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  • How fast can GP7s adn GP9s go?

  • General discussion about locomotives, rolling stock, and equipment
General discussion about locomotives, rolling stock, and equipment

Moderator: John_Perkowski

 #1338974  by JonCavender
 
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?
 #1338999  by DutchRailnut
 
depends on gearing, a standard GP7 or GP9 was good for 65 to 70 mph.
 #1339009  by JonCavender
 
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.
 #1339031  by Allen Hazen
 
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.
 #1339088  by JonCavender
 
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.
 #1339104  by Pneudyne
 
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
 #1339114  by Allen Hazen
 
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.)
 #1339373  by edbear
 
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.
 #1339416  by Allen Hazen
 
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.
 #1536831  by Engineer Spike
 
According to the book New Haven power, their GP9 fleet was geared for 83 mph.

As to why the GP series didn’t have availability of the fastest gearings available on the F series, a couple of factors come to mind. First, it was likely that a GP could be geared for 100+. They used the same trucks. I think that I’ve read somewhere that the GP had some slightly different wiring to make them load faster for switching work. I don’t think that would have restricted the top speed. Maybe more steps of transition may have been needed. Another factor could have been warranty related. A GP would more likely be stolen for freight work. The high continuous speed would have made it really easy to cook a motor. Next the carrier is crying to EMD about excessive motor failure. Finally EMD has to prove that the unit is being abused, which might be hard to prove. This might result in paying for failed motors, even though it was no fault of EMD.
 #1543151  by Zanperk
 
Carbody units have better power to weight ratios, which is why they used them in pre-war diesel-electric power units. Operating over 79mph in the U.S. required cab signals, so that was probably an issue in the how/why of the gear ratio offerings as well.

Plenty of roads had EMD hood units in passenger service: CNJ and IC GP7s, GP9s on the N&W (geared for 77mph), Wabash ran them on the City of St Louis, CNW & SP had SD9s in commuter service.

Noel Weaver preferred running the NH GP9s to the FL9s: https://www.tapatalk.com/groups/thenhrh ... t5876.html

By 1960 most everyone had figured out that the post-war carbody fleet orders should have been hood units, with steam generators and taller gearing for units in the passenger pool.