PRR Herald GG1 Technojargon

Why is it called the GG1?

The Pennsylvania Railroad had a standard system for identifying locomotives by wheel arrangement. For example a 4-6-2 was a K, a 2-10-0 was an I, a 2-8-2 was a L. subsequent models would get a number such as K2, K3, K4. Of importance here, is a 4-6-0 was a G. When articulated locomotives were introduced, either electric or steam, it was classified as two locmotives back to back. The GG1 is a 2-C+C-2 in Diesel terms, but a 4-6-0+0-6-4 in steams terms, so it was two G lomotovies back to back, hence GG. First revision makes it the GG1 (there was no GG2, but all electrics got a trailing number, although all steamers did not.)

What is Quill Drive?

Quill drive refers to the hollow tube or 'quill' with disk shaped plates on either end (one is a gear). The motors powering each axle (two each in the G's case) apply power to this qull rather than directly to the axle. The axle passes through the quill and the spked wheels are just outside the quill plates. The plates each have six spring cups attached to their outside faces. They jut out between the wheel spokes, with each end of a spring cup cylinder facing each of the adjacent spokes. They apply the power from the quill to the spokes, which spoke depending on the direction of force applied. The axle can turn freely within the quill, but only as far as the spring cups will allow it to. In this way, as the quill and spring cups absorb the shock from the motors, giving a smoother application of power (better on the loco) and a smoother ride (better on the track).

This is the way I understand it, anyway.

More modern locos with smaller and ligher motors have them geared directly to the axles. Older ones had jack shafts not unlike steam locomotive rods that conveyed power without the motors resting directly on the axles. The GG1's prececessor, the P5a, also used spring cups, but on only one wheel per axle rather than two in the case of the GG1. The distibution of the cups among two wheels per axle eliminated many of the problems the P5a had with damaged and worn out cups and broken axles.

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