locomotive, thinking that such would have broader appeal than had been the case with the earlier U50. In turn that indicated that 24 engine cylinders were required, hence a pair of 7FDL-12 engines. As catalogued, the U50C was fitted with GE’s standard FB3 trucks, but the UP – in the event the only customer – instead opted to recycle some of the trucks from the retiring GTEL8500 fleet. These were an earlier floating bolster design.

The U50C could be seen as being a notional diesel-electric counterpart to the catalogued-but-never-built Alco DH650 diesel-hydraulic, which was dimensionally the same as the DH643 built for the SP, and which accommodated two 12-251 engines on six axles.

In respect of British Commonwealth wheel arrangement designation practice, the trade journal ‘Diesel Railway Traction’ 1956 May issue carried a subject article in which it was said:

In respect of British Commonwealth wheel arrangement designation practice, the trade journal ‘Diesel Railway Traction’ 1956 May issue carried a subject article in which it was said:

‘The + sign is used only when the buffing and drawgear are fitted on the bogies and when the buffing and drag stresses are transmitted directly bogie to bogie and not up to the cab under-frames at the pivots. Those subsidiary articulation systems between bogies which are for guiding purposes only are not considered.’

The subsidiary articulation systems comment almost certainly referred to devices such as the centralizer, originally developed by SLM, but very quickly taken up by English Electric. GE, which had a history of developing and patenting various stability devices, most notably in connection with 2-C+C-2 running gear, also developed and patented its own version of the centralizer, initially for the South African Railways (SAR) 32 class (U18C1 model) with 1-C-C-1 running gear (which was equipped with GSC trucks designed to be used with a centralizer), but later for C-C locomotives (U20C et seq) for SAR and other railways.

An interesting case of wheel arrangement mis-designation was that of the New Zealand Railways (NZR) Df class diesel-electric of 1954, which initially and until the early 1960s was listed as 2-Co+Co-2. But an early 1960s article in the New Zealand Railway Observer magazine explained that it was in fact 2-Co-Co-2. There was no articulation joint between the bogies, the buff and drag forces passing through the main frame between the main truck pivots. But there was an English Electric centralizer (lateral coupling) device between the inner ends of the main trucks; this did not transmit any longitudinal forces. Thus by happenstance I learned about the distinction quite early on. I suppose that given that the couplers were mounted on the outer ends of the main trucks, and there was a visible interconnecting device, assuming that it was a full articulation joint was an easy mistake to make. Later I learned that 2-Co-Co-2 was an extremely rare wheel arrangement, with a worldwide total of 12, namely the 10 in New Zealand and the pair of GE steam turbine electric protypes tested on the UP. The latter had their stability devices set up for cab-leading operation, hence the nose-to-back orientation when used in pairs. On the other hand, 2-Co+Co-2 was more common, with an estimated worldwide total of 495, all being electric, of which Japanese National Railways had the first (1925), the most (237), and the last (1958), although probably not the most famous.

An unusual case was that of the New South Wales 46 class electric locomotives. These definitely had Co+Co (articulated) running gear, but with a bar-type rather than a single-point truck interconnection. They also had what looks like (from the photographic evidence) a centralizer.

Re the ‘competition’ between running gear and fuel tanks in respect of longitudinal space, that evidently came up with the SAR 32 class (GE U18C1), which had longer 1-C trucks in place of the usual C trucks of the U18C. In that case it was addressed by placing an auxiliary tank in the bottom of the body space normally reserved for the optional steam heating boiler, not required by SAR. (The upper part of that space was occupied by the inertial filtration equipment, an extra that SAR required.)

With the extra weight that eight axles could carry for a given axle loading, simply extending the locomotive length as required to fit the desired size of fuel tank might be another possibility. There is some history of that kind of frame extension in Australian practice. For example, I understand that Clyde stretched the G12 model from 43’0” to 44’6” over end frames specifically for Queensland Railways (QR) to allow the fitting of a suitably large fuel tank. Much later, something similar seems to have happened with the QR 2600 class, GE U22C model. Notwithstanding its designation, this was derived from the light-frame version of the U26C, not the baseline U22C (which was simply an uprated U20C). QR required 12’6” wheel base trucks (I think for bridge loading reasons) instead of the standard 10’5½”. Accommodating these without any loss (in fact with a small increase) in intertruck (i.e. fuel tank) space required that frame be lengthened from 55’6” to 60’0” (and with no increase in total weight in this case).

I suppose though the question would be whether the putative haulage capacity gains of the eight axle span bolster running gear would offset the extra first and ongoing costs. And even if the numbers stacked up, there is also the perceptual issue that tends to work against anything that looks to be more complicated, complex and difficult, even if it works well in practice.

Cheers,

16

Wow, there’s quite a range of points there…

I’ll try to address them, if not in the order they appear.

I’m not sure that the main line locomotives can be lengthened. For the last thirty years, all Australian main line locomotives have been 22 metres long. This may be a coincidence but I don’t think so. There are standards out there but I’m not sure that I have access to them. The only units longer than 22m are the new Progress units for use in Queensland on 1067mm gauge. Also height restrictions are more severe than even the former New York Central clearances. Australian locomotive trucks are generally smaller and lighter than domestic USA trucks. The few 180 tonne units have trucks that look like USA domestic trucks but I don’t know if the height is the same.

It wasn’t just the G12s that were 18 inches longer… All the G8s and all the DL-531s were also exactly 18 inches longer. But as I point out above, we may have hit the limit on length.

Regarding South Africa, the truck interconnection was not exclusive to GE. The diagrams of the EMD GT26C units in South Africa also show some form of interconnection under the fuel tank. If my HO scale model of an SAR GT26C is accurate, these have diagonal links between the opposite inner sides of the trucks. But the shallower fuel tanks must be lower in capacity.

As to centralisers, The NSW 46 class were built by Metropolitan Vickers -Beyer Peacock in a factory built for diesel and electric locomotives (in Stockton on Tees, if I recall correctly). Metropolitan Vickers had articulation links on locomotives supplied to South Africa and to Japan. In fact M-V built the first of the 2-C+C-2 locomotives in Japan.

Queensland were very serious in meeting the Cooper loadings on their bridges. Over our summer of 1970-71 I was able to talk my way into assembling locomotives at the English Electric plant in Rocklea, a suburb of Brisbane. I was given a week in the design office which was really great

17

The GT26MC’s had what we called at EMD “inter-bogie control”. Long triangular frames that had vertical pivots on the bogie end transom met under the fuel tank and were connected laterally with a spring assembly that required a difficult adjustment so it didn’t adversely affect tangent track running. I believe, but am not certain because it was before my time in the bogie design group, that this was added at the insistence of Dr. Scheffel at SAR. EMD was not a proponent of it but the customer is always right. It adversely affects curve entry and exit lateral wheel forces while improving them in the body of the curve. It also hinders bogie rotation thru crossovers.

Dave

18

BDA wrote the following post 7 days ago:
I am interested to know how the four bogie systems work as in how they articulate for track curvature .

I am not sure that this particular request item has yet been addressed directly.

There is a curving diagram of the Illinois Terminal C class locomotive #1595 available here, which gives a general idea:

Imgur

Essentially, each span bolster with its two trucks effectively forms a B-B locomotive with short truck centres. Then the main frame rests on each span bolster. From the viewpoint of the main frame, it is part of a two-truck locomotive – it won’t “know” that what it sees as the trucks below it are in fact span bolsters, themselves mounted on trucks.

Clearly, the details vary from case to case. The Illinois Terminal C class was an extreme case, in that it was designed to negotiate 35 ft radius street trackage curves. Thus the trucks could rotate significantly with respect to the span bolsters, which in turn could rotate significantly with respect to the main frame. With the full-sized examples, the required rotation of trucks and span bolsters is much less, possibly just single digits in degree terms.

Notwithstanding the wealth of patents that deal with various aspects of locomotive running gear and trucks, I have yet to find any that are specific to the span bolster case. Given GE’s prolific patent activity in the general field over many decades, it is reasonable to assume that when it came to use the form, it was already established and not patentable.

I mentioned earlier that span bolsters sometimes were also used for freight cars. As an extreme case, I have a 1962 Hitachi item on a double span bolster unit, presumably Cape gauge for use in Japan. Each upper span bolster loaded on to two lower span bolsters. The outer of these loaded a pair of four-axle trucks, the inners loaded a pair of three axle trucks, for a total axle count of 28.

bogie_engineer wrote the following post 7 hours ago:
The GT26MC’s had what we called at EMD “inter-bogie control”. Long triangular frames that had vertical pivots on the bogie end transom met under the fuel tank and were connected laterally with a spring assembly that required a difficult adjustment so it didn’t adversely affect tangent track running. I believe, but am not certain because it was before my time in the bogie design group, that this was added at the insistence of Dr. Scheffel at SAR. EMD was not a proponent of it but the customer is always right. It adversely affects curve entry and exit lateral wheel forces while improving them in the body of the curve. It also hinders bogie rotation thru crossovers.

With conventional trucks, e.g. B-B and C-C, the benefits (or disbenefits) of interbogie control are I think situational. Some systems said yes, probably those with many long and relatively tight curves, some said no. With say the 1-C-C-1 wheel arrangement though, the centralizer was said to counter the negative effective of the trailing pilot truck on the trailing main truck when curving, so was perhaps better justified, at least in cases where relatively light track structures were used. As an illustration, Nigerian Railways used it on its light track 1-C-C-1 locomotives built by Hitachi, but not on its main line 1-C-C-1 locomotives built by MLW (even though MLW did have its own version of the centralizer). The light track locomotives also had axle spacings arrangement for significant bending moment relief (as measured by the Talbot method).

SAR appears to have had the largest number of locomotives so equipped. That started with the 5E class B-B DC electrics of c.1954, and was subsequently applied to most, although not all of the following electric and diesel types. Before the 5E, SAR had used electric locomotives with articulated trucks, B+B, then C+C, then 1-C+C-1. The latter had a bar-type intertruck articulation, plus some kind of spring-loaded intertruck device. Whether or not this was a centralizer is not completely clear from the available description, but it might have been.

In Switzerland, the centralizer was much used, and was also developed for tribo locomotives, starting with the Rhaetian Railway Ge6/6 II class. English Electric adopted the centralizer in 1951 as one approach to combatting excessive flange wear on then-new C-C electric locomotives in Brasil.

Some references on centralizers are:

ILE paper #484 of 1949 January, ‘The latest development of the Electric Locomotive in Switzerland - Its Mechanism and some Problems, Dr. Gaston Borgeaud (SLM).

ILE paper #603 of 1959 December, ‘Methods of Reducing Flangewear on Diesel and Electric bogie Locomotives, by W.L. Topham (Vulcan Foundry/English Electric).

Mathematical Gazette 1964 October, ‘The Theory of the Centralizer or Transverse Coupling in Electric Locomotives’, by R. B. M. Jenkins, pp.296-304.

UK patent 611237 (SLM)

UK patent 742129 (English Electric)

US patent 3054361 (GE)

US patent 2994284 (GSC, mentioned in connection with the 1-C truck))

Cheers,

19

Dave,

Thanks for the explanation. The system you describe is similar in principle to that fitted to the Commonwealth Railways NT class locomotives, more correctly to the first three units. These were built by Tulloch Limited in Sydney to a Metro Cammell design and used one of the earliest bogie designs using four rubber-metal pads to take the load directly to the frame. The axle loads were arranged so that the centre axle had the heaviest axle load (about 12 tons) while the outer axles carried less than 10.5 tons in order to reduce lateral forces in curves. The roughly triangular links were a

20

M636C:

It wasn’t just the G12s that were 18 inches longer… All the G8s and all the DL-531s were also exactly 18 inches longer.

As I understand it, when Victorian Railways (VR) ordered the Clyde G8, it was at the 43’0” standard length. (VR Newsletter 1954 October). Presumably it then agreed to the 44’6” length requested by QR for the G12. But then subsequent deliveries (of the G8B) were shortened to 40’8”. Clyde was first to build the GR12 model, for QR (1450 class). Its version had 12’6” wheelbase trucks and was 49’2” over end frames. The EMD version had 12’2” wheelbase trucks and was 47’4” long. If one goes back to the first QR 90-ton locomotives, the 1150 class from GE and the 1200 class from English Electric (EE), both had a 45’0” total wheelbase as well as 12’6” wheelbase trucks. (At the time, GE’s customary export C truck was of 10’7” wheelbase.) In both cases the total wheelbase was a larger fraction of overall length than was usual, and both locomotives were evidently longer than they needed to be to accommodate the requisite equipment. So perhaps QR had specified not only the 12’6” truck wheelbase, but also the 45’0” total wheelbase for bridge loading reasons, but soo