F-Units + 6 Axle Line-ups

[DavidH66]

I've noticed pictures in the 70s of freight F-units hooked up with GP's. I was wondering did any railroad use F Units connected tot here 6 axle units?

Is there any photographic evidence?

[erikem]

The D&RGW used SD's hooked up with F's, with the lash-up referred to as a Perlman Mallet.  The F's were usually the controlling locomotives as traction motor heating was more pronounced with 4 axle units than 6 axle units.

[Overmod]

KCS had some F cabs converted to "B" units by plating over the windows.  I remember seeing these in consist with six-motor units either in the mid-'80s or early '90s.  They were painted white (the 'ghost' scheme, I believe) which made them VERY visible in a consist.  Crews would wave and point back...

The inherent issue is not four- vs six-motor units as much as it's that the gear ratios match.  And that the degree of motor cooling be respected.

[BaltACD]

The F's and six axle SD's had different life cycles.  Once carriers began buying significant numbers of SD locomotives, they were scrapping the F's in even higher numbers.  Nearly all freight locomotives are geared for a top speed of 70 MPH.  In the very early days of the F's some carriers took delivery of some that were geared for 50 MPH (which lowered the minimum continuous speed rating) and used these in helper service, as time went on and more was learned about the overall performance of diesel electric locomotive they had their gearing changed to the 70 MPH gearing to be compatible with the rest of the locomotive fleet. 

There were the FP versions that were fitted with steam generators and 98 MPH (which raised the minimum continuous speed rating) passenger speed gearing, some FT's that were delivered to the ATSF were also configured for passenger operations.

The minimum continuous speed is the speed at which the locomotive can run 'all day' at maximum throttle position and electrical load without overheating the electrical components (traction motors & generators). 

[erikem]

Assuming that the gear ratios and rime mover power are the same, a 6 axle unit will require less motor current for a given throttle setting and locomotive speed than a 4 axle unit. If the controlling F-unit i run in a manner to prevent traction motor damage, then the SD's will automatically be protected.

For what it's worth, the Perlman Mallet's date back to the early days of MU'ing dis-similar units. A more modern version would be a mix of DC and AC units.

[timz]

No reason mixed consists would have been rare, though it was less common on some RRs (e.g. Santa Fe) . If the RR has a bunch of F-units and starts getting SD9s or SD24s or SD40s there's no objection to mixing them as long as the speed at full throttle doesn't drop below 11 mph. SD40s and F7s probably ran together frequently on Donner Pass circa 1967, and no doubt pics have appeared in print.

http://www.snowcrest.net/photobob/nsd27.html

For what it's worth, SDP45s often ran with FP7/F7Bs on SP before and after Amtrak took over.

[Redore]

Back in the 50's and 60's this was a convenient way for GN to move SD7's and 9's in and out of ore country to the shops in Superior.  They would be MU'd with a set of F's on a road ore train and run up to the Range to be traded with another unit due for service.

In later years, GP38's and SD40's had about the same horsepower per axle and were interchangeable based on horsepower.

[rcdrye]

timz

For what it's worth, SDP45s often ran with FP7/F7Bs on SP before and after Amtrak took over.

With an FP7 leading, the FP7 loaded first, but the SDP45s provided the kick.  An 11 car Coast Daylight with an FP7/SDP45/SDP45 lashup would be up to about 30 MPH in its own length.  Both classes were geared 60:17 for about 77 MPH top speed.

[WSOR 3801]

SOO F-units didn't have MU connections on the nose, so they were always leading or trailing.  Many times they ran 2 F-units with a U30C in the middle, or SD40s.  The SOO F-units also lasted pretty late, so there should be pictures of this. 

[beaulieu]

There are many pictures of one Soo Line F7 coupled to a Soo Line SD40. Combos with a single SD40-2 weren't uncommon either.

[dumpsterman]

i remember reading an article, i wish i could remember which magazine, that was about a train on the EL in bad weather that had 2 sd 45's bracketing an f unit pulling a grade and stalled. the f unit would keep slipping. so the crew tried isolating the f unit and go alone with just the 2 sd 45's. with brute force the 2 45's got the train going and made the grade!

[blue streak 1]

Slightly off the topic ---  SOU RR would often run passenger trains with one E unit and a FP-7 or PA-4

[samfp1943]

Was just looking around, and wondered about some of the "F" units, and a few different combinations they had been photographed with over time; in the real railroad world.  Not many 'SD's , but seemed to find company with many different 'Geeps'. 

http://www.railpictures.net/viewphoto.php?id=386359&nseq=24

http://www.railpictures.net/viewphoto.php?id=353970&nseq=52  CNR

http://www.railpictures.net/viewphoto.php?id=269393&nseq=78  B&O

http://www.railpictures.net/viewphoto.php?id=349424&nseq=86   SP

http://www.railpictures.net/viewphoto.php?id=409500&nseq=100  Wabash/ NS Heritage SD

http://www.railpictures.net/viewphoto.php?id=431479&nseq=104  WM  (F-7w/ RS-3  )

http://www.railpictures.net/viewphoto.php?id=364011&nseq=126  WM  ( F, SD, & RS-3)

http://www.railpictures.net/viewphoto.php?id=308246&nseq=130  Soo

http://www.railpictures.net/viewphoto.php?id=424567&nseq=156  NP

http://www.railpictures.net/viewphoto.php?id=2021&nseq=1182  CRR/L&N

http://www.railpictures.net/viewphoto.php?id=143220&nseq=1223   BAR/N&W

http://www.railpictures.net/viewphoto.php?id=28565&nseq=1465  GNR [ F-7A W/Homemade plow]

http://www.railpictures.net/viewphoto.php?id=47427&nseq=1480  PC [ w/GE and EMD Freight Units]

http://www.railpictures.net/viewphoto.php?id=47427&nseq=1480  CRR [Mine Run]

[ Disclaimer: None are my photo's , just  posted  on Rail Pictures.net ]

[rcdrye]

samfp1943

http://www.railpictures.net/viewphoto.php?id=349424&nseq=86   SP

http://www.railpictures.net/viewphoto.php?id=308246&nseq=130  Soo

A couple of observations on the SP and Soo photos:

In the SP photo the F9M 6255 is carrying X9103 in its number boards - since the trailing unit is Krauss-Maffei 9104 it's a good guess that K-M 9103 suffered a road failure and 6255 is its replacement.  The K-M is six axle, but diesel-hydraulic.  The K-Ms didn't usually mix with other power.

The Soo photo shows winter practice, with the F7 leading (and nose louvers taped over).  In the summer, the F7 would more often be found trailing, with visibility trumping drift-bucking capability.

[CPM500]

EMD 6 axle units (40 and 45 series) have Performance Control circuitry, which limits hp at low speeds.

[CSSHEGEWISCH]

The issue of TRAINS which honored EMD's 50th Anniversary included a photo which showed a brand-new SD45-T2 in multiple with one of the last F's on SP's roster.

[timz]

rcdrye

samfp1943

http://www.railpictures.net/viewphoto.php?id=349424&nseq=86   SP

it's a good guess that K-M 9103 suffered a road failure and 6255 is its replacement.

The train originally had 9103 and 9104, and 9103 had to be set out somewhere, and they picked up the 6255 somehow, or maybe had it already between the two KMs, and their orders were addressed to X9103 so they had to continue with that even though engine 9103 was now sitting on a spur miles to the east?

[rcdrye]

timz

The train originally had 9103 and 9104, and 9103 had to be set out somewhere, and they picked up the 6255 somehow, or maybe had it already between the two KMs, and their orders were addressed to X9103 so they had to continue with that even though engine 9103 was now sitting on a spur miles to the east?

That sums it up.  It's unlikely that 6255 was between the K-Ms, though I believe they could MU.  Both versions of the K-Ms and the Alco DH643s were kept pretty much to themselves for as long as they were kept around at all.