FB-3 variant queries

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FB-3 variant queries

Postby Allen Hazen » Sun May 05, 2013 8:19 pm

Famously, the FB-3 truck used on GE's (domestic) six-axle units from 1966 until the introduction of the "roller blades" truck on the Dash-9 came in visibly different versions: truck castings by Adirondack versus truck castings by GSC. (With the further complication that Adirondack changed its design at some point: early versions have a very visible "shelf" over the center axle, later don't. The Adirondack trucks are still distinguishable from GSC's. Two spotting features: (i) the region of the side frame over the outside axles is squarer or boxier on the Adirondack trucks than on GSC's (I can't do much better than that as a description, but compare a bunch of photos and the difference will start to jump out at you!), (ii) GSC trucks have hoes in the sideframes about midway between the outside axles and the centre one, whereas on Adirondack trucks the holes are much closer to the end axles.)

So, a couple more truck-trivia queries:
(1) How do the numbers of trucks of the two versions compare?
(2) When did Adirondack stop supplying trucks for GE six-axle locomotives?

I tried to get a bit of a handle on this by doing a small photo-census. Marre and Withers's "The Contemporary Diesel Spotter's Guide" has about 85 photos of U30/33/34/36C and C30-7/30-7A/36-7/36-8/32-8/39-8 units with FB-3 trucks. Counting (I lost track at some point, but with this small a sample only a rough indication is to be expected) I found that
(a) Adirondack trucks VASTLY outnumber GSC on the earlier (U-series) units, but
(b) GSC trucks get more common over time, and are on most of the C40-8.

Bonus question:
(3) When did Adirondack change its design?
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Census data

Postby Allen Hazen » Sun May 05, 2013 10:01 pm

O.k., that was embarrassingly sloppy of me! Here are the actual "census" figures from (the 2008 edition of) Marre and Withers. The photos are roster shots. In two cases there are two photos of the same individual locomotive: I have not double-counted in those cases. I have looked only at the truck closer to the camera (in most cases the truck at the cab end, but in a few N&W or NS cases the one at the long-hood end): I know these locomotives could be, and sometimes were, equipped with two dissimilar trucks but... well, the pictures aren't all that big, and I had to use a magnifying glass on some anyway.

So,
Code: Select all
Model       # with AD trucks              # with GSC trucks              Notes
U30-C  --        10  --                          3 --                          (1)
U30-CG --        2  --                          0 --
U33-C --          7  --                          2
U34-CH --       1   --                          0
U36-C --         5    --                         1
P30-CH --       1    --                         1  --                         (2)
C30-7 --          7    --                        4
C36-7   --        3    --                        7   --                        (3)
C30-7A  --       2    --                        0
C32-8   --        3    --                        0
C39-8   --        2    --                        5   --                        (4,5)
C40-8 --          1     --                     14    --                       (6,7)

Notes:
(1) A possible straw in the wind: the one photo of a unit from the last U30C order (UP's 1976 order) has GSC
(2) Only one order of this model was built, and Amtrak didn't have any other 6-axle GE units, minimizing the chance of a truck-switch by maintenance people, so this suggests that GE was happy to mix the two types of truck even on a single order!
(3) Two photos are of units from Conrail's single order for the model: one with each type of truck
(4) Includes both C39-8 and C39-8E
(5) Photo of one Conrail unit dark enough that I couldn't tell which type of truck it had
(6) Includes C40-8W, C41-8W, and CSX's C44-8W
(7) Photos of two Conrail units too dark to tell

Comment: if I'm right in thinking Adirondack had exited the market before the end of production of FB-3 equipped models, ANY Adirondack trucks on the later models must be from trade-ins (or retrofitted in railroad shops). I didn't, however, notice any early AD trucks (= with the shelf over the center axle) on late units.

Question 4: How long does a truck frame last on the average? (At some point I would assume cracks show up and the frame is scrapped...)
Question 5: Did AD trucks wear worse than GSC? (I don't think this is likely, but covering all the possibilities I can think of: this would be a CONCEIVABLE reason for the declining proportion of AD trucks in later years!)
Last edited by Allen Hazen on Sun May 05, 2013 10:14 pm, edited 1 time in total.
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Just for the record...

Postby Allen Hazen » Sun May 05, 2013 10:08 pm

Just for the record... GE "dual-sourced" truck frames right from the start. The FB-3 truck was introduced on the "Phase 2" U28C in 1966. Marre and Withers don't cover the U28C (or, for that matter, the U23-C...), but the first reference book I looked at for U28C images (Marre's "Diesel Locomotives: the first 50 years") had photos of two 1966-built units: a L&N U28C with Adirondack trucks and a Santa Fe U28CG with GSC.
Which shouldn't be surprising. The earlier, drop-equalizer, truck used on, e.g., U25C and E-44 electrics also had frame castings from both AD and GSC, though there is not as much visual difference between them as on the FB-3.
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Re: FB-3 variant queries

Postby Allen Hazen » Tue May 07, 2013 2:41 am

Webcrawling in search of relevant information (I found, for example, a report on soil pollution remediation at the former Adirondack Steel Castingssite in Watervliet, New York... which, frustratingly, failed to say when manufacturing at the plant ceased) I found this, from an article in a Soo Line historical society magazine article on the Soo's 1968-built U30C:

"General Electric during this time had two sources for the truck castings, General Steel Castings and Adirondack Steel Castings, and the Soo units were to come with two side frame designs that differed visually from one another. Although interchangeable, each locomotive was built with trucks having the same casting pattern."

Confirming that GE was willing to use both sorts of truck frames in filling a single order, but (at least in this case) didn't send an individual unit out from Erie with one of each.
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Re: FB-3 variant queries

Postby Allen Hazen » Tue May 07, 2013 2:56 am

Well, a date at least. A confident-sounding correspondent at
http://www.trainorders.com/discussion/r ... ?6,2384121
(in a string that starts discussing a recent South African order of diesels from GE but also has some information about trucks and their sources*) says that Adirondack went out of business in July 1987. (Leaving open, however, the question of when they last supplied FB-3 truck castings to GE...)

*Including the tidbit that the lighter-weight, welded rather than cast, version of the "roller blades" truck-- a truck that first appeared on the NR-class diesels for Australia's Pacific National and has since been used on a variety of GE locomotives for customers with lighter axle loadings than North American railroads-- was in fact designed by GE's Australian locomotive-building affiliate, Goninans.
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Re: FB-3 variant queries

Postby Engineer Spike » Wed Jun 05, 2013 5:31 pm

Adirondack has been gone for a long time. It was along the D&H, across the main from Colonie Shops. Now there are just piles of bricks.

I'm sure that GE could have sent a set of prints for the casting to any capable foundry. I habe seen Blomberg trucks with GSC, Rockwell, and Dofosco logos on them.
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Re: FB-3 variant queries

Postby Pneudyne » Mon Oct 05, 2015 5:57 pm

In searching through my stack of GE materials (mostly on export models) a while back, I came across the attached item about the U50C, something that I had forgotten that I had.

RA 19690224 p.20.jpg

RA 19690224 p.21.jpg



Interesting is that the U50C was sketched and described as having the same floating bolster, non-equalized C-trucks (FB-3?) as were used on contemporary domestic single-engined six-motor Universal models.

But UP’s decision to recycle the GTEL8500 trucks for use on its U50C fleet stymied that idea. Nevertheless, the odd thing is that GTEL8500 trucks were of the floating bolster type, as best I can determine the first such application by GE on a domestic market model.

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Re: FB-3 variant queries

Postby Allen Hazen » Tue Oct 06, 2015 9:45 pm

Thank you for posting that "Railway Age" article! I think I saw it when it was new, and have remembered ever since that the drawing showed FB-3 trucks (looks like the early Adirondack version).
--I think the impetus for the U50C probably came from the Union Pacific (they were roughly contemporaneous with the "Centennial" units from … that other locomotive builder … and after that Union Pacific's motive power department seems to have regained its sanity). My (entirely speculative) feeling has been that GE hoped, however, to sell it to other railroads. The key bit of evidence is that it was a 5,000 hp unit with two 12-cylinder engines, and not the 8-axle, twin 16-cylinder, monstrosity that they COULD have designed: U.P. was into buying crazy stuff at the time, but GE might have thought the smaller unit might appeal to … saner … motive power departments. But the fact that artwork was produced showing the "standard" three-axle truck instead of the GTEL trade-in trucks U.P. ordered also suggests that GE might not have thought of this as "something only Union Pacific could love."

--Do you suppose a slightly different frame design would have been needed if GE had built U50C with its standard 3-axle truck? Or did the placement of the centre plate and the ducts for traction motor ventilation on the GTEL match closely enough with that on GE's standard 1966-line of (domestic) U series to make the GTEL truck and the later FB-3 interchangeable? The equal (or very nearly equal) axle spacing on the GTEL truck suggests it MIGHT have been compatible with the later design. (For comparison: GE's non-floating-bolster C truck used on the U25C and early U28C was interchangeable with the Fairbanks-Morse single-drop-equalizer trimount used on the "Train Master": the Virginian sometimes switched trucks between their Train Masters and their EL-C (=E33) electrics. The Train Master truck differed enough from Alco's trimount, however, that, when the Norfolk & Western asked for C-630 units with trucks from Train Master trade-ins, Alco had to modify the frame design to accommodate them.)

--In the event, ONE of the problems with the U50C was that the trucks used weren't robust enough for the very heavy locomotive: truck frames started to crack. I've long wondered whether the trucks shown in the drawing might have been better. (Hmmm… I had assumed that the U50C was heavier than the GTEL units, but apparently not: Wikipedia says that the final U.P. turbines weighed 849,212 lbs, which would give an average weight for a single unit a bit heavier than a U50C: my memory is that the U50C weighed just under 210 (short) tons apiece.)
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Re: FB-3 variant queries

Postby Pneudyne » Wed Oct 07, 2015 7:34 pm

With truck interchangeability, I suspect that the devil is in the detail. That said, it probably would not have been a major engineering effort to accommodate both the GTEL8500 truck, with its symmetrical axle spacing, 7’3” each side, and its exactly central centre pivot, and the FB-3 under the U50C.

Lee gives the weight of the GTEL8500, without tender, as 849 248 lb. That’s a very remarkable implied precision for a parameter that was not usually quoted to greater than ±2 percent precision. (And as I recall, the Apollo program was mostly calculated on the basis of three significant digits...) Anyway, let’s say roundly 850 000 lb, which in turn gives an axle loading of roundly 71 000 lb.

The GTEL8500 may have come out somewhat heavier than expected, as an early reference mentions a 68 000 lb axle loading. The GTEL4500s were a bit above this, around 69 000 lb, I think, but the 68 000 lb is a plausible original target given that late UP steam locomotives were built to a 67 500 lb nominal maximum (which was up from the 65 000 lb that had applied to the early Challengers and the 59 000 lb that had applied to the 4-12-2s.)

Cockle gives the U50C weight as 442 660 lb, which gave an average axle loading of close to 74 000 lb.

So those UP GTEL8500 trucks were carrying a bit more weight when used under the U50C. Whether that was a critical increment in durability terms is hard to say. That had come from a fairly hard life under the GTELs, which would have included quite a bit of high-speed running, and a high proportion of time at near full power or full dynamic braking. So maybe they were approaching their fatigue life when transferred to the U50C fleet. And as well as a higher axle loading, the U50C had a higher nominal power-per-axle number, 833 hp as compared with 708 hp.

In visual (photographic evidence) terms, the GTEL trucks seem to have had slightly shallower frame box-section skirts than the FB-3 trucks, but that might not mean very much. For example, the loading patterns were somewhat different, with the GTEL trucks having four primary springing loading points (two major and two minor, as it were) as compared with the three of the FB-3. And the GTEL bolsters loaded the frame inboard of main box-sections, so presumably had appropriate lateral strength.

I imagine that GE was ever hopeful of a wider market for its twin-engined locomotives. That is probably why it had earlier announced the (never-built) U56 along with the U28B/C. But the U50C was something of a step-out. Whereas the U50, U56, C855 and DD35 were all essentially a pair of their respective makers’ standard high-power B-B locomotives of the period on a single eight-axle chassis, the U50C sought to offer substantially increased power output on a C-C chassis that was not too much heavier than the upper-end-of-the-range norm for that type. Whilst the U50C suffered from non-trivial execution problems, in hindsight one might say that concept itself, of a 5000 hp-or-thereabouts C-C, was unlikely to have caught on, even with flawless execution.

I suppose that from the UP viewpoint, the U50C was proximate to being three-quarters of a DDA40X Centennial, although with a slightly more favourable adhesive weight-to-power ratio. On the other, the DDA40X had a lower MCS, namely 11.25 mile/h, compared to the U50C’s 14.7 mile/h, perhaps not insignificant on some of the UP’s long grades where operating speeds might have fallen below 15 mile/h. Reputedly the U50Cs were afraid of going west of North Platte.

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Re: FB-3 variant queries

Postby Allen Hazen » Thu Oct 08, 2015 10:59 pm

Cockle?
The figure I remember for the U50C is the one given in the article: 417,000 pounds, or 69,500 per axle. Perhaps the GE figures the article is based on -- issued before the first U50C was delivered -- were overly optimistic, and the weight blew out beyond the initial engineering estimates… But I think 74,000 pound axle loading would have been considered very high in 1970.
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Re: FB-3 variant queries

Postby Allen Hazen » Thu Oct 08, 2015 11:42 pm

Well, the Technical data section of "The Diesel Shop" <thedieselshop.us> gives the higher weight for the U50C. (I have found errors on that site, but…)
On the other hand, GE's operator manual for the U50C is available at George Elwood's invaluable "Fallen Flags" rail image site, at http://www.rr-fallenflags.org/manual/U50-OM.pdf
The arrangement of equipment diagram at the end of the manual shows the GTEL trucks, so it, at least, was prepared with knowledge of the final configuration. And the weight quoted in the data table near the beginning is 417,000 pounds.

I don't know what to believe. My suspicion, however, is that the U50C as it was finally built was a lot heavier than it had initially been planned.

(Does anyone have a guess as to just how much weight was saved by the -- disastrous, in the event -- decision to use aluminum rather than copper cabling?)
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Re: FB-3 variant queries

Postby v8interceptor » Fri Oct 09, 2015 2:11 pm

Allen Hazen wrote:Thank you for posting that "Railway Age" article! I think I saw it when it was new, and have remembered ever since that the drawing showed FB-3 trucks (looks like the early Adirondack version).
--I think the impetus for the U50C probably came from the Union Pacific (they were roughly contemporaneous with the "Centennial" units from … that other locomotive builder … and after that Union Pacific's motive power department seems to have regained its sanity). My (entirely speculative) feeling has been that GE hoped, however, to sell it to other railroads. The key bit of evidence is that it was a 5,000 hp unit with two 12-cylinder engines, and not the 8-axle, twin 16-cylinder, monstrosity that they COULD have designed: U.P. was into buying crazy stuff at the time, but GE might have thought the smaller unit might appeal to … saner … motive power departments. But the fact that artwork was produced showing the "standard" three-axle truck instead of the GTEL trade-in trucks U.P. ordered also suggests that GE might not have thought of this as "something only Union Pacific could love."




My copy of the "Second Diesel Spotters Guide" includes a photo of a U50C testing on Erie Lackawanna (in consist with an EL U33C, IIRC) so perhaps they were trying to interest other potential customers.
Did GE use EL trackage for testing new locomotives on a regular basis? That is to say; orders for other customers rather than sales demonstrations for the railroad itself?
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Re: FB-3 variant queries

Postby Pneudyne » Fri Oct 09, 2015 3:29 pm

Allen Hazen wrote:Cockle?


That is the book:

“Giants of the West”
George R. Cockle
Overland, 1981 ISBN 0-916160-12-2

It covers the GTEL4500, GTEL8500, coal-burning GTEL prototype, U50, DD35, C855, U50C and DDA40X locomotives, with also mention of the GE steam turbine electric prototypes.

The data pages are unattributed, but look as if they come from railroad rather than OEM data.

Allen Hazen wrote:I don't know what to believe. My suspicion, however, is that the U50C as it was finally built was a lot heavier than it had initially been planned.


Another source is:

“Roaring U50’s....”
Rev. Harold Keekley
George R. Cockle and Associates, 1978
ISBN 0-916160-06-8

On page 40, the data given for the U50C shows the weight as “417,000 + lbs.”

The inclusion of the “+” sign, is I think, ominous.

But then the inside front cover of the book includes photographs of the builder’s plates for one each of the U50 and U50C.

That for the U50C refers to S/N #37273, and shows the weight as “435/435”. I think that this was the first of the second batch.

One might reasonably deduce that:

The original design target weight was 417 000 lb.

The first production batch was seriously overweight at close to 443 000 lb.

There might have been some paring back to get the second batch down to 435 000 lb. But then 435 000 lb is just within the 2% tolerance band, so it might also have been just the way that one example turned out. (Or maybe GE had followed the alleged precedent of Lima in weighing its Allegheny steam locomotives, namely leaving off certain parts and/or supplied before weighing and then subtracting them from the weighscale number because they weren’t there....)


Allen Hazen wrote: (Does anyone have a guess as to just how much weight was saved by the -- disastrous, in the event -- decision to use aluminum rather than copper cabling?)


I have no idea. A good starting point might be to estimate the weight of copper wiring is (excluding that in the machines themselves) found in a large C-C locomotive, and work from there. One would need to have some idea as to what (presumably larger) cable cross-section would be required for aluminum relative to copper.

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Re: FB-3 variant queries

Postby Allen Hazen » Fri Oct 09, 2015 7:15 pm

V8 interceptor--
The Erie, later E-L, main line doesn't go through Erie PA, but isn't far away. E-L was a good GE customer (for U25B, U33C, etc), and had dealt with GE's test department before: the ABBA test set 750 had been run on the Erie (and in Erie colours) for several years n the mid and late 1950s. I have always assumed that 5000 was tested on the E-L(*) just because it was a convenient place for testing, not because GE was particularly targeting E-L as a potential customer. But that was just an assumption.

(*)The caption of the photo in "Second DSG," if I remember correctly, says that it was in primer, having been rushed out of the GE plant ahead of a strike. Since the photo is b&w, it's hard to tell the difference between light gray primer and UP yellow!

----

Pneudyne--
Thanks for the references! … It does sound as if 417,000 pounds was an, um, aspirational figure!
(I've always wondered about the ethics of Lima's deliberate under-weighing of the 2-6-6-6. Whatever C&O's permanent way department would have thought about it, there is also the issue that locomotive engineers' (train drivers', in non-US terminology) pay was based in part on weight on drivers of the locomotives they operated -- it seems to me that for C&O to accept an understatement of the locomotives' weight amounted to a conspiracy to defraud its unionized workers out of their contractually guaranteed pay!)
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Re: FB-3 variant queries

Postby Pneudyne » Tue Oct 13, 2015 8:35 pm

And one might say that sometimes the designers were setting their weight aspirations too low....

Whilst “aspirational” does seem to be the best fit for the 417 000 lb number, another possibility is that 417 000 lb was the base weight for the “bare bones” version with FB-3 trucks (assumed to be lighter than the GTEL trucks) and without dynamic brakes or any other extras. Keekley’s “417,000+ lb” number might have been intended to convey that idea.

To test that notion further, I looked firstly at the FM Train Master case, using the weights given by Sweetland (1). I chose the TM because it appears to have been the first American domestic market C-C unit that was designed to be approximately equivalent to 1½ regular B-B freight units in the 1500 to 1600 hp range, both in terms of power and adhesive weight, rather than simply a similarly powered six-motor version of a regular four-motor unit. The U50C could be thought of as having been a later development along the same vector started by the TM.

The “bare bones” TM weighed in at 343 000 lb, that number increasing to 366 000 lb for the fully-equipped version. Ballast could take that to 375 000 lb, and overballasting, as done for the VGN examples, to 396 600 lb. Against that, a spread for the U50C ranging from 417 000 to 443 000 lb seems not to have been impossible, although unlike the TM, I don’t think that the U50C had a train heating boiler option to add significant weight, so that works against the idea somewhat.

For a moment accepting that the 417 000 lb “bare bones” weight was realizable, would UP have wanted or needed a heavier version? Well, the GTEL8500 put 8500 hp on 850 000 lb, or 4250 hp on 425 000lb for each half. So with 5000 hp, the UP may have been reluctant to drop below the 425 000 lb number, and may even have been looking for an increase to better cope with the increased power. No doubt the U50C had a more sophisticated wheelslip control system, but then it had an 8-notch throttle as compared with the 20 notches for the GTEL, and so the starting tractive effort increments were larger. (I don’t know if the U50C had the humping control, which GE also offered as a smoother way to control starting and low speed tractive effort.)

If one views the U50C as being three-quarters of a DDA40X, which weighed 545 000 lb (according to Cockle), then the U50C target weight would have been just 409 000lb. But the DDA40X trucks were probably of the high-adhesion type, whereas those GTEL trucks on the U50C definitely were not. Conservatively one might impute an effective 10% adhesion weight advantage for high-adhesion trucks, which would in turn suggest 449 000 lb for the U50C.

So playing with the numbers doesn’t exactly move the alternative theory into the implausible class. But the “weight” of history still points to underestimation during the design process as the primary suspect.

I also looked at the Alco DH643 case. This was primarily an experiment with hydraulic transmission, and was intended to be proximate to the Krauss-Maffei ML4000. But if one neglects the transmission aspect, the DH643 may be seen as an intermediate step along the same C-C unit vector that connects the TM to the U50C. Strapac (2) gives the original weight estimate for the DH643 as 373 000 lb. There is no commentary about weight gain between inception and realization, but evidently that did happen. In his tabulation of the SP diesel-hydraulic fleet, Strapac quotes the “invoice weight” for each of the Alco DH643s as 400 900 lb. Steinbrenner, in his Alco history, “mentioned 200 (short) tons, which is in reasonable agreement. Railway Gazette (1964 October 16) gave 174 long tons, roundly 390 000 lb. And Keller gave 180 tonnes, roundly 396 000 lb. So as with the U50C, we’re seeing a range of weights quoted, and with a spread of about the same magnitude. But in the DH643 case, it is known that the “low” number was an estimate, not an actual, and putting the DH643 weights alongside the U50Cweights, does suggest that the U50C ”low” number could well have been an estimate.

Returning to, or rather getting closer to the FB-3 truck itself, and I think germane to the topic, is GE’s pathway to the FB-3 truck. A quick initial look comes up with the following.

The starting point for GE domestic-market C-trucks – at least in the post-WWII era - seems to have been the New Haven EP-5 rectifier electric locomotive. This had an inside-equalized, single-swing bolster trimount type truck, evidently designed for good riding and tracking at high speeds. As well as the two (per side) customary between-the-axles primary coil springsets, it also had outer, stirrup-mounted springsets. I am not sure when such were first used, but they seem to be strongly associated with the Fairbanks-Morse Train Master, which had rigid-bolster trimount trucks. Another feature of the EP-5 trucks was that the spring pair between the centre and outer axles were separated to allow room for the bolster elliptic springs between the coil springs.

Next was the Virginian E33 electric locomotive. One imagines that in deference to its lower speed freight haulage role, it had simpler outside-equalized rigid bolster trimount trucks, with the usual two primary springsets per side. VGN itself may have seen swing-bolster trucks as an unneeded luxury for its operations. For example, its preceding EL-2B motor-generator electric locomotives had rigid-bolster B-trucks, whereas for example GE’s more-or-less contemporary GTEL prototype had swing-bolster B-trucks, also with span-bolsters.

Then the UP GTEL8500 was different again. It had inside-equalized trucks, with four primary springsets per side, and rubber-sprung floating double bolsters. By this time GE had adopted floating bolster trucks, in both B and C forms, and outside-equalized, for its standard export road locomotives. So one assumes that it wanted to try the rubber-sprung floating bolster in domestic service, as well. And although the GTEL8500 was a freight locomotive, with a 65 mile/h top speed, either GE or the UP, or both, had decided that it lateral motion rather than rigid-bolster trucks were preferable, perhaps in consideration of the fact that it would do quite a bit of relatively fast running. The preceding GTEL4500s had had swing-bolster B-trucks, and UP’s history had included paying more attention than average to steam locomotive springing and lateral control systems.

It might be noted that for its export road locomotive designs with C trucks, GE had started with the rigid-bolster then had moved through swing motion to the floating bolster design, in all cases with the pivot more-or-less central.

The Pennsylvania E44 followed the Virginian E33 in using rigid-bolster trimount trucks. On the one hand that looked logical, given that it was a freight locomotive. But on the other hand, Pennsy’s freight experimentals, the E2b, E3b and E3c had all used swing-bolster trucks. In particular, the E3c had single-bolster trimount trucks similar in principle, although not in detail, to the EP-5 trucks. And the Pennsy had had a history of paying careful attention to the tracking and riding qualities of its electric locomotives. In the case of the E44, it might have been that the champions of mechanical simplicity won out over those who were more concerned about riding and tracking performance.

The choice of the rigid-bolster trimount type for the U25C would seem to have been made on the same basis, that it was essentially a heavy freight locomotive, and that simplicity was paramount.

The standard export models were equipped with floating bolster, outside-equalized C-trucks through the 1960s, but the non-equalized form had made its appearance on special export variants from circa 1963. So all of the elements were in place for a domestic C-truck with floating bolster and non-equalized, and with its pivot essentially central. One has the impression that GE was never a highly enthusiastic user of the trimount form.

Cheers,




(1) “Train Master”; Diesel Era with David R. Sweetland; Withers, 1997; ISBN 1-881411-13-3.
(2) “Southern Pacific Historic Diesels Volume 2 Diesel-Hydraulic Locomotives”; Joseph A. Strapac; Shade Tree Books, 1993; ISBN 0-930742-15-X.
(3) “High Power Diesel-Hydraulics”; Rolf Keller (of Voith); Institution of Locomotive Engineers Paper No. 687. 1967 March.
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