im doing a scince fair project and i need how fast was a gp9’s top speed?
This would depend on the gear ratio specified by the railroad when they ordered the loco from EMD.
malc.
Further to my previous post, EMD would supply the following gear ratios for F7s, so GP9s were probably available with the same choices:-
65/12…55MPH
62/15…65MPH
61/16…71MPH
60/17…77MPH
59/18…83MPH
58/19…89MPH
57/20…95MPH
56/21…102MPH
The figures refer to the number of teeth on the axle gear (first figure) and the number of teeth on the traction motor pinion (second figure).
Malc.
Going on further, note that one of the gears always has an odd number of teeth and the other an even number, this extra odd tooth is known as “the hunting tooth” and is to ensure even wear of the gears in service by ensuring that each tooth meshes with a different one every revolution of the gears.
Malc.
I seriously doubt a GP9 was ever operated at 102 mph in any kind of service, or at any speed above around 80 mph for that matter.
I agree, I was merely quoting the ratios available from EMD. It is extremely doubtful if any railroad would order GP9s for such high speed service.
Malc.
Several roads had GP9’s with high-speed gearing for passenger service, and those may have spent some time at 80 MPH or possibly a bit faster if they were running late.
I would guess that the maximum speeds for each gear ratio are theoretical in part based on the construction and rotational speed of the traction motors. There are probably other considerations that would limit the maximum speed on optimal track.
Traction motor armature RPM is the limiting factor regardless of gear ratio. Over speeding a motor can quickly wreck it. There is a very small air gap between the spinning armature and the stationary field pole pieces and over speeding can cause the armature to expand enough to touch them thereby wrecking the motor.
A locomotive ordered for example, for mine runs involving switching and heavy slow speed work, often on steep grades would benefit from a low gear ratio to give the high tractive effort necessary for this type of service.
A locomotive ordered for commuter passenger work would more likely have a medium gear ratio to give a compromise between good acceleration between station stops and a reasonable turn of speed between stations.
Locomotives for express passenger work would be ordered with high ratios for high speed but sacrificing good acceleration.
When ordering locomotives and deciding on the gear ratio required the railroad would take into consideration the type of service, the topography of the line, the maximum permissable line speed and whether the loco was to be used in one type of service or multi-purpose, always a compromise.
Malc.
There are ways–I don’t know how–that the locomotives can be run well in excess of their rated speed. The Grand Trunk Western’s passenger GP9s (and 18s) were geared for 83 mph, but I was on a run of the Mohawk in 1970 in which time had to be made up–and we were definitely doing 100 or better with a pair of those (this from milepost timings of 35-36 seconds, noted by three or more people in the vestibules, including myself).
It is quite common for a locomotive to have its gear ratios changed during its life to make it suitable for duties other than that for which it was originally purchased. Here in England it is not uncommon for locomotives of the same class to have different gear ratios and therefore different maximum speeds. Obviously there is always a safety margin between the maximum allowable speed and the speed at which the traction motors self destruct.
Here in England exceding the maximum speed, be it line speed or loco or unit speed is a serious disciplinary offence and is regularly checked by either downloading the train data recorder, radar speed checks or timed occupancy of track circuits. I earn my living by driving trains and know that one eye must always be on the speedometer when running at maximum speed as it can be very easy to creep over the maximum. The main problem that I have had when running at maximum speed is traction motor flashovers.
Malc.
I run Ex GTW GP-9 4545 & 4554 everyday in both freight and passenger service and I am sure they went over 100 many times. Now they are regulated to 10 and 15 in shortline frgt and dinner train service.
What makes you so sure they went over 100 many times? Have you done it yourself or know someone who has?
About 9 years ago I rode behind Ex GTW GP-9 4545 on the Adrian & Blissfield railway in Michigan, Is this where you run them?
Malc.
ICs GP9s were geared 62/15 to run at a top speed of 65 MPH. So were they’re GP7s.
I enjoy seeing photos of a high nose locomotive
Larry
watchingtrains@yahoo.com
I would enjoy mail from Washington state
Railfan also New York
Yes GTW 4545 is now ADBF 1751 and GTW 4554 is ADBF 1752, I have never had them at 100 but have talked to some retired GT engineers who have. As I post this I am returning from operating the dinner train where they did both did a great job hauling the varnish 50 years after being built.
Ask them how it was done–I’m glad somebody believes me!
However, the GTW passenger GP9s were in the 4900s–if these are the original numbers of the units you have on ADBF, those were more routine freight units with 65-mph gearing (I think the passenger Geeps were regeared after Amtrak took away the GTW passenger service). In fact, they should be different from each other–the original GTW unit–4545–didn’t have dynamic brakes, but the 4554 was built for Central Vermont and transferred to GTW, and should at least have the housing for d/b.
From what I have been told 4545 was used as protection power in passenger service but did spend most of its career hauling freight (as it does today). 4554 does have the blister for DB but they were taken out long ago. On a different note, in the summer of 05 they both were repainted and while sanding and preping found GTW bloody nose red and blue and the old green and gold of both GTW and CV. They now wear a version of NYC lightening stripe only in CN green and gold.
My mom rode the GTW back in the steam era.She says it was the fastest train she ever rode.I’m sure they ran just as fast after dieselization.The GP9s could easily have run over 100MPH.
wow this topic was verry active thanks.