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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