Watching “Cajon II” by Pentrax video has brought up a question for me. The video covers Santa Fe, Southern Pacific, and Union Pacific operations over Cajon pass in California. Santa Fe it seems used mostly 4 axle power with GP60M/GP60B lash ups, B40-8’s, B40-8W’s, and even some use of GP30’s and GP35’s running next to some 6 axle units, mostly C40-8’s with some SD45’s. The SP used all 6 axle power in the form SD40’s and 45’s in their different variations. UP had a mix of 4 and 6 axle power but mostly 6 axle power. How did the prototypes dictate what kind of power to use?
Once you figure out the HP/ton you need for keeping the schedule, you figure out what the speed on the ruling grade works out to. If it’s above 20-25 mph, you only need 4 axles. The extra 2 axles of a six axle are a wasted investment and dead weight to haul around. If it’s below 20-25 mph, but above 12 or 13 mph, then six axle DC units are what you need. If it’s below that, then you either need six axle AC power or helpers or both.
Of course if we’re talking about the big Class 1’s in 2009, six axles are the primary power for almost all road freights. It is interesting to note, however, that 4 motored locomotives may make a comeback in the form of the GE ES44C-4…
Way back when like first generation four wheel trucks were the power of choice and six wheel trucks were used for lightweight branchline usage to spread the weight. Now four wheel trucked engines are considered utilitarian for the most part and with HP increase and weight the tractive effort from six axles make them attractive for main line power. It is really going to depend on the era and service you want to consider to be definitive. For example mostf railroads opted for E units of passenger usage that had an idler set of wheels between two powered axles and smoothed the ride considerably. ATSF stuck with F units with four wheel trucks because E units turned out to be terrible at climbing grades and ATSF had to get past the rockies and out of the LA basin so they weren’t popular with that railroad. Again it depends on the railroad and usage to be definitive
Why were the old Amtrak EMD “SDP-45 (??? - maybe -40)” locomotives such a big failure? They were banned by the AT&SF for what reasons? Were they A-1-As or C-Cs? Too many derailments? They were ugly, but no uglier than the B-B -40s that replaced them. A design fault at EMD? Just curious.
No, I’m not saying that the GE “Genesis” series are beautiful! My kids, if I had any, could make a more aesthetically-appealing locomotive design! How much extra would a bit of a snoot, ala the PA or FM ‘A’ units cost? Even an EMD “bulldog’” nose would help. The crews would appreciate a hot tub in there! Now, with the slack in orders, GE should do something about that!
Way back when, the 180-ton six-axle locomotive was the standard unit, and the lightweight six-axle, six-motor or four-motor, locomotives for branch-line use were the option, exercised by relatively few customers in proportion to the standard unit. Somehow Trains got that backward.
RWM
Running totally from memory here, so I’ll gladly be corrected -
IIRC, the SDP40’s had tracking problems with their C-C trucks, leading to some derailments. I don’t recall the specific truck used, or whether other railroads used it with any level of success.
One would have to know the rationale under which a C-C locomotive (as opposed to a B-B) was purchased to be able to come to a conclusion about their suitability. It may well have been expedient to use an otherwise established model, slightly modified for passenger service.
Such locomotives were known as “cowls” because unlike the F’s that preceded them, the outer “skin” of the locomotive had no structural value, simply being SD’s with a fancy wrapper. The carbody of the F’s and E’s was an integral part of the structure of the locomotive.
On these SDP40Fs the water for the steam generators was carried above deck. When running at passenger train speed on marginal track, the water could slosh around. Surf’s up, and off they go. ATSF never had any problems with them, and bought a few in trade for some switching type engines.
They were based on the SD40-2, and if Amtrak failed they could be used as freight engines. There were similar engines made for MILW for commuter trains with Head-End-Power, but no steam gens. These F40Cs never had any problems with tracking, even on MILW track.
The other EMD 6-axle passenger power (SDP35, SDP40, SDP45, FP45) all had the water tanks down low, between the trucks.
A few months ago there was a discussion on the SDP40F and what was the reason why it was a failure I had a cousin design and run a program with the specs of the units and the only reason he came up with was Surge of the water tanks also.
As I recall the manual said 2150 gallons of water down below next to the fuel, plus 1350 gallons on deck.
Studied, tested multiple times, never proven. In fact, no reason was ever discovered. It could be that it was some not-quite-freak combination of factors (track, wheel profile, speed, track spiral, etc, etc.) that caused some bad behavior, but nobody ever found a smoking gun. The SDP40F was probably the most extensively tested locomotive of it’s day. I had to read through something like a dozen different instrumented test reports conducted by the frt RRs, Amtrak and the FRA. It’s not that the water tank couldn’t have been a contributing factor, it’s just that nobody really knows.
It’s interesting that Alco’s early RSD series (the ones that looked like six-axle RS-3’s) had similar issues of derailing except on the Santa Fe, whose track was apparently good enough that there wasn’t a problem.
BTW when the SDP derailment problems came up, Amtrak leased two DMIR SD-9s to use on passenger trains. Missabe 129-130 both came from the factory with steam generators to be used as back-up power for the Missabe’s RDC-3 and/or to use on company excursion trips with their vintage passenger cars.
When Amtrak was testing RoadRailers, they ran in test up and down the NEC at speeds up to 105 mph no sweat. When the same equipment went into test over one of the intended routes - the ATSF - it experienced all kinds of truck hunting just getting to 90 mph. (Turns out there were improperly preloaded constant contact side bearings) But it shows that minor differences in track geometry can mean a lot.
Depends on where your goin, and how fast you need to get there. There are a lot of tracks on the BNSF in which I am a locomotive Engineer for that do not allow six axle locomotives. That is why you will notice that a lot of locals, and yard power is simply four axles. Anything that has a lot of tonnage behind it is typically a six axle, but sometimes the retards workin in the pitt throw a bunch of four axles on the lead to make up for the lack of a six. When they do this they just make our job harders because we have to walk through all the motors and start cuttin out dynamic brake because its usually way of the 28 we are allowed. Anyways four axle locomitives are mainly used for locals, and yard work and occassionaly the result of lazy diesel shop foremans.
If I recall correctly, AT&SF (Santa Fe) had a large (maybe the largest) fleet of RSD-3s, the ugly black ones. I assume they were used on light-railed branches, not in 90-m.p.h. ATS territory. I don’t remember any stories of the RSD-3s derailing a lot on any roads. As far as the SDP-40s go, couldn’t they have easily installed baffles in the water tanks? The EMD side bearings seems to have been the most likely problem. I don’t miss the SDP-40s, especially in that early Amtrak “Rudolph” scheme.
With the downturn in business, a lot of older EMD 4-axle units have been ‘mothballed’. Our Sweetgrass and Great Falls Div. branches, out of Shelby, MT (on the High Line) now sport a lot of Dash 9-44CW, etc., where the GP-38 once reigned. These are not “132# gorilla” branches, but the loco count is down. We even have some (Yuck!) SD-70Ms, etc., coming up on coal trains, heading west, much to the chagrin of the MRL. The dedicated ‘switchers’ are history, being replaced by GP-38s. This is DP territory, with locos being dropped off or added to the unit trains. Wish we had a “Dedicated Hostler” who really knew how to set up DP units! Guess “Mechanical”, in Fort Worth does, too!!!
Just use 6 axle AC power on everything like CSX does. That way you never have to worry about outdated 4 or 6 axle DC locomotive issues. LOL.
That may be true on the mains, but there’s still some '38’s working on CSX.
On the railroad where I 'm employed we use 4 axle power on tracks which have worn rail and ties. Six axle power is much harder on rail and ties, especially on curves.
Sounds like what happened on D&RGW’s Monarch branch. It was standard-gauged in the mid-1950’s and the original plan was to use SD7’s because of the grades (up to 4%). However, the long wheelbase caused derailments on some of the curves so GP9’s became the standard power on the branch.