i have a few questions about some of the first gen geeps (GP's). has there ever been a GP9 or GP7 with D-2 upgrades. what is the deal with the elevated hood on the GP30s i thought that was the weirdest thing being the fact that it is the only locomotive of emd design that has such a thing/
one more question is why would anyone want a GP anyway they could hardly pull any thing compared to a SD7 which is a 1500 hp loco and a GP50 which is 3500hp could outpull it with twice the horsepower and half the tractive effort
TE ratings (starting)
GP7- 65000 lbs 1500hp
GP50- 65000 lbs 3500hp
SD7- 91000 lbs 1500hp
so theoretically an sd7 could out pull any GP loco
so ithe question stands why would anyone want one?
Well to make your comparison complete you'd have to compare an SD-7 to an SD-50 also.
GP's were essentially F-units with road switcher engines, which allowed these "General Purpose" engine to be used for a variety of jobs - yard switcher, wayfreight engine, yet they could also be used as a passenger engine. F-units had limited visibility to the rear so were fine on passenger trains or mainline freights, but didn't work well as switchers or wayfreight roadswitchers.
SD "Special Duty" engines could be bought with all six axles powered, giving them more pulling power and making them better for some purposes, like heavy ore trains. They could also be ordered with the center axles unpowered idlers, for lines where the railroad only needed the power of four axles but needed to distribute the weight of the engine on six axles, due to light rail or other limiting factors.
Builders made / make different engines for different purposes...it would be like saying "why should GM make little Chevy Cavaliers when a Cadillac Escalade is so much better - why doesn't everyone buy an Escalade??"
There have been 'upgrades' to older GP7/9 locomotives that replace the electrical controls with 'Dash 2' style modular equipment. The ex-BN 1400 series and ex-ICG GP11 programs did just that.
The 'high brow' on the GP30 was basically a GM styling feature. There was some additional electrical cabinet stuff up there due to the increased space it offered.
You are confusing calculated starting T/E vs Continuous T/E. That 65,000 vs 91,000 lbs of starting T/E is basically 25% of the weight on the drivers(The SD weighs about 50% more). The key number is the 'Continuous T/E' at the 'Minimum Continuous Speed'. The GP's have a MCS of about 12-13 mph(depending on gear ratio). The SD7 has a MCS of around 7-8 mph(at the same gear ratio). What this means is that the SD7 will be out of red zone(short time rating) faster than the GP7. The GP7 will outpull that SD7 above 50 mph. At that speed, the 6 traction motors in the SD7 are sucking up the output of the main generator. This is known as 'Amping Out'. That GP7 with only 4 traction motors sucking juice and will not 'Amp Out' the main generator until a higher speed and will maintain continuous T/E higher than the SD7 at those speeds.
The bottom line is that the SD7 will pull more tonnage all day long in the 25-40 mph range, but the GP7 will deliver more continuous T/E over 50 mph.
In the case of the GP50, there are some additional technologies that come into play. The '50' line of engines had the radar controlled 'SS' wheel slip/correction feature where a small amount of wheel slip was dialed in by the computer and this heated the 'contact patch' where the wheel/rail meet - Resulting in a large increase in Continuous T/E. Of course this system was not perfect and wild excursions in wheel slip can still happen. But with 3500 hp, the GP50 does not lose Continuous T/E as fast as that SD7 or GP7. Still, it is not a good choice for short line or regional trains that never get over 35-40 mph(but the used price may be just too good of a deal).
The question about 'Why would I want a GP rather than an SD? There can be multiple reasons:
Also, there were 'lightweight' SD7/9 built(150 tons total weight/50,00 lb axle loading) that only have about 75,000 lbs of Starting T/E. The Milwaukee Road had a fleet of them for use on light rail branches.
Jim
Modeling BNSF and Milwaukee Road in SW Wisconsin
wisandsouthernkid why would anyone want a GP anyway they could hardly pull any thing compared to a SD7 which is a 1500 hp loco and a GP50
I would imagine that the fact that the GP7 came out years before the others was a major factor. Why buy a 1949 chevy, when you could buy something else, later, down the road a piece? The GP7 was better than what came before it, the F7.
Thanks to Chris / CopCarSS for my avatar.
While there were some relatively light SD7's and SD9's that were purchased because the extra axles were needed for weight distribution on light-rail branches, all of them were equipped with six traction motors. EMD did not have an equivalent to the RSC2/3 or DRS6-4-15.
jrbernier The 'high brow' on the GP30 was basically a GM styling feature. There was some additional electrical cabinet stuff up there due to the increased space it offered. Jim
No, it was the other way around! The GP30 electrical cabinet was taller than that of previous units and GM stylists devised the "hump" to conceal it. I'm pretty sure of this since I have an early GP35 brochure and this makes a big deal about the lower electrical cabinet being an improvement over the GP30.
The GP30 and GP35 had a more complex switching requirement than later units because of limitations on the D32 DC generator at the high power, compared to later units with alternators.
I'm not sure how they coped on the SD24 which was in the same power category but there might have been more space on the longer SD frame for a wider cabinet, since there were two more motors to switch.
M636C
Don't get me started on the SD-24 .. they had tons of electrical equipment !! you just had to look around to find all the hiding spots for the devices.
M636Cjrbernier The 'high brow' on the GP30 was basically a GM styling feature. There was some additional electrical cabinet stuff up there due to the increased space it offered. Jim No, it was the other way around! The GP30 electrical cabinet was taller than that of previous units and GM stylists devised the "hump" to conceal it. I'm pretty sure of this since I have an early GP35 brochure and this makes a big deal about the lower electrical cabinet being an improvement over the GP30. The GP30 and GP35 had a more complex switching requirement than later units because of limitations on the D32 DC generator at the high power, compared to later units with alternators. I'm not sure how they coped on the SD24 which was in the same power category but there might have been more space on the longer SD frame for a wider cabinet, since there were two more motors to switch. M636C
If you saw the original "GP22" (first GP30 built) it lacked the front part of the streamlined casing and was very ugly. It went to the SAL and later the SCL.
The SD35 benefitted from the fact that the GP35 went into production first, allowing for some electrical changes before the first SD35 was built.
Murphy Sidingwisandsouthernkid why would anyone want a GP anyway they could hardly pull any thing compared to a SD7 which is a 1500 hp loco and a GP50 I would imagine that the fact that the GP7 came out years before the others was a major factor. Why buy a 1949 chevy, when you could buy something else, later, down the road a piece? The GP7 was better than what came before it, the F7.
Take the Frisco (SLSF) for example during the early 1950s they bought both GP7s and F7s in the same years. The F7s had 24RL brake systems and dynamic brakes to be used on road freights, while the GP7s were bought with cheaper 6BL brake systems and lacked dynamic brakes, and were intended to be used solo on wayfreights and branchlines. Management did not consider that GP7s with the 24RL brakes and dynamics could also serve both duties, their thinking was still based on steam locomotive practices with separate locomotives for each service.
Beaulieu the first GP30 #5629 later #1962 went to Union Pacific as their #875. The second GP30 demonstrator #5639 went to Seaboard as their #534. Diesel data from A J Kristopan's website.
Ed
beaulieu If you saw the original "GP22" (first GP30 built) it lacked the front part of the streamlined casing and was very ugly. It went to the SAL and later the SCL.
I agree that EMD did not have a domestic equivalent to the ALCO or Baldwin lines of A1A-A1A trucked diesels, but EMD did export some G12s that were A1A-A1A truck equipped.
CSSHEGEWISCH While there were some relatively light SD7's and SD9's that were purchased because the extra axles were needed for weight distribution on light-rail branches, all of them were equipped with six traction motors. EMD did not have an equivalent to the RSC2/3 or DRS6-4-15.
Also beyond 3800HP in EMD and 4000 HP in GE you would begin to see adhesion issues. Remember that the last GP series produced were the GP60 series for the Rio Grande and the Tex Mex railway the Last B truck for Freight use were the B-40-8W for the Santa Fe. I have asked a few engineers on the now BNSF what they thought of the GP60M and the B-40-8W and they are SLIPPERY they hate them on wet rail. Remember that above 1000HP per axle you have issues getting the power down and anymore we are at that limit.
The last GP60s were actually built for SP in 1993-94. The 9794 is the last GP60 built and it still wears unpatched SP colors.
The Rio Grande and Tex Mex units were tacked to the end of an SSW (SP) order in 1989-1990.
jrbernier There have been 'upgrades' to older GP7/9 locomotives that replace the electrical controls with 'Dash 2' style modular equipment. The ex-BN 1400 series and ex-ICG GP11 programs did just that. The 'high brow' on the GP30 was basically a GM styling feature. There was some additional electrical cabinet stuff up there due to the increased space it offered. You are confusing calculated starting T/E vs Continuous T/E. That 65,000 vs 91,000 lbs of starting T/E is basically 25% of the weight on the drivers(The SD weighs about 50% more). The key number is the 'Continuous T/E' at the 'Minimum Continuous Speed'. The GP's have a MCS of about 12-13 mph(depending on gear ratio). The SD7 has a MCS of around 7-8 mph(at the same gear ratio). What this means is that the SD7 will be out of red zone(short time rating) faster than the GP7. The GP7 will outpull that SD7 above 50 mph. At that speed, the 6 traction motors in the SD7 are sucking up the output of the main generator. This is known as 'Amping Out'. That GP7 with only 4 traction motors sucking juice and will not 'Amp Out' the main generator until a higher speed and will maintain continuous T/E higher than the SD7 at those speeds. The bottom line is that the SD7 will pull more tonnage all day long in the 25-40 mph range, but the GP7 will deliver more continuous T/E over 50 mph. In the case of the GP50, there are some additional technologies that come into play. The '50' line of engines had the radar controlled 'SS' wheel slip/correction feature where a small amount of wheel slip was dialed in by the computer and this heated the 'contact patch' where the wheel/rail meet - Resulting in a large increase in Continuous T/E. Of course this system was not perfect and wild excursions in wheel slip can still happen. But with 3500 hp, the GP50 does not lose Continuous T/E as fast as that SD7 or GP7. Still, it is not a good choice for short line or regional trains that never get over 35-40 mph(but the used price may be just too good of a deal). Jim
Jim or anybody,
At what HP level did the SD's stop "Amping Out" and truly become suitable for high speed work(50-70 MPH) w/o having a high speed gear ratio like 60:17 or 59:18????
It seemed that through the 70's and into the 80's and 90's that RR's by and large with a few exceptions entrusted their high speed hotshots to locos like the GP40-2, the B36-7, the GP50 and those slippery race horses the GP60 and B40-8's. Other than the SD45 and SD45-2 they seemed to only give the high speed nod to the SD40-2 usually when those units were geared high like UP's 8000 series and CNW's Falcon units.
What was the "tipping point" that RR's consider C-C's a true high speed locomotive as well as a lugger??
Was it the SD70 and C40-8???
Well SD-9's could be used in passenger service, DMIR 129 and 130 were both equipped with steam generators (primarily so they could back up the road's RDC and pull a passenger train) and in the early seventies were leased to Amtrak during the winters. AFAIK they had the same gearing as the other SD-9's the Missabe owned, and both were used in iron ore service regularly. They were used for years on excursion trains on the Missabe, like shipper's tour trains etc.
Course I guess in 1955 if you wanted a six-axle diesel for passenger trains, you'd normally order an E unit from GM rather than an SD.
BTW I don't know where I got that about SD's being available with A-1-A trucks, must have been having a bad day!!
wjstix Well SD-9's could be used in passenger service, DMIR 129 and 130 were both equipped with steam generators (primarily so they could back up the road's RDC and pull a passenger train) and in the early seventies were leased to Amtrak during the winters. AFAIK they had the same gearing as the other SD-9's the Missabe owned, and both were used in iron ore service regularly. They were used for years on excursion trains on the Missabe, like shipper's tour trains etc. Course I guess in 1955 if you wanted a six-axle diesel for passenger trains, you'd normally order an E unit from GM rather than an SD. BTW I don't know where I got that about SD's being available with A-1-A trucks, must have been having a bad day!!
"I Often Dream of Trains"-From the Album of the Same Name by Robyn Hitchcock
edbentonAlso beyond 3800HP in EMD and 4000 HP in GE you would begin to see adhesion issues. Remember that the last GP series produced were the GP60 series for the Rio Grande and the Tex Mex railway the Last B truck for Freight use were the B-40-8W for the Santa Fe. I have asked a few engineers on the now BNSF what they thought of the GP60M and the B-40-8W and they are SLIPPERY they hate them on wet rail. Remember that above 1000HP per axle you have issues getting the power down and anymore we are at that limit.
High hp 4-axles are still popular for passenger service with Amtrak and various commuter lines, the fastest being GE's 4,200 Genesis. I don’t think there’s been a new 6-axle passenger diesel in the US since the SDP40F in the 70s, though some of Alaska RR’s SD70MACs have HEP for use with passenger cars.
Passenger and Freight are 2 differant animals. I look at Passenger trains like a passenger car in a way lightweight and you want 2 things High speed and Accelaration. Freight trains are HEAVY and need all the pulling poweryou can put at the railhead most of the time. Even on a hotshot Intermodal train you need sometimes dragging power with Doublestacks in the consist. Think of freight trains as a Heavy truck going down the road yes they may not get up to speed very fast however once they are there they normally will keep running at that speed til it hits a hill then it digs in her heels and pulls. The other issue the frieght lines were running into was axle loading with the GP series at the end. The GP 60M could not even be filled to FULL tanks without putting it overweight.
Now you you mentioned the Genesis series for passenger trains. They were designed to meet Amtraks designs and not anyone elses. Amtrak can not even find buyers for the F40 retired that they have for freight RR to buy.
Lyon_Wonder[High hp 4-axles are still popular for passenger service with Amtrak and various commuter lines, the fastest being GE's 4,200 Genesis. I don’t think there’s been a new 6-axle passenger diesel in the US since the SDP40F in the 70s, though some of Alaska RR’s SD70MACs have HEP for use with passenger cars.
There were C-C passenger locomotives ordered after the SDP40F debacle. There was the GE U34CH the New Jersey DOT bought for use on Erie Lackawanna commuter lines out of Hoboken NJ. Basically they were EL spec U36C's with HEP. One of the first units in the counrty so equipped though they did lack the engine brake isolating feature so that EL would dissauded from using them in freight service on the weekends. They did from time to time anyway.
There was also the the EMD F40C's that was purchased by a preMETRA, preRTA commuter authority, I forgot the name, for use on Milwaukee Road commuter lines out of Union Station Chicago . They were recently retired after thiry years of unevently service. And they had none, none of the tracking problems that the Amtrak SDP40F had. They had the same HTC trucks that were blamed for all the derailments the Amtrak units had. It kind of makes you think what could have been had Amtrak converted their heritage rolling stock to HEP earlier. They might not have ordered as many F40PH's if they had ordered the F40C.
IIRC the SDP40F problems were what caused Amtrak leased those DMIR SD-9's I referred to earlier. Apparently when the SDP40Fs were withdrawn Amtrak found itself short of motive power.
The U34CHs were bought as dual service units, but never went too far in freight service due to the fact that they were needed for passenger and couldn't be "out of town" so to speak. They could be set for either service, with the passenger mode being a constant speed to run the extra alternator to power the cars. They still sounded great when loading though. Ironically, they were technically the first U36Cs, they had the 3600hp engine, first, but since they were actually rated at 3430 hp for traction due to the extra energy for the lighting they didn't really get the credit. They were also geared for passenger speeds, and supposedly weren't the best engines for pulling, I think they were used on intermodals from time to time.
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