scottychaos wrote: Widecabs were never a problem with 4-axle engines, and there is nothing to suggest that was ever true.Scot
Widecabs were never a problem with 4-axle engines, and there is nothing to suggest that was ever true.
Scot
The GP60Ms rode very poorly, much worse that a standard GP60. Since the GP60 is the same locomotive as the 60Ms except the cab, suggests there is a problem.
An "expensive model collector"
Someone reported that BNSF has been running (or is in the process of running) 10K ton stack trains. That is pretty amazing and certainly would warrant the use of 6-axle power especially on the western grades. However, I personally do not see the 10,000 ton stacker becoming the norm. Remember, ATSF had no problems with the B40-8 on its intermodal trains. Certainly these locomotives had weight restrictions as do all loco's but those stacktrains that were ran back in the early 90's weren't baby trains by any means. I have train videos from "Big-E productions" which showcase the old pre-BNSF transcon and the old SP Sunset route (He can thank me for the free advertising later). Many of those trains ran B40-8's, B40-8W, GP60's, and yes even the dreaded GP60 wides. By the way, I did happen to catch some GP60's on an intermodal down in Austell, GA back in April. NS also runs them at times on trains between Harrisburg and Croxton, NJ.....I think.
MLG4'8.5"
Here is an interesting article about the first 4-axle widecabs:
http://www.qstation.org/GP60M_135/
the article *does* say:
"Early in its research, the cab committee had discussed the production of a GP60 with a cowl body. However, EMD had concluded that the utilization of a cowl body, coupled with a safety cab, would be pushing the weight envelope for four-axle locomotive, and theoretically would have exceeded 305,000 lbs, which would have made the design one of the heaviest four-axle locomotives ever built. So with weight now being a primary concern, the Santa Fe ruled out the possibility of this design."
Weight was a concern..but with a cowl body on a 4-axle engine..this is a "cowl body" loco:
http://www.northeast.railfan.net/images/atsf5266.jpg
But this design was never built in a 4-axle version.
the article suggests the GP60M was very sucessful! no mention of the cab being to heavy.
http://www.northeast.railfan.net/images/tr_sf115.jpg
The only reason 4-axle wide cabs died out is because 4-axle units died out...the timing of the die out just happened to be at the era when wide cabs were coming into prominance..but 4-axle units didnt die out because of the widecab..they died out because they were 4-axle units, period.
scottychaos wrote:the debate of "why only 6-axles these days and no more 4-axles" has nothing to do with the weight of a wide-cab..there were 4-axle widecabs built, both EMD and GE..a 4-axle loco can handle a wide-cab just fine:
the debate of "why only 6-axles these days and no more 4-axles" has nothing to do with the weight of a wide-cab..there were 4-axle widecabs built, both EMD and GE..a 4-axle loco can handle a wide-cab just fine:
Newyorkcentralfan wrote: Just because wide cab BBs were constructed doesn't mean that they were successful. That they aren't still being made and are being cast off by the class ones while wide cab CCs of them same vintage and similar horsepower are being kept supports the conclusion that wide nose BB they are a problem for them.
Just because wide cab BBs were constructed doesn't mean that they were successful. That they aren't still being made and are being cast off by the class ones while wide cab CCs of them same vintage and similar horsepower are being kept supports the conclusion that wide nose BB they are a problem for them.
No, it does not support that conclusion. The fact that BB's arent being made anymore, or are being "cast off" has to do only with the fact that they are BB's, and railroads dont want new BB's anymore..it has absolutely nothing whatsoever to do with the cab.
If railroads really did want EMD or GE to produce new BB's, but the Widecab was a problem, as you suggest, then why not just build BB's without widecabs?! ;)
but that never happened...
Newyorkcentralfan wrote: Just because wide cab BBs were constructed doesn't mean that they were successful. That they aren't still being made and are being cast off by the class ones while wide cab CCs of them same vintage and similar horsepower are being kept supports the conclusion that wide nose BB they are a problem for them. scottychaos wrote:the debate of "why only 6-axles these days and no more 4-axles" has nothing to do with the weight of a wide-cab..there were 4-axle widecabs built, both EMD and GE..a 4-axle loco can handle a wide-cab just fine:
The only class on e casting off their 4-axle widecabs is the CN and that is because the GP40-2WLs are aged and most have spent a lot of time in storage over the last ten years.
One thing you have to understand is that stack trains aren't "light" anymore. The BNSF experimenting with 10k ft stackers is the proof. CR once had a dedicated 4-axle fleet for its TV (TOFC) and stack trains comprising GP40-2s, B36-7s, and B40-8s. But in the early to mid 90's they switched to 6-axle power due to the increasing weight and length of the trains.
You guys are forgeting that there is still one RR using almost exclusively 4-axle power for intermodal trains in a certain area of their system, Norfolk Southern. Their GP59/60s and B23-8s are still the standard intermodal power on the line from Birmingham through Atlanta to the Carolinas. I had one guy on this forum say he sees them so often he would rather see the dash-9s that everyone else has grown tired of. When I was in Greenville, SC on the main only one of 4 intermodal trains had 6-axle power on it.
JonathanS wrote: timz wrote: arbfbe wrote:An SD40-2 and a GP40-2 with all paramaters the same except the number of tracton motors will run, for all practical purposes, at the same top speed.Yes, they'll be close-- but if you choose the tonnage so their top speed is 70 mph on the level, the SD might creep ahead of the GP, which has reached its voltage limit. (That's assuming 62:15 gearing.) JonathanS is right about back EMF being a factor-- he's just backwards about which engine has an advantage.If I have it backwards why did the New York Central, The Atlantic Coast Line, Illinois Central, et. al. purchase GP40s, U30Bs, and C430s for the high speed freight instead of SD40s?
timz wrote: arbfbe wrote:An SD40-2 and a GP40-2 with all paramaters the same except the number of tracton motors will run, for all practical purposes, at the same top speed.Yes, they'll be close-- but if you choose the tonnage so their top speed is 70 mph on the level, the SD might creep ahead of the GP, which has reached its voltage limit. (That's assuming 62:15 gearing.) JonathanS is right about back EMF being a factor-- he's just backwards about which engine has an advantage.
arbfbe wrote:An SD40-2 and a GP40-2 with all paramaters the same except the number of tracton motors will run, for all practical purposes, at the same top speed.
If I have it backwards why did the New York Central, The Atlantic Coast Line, Illinois Central, et. al. purchase GP40s, U30Bs, and C430s for the high speed freight instead of SD40s?
Mostly because they had few grades of consequence and they didn't need the extra low speed tractive effort on a regular basis. ACL did start going over to six-motor power in the mid-1960's with SD35's, U25C's and C628's.
JonathanS wrote:For a four axle locomotive and a six axle locomotive traveling at the same speed the six axle locomotive must overcome 50% more back EMF than its 4 axle cousin must at any speed.
arbfbe wrote:[ The number of axles has absolutely nothing to do with the speed of the locomotive. The horsepower of the prime mover, the gear ratio of the locomotive and perhaps the transitional steps applied will determine the maximum speed of the unit. An SD40-2 and a GP40-2 with all paramaters the same except the number of tracton motors will run, for all practical purposes, at the same top speed. Since the GP will weigh a bit less than the SD the top speed of the GP may be just a few MPH higher when operating as a single unit but this will be lost when a train is attached. IT would be the same with a GEVO C unit vs a GEVO B unit. If you just cut out two traction motors on the GEVO C and ran it against teh GEVO C with all TMs running the top speed would still be the same.That is for the theoretical. The reality is that all the engines have an overspeed function built into the speed recorder. If the TM spin too fast they start to come apart. The copper windings do not hold together at high speeds and will be thrown off the armature. The armatures are wrapped with steel windings to help hold the windings in at high speed. So the overspeed is set to stop the locomotive before the steel banding or copper coils come loose. A higher gear ratio means a higher overspeed setting while a lower gear ration has a lover overspeed setting. A top speed of 72 mph seems common these days for freight locomotives. Keep in mind the Traction Motors are rotating 5-7 times the rotational speed of the wheels and the wheels are solid steel not likely to spin apart.
The number of axles has absolutely nothing to do with the speed of the locomotive. The horsepower of the prime mover, the gear ratio of the locomotive and perhaps the transitional steps applied will determine the maximum speed of the unit. An SD40-2 and a GP40-2 with all paramaters the same except the number of tracton motors will run, for all practical purposes, at the same top speed. Since the GP will weigh a bit less than the SD the top speed of the GP may be just a few MPH higher when operating as a single unit but this will be lost when a train is attached. IT would be the same with a GEVO C unit vs a GEVO B unit. If you just cut out two traction motors on the GEVO C and ran it against teh GEVO C with all TMs running the top speed would still be the same.
That is for the theoretical. The reality is that all the engines have an overspeed function built into the speed recorder. If the TM spin too fast they start to come apart. The copper windings do not hold together at high speeds and will be thrown off the armature. The armatures are wrapped with steel windings to help hold the windings in at high speed. So the overspeed is set to stop the locomotive before the steel banding or copper coils come loose. A higher gear ratio means a higher overspeed setting while a lower gear ration has a lover overspeed setting. A top speed of 72 mph seems common these days for freight locomotives. Keep in mind the Traction Motors are rotating 5-7 times the rotational speed of the wheels and the wheels are solid steel not likely to spin apart.
No!!! Whenever a DC motor is rotating it is also acting as a generator in the reverse direction as the applied voltage. The amount of power it develops in reverse is a simple function of speed. For a four axle locomotive and a six axle locomotive traveling at the same speed the six axle locomotive must overcome 50% more back EMF than its 4 axle cousin must at any speed. That leaves more horsepower available to move the train on a 4 axle locomotive. So, talking DC machines only with the same horsepower and the same gear ratio and for a train where neither locomotive is Tractive Effort limited a 4 axle locomotive will always be able haul the same train at a higher speed than can its 6 axle counterpart. That is simple physics. Every motor is also a generator AT THE SAME TIME.
JonathanS wrote: With the AC drives you do not need to have 4 axle locomotives to get the higher speeds. 4 powered axle DC locomotives were able to achieve higher speeds with the same horsepower than 6 powered axle locomotives because of the back EMF inherent with DC motors. With the variable frequency drives on the ACs if you want more speed just crank up the frequency. Doesn't matter that there are six motors, the speed is determined by the freq drive.So if I have a six motored locomotive that can apply all 4400 or 4300 Horsepower equally at 10 mph and at 70 mph and has the tractive effort to pull a long (or short) train why would I even consider a 4 axle locomotive that is less capable.
With the AC drives you do not need to have 4 axle locomotives to get the higher speeds. 4 powered axle DC locomotives were able to achieve higher speeds with the same horsepower than 6 powered axle locomotives because of the back EMF inherent with DC motors. With the variable frequency drives on the ACs if you want more speed just crank up the frequency. Doesn't matter that there are six motors, the speed is determined by the freq drive.
So if I have a six motored locomotive that can apply all 4400 or 4300 Horsepower equally at 10 mph and at 70 mph and has the tractive effort to pull a long (or short) train why would I even consider a 4 axle locomotive that is less capable.
timz wrote: gabe wrote: the second and fifth tractive motor could be turned off at speeds over 35-to-45 mph, which would effectively turn an SD-70 into and E-70. There is probably a good--if not an obvious--reason this is not done. Because there's no advantage-- the unit won't pull any harder with four motors. If it did, should we guess it would pull even harder with two motors? And it would be a real hot rod with one?
gabe wrote: the second and fifth tractive motor could be turned off at speeds over 35-to-45 mph, which would effectively turn an SD-70 into and E-70. There is probably a good--if not an obvious--reason this is not done.
There is probably a good--if not an obvious--reason this is not done.
No it won't be a hot rod with two traction motors working on SD70. That would be over 2000 HP per traction motor! That would surely burn out in short order any of the available DC traction motors such as the D87.
To answer Gabe's question the reason is probably it would involve some overly complicated switch gear. More stuff to maintain and greater possiblity for it to brake down in operation. Besides the HP per axle of the modern 4400 HP six axle locomotive is about the same as a GP40-2 and with a much better electrical transmission even a modern DC Traction six axle will put more of that HP/tractive effort to the rails than the GP40-2 which the gold standard of fast freight motive power of the last generation.
There is a traction motor cut out feature on all modern diesel locomotives but it generally used when a traction motor grts burn out during operation but then the locomotive is HP limited with the prime mover not putting out its full HP in order to protect the remaining traction motors.
scottychaos wrote: chad thomas wrote: - Wide cabs are too heavy for 2 axle trucks, and most new road locos are wide cabs. the debate of "why only 6-axles these days and no more 4-axles" has nothing to do with the weight of a wide-cab..there were 4-axle widecabs built, both EMD and GE..a 4-axle loco can handle a wide-cab just fine:http://www.railpictures.net/viewphoto.php?id=182078&nseq=11http://www.rr-fallenflags.org/ge/ge809abp.jpg http://www.northeast.railfan.net/images/bnsf500.jpg Scot
chad thomas wrote: - Wide cabs are too heavy for 2 axle trucks, and most new road locos are wide cabs.
- Wide cabs are too heavy for 2 axle trucks, and most new road locos are wide cabs.
http://www.railpictures.net/viewphoto.php?id=182078&nseq=11
http://www.rr-fallenflags.org/ge/ge809abp.jpg
http://www.northeast.railfan.net/images/bnsf500.jpg
Agreed, but the GP60M is still not well liked by some engineers..
I am not offering my personal opinion about ATSF/BNSF's wide cab 4 axle fleet (GP60M,B40-8W). I thought they were cool looking units....However, I have read the opinions of engineers who operate them(Motorbooks "Modern Diesel Locomotives" is one source)and some do complain about the issue I mentioned, the GP60M in particular is singled out for offering a rough ride...
"I Often Dream of Trains"-From the Album of the Same Name by Robyn Hitchcock
JonathanS wrote: 4 powered axle DC locomotives were able to achieve higher speeds with the same horsepower than 6 powered axle locomotives because of the back EMF inherent with DC motors.
gabe wrote: Something that I have always wondered:Some high-end car manufacturers build motors that are eight or twelve cylinders but can be shifted to a six or a four while in use depending upon the type of driving so as to save on fuel efficiency while retaining high performance.I was kind of expecting to see this with a locomotive manufacturer--the second and fifth tractive motor could be turned off at speeds over 35-to-45 mph, which would effectively turn an SD-70 into and E-70. There is probably a good--if not an obvious--reason this is not done. But I have always thought it would be a good idea, as you could get all of the benefits of a 4 and a 6 axle unit in one engine this way.Gabe
Something that I have always wondered:
Some high-end car manufacturers build motors that are eight or twelve cylinders but can be shifted to a six or a four while in use depending upon the type of driving so as to save on fuel efficiency while retaining high performance.
I was kind of expecting to see this with a locomotive manufacturer--the second and fifth tractive motor could be turned off at speeds over 35-to-45 mph, which would effectively turn an SD-70 into and E-70.
There is probably a good--if not an obvious--reason this is not done. But I have always thought it would be a good idea, as you could get all of the benefits of a 4 and a 6 axle unit in one engine this way.
Gabe
Gensets have been developed as a more practical application of the same principle considered in the first paragraph. Cutting out traction motors under a 710 engine with all cylinders firing isn't going to affect fuel consumption greatly.
CNW 6000 wrote:It was meant as a joke. Google Chuck Norris Jokes and you'll see what I mean.
googled chuck norris, scanned the first 6 pages of results..
still dont get it..
Dan
CNW 6000 wrote://off topic! Wasn't Chuck Norris originally a 4 axle locomotive?//back on topic...Sorry! I couldn't resist!
//off topic!
Wasn't Chuck Norris originally a 4 axle locomotive?
//back on topic...Sorry! I couldn't resist!
I dont get it...
chad thomas wrote:- Wide cabs are too heavy for 2 axle trucks, and most new road locos are wide cabs.
SD60M wrote: timz wrote: "most of these big 6's don't utilize all of their hp or traction effort even on the big grades with lighter intermodal trains."And the four-axles would? Because they'd have less total horsepower? You're saying trains today are overpowered?In a way yes. About 3 months ago i was going to school and was stopped by an intermodal train it had 3 UP SD70M's an and only 20 cars?!?? Thats a strange site to see i bet a single GP38 could handle that train with no problem!
timz wrote: "most of these big 6's don't utilize all of their hp or traction effort even on the big grades with lighter intermodal trains."And the four-axles would? Because they'd have less total horsepower? You're saying trains today are overpowered?
"most of these big 6's don't utilize all of their hp or traction effort even on the big grades with lighter intermodal trains."
And the four-axles would? Because they'd have less total horsepower? You're saying trains today are overpowered?
Until they get to the yard that needed the other two locomotives for another train or two, then you are stuck with one locomotive for 3 trains going 3 different places.
Colorado Railfan wrote: diningcar wrote: Not yet mentioned but significant: Diversity!!!The major long haul RR's want to be able to use their power whenever and wherever there is a need. If a solid grain filled hopper train arrives at LA the power may be used on a intermodal train, probably with fewer units than were on the grain train. Many other examples could be mentioned but it seems obvious that diversity is a major criteria when purchasing power. I'm not sure I understand this reasoning. My limited experience tells me that the more models and makes you add to your fleet, the more expensive it gets to maintain it. Diversity seems less economical.
diningcar wrote: Not yet mentioned but significant: Diversity!!!The major long haul RR's want to be able to use their power whenever and wherever there is a need. If a solid grain filled hopper train arrives at LA the power may be used on a intermodal train, probably with fewer units than were on the grain train. Many other examples could be mentioned but it seems obvious that diversity is a major criteria when purchasing power.
Not yet mentioned but significant: Diversity!!!
The major long haul RR's want to be able to use their power whenever and wherever there is a need. If a solid grain filled hopper train arrives at LA the power may be used on a intermodal train, probably with fewer units than were on the grain train. Many other examples could be mentioned but it seems obvious that diversity is a major criteria when purchasing power.
I'm not sure I understand this reasoning. My limited experience tells me that the more models and makes you add to your fleet, the more expensive it gets to maintain it. Diversity seems less economical.
I think he meant to say uniformity. It is easier and cheaper to maintain one or two similar models than to have to keep up with the quirks of a dozen different ones.
Our community is FREE to join. To participate you must either login or register for an account.