TOM L. Wrote:
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> In my new Christmas book "Rock Island Steam Power"
> I see that the Rock Island had some locomotives
> (#950-979 and 2540-2549) which were built with
> large reversing wheels in their cabs to control
> the valve gear through a screw-type arrangement.
> This arrangement was called Screw type or
> Precision gear. Apparently it was okay for
> passenger and through freight service, but was too
> slow and drawn-out for yard or local service where
> much switching was done.
>
> I wonder if other US railroads used this reversing
> wheel arrangement, and to what extent.

One thing that I learned through the years of operating machinery is that most
machines and/or devices are encumbered by a trade off...what you gain in one thing, you lose
in another. You just pointed out one in your paragraph Tom, with the example of that type
of reversing gear. I think the screw reverse allowed for much finer adjustment of the cutoff.
Can't think of any US roads that used them in the West. but didn't the NYC have them on some
of their locomotives? CPR 2860 has this type I believe.