November 20, 2020 07:50PM avatar
Lenicheck Wrote:
> It is apparent from the attached photo that the
> Uintah 2-6-6-2 #50 is configured to have the two
> sets of piston valves set in opposite directions
> for running- one radius rod is up and one is down
> (see the red highlights). How is this possible . . .

Kelly Anderson Wrote:
> The eccentric cranks are set differently:  the rear
> one leans to the rear for indirect motion, and the
> front one leans to the front for direct motion.  This
> was pretty common for articulateds so the one
> engine's radius rods would counterbalance the
> other's.

Here's another illustration -

From the top of page 23 of Robert J. Church's fabulous and highly detailed story of the S.P.'s Cab Forward locomotives, copyright © 1982 (which reminds me how old I'm getting, since it seems like about three years ago that I acquired my brand-new copy still hot off the press . . . )

I had mis-remembered that the later cab-forwards were also arranged this way, but all of the photos and the very detailed drawings of the AC-4, AC-6, AC-7 and AC-12 locomotives - as well as the conventional AC-9s built as coal-burners - show the eccentric cranks all pointing forward when both engines are in "rods down" orientation so that the radius rods would all be down when in forward motion.*  (Note that I said "pointing forward", not "pointing toward the smokebox" . . . )

- El Abuelo Histœrico, Greengo y Curmudgeoño de los Locomoturas Viejos y Verdes,
aka Der Grossväterlich DünkelOlivGrünDampfKesselMantelLiebHabender

*  The caption for the above photo may have things backwards too, but that shouldn't be a surprise since the entire locomotive is backwards, and having the Johnson Bar in neutral for the photo (dead center – neither forward nor reverse) doesn't help clarify the situation.  Assuming that the piston valves are the far more usual inside admission, the radius rod of the forward (left) engine would drop and the radius rod of the rear (right) would rise as the engineer set the gear for forward motion (toward the left in the above photo).

Edited 1 time(s). Last edit at 11/20/2020 08:32PM by Russo Loco.
Subject Author Posted

Uintah #50 valve gear Attachments

Lenicheck November 20, 2020 10:14AM

Re: Uintah #50 valve gear

RDannemann November 20, 2020 10:22AM

Re: Uintah #50 valve gear

Kelly Anderson November 20, 2020 10:38AM

Re: Balancing articulated valve gear Attachments

Russo Loco November 20, 2020 07:50PM

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