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I was just wondering if any of yall have seen this to. Twice already I have seen an SD90MAC on a general fraight. A couple of days ago on an auto rack with an SD70M and today on a rock with a Dash 9 and 8. I thought they were strickly for coal only, and they were never uesd for general fraight.
RE: UP SD90MAC on Other Trains, plainsman, Apr-02-03, 04:52 PM, (1) RE: UP SD90MAC on Other Trains, ssw_96, Apr-02-03, 06:05 PM, (2) RE: UP SD90MAC on Other Trains, Lone_Gunman_SG, Apr-02-03, 07:00 PM, (3) RE: UP SD90MAC on Other Trains, UP Wings, Apr-02-03, 09:50 PM, (4) RE: UP SD90MAC on Other Trains, JonN, Apr-02-03, 10:14 PM, (5) RE: UP SD90MAC on Other Trains, plainsman, Apr-03-03, 00:15 AM, (6)
Actually, the SD90Mac is two quite different locomotives. The 6,000 HP version was never intended to use on coal, as it's high horsepower output would be largely wasted on that application. These high horsepower locomotives were originally intended for intermodal work, along with thw 6,000 HP CW60AC. I saw quite a few of the CW60AC units on trailers but they seemed to have moved to the general merchandise mixed freights. I am seeing the SD90Macs in that role now as well. The 4,300 HP version, although originally seen as a temporary fix until the bugs could be worked out of the 6,000 HP prime movers, has actually seemed to be the more successful, and it is frequently seen on the coal trains. It can generate as much pull as the 6,000 HP version, it just is not as fast for any given consist. The CW60AC/44 was also in the same position, but I see fewer of those on the coal trains, more on heavy freight now. Bob
In the early part of 2002 when the "true" SD90MAC's with the funky cab design were taken from regular pool service on the ArkLaTex lines, they were replaced for a while by SD90/43MAC's. Now I see them on coal and grain trains the most, as well as general merchandise and occasionally a intermodal train. Also quite a few AC6000CW's have been running regular freights in Arkansas and Texas. Basically, any engine can be used for any time of service if it comes down to it. If any have read the book the Blue Streak by Fred Frailey, thats a good example. Scroll through the book and see the Blue Streak running with SW1500's and SD45's.
that seems kinda dumb, only using Dash 9 and 8's on coal trains? maybe there should just be longer general freight trains :pMy new e-mail is Arcanine241@yahoo.com premium add-ons
Dash 9 and 8's are not on coal trains. That falls to the AC units (AC600, AC4400, SD90MAC, etc). These are used mainly for sprinting across the plains, not for major trackive efforts. But still good for fast trains.
AC traction is the ideal form of motive power for low-speed drag trains like coal, because AC traction motors don't overheat at low speed + high power the way DC motors do. At high speed and lower power however, the efficency of AC motors falls below that of DC motors, so at high speed, an AC4400's performance actually dips below that of a Dash 9 at the same speed. This is why SD70Ms and Dash 9s are the preferred locomotives for high speed trains, rather than their AC counterparts. Jonathan N, Milepost 180, CP Belleville Sub.
The real advantage to the AC traction motors in unit coal service is the ability of these motors to work with advanced wheelslip controls to greatly increase the adhesion, and therefore the starting tractive effort. The additional tractive effort amounts to about 40,000 pounds more pull for a CW60AC/44 verses a CW44-9. These coal trains may not move as fast as the intermodal, but most are running at or above 40 mph, well above the range where overheating is an issue. The additional pull does however, greatly assist in getting a 14-15,000 ton train moving from stops. Since the AC units are much more expensive than the DC counterparts, the economic considerations would seem to focus their use in those roles in which they provide substantial useful advantage. Bob
