Hi All,

Looking at the facebook page for the restoration of Florida East Coast # 148, new side rods are shown as having just been cast for the engine. Someone asked what was wrong with the old rods and it was answered that they had been zinc plated while the engine was overhauled at the New Hope and Ivyland in the 70's, and if not done properly, the zinc plating could cause fatigue cracking from making the metal too brittle. If this is the case, why would the zinc plating have been done in the first place? Just to prevent corrosion?

Thanks,
John

Zinc plating, or galvanizing, is a common method of corrosion protection. The most common method, hot-dip galvanizing, can be an issue with high-strength low-carbon steel because the process introduces hydrogen into the steel which diffuses into the steel and forms bubbles at the metal grain boundaries. These bubbles put pressure on the grain boundaries which decreases the energy required to pull the grains apart and results in hydrogen-induced cracking. Alloys with a tensile strength of about 1000 MPa and greater are the most susceptible. Hydrogen introduced during a plating process can be diffused out by heating the work piece to around 400 F for a few hours. Hydrogen diffusion during welding can be minimized by preheating and post heating. When I was involved in similar work, we used to bake the piece in an inert atmosphere of Nitrogen after fabrication and cleaning.

Thank you very much!

John

I really wonder if the new rods were Cast?

Side rods are always forgings, never castings. The forging process orients the grain of the steel and makes a very strong and resilient part.

You are welcome. To be clear, I'm not saying that this was the case with 148's rods. I believe the new rods were fabricated at Strasburg Rail Road so Mr. Kelly Anderson may be the best resource for the particulars on the issues with the old rods and certainly is the best source for information regarding the fabrication of the new ones.

Sorry, nowhere did it say that the rods were cast, I used the wrong term due to my lack of knowledge with the subject.Thanks for the tip re: asking Mr. Anderson. My main curiosity was why zinc plating would be applied if it could result in metal fatigue. Was this something commonly done to locomotive rods?

John

Glover Machine Works regularly cast side rods for their steam locomotive production.

We had a similar discussion a few years ago about waterjet/plasma-cut rods and whether they 'needed' to be forged to have the right metallurgical characteristics. I took the position that progressive forging rather than selective material removal to near-net-shape was a better method of rod fabrication, but several very prominent (and highly experienced) shop people, if I recall correctly including Kelly, thought that cutting mild steel to make rods was acceptable practice. A decent near-net-shape casting using better modern methods might have the same relative lack of internal flaws/stress raisers as a piece cut from rolled plate away from edges.

On the other hand, the idea of using a general sand casting, unforged, as a rod leaves me worried, no matter how well the surfaces are dressed.

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Is there a particular reason for staying with the split brass on the small end?

Thanks for setting the record straight Mr. Anderson.

John

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And here I thought that the questionable policies coming out of Amtrak lately were due to the fact that the guy in charge was only just moonlighting from his (all) day job on the SRR and so he was severely sleep deprived. Thanks for the clarification on that - I edited my post accordingly. Since there seems to be some question in this thread as to the fabrication procedure, can you please go over how the rods were processed? Thank you.

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