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Doc's Classic Period Walking Beam Engine

Hi folks, Doc here. As I noted in the Evolution of the Erector Walking Beam Engine, at least one version of WBE was featured in Erector manuals during every model year from the mid-20's up until the end of Gilbert Erector production in 1962. The first of these to appear, shown below, was a large but rather haphazard design, looking not unlike an old fashioned spinning wheel. It consists of a tall, rectangular framework made from "angle" girders (2 B or C girders screwed together using CH angles). The "walking beam" itself sits atop the framework, while the large spoked flywheel hangs off one side of the frame near the end. The piston assembly sits atop a small platform located on the ground under the framework. A P58 motor, also sitting on the ground, drives the flywheel via a string and pulleys. A "governor" assembly atop the piston platform is also driven by a string and pulleys. Overall, this is not a bad looking model, but the design is very inefficient from a space standpoint. The flywheel is suspended way out on an upper corner of the large framework. This framework must be screwed to a wooden base of some kind, as does the motor and piston/governor assembly, both of which are loosely arranged to fill up the enormous empty space beneath the framework.

An interesting feature of this model can be found in the flywheel's drive axle/pulley assemby. I admit that as I studied the manual illustration prior to building the model, I was temporarily "stumped" by this feature. The image at right shows the area in question. It appears that the flywheel and both large drive pulleys are all on a single axle which is supported by a P79 car truck at each end (although the rear P79 is not shown in this view). Well, this is all fine, and exactly what you might expect to see in this situation. But do you see the problem? Upon close inspection, you can see two CJ 24-tooth gears, with a an 11-hole strip bolted to one of them (also, see the photo below). As the axle rotates, the strip moves up and down, causing the walking beam to "walk." All well and good, except ... how does the 11-hole strip magically pass through the axle upon each rotation? It can't, of course.

I had never seen this particular structure on any other Erector model, and at first I thought that it must be an error in the illustration; certainly, there are plenty of these in Erector manuals. However, in the event that it wasn't an error, how could this work? I came up with a solution, and whether or not it is the same one that Gilbert intended, I don't know. But, it works, and it does explain the need for two CJ gears (see photo at right).

Essentially, I "broke" the axle into two pieces by using two shorter axles instead of one long one. I screwed a CJ gear to one end of each one, then joined the two gears together using a long screw, which passes through the lower end of the 11-hole strip. Now, as the axle rotates, the 11-hole strip passes through the gap in the drive axle, and the beam can "walk" as it is supposed to.