LAST EDITED ON Aug-11-04 AT 02:08 PM (EST)
Hello again,
Glad the other data was helpful! Thanks Dave for handling the GE units. One suggestion, you might download the V4.5 physics files, even if you don't choose to use the physics. The information section will give much of the information about the locomotives in the files, and there are over 70 locomotives modeled. Here are some of the files:
phyv45.zip
dda40x45.zip
cl80v45.zip
emd-fv45.zip
Now as to the EMD SD series, the first generation SD7 units were six axle designs with much of the same electrical and mechanical components as the F7 and GP7. The main difference was that these weighed over 360,000 pounds as operated by most roads (Milwaukee Road had some light 298,000 pound versions for use on low quality local rail lines). This combined with the 24-25% good weather adhesion to allow them to start a much heavier train. In addition, since the 1,500 HP was distributed to six axles instead of four, the additional traction motors allowed these to operate at very slow speeds under full throttle. These became a favorite of ore haulers, which did not need HP for speed to clear their lines, but needed high tractive effort to start and pull their heavy trains. The SD9 upgraded the HP to 1,750, and added improved traction motors as in the GP9. SD7s began production in 1952, SD9s in 1954, and 1,800 HP tweaked SD18s began in 1960. Some SD18s used recyled components from RSD5 Alco tradeins. All these units (SD7,SD9, and SD18) were commonly refered to as Cadillacs.
The SD24 was the initial turbocharged six axle design from EMD, and it sort of changed the way these locomotives were used. Not really the drag specialist like the previous versions, it saw a lot of road service on merchandise freights, and often combined with other types to run priority consists with long trains. Union Pacific frequently used the SD24 in combination with GE U50B units on long fast merchandise freights. It was common to see GP40s and U25Bs with SD24s running on the BN as well. These usually operated at just under 375,000 pounds.
The SD35 was the next version, and the last to use the 567 prime mover. It began production in 1964. These were mainly used by Eastern railroads on coal service. At about 174 metric tons, these could start a pretty heavy train even with 25% adhesion. The SD35 used D67 traction motors and D32 generators. A nonturbocharged SD28 was also available, but only 6 units were made.
The SD45 was the next version to come out, beginning production in 1965. It used 20 cylinder in place of 16 cylinder prime movers, and had 3,600 HP. Going to the 645 series engine, these were intended to give fast roads way to step up the line speeds on through priority consists. Santa Fe in particular used a lot of these on their reefer trains, and it was common to see 4 SD45s blasting alongside Route 66 in Arizona and New Mexico, with lots of orange reefers in tow. The SD45 was not really as widely accepted as EMD had expected, partly because of problems with the long crankshaft, but more fundamentally, it used more fuel, and few roads could use the extra speed. At typical 385,000 pound weights, it was limited by its adhesion and traction motors. The SD40 came out about a year later. It would match an SD45 in most performance up to about 40-45 mph, and since both had the same traction motors and weight, it had the same starting tractive effort and continuous tractive effort as the more powerful SD45. It became a well liked unit for all kinds of service. The unturbocharged SD38 came out in 1967, and it was mostly used by mining roads to replace aging SD7s. It had 2,000 HP but at about 373 metric tons, it would start about as heavy a train as a SD45, it just would not move it as fast, or accelerate as quickly from stops. Since neither of these factors bothered the mining roads, they were prefered for their simplicity and reliability.
The SD40-2 added computer electronics and became one of EMDs most popular locomotives. Almost 4,000 units were sold in the US and Canada. These were built most commonly on 387,500 pound versions, but some were as light as 358,000 pounds built especially for the Milwaukee Road to handle their light track, up to 418,000 pound coal hauling heavyweights. The heavy SD40-2s could actually start a significantly heavier train than a more powerful but lighter SD45.
The SD50, like the GP50, added wheelslip control, and brought horsepower back up to 3,500-3,600 but out of 16 instead of 20 cylinders. These units were stressed very hard in the 645 configuration, and the wheelslip controls made the units buck and shake and squal under load, and crews had not really figured out how to appreciate the new technology, so they wwere not always well liked.
The SD60 added the 710 prime mover and at 3,800 HP and 395-400,000 pound typical weights, these were used in all types of service. The wheelslip control was improved, and adhesion got up around 30% of weight.
The SD70 moved to 4,000 horsepower and came in both the DC SD70M and the AC SD70Mac. The DC version was mainly used by Union Pacific and Norfolk Southern. These tended to be assigned to priority consists which in modern freight is usually intermodal and autorack trains. The DC equipment has a little advantage in acceleration over the AC models, and is much less expensive. Since these trains are usually lighter, the additional tractive effort of AC locomotives is not needed. The SD70M units can get 32-34% adhesion under good conditions.
The SD70Mac units use AC traction motors and computer controls to get over 40% adhesion. At 410-424,500 pounds, these units are able to put up to 180,000 pounds toward starting a heavy train under ideal conditions, but most are rated at 175,000 pounds for the typical 415,000 pound units seen on BNSF. They can hold a continuous 137,000 pound tractive effort, and maintian this at very slow speeds. EMD units maintain traction control at the truck level, which may slightly handicap them in comparison to GE AC units which control at the axle level.
The SD90Mac was the EMD attempt to move railroads to 6,000 HP units. Not many roads have been pleased with these units on high speed intermodal service, and many have been downgraded to 4,300 HP SD90/43s. These are popular on the Union Pacific in coal and low priority trains. The irony is that you often see the high tech SD90/43Macs on the low tech drag freights with tank cars and gondolas.
The SD75 was another attempt to upgrade the performance of the DC SD70M. It added 4,500 HP in early Santa Fe units, but was lowered to 4,300 HP to get better reliability in most of the orders. These used to run mainly on the high speed consists, but a few are now slipping back into general service.
Hope this helps, and please ask questions if this does not cover your needed information.
Bob Boudoin
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