Welding cracked spokes in 2004:

http://abpr.railfan.net/abprphoto.cgi?j ... 879_FC.jpg

This welding raises a few related and semi-related questions in my mind which are out of technical curiosity and in no way alledging anything or trying to start a flame war. I weld where I work - metals and plastics, but cast iron is not one of them. I have seen it done and it can be tricky espectilly if the iron is garbare to start with - turns to sand under the arc. Were all the drivers cast steel? If so, please forgive me as some of the following questions may be irrelevent.

1) How were the cracks detected - rust lines or periodic testing, etc.?

2) With the amount of welding done, were the welds stess relieved?

3) Did the heavy welding produce any distortion or cracks elsewhere on the wheel?

4) Why did the N&W use spoked drivers such as 1218's (which don't appear to be too beefy) so late in the era when Boxpok was already a proven design for high power engines? I think the 1218 had power that rivaled a Big Boy's - which had Boxpoks.

They are cast iron and while cast iron used in driver castings is weldable it should not be welded upon with weight on the drivers...also, they need to be out so that proper pre and post weld tempuratures can be maintained.
Please, no one take what is shown in this photo as an acceptable method of doing a weld repair on a driver.

So Jason, should one weld it with the tire on or off? Tire on, the center casting is compressed together, but would that affect the internal stresses set up by the weld? Might it actually cause that section of the wheel center to shrink as the metal in the weldment contracts as it cools? Tire off, how would you prevent other stresses from altering the external circumference?

What rod would you use? Peening between passes?

I've had a limited amount of luck welding various things made of varying qualities of CI, and always interested in learning more.

dave

Any welding to wheel centers should be done with the tires removed, since the shrink fit does stress the wheel center as Dave alluded to. Tires should also be removed before pressing wheel centers off or on the axle for the same reason. If distortion occurs at the circumference of the wheel center, it should be re-turned and either a new tire fitted, the circumference built up with weld and re-turned, or the old tire should be shimmed (least preferable option).
-Chris
Arizona Steam Mafia

Dave per scott lindsay the tire should remain on while doing weld repair. It can then be removed after, center turned and shim applied. Can't tell you why exactly but thou shalt not question thine master!
So far as rod...high nickel cast iron rod, preferably from eutectic. They are a metallurgical lab that specializes in the formulation of welding rods. The best of the best!

One vote off, one vote on. Survivor Wheelshop.

Eutectic is great - but i am trying to locate a Magic Wand rod I had a sample of years ago, and have never found since. The guy who gave it to me didn't know the spec. It ran a gorgeous bead on straight DC or AC, and all the slag cam up to the top of the bead, where it hardened into a skin you could just pop off with a tap! I repaired a bad exhaust nozzle and stand with this stuff, and you couldn't have asked for nastier castings.

dave

Some interesting contrasting opinions here. Wonder what the EBT did back when the engines were in service? Any sign of previous cracks being welded?

Les

The EBT brazed the wheels back in ICC days. Evidently there was a problem with drivers on that class of engine. There is a time to weld and a time not to weld. The iron in these wheels is not weldable.

Brazing would probably work, but depending upon the number of cracks/breaks, it may be cheaper to get a new wheel. For brazing you must remove the wheel from the axle and take the tire off as well as remove the crankpin if it is in the heat zone. Ideally the entire casting should be heated to at least 500 deg F prior to the start of repairs and allowed to cool slowly. If only one spoke is broken, you may get away with localized heating, but you must be aware of unequal stresses that will occur with this method. A spoke repair near the rim may be done without removal of the axle, but again care must be taken because of unequal stresses.

If you weld an iron wheel and are using preheat, the tire should be removed. If you use a "cold weld" procedure, you may be able to keep the tire in place. Regardless, depending upon the amount of welding that is done, the tire should be removed and the wheel checked for eccentricity.

Just remember that when you put hot metal in a v-groove, whether it is brass, iron, or steel, the metal shrinks as it cools. If the spoke is held in such a manner (closed root) that it cannot move, all the stresses will be in the filler metal and heat affected zone. If the spoke has an open root that allows it to get shorter, some of these stresses will be mitigated, but the spoke will tend to pull the rim toward the center.

Steel wheel centers are much more forgiving.

It sounds to me that the best way to braze (if allowed) would be oven brazing equal heating and cooling.

BTW, what would be the ballpark cost of a replacement wheel installed be? The age and life stress of the CI wheels in service around the country may start showing cracks.

If you had to start from scratch and make a pattern, cast one wheel, re-use the axle seat, crankpin, tire, and key, it would entail a fair amount of labor. You would probably have to bore the pin hub on the quartering machine, and cleaning and measuring the tire can be a bit tricky if the tire seat is corroded or the tire is out of round. Depending upon the complexity and size of the wheel, and assuming a spoked wheel, you would probably be around $10k to $15k in materials. You should get away with $5k - $10k in labor to machine the wheel and assemble the whole thing.

A cast iron wheel center from the Heisler from Hell had spalled out around the axle, and was repaired with a sleeve. An engineer associated with the project (before I killed it by condemning the boiler) came up with this idea for a repair: make a backing plate with a pipe welded to the center of it, put the wheel center down over it with the pipe coming up through the center of the hole, and thermit weld the gap with a lot of filler material. Once done, the center could then be bored to the correct diameter, and the axle pressed in.

I have never heard of thermit used in this application, but might it be a worthy means of repairing fractured CI? What say Dennis and the other metallurgists on the list?

dave

To add to this conversation, does anyone have the total cost for the new driver set that was placed under 2719 a few years ago after the wreck?

I remember that the website had some great photos of the process of casting new wheel centers and the machining of the same.

These folks should be able to give us some special insight to this.

Take Care,

JD Johnson, Morehead and North Fork Railroad Historian