After having repaired the gear, using photo etched nickle silver replacement parts from Phil Light, I finished installing the Tsunami TSU-750 in the tender, with a 20 mm high bass speaker in the tank, as shown below.
As you can see, fitting in the decoder, speaker, capacitor and associated wiring required extensive modification of the tender shell. All this cutting, nibbling, soldering, filing and fitting wires into the tender and locomotive, required a lot of handling. After picking up the locomotive for the umpteenth time I noticed that another rod had popped loose. What came loose were two connected rods or links, with a set of pincers on one end of the assembly, and a bracket on the other than slipped a pin holding the main rod in place.
Just to be safe, I checked the other side of the locomotive and found that while this assembly was still attached, the clamp that held it to the drive rod pin was loose and slipping. So I was faced with repairing the damage on both sides of the engine!
Since I am not an expert in Walschaerts valve gear, I once again emailed my friend Phil Light, with an explanation of the problem and a photograph of the damage. Phil replied that the small link that connected to the third driver was called the eccentric crank, and that it was connected by the longer eccentric rod to the expansion link. Here is a diagram of the basic Walschaerts valve gear, which shows the eccentric crank and rod and its connections to the rest of the valve gear.
The names of the various rods and links are less important than how to reconnect them so that the engine works as it was designed. Snapping the eccentric rod back on the expansion link was straightforward. I simply had to use tweezers to tighten the pincers around the pin. The real problem was reconnecting the eccentric crank to the crank pin on the third driver (see above).
With the piston fully inserted into the cylinder and the rods in a straight line as shown, the crank should be fixed to the pin at a specific angle (25 degrees), and soldered in place so that maintains its angular relationship to the wheel as it rotates. This makes the eccentric rod move back and forth to rock the expansion link.
Once the eccentrics were arranged with the crank at the proper angle, the clamp was soldered to the crank pin using the same method as I did replacing the broken valve gear in the last post. A small square of paper is perforated with a sharp pin (I enlarged the hole a bit with a toothpick) and slipped over the crank pin to prevent the solder from fixing the drive rod to the wheel.
With the paper in place, the eccentric link clamp is pressed over it. Using a protractor, a 25 degree angle is measured and cut from paper, and used to set the correct angle for the eccentric link.
I then carefully applied a small amount of TIX liquid flux to the top of the eccentric pin.
A hot soldering iron with a very small drop of solder is applied to the top of the pin, being careful not to hold it on the pin too long.
With the repairs made to the running gear, the engine was reassembled and run without incident. Here No. 14 takes the siding at Rockhill while a coal drag chugs by on its way to Blacklog. You can clearly see the eccentric link and rod successfully operating on the engineer's side.