Re: What were the reasons for the K-27 valve gear differences?

Hi, Kevin -

When superheating was added to a locomotive the hotter, dryer (and usually higher-pressure) steam
required that the slide valves be replaced with piston valves.  If Stephenson valve gear was used, the
piston valves would almost always be inboard of the cylinders to line up with the (original) valve gear;
if Wahlshearts gear was used, the piston valves would usually be outboard of the cylinders.

When K-27s #454, 456, 458 and 461 were first superheated, their inside-the-frame Stephenson gear was retained and the cylinder castings had the valves inboard of the main piston. When Walschearts gear was later added to these engines an extra "offset" crank was used so that the original inboard-valve cylinder saddles could be retained - this was a lot cheaper than casting new ones with the valves outboard. (Inboard / outboard valve location is NOT the same thing as inside / outside admission of the steam.)

See [ngdiscussion.net] et seq for further information.

- Russ



Edited 1 time(s). Last edit at 02/11/2021 12:52PM by Russo Loco.