First of all, a little about the 2. In 2014, SCPC 2 ran over 1,000 miles on four different railroads across the west coast, and everything relating to her rebuild (completed in 2013) performed very well. However, a few items were not addressed in the initial project as time constraints of the west coast tour just would not allow everything to be completed before departing for California. These were remachining the piston rods, pistons and ring grooves, new piston rings, redesigned packing, new crosshead wedges, remachining and relining the crosshead guides, and remachining the crosshead slippers. Although there was no evidence of blow by, and the bores and pistons were inspected prior to being put in service, the author decided to finish these last few items before returning the 2 to service Memorial Day weekend.
In January the author and his crew of volunteers ("Team Chiggen") stripped the cylinder saddle of covers, crossheads, guides, pistons, etc and began the process of rebuilding. In order to assure perfect concentricity and no taper of the piston rod, the best method of machining is to rough machine to round, then use a tool post grinder to assure surface finish and concentricity. At the same time, the team turned the ring grooves, preparatory for new rings.
The specification for engines this size is for a the ring groove to be .005" over the width of the rings to assure steam tightness. Meanwhile, new rings were purchased from Niagara Piston Ring to specific dimensions. Although Team Chiggen is more than capable of making piston rings in house, it is less expensive to source completed rings than to buy the rough material to manufacture from scratch.
At the same time, the original rod packing on the locomotive left a lot to be desired. The author had researched going to a La France style packing similar to what the Cumbres and Toltec, and the Durango and Silverton use on their locomotives, and found a very competitively priced version available through That Steam Guy. This owner - though not associated with the seller - is quite happy with the product. In response to more recent steam locomotive practice, also installed were four packing elements per side based upon the South African Railway and Chinese data for multiple packing elements rather than the more familiar two.
While piston work was underway, Team Chiggen remachined and set up the crosshead guides in order to maintain perfect alignment of the piston rod within the packing gland to prevent premature wear of the piston rod, rings, pistons, and bores. After the guides were machined and and temporarily installed, string lines were run through the bores perfectly in alignment with the cylinder and checked against the guides to assure parallelism.
On the left side, all was well, but the right side (shown at right) required work to bring the guides into specification with the bores, thus demonstrating the necessity of doing this type of work, even if things "look ok."
After a little effort, the piston, rod, and ring assembly were ready to re install on the right side. Those with keen eyes will notice the presence of double rings in each groove. The owner decided to do this rather than two wide rings due to the overwhelming evidence to support the higher sealing abilities of multiple narrow rings over wide ones.
Now, in order to assure the piston rod is running parallel to the bores and crosshead guides, the crosshead slippers themselves must be machined and fit to assure the center line of the tapered socket is in the right place. The accompanied photos show one of the four remachined slippers ready for installation, and the entire assembly, straight and true, with a new machined crosshead wedge to assure years of trouble free operation.
So after all this work, there is no better way to prove if it all works than to try it. So last Sunday was test day: Team Chiggen fired the locomotive up, and put her on the head end of the last passenger train of the day. Rest assured that diesel is in isolation, and the Chiggen is pulling the consist up the 1.2% grade to the top of Snoqualmie Falls. Everything performed admirably and the team called the test so successful, there was a second charge up the hill just for fun!
So for all of you in the local area, come on out this Saturday through Monday (Memorial Day Weekend) and take an excursion at Northwest Railway Museum behind the new and improved SCPC 2! Fares and times are here. And remember, there is full summer season of steam this year, and a variety of special programs including Snoqualmie Railroad Days in August, so check out the details on the Museum's web site at www.trainmuseum.org
A special thanks to Team Chiggen: John Graddon, Adam Phillips, Zeb Darrah, Karl Klontz, Nathan Iverson, Steven Hughes, Mark Speer, Mike Donnelly, Jason Hill, CJ Vargas, Bill Gejerstad, David Wilhite, Andy Walker, Ken Liesse, Jason Sobcynski, and many others who help make this all possible!
--SCPC winter work was a guest post by Northwest Railway Museum Curator of Collections Stathi Pappas--