3D CAD saves the day

…or at least an hour anyway.

As I was working my way through design of the running gear for 622, the reach rod for the reverser proved to be an interesting conundrum.

According to the drawing from Baldwin, the lever for lifting the valve gear is supposed to be 21 inches long. This, along with the length of the Johnson bar, would determine the amount of force the engineer needed to apply to the Johnson bar to overcome the steam pressure and move the valve.

When I drew this in OnShape, however, I found that the end of the lever would then be inside the boiler! Meanwhile, the drawing shows the reach rod running below the tops of the drivers at mid-gear. An 18-inch lever makes the model match the drawing.

What’s more, the 3D model identified that the house bracket (properly the wheel cover) needs to be thinner to accommodate the reach rod and move it safely out of the firebox. I’ve circled the planned etched pocket in the screen capture above.

How did they figure these things out before 3D CAD? Oh wait!  That’s why the original draftsman made the error!


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