How fast can GP7s adn GP9s go?

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How fast can GP7s adn GP9s go?

Postby JonCavender » Sat Jul 11, 2015 5:07 pm

These are road switchers built by General Motors EMD from the late 40's to the early 60's. Southern Pacific used them even for commute passenger train service between San Francisco and San Jose, California until CalTrain took the operation over circa 1985/1986.

How fast have American RR's been know to run these engines at sustained speed for long stretches 15 miles or more?

What speed can even GP9P's go?
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Re: How fast can GP7s adn GP9s go?

Postby DutchRailnut » Sat Jul 11, 2015 7:35 pm

depends on gearing, a standard GP7 or GP9 was good for 65 to 70 mph.
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Re: How fast can GP7s adn GP9s go?

Postby JonCavender » Sat Jul 11, 2015 8:58 pm

DutchRailnut wrote:depends on gearing, a standard GP7 or GP9 was good for 65 to 70 mph.


Thank you. I guess the number of engines and the weight of the train load would also have something to do with it.

I am running Trainz 2012, a train simulator game. I am building a custom route based on the Mojave Subdivision in southern California. I have a Santa Fe Superchief passenger train (Pullman stainless steel cars) head by a N & W GP9P doubleheader. 2 each Santa Fe F7 A and B units are pushing this same train. The speed limit for this mainline route is 70 MPH. I like the gear-whir sound from the GP7/9's as the blowers were gear-driven. Same with GM/EMD F7/A7 bulldog nose locos. I like the engine 2-cycle exhaust grunt of the Geeps and TS 12 does a marvelous job at reproducing this sound. The GM/EMD car-body/streamline locomotives of the 50's have the same gear whir sound but not nearly as much grunt as the Geeps.

I ask about speeds wondering if Geeps would have ever cut it for speed on the Mojave mainline doing passenger service.

The P in GP9P actually designates this engine for passenger use.

The grades are steep: 2+ % and 2 GP9P's alone had slipping wheels pulling this 14-car passenger consist so I threw so GM F series streamliners on the end for helper duty.
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Re: How fast can GP7s adn GP9s go?

Postby Allen Hazen » Sun Jul 12, 2015 1:24 am

GP7 and GP9 were, mechanically, almost the same as F7 and F9 (give or take details like how the traction motor blowers were powered). Most importantly, in this context, they had the same trucks, motors and wheels.

EMD offerd a range of gear ratios on these models. The most common one gave a top speed of 65 mph. There was a slower one (gave better low speed continuous tractive effort: the Pennsylvania had a few F3 with this gearing, which they classed "EH15": H for helper service). The others all offered higher top speeds (at the cost of higher minimum continuous speeds). I think the fastest version gave 105 mph: I think CN had some FP7 or FP9 with this gearing.

I don't know if GP7/GP9 were actually built with the highest-speed gear ratios, but I don't see any reason in principle why they couldn't have been.
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Re: How fast can GP7s adn GP9s go?

Postby JonCavender » Sun Jul 12, 2015 7:21 pm

Allen Hazen wrote:GP7 and GP9 were, mechanically, almost the same as F7 and F9 (give or take details like how the traction motor blowers were powered). Most importantly, in this context, they had the same trucks, motors and wheels.

EMD offerd a range of gear ratios on these models. The most common one gave a top speed of 65 mph. There was a slower one (gave better low speed continuous tractive effort: the Pennsylvania had a few F3 with this gearing, which they classed "EH15": H for helper service). The others all offered higher top speeds (at the cost of higher minimum continuous speeds). I think the fastest version gave 105 mph: I think CN had some FP7 or FP9 with this gearing.

I don't know if GP7/GP9 were actually built with the highest-speed gear ratios, but I don't see any reason in principle why they couldn't have been.


The passenger Geeps like the GP9P probably would have had taller gearing.
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Re: How fast can GP7s adn GP9s go?

Postby Pneudyne » Sun Jul 12, 2015 9:07 pm

The attached brochure excerpts show the available gear ratios and corresponding speed maxima for the EMD F9 and GP9 models.

The F9 was available with eight different gear ratios that gave respective speed maxima between 55 and 102 mile/h.

The GP9 was available with six different gear ratios that gave respective speed maxima between 55 and 89 mile/h.

Thus the GP9 options lacked the two highest speeds available for the F9.

As Allen has said, there does not appear to be any technical reason why the GP9 could not have been fitted with either of the two “very fast” gear ratios that were available for the F9.

But at the very highest speeds, I imagine that the GP9 would not have been very aerodynamic, and that the better forward lookout from the F9 might have been preferred by enginemen.

Cheers,

EMD F9 p.03.gif

EMD GP9 p.03.gif
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Re: How fast can GP7s adn GP9s go?

Postby Allen Hazen » Sun Jul 12, 2015 11:51 pm

Thanks, Pneudyne, for posting those!

As to Geeps at very high speeds… I think the aerodynamics of the locomotive carbody is probably not of great importance even at 100 mph. (Gaps between cars and under their floors are, I think, likely to contribute more air resistance than the shape of the locomotive. The rounding of the corners on an F-unit's carbody will make SOME improvement, but I suspect it is marginal.) … The Geep has a wheelbase that is a few feet longer than an F's: I don't know if this has a detectable effect on tracking and ride, but if it does it might even make a Geep BETTER at speed!

The New York Central (probably other railroads as well, but NYC I know for sure) used pairs of Geeps on fairly fast trains (I think "James Whitcomb Riley" was the name of one named train entrusted to them)… and had their Geeps set up for long-hood first operation. So whether or not engine men would have preferred the better visibility of an F-unit cab, management didn't think it was a BIG issue.

(Jon Cavender-- As a matter of locomotive aesthetics, many passenger GP-7/GP-9 were "torpedo boats": the need for extra tankage under the frame to accommodate water for the steam generator force the air reservoirs to be mounted on the roof of the long hood, looking like … Not all passenger Geeps had roof-mounted reservoirs, and for relatively short runs the need for extra tank capacity under the frame might not be pressing. So, if you are planning something and wondering about the looks, both options are open.)
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Re: How fast can GP7s adn GP9s go?

Postby edbear » Tue Jul 14, 2015 8:23 pm

The New Haven's 1200 series GP-9s regularly hauled through trains between Boston and New Haven from the time delivered (about 1957) until both orders of FL-9s were up and running about 1960. They could also be found handling Boston-Providence commuter trains and all types of freight, local and through. Back about 1974 or 75 I caught a Penn Central operated Amtrak train at Dedham Road just west of Route 128 station with an E unit and New Haven GP-9 for power.
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Re: How fast can GP7s adn GP9s go?

Postby Allen Hazen » Wed Jul 15, 2015 2:01 am

Ed Bear--
That jogs a memory. Remember the United Aircraft Turbotrain? Fast and fun (the engineer's compartment had a glass rear wall, and passengers in the front dome could look over the engineer's shoulder as the train tilted through curves) but not mechanically reliable… My recollection is that Amtrak, in the 1970s, when the Turbo was down, would replace it with a short (two car? maybe sometimes one?) train pulled by a GP-9.
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