FB-3 variant queries

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Re: FB-3 variant queries

Postby Pneudyne » Fri Oct 16, 2015 7:42 pm

Allen Hazen wrote: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.?


That’s an interesting operator’s manual. The data tabulation shows a truck wheelbase of 13’7”, which I suspect would be associated with the FB3 design, as the GTEL8500 trucks were of 14’6” wheelbase. The way the manual is written, it creates the impression that dynamic brakes were standard, not optional equipment. Anyway, it looks as if the manual was written with mixed information, from both the core design and the actual production variant for UP. Perhaps not quite the best editing job by GE....

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Re: FB-3 variant queries

Postby Allen Hazen » Sat Oct 17, 2015 12:42 am

Pneudyne--
Thanks for the essay (two posts back) on the history of GE's C-truck designs! I think that's going to be one of the posts to this forum with permanent value.
As for the Pennsylvania E-44… This design was basically, was it not, just an uprated version of the E-33 built for the Virginian. So I think that the instinct of GE's engineering staff would have been to use the same truck design.
I believe that GE was initially unwilling to go for six-axle designs for 2500 hp diesels, feeling that the U25B's wheelslip control, if properly maintained, would allow competent locomotive drivers to use 2500 hp with four axles. (One of the very nice essays, based on original GE documentation, on the Davis brothers' "Railroad Locomotives" website, b.t.w., is about the history of GE's wheelslip control schemes for high-horsepower domestic U-series locomotives:
http://railroadlocomotives.blogspot.ca/ ... 5-u36.html )
They gave in to customer demand and offered the U25C after the first E-44 were built. So the choice of truck for the U25C was just to use an off-the-shelf design already in use on another model.

As for GE never being really an enthusiast for the trimount style of truck… Well, it was one thing they dropped at the first major redesign of the domestic U-series in 1966!
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Re: FB-3 variant queries

Postby Pneudyne » Sat Oct 17, 2015 4:59 pm

Allen Hazen wrote:I believe that GE was initially unwilling to go for six-axle designs for 2500 hp diesels, feeling that the U25B's wheelslip control, if properly maintained, would allow competent locomotive drivers to use 2500 hp with four axles. (One of the very nice essays, based on original GE documentation, on the Davis brothers' "Railroad Locomotives" website, b.t.w., is about the history of GE's wheelslip control schemes for high-horsepower domestic U-series locomotives:
http://railroadlocomotives.blogspot.ca/ ... 5-u36.html )


Yes, it would appear that GE thought that 625 hp/axle should have been manageable, in part perhaps because the GTEL8500 was at 708 hp/axle. The Davis brothers essay is excellent. The 16-notch throttle was also part of the package, intended to provide finer graduation of starting and low-speed tractive effort. That followed the precedent of the GTELs, which had 20-notch throttles in deference to their high power-per-axle as compared with diesel practice. Presumably the choice of 16 notches (and the manner in which they were obtained) was dictated by the need for not-too-complicated backward compatibility with existing diesel 8-notch throttles. Although that said, the GTELs were later fitted to control trailing 8-notch diesels, although the exact manner in which that was done seems not to have come to light, at least in the railfan domain.

Allen Hazen wrote:They gave in to customer demand and offered the U25C after the first E-44 were built. So the choice of truck for the U25C was just to use an off-the-shelf design already in use on another model.


Possibly there was an element of: “we don’t think that you need six axles, but if you must have them, then take these trucks....”

Allen Hazen wrote:As for GE never being really an enthusiast for the trimount style of truck… Well, it was one thing they dropped at the first major redesign of the domestic U-series in 1966!


By then GE had likely moved from denial through resistance and acceptance to commitment, and had decided to do a proper job of the domestic C-truck, fully aligned with its own precepts.

Re the GTEL8500, apparently as originally envisioned, and as shown in an early model, it had outside-equalized rather than inside-equalized trucks. A photograph of this model is shown in Cockle, page 60, and also in an article in Diesel Railway Traction, 1957 May, copy attached. The cutaway drawing shown by Lee (page 26) was also of this original with outside-equalized trucks. Outside equalization was consistent with GE’s established practice; possibly the change to inside equalization was done to save some weight when it was seen that there was some weight growth from the original estimate.

from DRT 195705 p.188.jpg


Allen Hazen wrote:As for the Pennsylvania E-44… This design was basically, was it not, just an uprated version of the E-33 built for the Virginian. So I think that the instinct of GE's engineering staff would have been to use the same truck design.


I wonder though whether the Pennsy might have wanted something better, but was dissuaded by GE because of the cost and/or timing for the required re-engineering.

Allen Hazen wrote:Pneudyne--
Thanks for the essay (two posts back) on the history of GE's C-truck designs! I think that's going to be one of the posts to this forum with permanent value.


Thanks, Allen. Please bear in mind though that it was a “back-of-the-envelope” exercise based upon readily available data and not any deep research.

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Re: FB-3 variant queries

Postby Allen Hazen » Sat Oct 17, 2015 9:59 pm

Re:
"I wonder though whether the Pennsy might have wanted something better, but was dissuaded by GE because of the cost and/or timing for the required re-engineering."

Given the financial status of the PRR by 1960, I doubt they would have asked for anything but the cheapest option!
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Re: FB-3 variant queries

Postby Engineer Spike » Tue Dec 26, 2017 5:39 pm

I am wondering if the developments of trucks on various GE electric locomotives, and the turbines has nothing to do with diesel development. We may be overthinking this whole thing. I think Alco has more to do with this than anything else.

GE had been in partnership with Alco until GE became concerned with Alco’s quality control, and their after sale service and parts. In the 1940s and 1950s, some railroads bought some of each brand of diesel. Some of this was the thought that any diesel was better than steam. Other lines were willing to pay to see who actually made the best mousetrap.

By the late 1950s, EMD and Alco has proven themselves to have the best products. Both had significant market share, and had driven out also rans Baldwin, Lima, and FM. GE couldn’t come in with something totally foreign. Except for the CB diesel, the same parts that were stocked for Alcos worked on GE. Truck/traction motor sets might be no exception. A railroad could have spare trucks that could be swapped around its 6 axle Alco and GE fleet, much like New Haven, for example could do so for its U25B/C425 fleet. It was more to the late 1960s that both GE and Alco had developed new truck designs. This very well may have been due to the deficiencies of the tri mount trucks, and the much higher outputs of 3600 hp locomotives.

Two suppliers may have just been an anti trust deal. It just as well could be so any supplier issues such as cost could be controlled. I’m surprised this FB design lasted until ratings exceeded 4000 hp. GM came out with a truck with all motors facing the same direction way back with-2. MLW did likewise shortly earlier.
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Re: FB-3 variant queries

Postby Allen Hazen » Wed Dec 27, 2017 1:51 am

Engineer Spike--
Somewhere, a long time ago, I read a claim that when the first MLW M-630 or M636 were traded in to GE, GE's engineers were impressed by the Dofasco trucks of the MLW units… with the suggestion that this had something to do with the adoption of a new truck design on the Dash-9 and AC4400 units. I don't know whether there is any truth to this: it would be surprising if so, since GE had used truck similar to MLW's on many export CC units before this.
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Re: FB-3 variant queries

Postby trainiac » Sat Feb 03, 2018 10:11 pm

Somewhere, a long time ago, I read a claim that when the first MLW M-630 or M636 were traded in to GE, GE's engineers were impressed by the Dofasco trucks of the MLW units… with the suggestion that this had something to do with the adoption of a new truck design on the Dash-9 and AC4400 units.


It would not surprise me that the MLW Hi-Ad was instrumental in the development of the GE Hi-Ad truck. After all, the AC4400CW prototype and all Dash 8-40CM's rode on MLW trucks. But here's the most telling detail: the rubber pad secondary suspension on the GE Hi-Ad is almost a carbon copy of the MLW design, right down to the shape, size and positions of the rubber pads - which are angled around a traction pin outboard of the middle axle (4" farther outboard on the GE design).

High-adhesion trucks from all builders tend to use a stiff secondary suspension (to reduce weight transfer), a soft primary suspension (to equalize axle loads) and motors all facing the same direction (to balance motor forces). The EMD HT-C and MLW Hi-Ad incorporated all three; both used tall primary springs (resulting in a tall truck frame). The HT-C had wear plates that kept the bolster horizontal while the MLW version went bolsterless (as did the later EMD HTCR and GE Hi-Ad).

By adopting the "roller blade" axle housing, GE was able to use tall primary springs on their Hi-Ad while making the truck frame lower than either the MLW Hi-Ad or EMD HT-C. EMD did the same by bringing the springs down to axle level on the HTCR.

I’m surprised this FB design lasted until ratings exceeded 4000 hp. GM came out with a truck with all motors facing the same direction way back with-2. MLW did likewise shortly earlier.


I am too, actually. The FB-3 was possibly a cut above the EMD Flexicoil in terms of adhesion in that it had rubber pads instead of springs for the secondary suspension. (It also might have benefited from GE's bigger traction motors). However, it's true that it didn't have the characteristics of later high-adhesion designs - the motors faced different directions, the primary springs weren't particularly tall, and movement of the bolster was not restricted.
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Re: FB-3 variant queries

Postby bogieman » Sun Feb 04, 2018 6:07 pm

trainiac wrote:
Somewhere, a long time ago, I read a claim that when the first MLW M-630 or M636 were traded in to GE, GE's engineers were impressed by the Dofasco trucks of the MLW units… with the suggestion that this had something to do with the adoption of a new truck design on the Dash-9 and AC4400 units.


It would not surprise me that the MLW Hi-Ad was instrumental in the development of the GE Hi-Ad truck. After all, the AC4400CW prototype and all Dash 8-40CM's rode on MLW trucks. But here's the most telling detail: the rubber pad secondary suspension on the GE Hi-Ad is almost a carbon copy of the MLW design, right down to the shape, size and positions of the rubber pads - which are angled around a traction pin outboard of the middle axle (4" farther outboard on the GE design).


At the time the Hi-Ad was developed Dofasco had a staff of truck design engineers who I believe actually did the truck design as they were the first supplier of those truck frame castings.

High-adhesion trucks from all builders tend to use a stiff secondary suspension (to reduce weight transfer), a soft primary suspension (to equalize axle loads) and motors all facing the same direction (to balance motor forces). The EMD HT-C and MLW Hi-Ad incorporated all three; both used tall primary springs (resulting in a tall truck frame). The HT-C had wear plates that kept the bolster horizontal while the MLW version went bolsterless (as did the later EMD HTCR and GE Hi-Ad).


The plates between the underframe and bolster on the HT-C truck are officially side bearing wear plates and are not intended to contact in operation. Per FRA rule, the clearance is to be between 1/4" and 1/2" stationary and are there to limit roll between the bolster and underframe. They do, however, come in contact at an adhesion level of about 25% as the traction force acting on the bolster from the truck frame exceeds the center bearing ability to prevent the bolster from tipping (the net moment acting on the bolster falls outside the center bearing diameter).

By adopting the "roller blade" axle housing, GE was able to use tall primary springs on their Hi-Ad while making the truck frame lower than either the MLW Hi-Ad or EMD HT-C. EMD did the same by bringing the springs down to axle level on the HTCR.


GE had severe problems with primary spring failures on the FB-3 truck and I was told that the "roller blade" bearing adapter was to provide for a longer spring which lowers the stress for the same static deflection. I also believe that the spring failures were a result of their source not doing as thorough an inspection of the springs during manufacture. When I designed the HTCR truck, I made the springs taller to eliminate the inner coils to allow for a single coil on each side of the bearing adapter. I didn't want the inner and outer coils to wear on each other as the axle ends displaced longitudinally during axle yaw. To insure the springs survived, they are made from "peeled" bar which adds some cost but removes the surfaces defects which are the main source of fatigue cracks in service.

The FB-3 was possibly a cut above the EMD Flexicoil in terms of adhesion in that it had rubber pads instead of springs for the secondary suspension. (It also might have benefited from GE's bigger traction motors). However, it's true that it didn't have the characteristics of later high-adhesion designs - the motors faced different directions, the primary springs weren't particularly tall, and movement of the bolster was not restricted.


The weight shift performance of the FB-3 is not significantly different than the Flexicoil. Using rubber secondary springs actually inhibits truck frame pitch which helps weight shift when the motors are not facing the same direction. The opposite is true with the motors all facing the same direction - a stiff secondary is required to limit pitch of the truck frame, if there is no pitch of the frame or bolster, there is no weight shift within the truck since all axles see equal spring and motor nose forces (a bit of an oversimplification). For reference, weight shift between axles in a locomotive is evaluated using the term "adhesion efficiency" which is the percent of nominal static load on the lightest axle at a locomotive adhesion level of 25%. For HT-C and HTCR trucks, the lightest axle is about 93% of static at 25% adhesion, for the Flexicoil, it is about 78% and similar for the FB-3. The GP (Blomberg to railfans) truck regardless of secondary suspension type (rubber or elliptic) is about 84%. These numbers are for the locomotive and include weight shift between trucks which is about 4% depending on truck center spacing.

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Re: FB-3 variant queries

Postby trainiac » Mon Feb 05, 2018 10:46 am

Thanks Dave! It's a delight to have clarifications from someone who actually knows things first-hand (as opposed to someone like me who doesn't).
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