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Pennsylvania GG1

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Posted by DSO17 on Friday, December 17, 2010 7:42 AM

 

cefinkjr wrote the following post on Thursday, December 16, 2010

 

DSO17:

 

     I think the manager was pulling your leg. The half-GG1 was supposed to be a snow blower.

 

 

Then the Wilmington Shops used a snow blower to move other motors around the shop area.

     Interesting. I never paid much attention to the half-G, but one of the foremen who oversaw its "conversion" told me it couldn't move on its own and had to be shoved by another engine. Googling PRR GG1 snow blower shows a difference of opinion. Due to the catenary arrangement at the shops, it seems like an electric shifter would be of rather limited usefulness. Do we have one of those inside jokes that float around the railroad?
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Posted by oldfirebox on Tuesday, December 28, 2010 4:57 PM

Levantine

Thanks, Mike.  One more question.  In the schematics I see a hinge at the midpoint of the articulated frame.  From which end of the locomotive did one truck swing, when rounding a curve?  Or was there some sort of pivot at the mid-point of each truck?

I don't know the details about the GG1's running gear design, but I think the main purpose of the 'hinge at the midpoint of the articulated frame' is to transmit longitudinal forces between the two trucks (I mean the frames with the 3 powered axles each). This is of advantage to the main frame as the couplers are mounted on the trucks. In case of slack running in or out the forces were transmitted directly from one truck to the other so the main fram has not to bear these forces.

The hinge can have a second purpose : to join the two trucks vertically (transmitting vertical forces). In doing so, the load transfer (change of axle loads) due to traction/braking efforts of the whole loco is kept very low. Without this joint the front end of a truck slightly moves upward and the rear end downward when the truck exerts tractive effort. Linking the inner ends of both trucks reduces the pitch movements of both trucks resulting in a minimum amount of laod transfer. A minimum of load transfer was desirable as the axles could gain slip independently from each other under reduced wheel/rail adhesion.

The hinge could even have a third purpose : to join the two trucks laterally. This feature is used to reduce the lateral wheel to rail forces when running through a curve. To understand this, you should first realize that a truck always would like to go straight ahead. Going through a curve means the truck has to turn around a vertical axis. This turning movement requires some sliding of each wheel against the rails. To turn a truck through a curve, a lateral force is required to overcome the wheel/rail friction because of the sliding movements. In most curves the outer wheel of the leading axle touches the rail head with its flange thereby getting the lateral force from the outer rail in the direction to turn the truck. In tighter curves the inner wheel of the trailing axle will also touch the railhead (of the inner rail) with its flange, thus getting a lateral force for turning the truck, too.

When two trucks are running independently from each other under a common main frame, one will find that (when travelling through a curve) they swing out under different angles in respect to the main frame, the leading truck having a smaller and the trailing truck having a larger angle. This is the reason for the hinge points of the inner ends of the truck frames not remaining face to face when running through a curve. When travelling through a lefthand curve the hinge point of the leading truck has moved to the left in respect to the hinge point of the trailing truck. Now consider the two hinge points connected to each other : this means the leading truck has to increase its angle of turn against the frame and the trailing truck has to reduce its angle. In doing so, the alignment of both trucks in respect to the curve has improved and the lateral forces at the wheel flanges are lower than without joining.

If the lateral joint is strict and stiff, it will lead to severe hunting of both trucks when running on tangent track at high speeds. Therefore, this joint is normally designed with a specific amount of play. But even if the play has been exhausted the joint is not made by a stiff link but by means of a pre-stressed spring.

Whether the linkage in case of the GG1 has which of these 3 options you can perhaps only decide by knowing more details, e.g. construction drawings of the linkage.

The design of such a linkage between the truck frames is very much "steam era thinking" - it was very much common practice at that time to put a considerable amount of effort into a good curving behaviour and low load transfer.

The main frame of the GG1 seems to me to rest on four spring loaded plates which are located in such a way to get the desired load distribution on the drivers and on the undriven axles. Longitudinal and lateral guidance could have been by two vertical pivots on the main frame, each fitting into a hole in the truck frames (location seems to be about midpoint between the second undriven and the first driven axle). It is possible, that these pivots do not transmit vertical loads (as a 'center plate design" would do), so that the main frame completely rests on springs - this would lead to a much smoother vertical ride (which has been reported).

In the era of the 20s and 30s a number of electric locos (having two trucks) had a linkage between their trucks. Today, the trucks are arranged at a much larger distance between them, and tanks on diesel locos and transformers on electric locos fill the space. Today, a linkage between trucks isn't a running gear design feature anymore. Instead, in some cases radial steering trucks are used to reduce the wheel flange forces and wear.

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Posted by BigJim on Thursday, December 30, 2010 7:09 PM


I don't know the details about the GG1's running gear design, but I think the main purpose of the 'hinge at the midpoint of the articulated frame' is to transmit longitudinal forces between the two trucks (I mean the frames with the 3 powered axles each). This is of advantage to the main frame as the couplers are mounted on the trucks. In case of slack running in or out the forces were transmitted directly from one truck to the other so the main fram has not to bear these forces.

I think that if you look at the diagram below, you will find that the couplers were in fact connected to the frame and not the trucks.

http://ctr.trains.com/~/media/images/online%20extras/gg1%20in%20layers/gg1-12-1024.ashx

.

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Posted by beaulieu on Friday, December 31, 2010 7:14 PM

The "frame" of a GG1 is like a span-bolster used by some multi-trucked locomotives (GE U50, Alco C855), in that the body shell is not directly attached to  the "frame".  Note there is an independent pilot truck on each end, but the axles that propel the locomotive are rigidly mounted to the frame.

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Posted by Old.Professor on Monday, March 20, 2017 8:43 AM

beaulieu

Before the advent of modern power electronics the equipment needed to control that amount of power was much larger and required a lot of cooling.

 

I think this is the answer to a question I want to ask--what is the "blower?" Is it just to cool the electrical equipment in the locomotive?

RME
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Posted by RME on Monday, March 20, 2017 10:43 AM

"Blower" for an electric locomotive like a GG1 almost certainly refers to 'traction-motor blower' -- the TMs being sufficiently loaded in most electric-locomotive and diesel-electric locomotive practice to require substantial forced cooling in service.

There would probably be blowers for other electrical equipment in the locomotive, especially for designs with 'positive pressurization' of the equipment spaces.  A locomotive that is notable is the New Haven EP5, which was nicknamed a 'Jet' because of its pronounced blower noise; the PRR E44 also produced a remarkably loud vacuum-cleaner-like noise (I'm not sure how much of this was purely traction-motor-blower noise).  In part this involves specification of smaller and faster-turning equipment to save space, weight or cost (just as vacuum cleaner motors are typically small and noisy for their expected power output!)

I don't remember GG1s producing anywhere near that level of blower noise either for its frame-mounted motors or for other electrical equipment. 

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Posted by DS4-4-1000 on Tuesday, March 21, 2017 6:18 AM

RME
A locomotive that is notable is the New Haven EP5, which was nicknamed a 'Jet' because of its pronounced blower noise; the PRR E44 also produced a remarkably loud vacuum-cleaner-like noise

The GE freight electric that was the contemporary of the EP5, known as the E2B on the PRR, was nicknamed "Screamer" on the PRR because of the loud blower noise. I saw one MUed to a P5 on the low grade coming up from Columbia and it was cover your ears loud.

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Posted by Fireflite on Wednesday, March 29, 2017 10:09 PM

daveklepper

Regarding visibility and operation of Amtrak passenger trains without a fireman on the GG-1s, recall that Neew Haven Penn Station is entirely grade separated, and now NY - Washington is, and only had one grade crossing at the time of Amtrak GG-1 operation.

 

[quote user="daveklepper"]

There were still grade crossings on the Philadelphia - Harrsiburg line, as well as the Port Road branch south from Columbia, PA.

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Posted by timz on Thursday, March 30, 2017 12:15 PM

daveklepper
New Haven Penn Station is entirely grade separated, and now NY - Washington is, and only had one grade crossing at the time of Amtrak GG-1 operation.

Far as anyone knows, about eight grade crossings between Wilmington and Washington in the 1970s.

RME
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Posted by RME on Thursday, March 30, 2017 1:13 PM

timz
daveklepper
New Haven Penn Station is entirely grade separated, and now NY - Washington is, and only had one grade crossing at the time of Amtrak GG-1 operation.
Far as anyone knows, about eight grade crossings between Wilmington and Washington in the 1970s.

 
Some of those would have to be private.
 
My understanding was that during the early Metroliner years, there were still three 'signaled' road crossings open, reduced to one fairly early in the '70s; I think perhaps indeed by the date Amtrak took over.  When I rode the train in 1969, I remember at least one grade crossing somewhere near Landover, MD. (complete with gates and flashing lights, and a white station wagon with those woodgrain side panels) which I recognized was unusual. 
 
I distinctly remember Trains covering this matter of closing or replacing the remaining grade crossings in at least one issue.  Someone with access to the 'archives' of the crossing database (or a suitable memory) could probably tell us how many of the 'eight' crossings were live in a particular year, and which specific roads were involved.
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Posted by timz on Thursday, March 30, 2017 4:47 PM

Yeah, I should have said I was just referring to public crossings. I'll check the chart when I get home-- I'm guessing at least six public xings south of Wilmington in 1981.

For starters, look at the 1980 historicaerials.com pics at 39.0177N 76.7648W and 38.9955N 76.8007W. (The latter might have been the last xing to close-- maybe 1983-84? Trains might have mentioned its closing.)

I looked at the track chart Mr Thompson sent me in 1985 that summarizes all the NECIP work. It shows 13 crossings eliminated by NECIP south of Wilmington-- no dates, tho. On the topo map, most (maybe all) of them look to be public.

Probably 38.9594N 76.8630W

Probably 38.9726N 76.8443W

Then the two mentioned above

39.1835N 76.6927W

The well-known Knecht xing 39.2611N 76.6873W

39.3104N 76.4970W

39.3624N 76.3686W

39.4566N 76.2097W

39.4655N 76.2007W

Aberdeen 39.5092N 76.1626W

Mechanics Valley Rd 39.6091N 75.9334W

Elk Neck Rd 39.6029N 75.8600W

Iron Hill 39.6458N 75.79085W

The January 1977 chart that Rails Northeast reproduced in 1978 says all the above were public crossings except, maybe, the Stony Run Rd xing at 39.1835N 76.6927. It adds the Ott's Chapel Rd xing at 39.65465N 75.7818W.

Looking at the 1974 timetable it seems there were then a couple more xings, at and east of Newark: South Chapel Rd and Ruthby Rd.

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