I see it mentioned in PRR GG1 reference material that the frame is articulated which allows it to negotiate tighter curves than it normally could. However, what does this mean, is there a pivot in the center? How does the carbody pivot?
The two pieces of the frame pivot in the center. The carbody is rigid. It sits on the frame with “feet” that ride in slots so the frame can rotate and move under the carbody. There’s a good picture of this out there somewhere… I’ll try to find it.
This was also true of the New Haven’s 2-6-2+2-6-2 EP2, 4-6-6-4 EP-3, EP-4, and EF-3 locomotives, the EP-3 tested by the PRR as the basis for the GG-1.
Most pre-WW2 electrics were articulated, NYC’s S-motors, PRR’s B1, P5, L6 and O1 are the only ones that come to mind that weren’t articulated. An articulated diesel that comes to mind is the Baldwin Centipede.
The following link is to a website that has posted some rough mechanical and dimensional drawings of the GG-1 family of PRR Electrics.
http://prr.railfan.net/diagrams/PRRdiagrams.html?diag=GG1_4800-E404453.gif&sel=ele&sz=sm&fr=
The engine as stated rides on two sets of castings that each have six drive wheels and a four wheel lead truck. Not asked but part of the story is the 4-6-0 steam classification on the PRR was the G class. Hence a 4-6-0+0-6-4 electric was obviously a GG class and the GG1 was the first and last in it. There is a difference in the castings in that one has a double keeper and one has a single keeper that fits in the slot of the double one. Then a large pin possibly as big as 12" in diameter is forced in to keep the trucks together. There isn’t a lot of difference between the real thing and the models except that the models eliminated the keepers and pins and made the pivot point at about the middle drive wheel to allow a smaller radius turn. Another aside is that the Baldwin Centipedes were failing when new rounding Horseshoe curve. Designed about the same as the GG1 it turned out they were so long that the blower in the carbody and the air duct to cool the traction motors would get misalligned significantly shutting off cooling air to the motors and causing overheating and shut down of the engines. Don’t really know how they fixed it but they did. G’s never had that problem but if you ever see any pictures of Don Wood taken at the Wilmington shops you will see spring loaded plates on the trucks of torn down G’s that pushed against the bottom of the carbody to blow air on the traction motors. They appeared in Trains many years ago and in pennsy Power by Stauffer.
Surprised this hasn’t been mentioned.
http://www.railpictures.net/viewphoto.php?id=100067&showcomments=true
There was a discussion of the GG1 in one of these forums about a year ago that included pictures showing details of the articulation, but I haven’t been able to find it. Maybe someone who is better at it can find it. There was also mention of the “G1” in Leo’s picture.
I tried again, and I found it. Picture of the articulation:
http://ctr.trains.com/~/media/images/online%20extras/gg1%20in%20layers/gg1-12-1024.ashx
Link to the forum discussion:
http://cs.trains.com/TRCCS/forums/t/182574.aspx
(I hope it works.)
You’re right and I was finally able to find the reply and link I referenced a year ago!!! Here it is:
I found a link on the Classic Trains website you should find of interest as it contains cutaway drawings of the interior layout.
http://ctr.trains.com/Online%20Extras/Equipment%20Rosters/2009/04/GG1%20in%20layers.aspx
The last two or three slides show the articulation in great detail.
The G1 (half GG1) is one of my favorite shop hacks. It didn’t really answer my question about articulation, though.
Thanks for all the great information, folks!
Yeah, but it was made possible due to the GG1 being basically two separate locomotives articulated together.
But where did this arrangement originate? Earlier Pennsy had borrowed EP-3 0354 from the for mainline testing, and liked its performance. And so one of the prototypes, the GG1, copied its arrangement—the 2-C+C-2 articulated design, but replaced its boxcab shape with the streamlined body we have loved so long.
But where did come up with the mechanical design? According to When Steam Railroads Electrified, by William D. Middleton, the bought its EP3 locomotives from General Electric, following a design developed for New York Central. In 1929, the NYC ordered 22 electric locomotives to serve the new Cleveland Union Terminal, taking passenger trains to and from the Cleveland Union Station, after steam locomotives were banned from the new station. New York Central trains were powered by the
From a simple Google search for prr gg1 frame.
http://www.steamlocomotive.com/GG1/quill.shtml
Search yourself. There is more. Just two 4-6-0’s back to back. Not a big deal.
Rich
It’s not as simple as you think it looks. I was looking for details on how it’s articulated, since the GG1 has a rigid body. Read earlier in the thread for those details. Thanks anyway.
But the New Haven already had the 1-C-1+1-C-1 (2-6-2+2-6-2) EP-2 articulateds in operation, two Praries back-to-back instead of two Ten Wheelers, and the GG1 arrangement used earlier on the New Haven EP-3 could just have easly been a logical development from the EP-2.
Don’t forget the Westinghouse motors built for the Milwaukee in 1919, which were two Pacifics’s back to back. Even earlier were the GE locomotives built for the GN and B.A.&P. had articulated B+B wheel arrangements. The original Milwaukee electric’s were 2-B+B. essentially an American articulated with a four wheel switcher.
The common element with the articulations was that the tractive forces were transmitted through the articulation between the truck frames rather than through the body.
{added note for readers unfamiliar with the details, Dave may know more than I do on the subject} The carbody of the GG1 and similar articulated electric and diesel locomotives is carried on the trucks in the way that a long rigid load would be carried on a pair of flatcars. There was a lot of engineering that went into the point of attachment between the carbody and trucks.
One advantage of articulation was that it reduced nosing (hunting) at high speeds, and that was further improved on the GG1 by the asymmetric wheel arrangement. Since the pulling force was carried through the articulation point, that force tended to straighten the trucks.
- Erik
This was also true of the EP-2 2-6-2+2-6-2, but was not true of the EP-1, which was a 2-4-0+0-4-2 or 1-B-B-1. There, the “B” or 4 wa pivoted like a regular truck, with the poney truck raidally pivoted from that truck. The were orginalliy built a B-B’s wihtout pilot trucks, which were added to reduce nosing on curves. The EP-2 was built around 1914, if I remember correctly. The EP-1 prototype was built in 1905.
In what way is the wheel arrangement of the GG1 assymetric?
While the GG1’s wheel arrangement for the whole locomotive was symmetric, the arrangement around the pivot points for each of the trucks was NOT symmetric. An FL-9 has an asymmetric wheel arrangement (B-A1A), but each of the trucks is symmetric around the trucks pivot points.
Hope this makes it a bit clearer.
- Erik