As far as I know, the EMD SD-7, a six-motor version of the then very popular GP-7, was the first six-motor freight diesel-electric locomotive using two six-wheel trucks.
My memory is that the initial order was only for two, ordered by PRR, espeically for Madison HIll, where one SD-7 could replace a single 2-8-0 on the hill, but one GP-7 or F7 could not.
The PRR liked, found it useful in other service, ordered more, and then others followed. The improvements incorporated into the GP-7 to make it the GP-9 were also applied to make the SD-9, which became popular.
The US Army modified RS1's (RSD1), which could be considered an export modification, predated the SD7 by several years. Alco was also beginning to market the RSD4 at the same time and Baldwin was selling 6-motor power to several roads. Also, the PRR only had the two SD7's, which were ordered and customized specifically for Madison Hill. A lot of SD7's were ordered by other roads to dieselize light-rail branch lines in the Midwest.
Hi - agree with Paul that Alco and BLW deserve credit for being the first kids on the block to tap into this market. And later FM upped the game on higher-horsepower with the Trainmasters. Art
Yes, but my memory says the Army modified Alco RS-1's had a-1-a trucks and not C trucks. In otherwords they added a center idler axle and kept the locomotive as a four-motor job. Am IO wrong on this?
Regarding Baldwin, I am not familiar with that product, and you are probably correct. But I do think the Alco RS-4 followed the SD-7, and did not preceed it. Againh, I may be wrong. FM also came later, if my memory is correct. Still, that keeps Baldwin first.
Hi Dave - the RSCs were A-1-A, the RSDs were C-C arrangement. BLW's AS616 was first in production in 1950, the RSD4s began production in 1951 and the SD7 came along in 1952. Alco addressed some design issues they had with the RSD4 in their design for the RSD5, which followed it into production. IIRC, first TMs are 1953 or so. Hope that helps, Art
Alco RSD-1s came out long before the others beginning in 1943. They were built to fulfill a need for locomotives on the Trans-Iranian Railway by the US Army, early locomotives were converted RS-1s repurchased from US railroads who received replacement locomotives a few months later, a large follow on batch went to Russia on Lend-Lease. EMD was the last builder to introduce a six-axle locomotive, the SD7, EMD's Demo was built in March, 1952 and later was sold to B&O. First production SD7s went to the Milwaukee beginning in April 1952. First production RSD4s went to the C&NW in March 1951.
baldwin pioneered 6-motor heavy road switchers, beginning with C&NW 1500, which entered service in feb. 1948, first of three for the road. a total of 83were built before the improved AS-16 was introduced late in 1950.
How many motors did the Baldwin Centipede have ? ( not a clue here)
Didn't Baldwin- Westinghouse have experience with electric locomotives with more than 4 motors ?
Randy
Randy Stahl How many motors did the Baldwin Centipede have ? ( not a clue here)
Eight. The Centipedes were 2-D+D-2 wheel arrangements.
W-e-l-l the Baldwin Westinghouse locomotives for the Milwaukee had six powered axles, driven by 12 motors. These were 2-C-1+1-C-2 wheel arrangements, so weren't quite the same thing as a C-C. I would be pretty sure that all of the B-W electrics with more than 4 driven axles and built before -say- 1940 had articulated truck frames.
- Erik
If you are talking about electrics, the New Haven EP-2, 1-C-1+1-C-1, and EP-3, EP-4, EF-3, and PRR GG-1 2-C+C-2 (4-6-6-4), but we were discussing diesels. Also, did not each of the C frames discussed above, three axles, have two motors powering each axle?
My thought was that the deisel electric locomotive can trace its roots back to Frank Spragues' streetcars. I don't think it was a quantum leap from straight electrics to diesel electrics. Don't mean to sidetrack the tread..
Don't worry abou tsidetracking, since all this information is relevant for the reason you pointed out.
Somehow, "SD-7" and "freight power" just don't seem to belong together. The SD-7 was much more about spreading weight over more axles than it was about power.
ChuckAllen, TX
The SD7 design involved more than spreading the weight for branchline operation. The SD stood for special duty, and with six traction motors to spread the load, they were better able to generate high sustained starting tractive effort and could lug loads at nine miles per hour that a GP of the same horsepower couldn't handle. Thus, they were often used for working heavy trains on mining branches as well as in main line situations where tractive effort at low speed was more important than high speed running.
beaulieu EMD was the last builder to introduce a six-axle locomotive, the SD7, EMD's Demo was built in March, 1952 and later was sold to B&O. .
EMD was the last builder to introduce a six-axle locomotive, the SD7, EMD's Demo was built in March, 1952 and later was sold to B&O. .
The EMD demo SD7 was sold to Southern Pacific. It was retired as SP #1518 under Union Pacific ownership. It was donated to the Illinois Railway Museum.
Bryan Jones
SD stood for "Special Duty." Four-axle freight ower was considered normal, starting with the 1939 FT. But just as the road-switcher type took over from cab units, with the N&W dieslizing almost entirely with GP-9's and no F-units, so six-axle power took over from four-axle as railroads liked the extra tractive effort available and starting and low speeds.
We need to realize something also Back when the SD-7 came out Prime Movers had only around 1500 HP or 250HP per TM the GP7 had 4 or 375 HP per TM and then they were still at the Limits of what the Electronics of the DAY could stand for Heat and Current without Burning out. Now we have the 4400 HP GEVO's and 4300 HP SD70M-2 in the DC side of things. We are at around 750 HP per Traction Motor and we are pushing the Limits of what Steel on Steel Physics can just about Handle.
Anyone Remember how Slippery the GP 50 and 60 Series or the U36 B-36-7 or the B-40-8's were and to a little bit the GP 40 line called way to much HP for weight you can shove into the frame of a 4 axle and stay in the Weight limits. Yeah GE had the 1050HP an axle with the P42 but passenger engines are geared Differant not to drag a load. We are not going to see a Brand new design in a DC powered Heavy haul Locomotive over 4000 HP for one reason AC TM's have NO Brushes to Waer Out No Windings to Squirrel Cage and are just about IMMUNE to heat.
Bryan Jones beaulieu: EMD was the last builder to introduce a six-axle locomotive, the SD7, EMD's Demo was built in March, 1952 and later was sold to B&O. . The EMD demo SD7 was sold to Southern Pacific. It was retired as SP #1518 under Union Pacific ownership. It was donated to the Illinois Railway Museum. Bryan Jones
beaulieu: EMD was the last builder to introduce a six-axle locomotive, the SD7, EMD's Demo was built in March, 1952 and later was sold to B&O. .
The fact is both Bryan Jones and beaulieu are right, half right because there were two SD7 Demonstrators. EMD 990 and 991 were the SD7 Demonstrators built in March 1952. The 990 was the light frame version SD7 and ballasted at 314,900 pounds. The 991 was the heavy frame version SD7 and ballasted at 372,800 pounds. The 990 was sold to Southern Pacific and the 991 was sold to the B&O.
See the SD7 roster here http://www.trainweb.org/jaydeet/sd7.htm .
See Diesel Era November/December 1995 for an SD7 history.
@EdBenton:
We are NOT at the limit of traction motors at 750 hp/axle.
You forgot your own SD90MAC-H, which had 1000+ hp/axle (okay, not all the horsepower reached the rails - there were things like air compressors, etc.).
The current limit is around 2.000 hp/axle, witness the electric locomotives (or the incoming Amtrak ACS-64).
These electric locomotives are rated for 6.4 MW (or 8580+ hp) on the rails (on four axles), as are their European brethren.
N.F.
Forgot to add that these are 'universal' locomotives using AC traction motors, and equally capable of hauling freight trains and passenger trains.
If you demand pure freight high-horsepower locomotives, I offer the Siemens Eurosprinter ES64F4 as an example
(ES=Eurosprinter, 64 = 6.4 Megawatts, F = Freight 140 km/h, 4 = four different voltages)
Cheers,
nfotis @EdBenton: We are NOT at the limit of traction motors at 750 hp/axle. You forgot your own SD90MAC-H, which had 1000+ hp/axle (okay, not all the horsepower reached the rails - there were things like air compressors, etc.). The current limit is around 2.000 hp/axle, witness the electric locomotives (or the incoming Amtrak ACS-64). These electric locomotives are rated for 6.4 MW (or 8580+ hp) on the rails (on four axles), as are their European brethren. N.F.
Although I do not know the "At-the-Rail" HP for the SD90MAC-H, the Gross rating for the 16-265H prime mover was approx. 6,300 HP so no need to subtract HP for the auxiliaries...
"I Often Dream of Trains"-From the Album of the Same Name by Robyn Hitchcock
carnej1 Although I do not know the "At-the-Rail" HP for the SD90MAC-H, the Gross rating for the 16-265H prime mover was approx. 6,300 HP so no need to subtract HP for the auxiliaries...
well, expect around 80-85% arriving from the diesel prime mover to the rails (a loss of nearly 20%), from my readings.
In contrast, electric locomotives are rated at their power at-the-rail (so, a traction transformer would drink a bit more than 7.1 MW from the catenary when pulling at 6.4 MW on the rails - the efficiency ratio on electrics is around 90%, if I am not mistaken)
General Electric manufactured C-C diesel electric locomotives well before any of those so far listed. In 1936 two C-C locomotives were delivered to the Illinois Central by GE. The 9200 was 1800 horsepower and the 9201 was 2000 horsepower.
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