Passenger model FP7 was used by SLSF starting in 1950-1951

Discussion in 'FP7' started by mountaincreekar, Apr 24, 2019.

  1. Frisco had a passenger model FP7

    San Francisco Railway (Frisco) #'s 5040-5051 Qty: 12 1950-1951

    I have not found any record of Frisco buying FP7B; Very few railroads did.
    Info from;

    Since the FP7 already housed all of the components needed for passenger service.
    The FP7's sales numbers appear very low; only 324 were produced by the time
    production ended on the model in late 1953.
    However, the FP7 solved a specific and very important need for railroads
    operating passenger trains in mountainous terrain.
    Looking at the locomotive from this angle it was actually a resounding success.

    The FP7 began production in the early summer of 1949 as a means for railroads to have a streamlined diesel pull passenger trains over stiff grades, a task for which Es were not well suited given their A1A-A1A truck setup that provided relatively poor tractive effort.

    Realizing this problem and railroads' desire to use the four-axled freight model
    in passenger operations EMD cataloged the FP7.
    The locomotive was 54-feet in length
    (four feet longer than the standard 50-foot carbody of standard Fs) thus
    enabling the engine compartment to hold both the needed water and generator.
    Aside from these added components the FP7 was near identical to the F7.

    It featured GM's 16-cylinder model 567B prime mover that could produce 1,500 horsepower and carried the company's D27C traction motors which offered 40,000 pounds of
    continuous tractive effort (and a mighty 64,000 pounds starting,
    then the most of any F available in EMD's catalog).

    It did, however, use a slightly upgraded main generator, the model D12D and
    featured dynamic braking a staple of Fs (multiple-unit control as also included).

    FP7 technical data: EMD FP7.HTML

    This sound that it was pretty neat puller.

    Sirfoldalot likes this.
  2. SLSF Passenger models EP7A
    I have not found any record of Frisco buying FP7B; Very few railroads did within USA.

    Info from;

    F9B SLSF (Frisco) 5140-5152 (F9B) 13 1954-1957
    They may of have matched these B's with the
    FP7A #'s 5040-5051 Qty: 12 ? and/or which others? (F9B) May been more freight like.

  3. Karl

    Karl 2008 Engineer of the Year Supporter

    No such animal as a FP-7B
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  4. gna

    gna Member Supporter

    I don't believe Frisco's FP7s had dynamic brakes, either.
  5. Karl

    Karl 2008 Engineer of the Year Supporter

    The 5126-5134, F-7B’s were the only Frisco B-units to come from EMD with steam and signal connection for use in passenger service. Twenty-one additional B-units, F-3’s, F-7’s and F-9’s, received post-delivery steam and signal line conversions. Neither the Alco FA-units nor the FB-units were equipped with steam or signal lines. The F-7B diagram notes “… for use with FP-7 Locos in passenger service”. The 9, F-7B units arrived after the FP-7’s, and their dual service capability as noted on the diagram seems to be an afterthought. I am not certain what type of consists the Frisco envisioned when this note was added to the diagram. Did management see only an A-B set, or did it envision A-B-A sets as well as A-B-B-A sets? The notation also implies that the Frisco had not thought about splicing one of these B-units between two E’s. There is ample photographic evidence that shows a B, F-unit spliced between a pair of redbirds, and likewise, a B, F-unit spliced between a pair of FP-7's. fp7a_5040_5051_diagram.jpg

  6. john

    john Supporter

    5043 Undated, taken at Fort Smith. Charles Lawrence Collection courtesy Fort Smith Trolley Museum

    Attached Files:

  7. meteor910

    meteor910 2009 Engineer of the Year Staff Member Supporter

    The only two Frisco F-unit cab units that had dynamic brakes were SLSF 5005 and 5007, F3A's that were rebuilt at EMD into equivalent F9A's in Feb, 1954. This was done so they could better mate with the d/b equipped F9B's and be used as run-through units for ATSF service out to the west coast. There is a neat picture in Chard Walker's book Cajon showing SLSF 5007 and its three mates bringing Symbol freight CTX into Summit on Cajon, Feb 1962.
  8. gna

    gna Member Supporter

    Those sheets are very interesting. I noted the 62:15 gear ratio, which is normally what freight units got. Some other roads had their FP7s geared 56:21 for passenger service, and later regeared when switched to freight duty. The weights for both freight and passenger service seem to imply that "switch hitting" was the plan all along. I presume 65mph top speed was more than enough for secondary passenger service.
  9. pbender

    pbender Member Supporter

    Somewhere I read a statement that indicated when the Frisco F units were used with the E units, the Consist was limited to 65MPH because of the gearing,

    My assumption is this was true for the GP7s with boilers too.

  10. gna

    gna Member Supporter

    Karl probably has the sheets for GP7s. Maybe he could be induced to share in the GP7 section...

    EDIT: Same Gearing. See Below. Already done. Sorry
    Last edited: Apr 26, 2019
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  11. Karl

    Karl 2008 Engineer of the Year Supporter

  12. Karl

    Karl 2008 Engineer of the Year Supporter

    This is true. When a dual service unit, GP-7, FP-7, or covered-wagon B-unit, was used in the same consist with one of the Redbirds, then the 65 mph limit would apply. There are several points to be made here. First of all, an exact match of gear ratios wasn’t a necessity. It would be a concern only at the extremes of the speed range. The maximum speed limit was in place to prevent the motor from turning into a bird’s nest of wire. When operated at low speeds at maximum amperage, the traction motors of locomotives geared for high speeds could get very hot. When operated at speeds in the middle, gear ratios weren’t so important.

    Secondly the difference between 70 mph and 65 mph is only 4 seconds per mile. That is in 70 mph territory, one would only lose 4 seconds every mile at 65 mph. If one examines the speed vs time chart, some inferences with regard to our speed-constrained passenger train consist of an E-8/F-7B/E-8 (vs E-8/E-8) can be drawn. As noted, placing that freight unit in our consist will reduce our top speed, and we’ll lose at least 4 seconds a mile wherever the speed limit is above 65 mph. On the other hand, the third unit will improve the acceleration, so that the train will get back to its maximum speed more quickly after station stops and speed restrictions. The 3-unit passenger train will spend more time running at its maximum speed (even though slower than a 2-unit train). Consequently, I believe that the 3-unit train will have faster average “acceleration speed” on the low end of the spectrum. Depending on the number of station stops and the number and nature of the speed restrictions encountered, this improvement on the “low side” could offset the lost time at the high end of the speed axis. The chart show that we get a lot of bang for our buck at the low end of the speed range.

    Lastly, even though the Frisco was a 70 mph passenger railroad, the question becomes how often did trains operate at the 70 mph maximum? This map depicts the Frisco passenger speed limits at the time the Frisco was buying passenger units. At first glance it appears that much of the railroad was capable of supporting 70 mph speed limits. A closer examination is in order.


    The Willow Springs Subdivision had a 70 mph limit, but a look at the speed restrictions in the ETT tell a different story. In order to learn more about the territory, the maximum speed limit map needs to be refined further. Over what portion, of the Subdivision can a passenger train operate at the maximum? The list of speed restrictions on curves covers the entire subdivision. In other words, passenger trains may travel at 70 MPH only on the tangent segments. The determining factor therefore is, the length of tangent, and does that tangent provide enough distance to recover speed from the previous curve before having to brake for the next curve. Even though tangent track comprises approximately 74.3 miles or 54.3% of the total mileage on the Willow Springs Subdivision, the two longest tangents on the subdivision are 2.54 miles and 2.43 miles and are located near MP C221-C224. The average tangent is but .31 miles long. So, there wasn’t much space for acceleration and braking between curves. It would take some real skill to keep the train at the speed limit.

    The Willow Springs Subdivision also challenged passenger train operation with its rugged topography. Not only are the curves numerous; they are sharp. Nearly 73% of the subdivision is restricted to 55mph or less. In this setting, a locomotive, which is geared for 85 mph may not be the best performer. I suspect that the Lebanon and Rolla subdivisions were much the same.

    It’s also interesting to look at the passenger speed limit map and note all the places where the Frisco operated the Redbirds at speeds well below their 85 mph max.
  13. Karl

    Karl 2008 Engineer of the Year Supporter

    I have attached chart, which depicts the service time-spans of Frisco passenger units. It's focus is on those units, which possess a cab, but I have included the 5126-5134 covered wagons because they were delivered with steam lines and signal lines. The other B-units were converted post-delivery and conversion dates were unavailable. When steam died on the Frisco, it had 87 passenger-capable diesel units. During a time when its passenger volumes were declining, the Frisco expanded its passenger roster further with the conversion of its B-units.

    Attached Files:

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