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Pennsylvania GG1

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  • Member since
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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.

  • Member since
    April, 2001
  • From: Roanoke, VA
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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

.

  • Member since
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  • From: NW Wisconsin
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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
  • Member since
    March, 2016
  • 1,262 posts
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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