Crosshead Walking on the Rod

softwerkslex · **Posted:** Tue Feb 22, 2011 12:58 pm

Page 10, "Steam Today", June 2008. In reference to Soo 2719. What does is mean when the crosshead has "walked" on the rod?

Dave · **Posted:** Tue Feb 22, 2011 2:56 pm

Possibly a way of referring to the crosshead raising and dropping as the main rod position shoves it up or down after some wear has built up in the gibs. Not a term I've heard used before.

dave

Kelly Anderson · **Joined:** Tue Sep 14, 2004 7:52 am **Posts:** 2477

Dennis Storzek · **Posted:** Tue Feb 22, 2011 4:22 pm

Might be... as I recall, this engine had new piston rods installed a couple years ago after the originals were cut to move it to Duluth.

Hillcrest · **Posted:** Tue Feb 22, 2011 10:16 pm

They were discussing the reason for cutting the piston rods, and stated while one rod was easily removed from the crosshead, the other rod had "walked" on the crosshead and could not be removed. With no other alternative and "go" time looming, they cut the right side piston rod with a torch. I've always wondered what that meant, and thought maybe the opposite, that the rod had seized in the crosshead and couldn't be driven out with the tools available at the time.

Cheers, Dave

Dave · **Posted:** Wed Feb 23, 2011 12:32 am

Kelly Anderson wrote:

softwerkslex wrote:

Page 10, "Steam Today", June 2008. In reference to Soo 2719. What does is mean when the crosshead has "walked" on the rod?

Perhaps they meant to say that the crosshead was working on the [piston] rod, i.e. that it didn't have a good fit on its taper.

I like this better than my idea. There's historic precedent, according to some sources "walking beam" engines were originally "working beam" engines until somebody misconstrued the accent of the British enginewright who was explaining it back in the late 1700 - early 1800s.

dave

Hillcrest · **Posted:** Wed Feb 23, 2011 2:34 pm

Maybe they meant it (the crosshead) "worked' on the rod and pinned the wedge in it so they couldn't get it out?? I don't know...and I will now give up.

Cheers, Dave

DBH · **Posted:** Wed Feb 23, 2011 2:48 pm

I think you are correct there Dave.

DBH

Bobk · **Posted:** Thu Feb 24, 2011 4:34 pm

The taper on the rod is moving within the crosshead. I take it that this is the piston rod and not main rod. I have heard the term before and it was described as I said.

Hillcrest · **Posted:** Thu Feb 24, 2011 4:52 pm

Bobk wrote:

The taper on the rod is moving within the crosshead. I take it that this is the piston rod and not main rod. I have heard the term before and it was described as I said.

They were talking about the piston rod and why it was cut. So Bob,does that mean the tapered end moved around enough in the crosshead casting to screw things up to the point they couldn't drive the wedge out and remove the rod from the crosshead??? I still don't feel like I understand what they meant...is this a forest-for-the-trees type thing?

Cheers, Dave

Aarne H. Frobom · **Posted:** Fri Feb 25, 2011 11:14 am

I suspect that is indeed what it means. The rod was driven so tightly into the tapered hole in the crosshead that available means couldn't drive it back out.

How could this happen? I know of one way: in the early excursion history of PM 1225 an engineman was, shall we say, a tad early in closing the cylinder cocks with the result that the forward-moving piston encountered a slug of water as the engine started. Not hard enough to do damage, but it made a jolt. At the next inspection it was found that the crosshead key was loose. (The key is retained by a welded-on keeper in anticipation of this event.) The piston rod had been driven about another quarter inch into the crosshead, requiring the keeper to be remade.

If this engine ever needs work to its rings and bore, it will no doubt be a real treat to get this rod out. Luckily, one of the few tools we salvaged from the old PM shops at Wyoming was a hydraulic wedge device that replaces the wristpin and forces the piston rod out of the crosshead. It works at many thousand lbs. pressure; its pipe fittings are the thickest I've ever seen. Presumably this will do the job, and presumably no such device was handy when the rod-cutting incident took place that was mentioned above.

This engine required work to its rod tapers. The pistons in it are from other 1200s, and were just thrown in the engine when it was placed on display in 1957. These engines had their pistons removed to facilitate dead towing when they were stored in 1951. At least we found pistons when we opened the cylinders; the other surviving 1200 has none. But the rod tapers were not matched to the crossheads, and so a lot of lapping was required to assure a tight fit when it was hammered together.

Aarne Frobom
One-in-Twelve, Michigan

John Ezovski · **Posted:** Fri Feb 25, 2011 12:28 pm

We found X-SP2479's crosshead's firmly attached to their piston rod. When it came time to separate, a number of "recommended" techniques were tried but each failed. Our master mechanic created a hydraulic press that he recalled seeing in an old document. His press functioned with grease recovered from an old driver grease cake. Pressure was created using a 7/8" fine pitch bolt. With this tool, there was virtually no effort required to separate the piston rod from the crosshead. When one of the crossheads separated, a report occurred that was heard some 30 feet away. This turned out to be a rather slick tool and not very difficult to create.

John Ezovski