Re: K-27's - First Four between 2nd & 3rd rebuild ...

Earl Wrote:
-------------------------------------------------------
> While there are no pics of an inboard piston valve
> mudhen with Stephenson gear to be found (yet),
> there IS evidence that they existed as such.
>
> First, there is a D&RG drawing dated in the mid-
> late teens of of a piston valve mudhen with "old
> style valve gear".  Secondly, the AFE's show 454,
> 456, 458 & 461 getting piston valves around 1918
> [but] not getting superheat and Walshearts gear
> fitted 'til the 1920's.


Thanks for the confirmation, Earl -

. . . and there's really no other reason for inboard piston valves; they lined up well with the existing Stephenson gear that was retained for a few years, and only required an extra link or offset crank when later converted to Walshearts. It was a LOT less expensive to add an offset crank to the Walshearts gear than to have yet another set of new cylinders cast with outboard valves to line up with Walshearts gear without the added complexity of the crank.  OTOH, the crank and its assoc­iated pins & bearings provided yet another source for wear and slop in the valve gear, so I'm guessing that #461 didn't remain 'square' as long as #455 after having her timing adjusted.

This drawing has been posted previously w/ pics of my HOn3 model (see [ngdiscussion.net]), but here I have tinted the offset crank (I don't know what else to call it) and its associated bearing block red for emphasis:


- Russ



Edited 7 time(s). Last edit at 03/23/2022 09:16PM by Russo Loco.