What kind of metal was used for side rods?

When "modern" steam had "lightweight" rods- what did that mean?

If you were going to create new rods today-would there be some alternate material you could use (especially if cost was no object), such as titanium or some exotic carbon composite

Finally, if you were constrained by cost-what would be used?

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Hi Supe - i think you are referring to Carbon Fiber, which is very light and strong, and used in some automotive applications. It was discussed as side rod material a few years back in an experimental vein, never applied practically to my knowledge. My buddy Dennis the Steel Guy recommends 4340 for this (and many other) components.

dave

Of course, if you change the side rod material, all of your counterbalancing has to be changed too.

carbon fiber would be my choice especially if cost were no object. with nice sealed super roller bearings, probably could knock off 80% of the counterweight, and decrease rotating mass significantly

I agree to a degree about the danger of failure,
although the carbon graphite would have so little mass compared with all the other components I think it would take all the destruction

I have seen them work with it at Lockheed, and was so impressed as to its ease of use, my son and I looked into making skateboards in the shop

then he blew out his knee...
so I never went any further

dr

Carbon fiber would be an interesting choice, though I'm not sure it would hold to the fatique cycles faced by locomotive side rods. Would the axial tensile / compressive forces wear it to pieces after a while?

Mind you, I've only worked with the stuff building hoods and intakes for race cars. Has anyone here used solid carbon fiber in similar applications to what it would face in side rods?

I'd probably stick with hardened 1045 or 4340 myself, your mileage may vary.

Considering that carbon fiber composites have found their way into aircraft - including high stress fighter planes, it's reasonably likely that a design could be developed for side rods. I worked somewhat with this material while in college when we constructed a carbon fiber monocoque electric race car as a student project. The material performs best in tension, so the trick is in designing the cross-section and fiber orientations to match the load paths and take advantage of the high tensile strength. As long as the rod was designed to keep its peak stresses below material cyclic fatigue limits, it should do alright.

Titanium would probably be a good metal selection as was stated. Magnesium alloys might be another choice.

Before everyone goes out and redesigns another part of a steam locomotive one should consider the locomotive forces. Railroad steam locomotives actually exert more pressure when a locomotive is compressing the main rod than when it is in tensile due to the difference of the two volumes on each side of the piston due to the piston rod. When designing/choosing a material to due a particular job you have to consider a number of factors including material cost, production capabilities, environmental concerns just to name a few. It amazes me how many factors go into a design. Remember the Delorian? How many stainless steel cars do you see today?

Robby

And for those unconcerned with metallurgy, tensile strength, or anything else, there's the approach to broken side rods that I saw at Northwestern Steel and Wire on one of their scrapyard 0-8-0's: just torch off the rod eyes and weld `em onto a length of I-beam.

I don't think I'd want to try that at much over 5mph.....................

I'm sure the quarter was REALLY precise on those drivers too!