Locomotives

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!

ndbprr:

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

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

BNSFwatcher:

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. 

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.

tree68:

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.

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. 

WSOR 3801:

On these SDP40Fs  the water for the steam generators was carried above deck.

WSOR 3801:

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.

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.

wjstix:

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.

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.