Oct 1, 2020
The "quill drive" diagram answered questions I've had for many years. I've read the term a hundred times, but it was never satisfactorily explained. Excellent! Thanks for the link.
Excellent article. I wonder if the Quill drive on the GG-1s is the same as that on the EP-3 Westinghouse Quills on Milwaukee Road?
I kinda figured that springs were part of the quill drive, identified as "torque springs" probably placed to absorb the immense starting torque of the electric motors and ease strain on the drive components and reduce chance of wheel spin. Cool stuff.
Fun Fact: In the late teens, the PRR fielded an 1-C+C-1 FF-1 electric, aka "Big Liz". Only one was built as a prototype for a planned extension of wire over the Alleghenies to Pittsburgh which never happened. Monstrously powerful, it had a penchant for pulling out drawbars and when tested in helper service, it mashed cars and forced them off the rails on curves.
Very cool! Clearly the helper crew didn't know about watching the ammeter and watching slack action ahead of the train the way crews learned decades later.
This photo shows the drive mechanism of the DD-1 which was similar to the FF-1, but with only two driver axles per motor.
Electric motors still were very large for the HP required. They had to be mounted in the body and use side rods to drive the wheels.
The DD-1 used a rotating counter weight for the side rods. Whereas the FF-1 appears to use a non-weightbearing wheel.
Wow, what a neat picture. Those are mighty large counterweights mounted at each end of the jackshafts.
I've always been a fan of the VGN's huge siderod electrics, but don't know much about them. Are the motors hung at the ends of each locomotive, almost looking like drive wheels? I can see a gap between the motor and the rail. There's a rod connecting the motor to one drive wheel. I wonder how the wheel adjacent to the motor was driven?
There is another connecting rod behind the main rod. It is always hidden behind the main rod since they move in snyc, which makes it hard to see. This is from the Brasstrains site looking at the ALCO HO model, which I think is easier to understand than old digitized photos of the actual train.
That's interesting. I wonder why they used a complex overlapping configuration when the PRR DD-1 configuration seems simpler to assemble and maintain?
Oh, that's a perfect illustration Trainiac -- thanks.
Maybe with with the motors hung below floor level in line with the drivers, efficiencies are gained without the wasted motion of jackshafts and their bearings, and with the motor weight closer to the rail, perhaps there's more stability with a lower center of gravity? I'm just guessing here.
No, that's not a guess, but a rational analysis. I had not considered mounting the motor down to lower the center of gravity. Also with the motor mounted close to track level, there was insufficient distance for a lead driver jack shaft. Obviously the only solution was a long rod to the rear driver. Thanks.
I had the same question.
That is a good article and very informative. Thanks for posting it. Also liking all the follow up pics and discussion here.
I found a neat link this morning. The quill drive also permitted "the driving wheels and axle to move in reaction to track conditions without affecting the meshing of the drive pinions and the bull gear", but I'm not sure I understand how.
The Quill drive consists of two axles, the inner axle for the wheels, and the outer (hollow tube) axle for the Quill. The driving wheels are of course attached to the sideframes with spring suspension, but the Quill drive and traction motor are rigid to the frame. The wheel's position is constantly changing inside the Quill axle because of the locomotive's suspension, but Quill and drive gears stay stationary because they are part of the truck structure. The wheel's axle bounces around inside the hollow quill drive axle, while the spring transmission compensates for any motion. The flexible springs keep constant pressure on the spokes, even if the Quill and driving wheel aren't exactly 'lined up,' ensuring the wheels keep turning forward over rough trackwork.
This is unlike a diesel locomotive where the traction motors are nose-hung. A diesel locomotive has a pinion on the traction motor and a larger axle gear it meshes with. The traction motor moves with the wheel to keep the gears meshed. The GG1 pinion meshes with the axle gear, but the axle gear isn't actually attached to the axle, there is still the spring transmission to get through before power reaches the wheel. This means the GG1 has a very low unsprung weight because even the traction motors are above the suspension system.
Thank you for an excellent description of the quill drive and its dynamic forces.
Ah ha -- I thought that the inside diameter of the Quill tube was the same as the outside diameter of the axle, but I now see that's not all the case. The Quill has a much larger diameter, allowing the axle full freedom of movement within it. All quite brilliant. Reading your description while looking at Hytec's illustration, it now makes sense.
The mechanical engineers of a hundred years ago were the same caliber of innovation as the computer engineers of today. Hats off to them.